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A Geographical Information System-Based Multicriteria Evaluation to Map Areas at Risk for Rift Valley Fever Vector-Borne Transmission in Italy
Abstract
Rift Valley fever (RVF) is a severe mosquito-borne disease that is caused by a Phlebovirus (Bunyaviridae) and affects domestic ruminants and humans. Recently, its distribution widened, threatening Europe. The probability of the introduction and large-scale spread of Rift Valley fever virus (RVFV) in Europe is low, but localized RVF outbreaks may occur in areas where populations of ruminants and potential vectors are present. In this study, we assumed the introduction of the virus into Italy and focused on the risk of vector-borne transmission of RVFV to three main European potential hosts (cattle, sheep and goats). Five main potential mosquito vectors belonging to the Culex and Aedes genera that are present in Italy were identified in a literature review. We first modelled the geographical distribution of these five species based on expert knowledge and using land cover as a proxy of mosquito presence. The mosquito distribution maps were compared with field mosquito collections from Italy to validate the model. Next, the risk of RVFV transmission was modelled using a multicriteria evaluation (MCE) approach, integrating expert knowledge and the results of a literature review on host sensitivity and vector competence, feeding behaviour and abundance. A sensitivity analysis was performed to assess the robustness of the results with respect to expert choices. The resulting maps include (i) five maps of the vector distribution, (ii) a map of suitable areas for vector-borne transmission of RVFV and (iii) a map of the risk of RVFV vector-borne transmission to sensitive hosts given a viral introduction. Good agreement was found between the modelled presence probability and the observed presence or absence of each vector species. The resulting RVF risk map highlighted strong spatial heterogeneity and could be used to target surveillance. In conclusion, the geographical information system (GIS)-based MCE served as a valuable framework and a flexible tool for mapping the areas at risk of a pathogen that is currently absent from a region.
... From the early generation of ecological studies that demonstrated the capability of RS data products in disease mapping [13][14][15][16], there had been a sustained proliferation of such studies in disease mapping and epidemiology. The application of geostatistical techniques to identify spatial heterogeneities in disease distributions, patterns, and trends as well as forecasting for epidemic preparedness planning had been demonstrated in studies by Chilès and Delfiner [17]; and Tran et al. [18] inter Remote Sensing Applications in Disease Mapping DOI: http://dx.doi.org /10.5772/intechopen.93652 ...
... Such models are then referred to as space-time models, especially due to the fact that they also include the observation dates of the mapped data. The theory behind incorporation of RS data in disease mapping and epidemiology was based on the field-observed association between environmental conditions and some of the disease-causing vectors [18][19][20], in particular how they vary in geographic space. For instance, some studies have demonstrated the association between radiation reflectance as measured by satellites and certain land cover types which have been used as environmental and climatic proxies for measurement of presence or absence of a disease and its vectors [21]. ...
... Most of the epidemiological studies that had mapped vector-borne diseases in the context of the environmental factors associated with those diseases [18][19][20] had based their assumptions on the established scientific evidence that those environmental factors were associated with the disease outcome of interest. To date an increasing number of disease mapping and epidemiology studies continue to use environmental and climatic data to map and predict disease distribution in defined geographic areas. ...
Disease mapping utilizes disease maps as visual representations of sophisticated geographic data that provide a general overview of the disease situation in a defined geographic area. Epidemiology is concerned with investigating the causes of diseases, and often, these causes vary in frequency and in space. This variation in space gave a niche to remote sensing to find its way into the public health domain as disease researchers sought to investigate the explaining environmental and climatic factors. Studies have demonstrated the potential offered by remote sensing application to disease mapping and epidemiology and to support surveillance and control efforts. We used some examples from a case study conducted in Eswatini in Southern Africa. Remote sensing imagery when combined with GIS spatial analyses techniques could support and guide existing disease surveillance and control programs at local, regional, and even continental scales. Researchers have also studied factors influencing the patterns and distributions of vector-borne diseases at a variety of landscape scales. However, successful application of remote sensing technology depends on the ability of nonexperts’ remotely sensed data and end users to access, retrieve, and analyze the data captured from satellites. The exploration of some of the opportunities presented by remote sensing to disease mapping and epidemiology is still unfolding as new opportunities are being presented.
... Usually habitat models are used to depict the potential distribution of a given species or disease, generally by mapping a suitability index. Recent examples are the WNV suitability map for Greece (Valiakos et al., 2014) and the Rift Valley Fever risk maps for Italy (Tran et al., 2013). During the last decades, several habitat models have been developed and applied for prediction under current and future climate (Araujo et al., 2005). ...
... Habitat models allow initial predictions of potential areas under risk, with relatively little input data and effort. As a result, the number of published applications has rapidly increased in the last years (Valiakos et al., 2014;Tran et al., 2013). However, frequently habitat models are uncritically applied without any verification by independent data, which may lead to unreliable species or disease distributions. ...
... Habitat models have often been used to map the potential distribution of diseases (Tran et al., 2013;Valiakos et al., 2014). These relatively quickly available maps can serve as an extra decision tool for veterinary authorities. ...
The Usutu virus (USUV) is a mosquito-borne flavivirus closely related to the better known West Nile virus, and it can cause mass mortalities of song birds. In the present paper, a dataset of georeferenced locations of USUV-positive birds was compiled and then used to map the geographical distribution of suitable USUV habitats in Central Europe. Six habitat models, comprising BIOCLIM, DOMAIN, maximum entropy model (MAXENT), generalized linear model (GLM), boosted regression trees model (BRT), and random forests model (RF), were selected and tested for their performance ability to predict cases of disease in unsampled areas. Suitability index maps, a diagram depicting model performance by the Area Under the Curve (AUC) vs. the True Skill Statistic (TSS), and a diagram ranking sensitivity vs. specificity as well as correct classification ratio (CCR) vs. misclassification ratio (MCR) were presented. Of the models tested GLM, BRT, RF, and MAXENT were shown suitable to predict USUV-positive dead birds in unsampled regions, with BRT the highest predictive accuracy (AUC = 0.75, TSS = 0.50). However, the four models classified major parts of the model domain as USUV-suitable, although USUV was never confirmed there so far (MCR=0.49 to 0.61). DOMAIN and especially BIOCLIM can only be recommended for interpolating point observations to raster files, i.e. for analyzing observed USUV distributions (MCR = 0.10). Habitat models can be a helpful tool for informing veterinary authorities about the possible distribution of a given mosquito-borne disease. Nevertheless, it should be taken in consideration, that the spatial and temporal scales, the selection of an appropriate model, the availability of significant predictive variables as well as the representativeness and completeness of collected species or disease cases may strongly influence the modeling results.
... The spatial risk of RVFV transmission within Egypt was estimated using a GIS-based multicriteria evaluation (MCE) approach [12], which allows to combine the (spatial) data on the different factors that may influence the risk of a given disease. In the case of RVF it is essential to account for the distribution of both the susceptible hosts and the vectors of RVFV [13]. All layers were transformed into a raster format, with 1 km × 1 km spatial resolution and the common UTM 35N projection. ...
... We mapped Cx. pipiens presence in Egypt based on the expected suitability of the land cover categories for the presence of this vector (values of 1 for presence and 0 for absence) estimated on the basis of a literature review and the opinion of experts [13]. Given that the same data was not available for Cx. ...
... Given that estimates by Tran and collaborators [13] were based on Corine land-cover categories, which are not available for Egypt, the corresponding categories from FAO-GeoNetwork land cover were extrapolated from the South of Europe, and used to map the distribution areas of Cx. pipiens in Egypt. If a FAO-GeoNetwork land cover category corresponded to a single Corine land cover category, its value for the presence of Cx. pipiens was that of Corine land cover category (0 or 1). ...
Rift Valley Fever (RVF) is a mosquito-borne zoonosis, which may cause significant losses for the livestock sector and have serious public health implications. Egypt has been repeatedly affected by RVF epidemics, mainly associated to the importation of animals from sub-Saharan countries, where the disease is endemic. The objective of our study was the improvement of the surveillance and control strategies implemented in Egypt. In order to do that, first we evaluated the legal trade of live animals into and within Egypt. Then, we assessed the risk of Rift Valley Fever virus (RVFV) transmission within the country using a multi-criteria evaluation approach. Finally, we combined the animal trade and the risk of RVFV transmission data to identify those areas and periods in which the introduction of RVFV is more likely. Our results indicate that the main risk of RVFV introduction is posed by the continuous flow of large number of camels coming from Sudan. The risk of RVFV transmission by vectors is restricted to the areas surrounding the Nile river, and does not vary significantly throughout the year. Imported camels are taken to quarantines, where the risk of RVFV transmission by vectors is generally low. Then, they are taken to animal markets or slaughterhouses, many located in populated areas, where the risk of RVFV transmission to animals or humans is much higher. The measures currently implemented (quarantines, vaccination or testing) seem to have a limited effect in reducing the risk of RVFV introduction, and therefore other (risk-based) surveillance strategies are proposed.
... Spatial multi-criteria evaluation (MCE) is a rapid and pragmatic knowledge-based method adapted for mapping disease suitability in the absence of large epidemiological datasets. Defined as 'a process that transforms and combines geographical data and value judgments (expert and bibliographic knowledge, including uncertainties, subjective and qualitative information) to obtain appropriate and useful information for decision making' [24], this method has been used to map suitable areas for RVF transmission in Africa, on a continental scale [25] and in Senegal [26], and in the European countries of Spain [27] and Italy [28]. However, the predicted maps could not be validated for European countries which are disease-free regions, while in Senegal the validation could only be performed in a qualitative way [26]. ...
... Thus, our results highlighted the importance of taking into account livestock data and the factor of animal trade in addition to environmental factors to develop predictive maps of RVF occurrence. Moreover, these maps increase the confidence level for the approach applied to RVF free-areas [27,28]. ...
... Indeed, the MCE approach we applied to four countries of eastern Africa was very similar to previous modelling studies that used the same approach in different geographic contexts [25][26][27][28]. All of these studies considered two main categories of risk factors: on the one hand, those related to domestic ruminant densities, and on the other hand, those related to vector presence (i.e., vector distributions or proxies of vector distributions, such as temperature, elevation, rainfall, and proximity to aquatic areas). ...
Rift Valley fever (RVF), a mosquito-borne disease affecting ruminants and humans, is one of the most important viral zoonoses in Africa. The objective of the present study was to develop a geographic knowledge-based method to map the areas suitable for RVF amplification and RVF spread in four East African countries, namely, Kenya, Tanzania, Uganda and Ethiopia, and to assess the predictive accuracy of the model using livestock outbreak data from Kenya and Tanzania. Risk factors and their relative importance regarding RVF amplification and spread were identified from a literature review. A numerical weight was calculated for each risk factor using an analytical hierarchy process. The corresponding geographic data were collected, standardized and combined based on a weighted linear combination to produce maps of the suitability for RVF transmission. The accuracy of the resulting maps was assessed using RVF outbreak locations in livestock reported in Kenya and Tanzania between 1998 and 2012 and the ROC curve analysis. Our results confirmed the capacity of the geographic information system-based multi-criteria evaluation method to synthesize available scientific knowledge and to accurately map (AUC = 0.786; 95% CI [0.730-0.842]) the spatial heterogeneity of RVF suitability in East Africa. This approach provides users with a straightforward and easy update of the maps according to data availability or the further development of scientific knowledge.
... The spatial resolution was theoretically justified given response variable sampling design (e.g. Tran et al., 2013) or by a known or estimated spatial error in the response variable (e.g. Johnson et al., 2017). ...
... Mosquito SDMs applied independent evaluation from updated field surveys from public health or targeted efforts (e.g. Tran et al., 2013;Ibanez-Justicia and Cianci, 2015). ...
Mosquito borne diseases (MBD) are a major global health concern. To aid MBD management efforts, the distribution of mosquito species is frequently investigated through species distribution models (SDMs). However, the quality these SDMs for management use has not been examined. We evaluated 127 publications of mosquito SDMs published between 1998 and 2020 and assessed each against a set of recently-developed, best-practice standards pertaining to quality of the response variable, predictor variables, model building, and model evaluation aspects. Mosquito SDMs were predominantly trained with presence-background response variables (77% of studies), bioclimatic predictor variables (39-63%), maximum entropy algorithm (54%), and evaluated by area under the receiver operating curve (36%) or confusion matrix metrics (34%). Aedes were the best-studied genus (70 studies). Pan-African (20%) and global (16%) distribution studies dominated. All published studies had one or more unacceptable standards within considered aspects, but no aspect observed unacceptable standards in all publications. The highest proportion of unacceptable standards were observed within predictor variables (60%), followed by model building (53%), model evaluation (34%), and response variable (17%). Response variable and model building demonstrated 8% and 0.2% increases in quality over time, but predictor variables and model evaluation exhibited 6% and 2% decreases in quality, respectively. Quality of mosquito SDMs has not changed since introduction of best practice standards. Quality of mosquito SDMs can be improved by ensuring known species temperature and precipitation thresholds are represented within the response variable. Resolution of predictor variables must be justified from ecological knowledge or statistically approximated. SDMs of mosquitoes require improved evaluation against independent data or creation of geographically-structured data. We encourage future mosquito SDM applications to utilize the most recent SDM standards and recommendations to improve applicability.
... Similarly, in Italy, a GIS-based multicriteria evaluation mapped the risk of Rift Valley fever transmission by integrating data on potential mosquito vectors and livestock densities. These studies underscore the effectiveness of GIS in enhancing disease surveillance, enabling precise mapping of disease prevalence, and facilitating targeted intervention programs [54][55][56][57]. ...
There is an increasing interest in the role of digital health in the healthcare industry, focusing on enhancing patient care through technologies such as electronic health records (EHRs), mobile health applications, telemedicine, and other advancements. The purpose of this review is to highlight the enormous potential of digital transformation tools in managing and mitigating neglected tropical diseases (NTDs), which affect millions of people worldwide, particularly in the Global South. To meet this purpose, we conducted a scoping review of existing literature and investigated the specific application of these technologies to NTDs. Briefly, the review entailed three main components: a bibliometric analysis, a content analysis, and the design of an ontological model to illustrate the relationships between technologies and diseases.
The review highlights the emerging use of smartphones as a promising tool not only to increase communication and awareness on NTDs but also to enhance the possibilities of their management. The findings also underscore the use of artificial intelligence in the development of new drugs, as well as the application of deep learning in predicting and detecting diseases and vectors. Content analysis stated the main NTDs in literature addressed by when associated to the use of digital health like dengue and malaria. From this review, an ontological model was developed to link diseases and digital tools used to combat NTDs in the Global South. These findings suggest that a new and growing field of research and application that utilises digital technology to address the challenges posed by NTDs.
The present scoping review identifies the significant potential of digital technologies in the fight against NTDs. Important barriers such as sustainable financing, data privacy, and the need for capacity building are recognised. A novel aspect of this review is the design of an ontological model to serve as a guide to new technological products applied to solve issues related to NTDs. The model connects concepts and major results found in the literature, indicating a structured approach to understanding and applying digital transformation in combating NTDs.
... También se considera de riesgo la introducción por medio de vectores infectados en sus diferentes estados biológicos (huevo, larva, pupa y adulto) que podría ocurrir desde largas distancias por diferentes medios de transporte, como aviones, barcos y vehículos de carretera (174). Algunas especies de mosquitos, vectores potenciales del VFVR, como Ae. aegypti o Ae. albopictus, comparten una adaptación ecológica similar para ovipositar en recipientes de agua (175). Además, los huevos de Ae. albopictus son capaces de sobrevivir períodos prolongados sin agua mostrando una verdadera diapausa biológica (176). ...
El Plan Nacional de Prevención, Vigilancia y Control de las Enfermedades Transmitidas por Vectores tiene la finalidad de disminuir el riesgo y reducir al mínimo el impacto global de estas enfermedades emergentes desde la
perspectiva de “Una Sola Salud”.
... También se considera de riesgo la introducción por medio de vectores infectados en sus diferentes estados biológicos (huevo, larva, pupa y adulto) que podría ocurrir desde largas distancias por diferentes medios de transporte, como aviones, barcos y vehículos de carretera (174). Algunas especies de mosquitos, vectores potenciales del VFVR, como Ae. aegypti o Ae. albopictus, comparten una adaptación ecológica similar para ovipositar en recipientes de agua (175). Además, los huevos de Ae. albopictus son capaces de sobrevivir períodos prolongados sin agua mostrando una verdadera diapausa biológica (176). ...
General Objective:
With a "One Health" approach, reduce the burden and threat of human diseases transmitted by Aedes.
Specific Objectives:
Improve the response to human diseases transmitted by Aedes at the local, regional, and national levels by establishing risk scenarios for preparedness and response activation at each level and scenario.
Strengthen coordination and communication mechanisms among the involved agents and administrations within their respective competencies, including situations of alerts and public health crises.
Enhance human health surveillance systems to ensure early detection of Aedes-transmitted diseases such as dengue, chikungunya, Zika, yellow fever, and any other associated emerging pathogens.
Strengthen entomological surveillance of Aedes mosquitoes to identify their presence and other entomological parameters in order to estimate the risk of disease transmission.
Reinforce entomological surveillance at ports and airports, including collaboration with airlines, shipping companies, and port authorities.
Strengthen entomological surveillance at airports to identify potential introductions of Ae. aegypti mosquitoes, in order to take measures to limit their early expansion.
Ensure that information from human, environmental, entomological, and citizen science surveillance is timely, accessible, and integrated to facilitate prevention, early detection, and control of Aedes-transmitted diseases.
Conduct risk assessments that help make decisions for prevention and control.
Ensure efficient vector control, taking into consideration environmental requirements for the optimal application of available measures, adapted to local circumstances, and sustainable.
Support the development of regional and local plans for prevention, surveillance, and control of Aedes-transmitted diseases.
Enhance risk communication to the population and citizen participation, leveraging technological channels for participatory communication to the public.
... Human Population Data/Ratio [30,71,104,106,126] Ditch shrimp of the genus Palaemonetes and Fish as predators [99] Birds [80] Horses [80] Animals in farms [56,61,63] To cite a few examples, in Europe as a whole, geographical accessibility, absolute humidity, and annual minimum temperatures were the strongest predictors for the presence of Aedes vectors [119]. In addition, the best environmental predictors of West Nile Fever outbreaks in Europe were climatic (maximum temperature of the warmest month and annual temperature range), human-related (rain-fed agriculture, density of poultry and horses), and topo-hydrographic variables (presence of rivers and altitude) [80]. ...
Mosquito-borne infections are increasing in endemic areas and previously unaffected regions. In 2020, the notification rate for Dengue was 0.5 cases per 100,000 population, and for Chikungunya <0.1/100,000. In 2019, the rate for Malaria was 1.3/100,000, and for West Nile Virus, 0.1/100,000. Spatial analysis is increasingly used in surveillance and epidemiological investigation, but reviews about their use in this research topic are scarce. We identify and describe the methodological approaches used to investigate the distribution and ecological determinants of mosquito-borne infections in Europe. Relevant literature was extracted from PubMed, Scopus, and Web of Science from inception until October 2021 and analysed according to PRISMA-ScR protocol. We identified 110 studies. Most used geographical correlation analysis (n = 50), mainly applying generalised linear models, and the remaining used spatial cluster detection (n = 30) and disease mapping (n = 30), mainly conducted using frequentist approaches. The most studied infections were Dengue (n = 32), Malaria (n = 26), Chikungunya (n = 26), and West Nile Virus (n = 24), and the most studied ecological determinants were temperature (n = 39), precipitation (n = 24), water bodies (n = 14), and vegetation (n = 11). Results from this review may support public health programs for mosquito-borne disease prevention and may help guide future research, as we recommended various good practices for spatial epidemiological studies.
... Mapping RVF risk areas NDVI Maps. RVF risk maps were generated using previously described criteria [31,[65][66][67][68]. Briefly, RVF emergence is a result of the complex interaction of the host, vector and environment. ...
Rift valley fever (RVF) is a mosquito-borne disease of animals and humans. Although RVF outbreaks are usually reported at 5-15-year intervals in sub-Saharan Africa, Zambia has experienced an unusually long inter-epizootic/-epidemic period of more than three decades. However, serological evidence of RVF virus (RVFV) infection in domestic ruminants during this period underscores the need for comprehensive investigation of the mechanisms of virus perpetuation and disease emergence. Mosquitoes ( n = 16,778) captured from eight of the ten provinces of Zambia between April 2014 and May 2019 were pooled ( n = 961) and screened for RVFV genome by a pan-phlebo RT-PCR assay. Aedes mosquito pools ( n = 85) were further screened by nested RT-PCR assay. Sera from sheep ( n = 13), goats ( n = 259) and wild ungulates ( n = 285) were screened for RVFV antibodies by ELISA while genome detection in pooled sera ( n = 276) from domestic ( n = 248) and wild ungulates ( n = 37) was performed by real-time RT-PCR assay. To examine the association between the long inter-epizootic period and climatic variables, we examined El Niño-Southern Oscillation indices, precipitation anomalies, and normalized difference vegetation index. We then derived RVF risk maps by exploring climatic variables that would favor emergence of primary RVFV vectors. While no RVFV genome could be detected in pooled mosquito and serum samples, seroprevalence was significantly high (OR = 8.13, 95% CI [4.63–14.25]) in wild ungulates (33.7%; 96/285) compared to domestic ruminants (5.6%; 16/272). Retrospective analysis of RVF epizootics in Zambia showed a positive correlation between anomalous precipitation (La Niña) and disease emergence. On risk mapping, whilst northern and eastern parts of the country were at high risk, domestic ruminant population density was low (< 21 animals/km ² ) in these areas compared to low risk areas (>21 animals/km ² ). Besides evidence of silent circulation of RVFV and the risk of disease emergence in some areas, wildlife may play a role in the maintenance of RVFV in Zambia.
... The results indicated that Cx. pipiens was the most dominant mosquito species in all sampled water bodies thus creating a big pool of potential vectors for filariasis and viruses like RVF, West Nile virus (WNV), St. Louis encephalitis and eastern equine encephalomyelitis (Ammar et al.,2012, Tran et al.,2013, Elhawary et al.,2020. ...
In tropical and sub-tropical areas of the world the most damaging pest of the livestock sector are cattle tick, Rhipicephalus microplus. The current study was aimed to generate phytochemical derived acaricides to control Rhipicephalus microplus populations, to maintain livestock herd production, minimize economic losses and to reduce uses of man-made chemicals acaricides. To achieve this goal, Adult immersion and larval package test were used to determine the feasibility of Berberium lyceum and Tamarixa aphylla against Rhipicephalus microplus ticks. Further, an In silico technique was employed to discover biologically active substances from both plants using docking method. Berberium lyceum and Tamarixa aphylla exhibited a reasonably high fatal effect at 40.0 mg/L on egg laying (index of egg laying = 0.19 and 0.19) respectively, thus inhibiting the oviposition (49.5 and 45.1, respectively) and the larval mortality (97% and 93%, respectively). Further, we also used Chem-Draw ultra-software (v. 12.0.2.1076. 2010) to illustrate different structures of38 known bioactive phytochemicals which are discovered in the PubChem database and verify the hypothesis that tick inhibition was linked to acetylcholinesterase (AChE). Barbamunine and rutin from Berberium lyceum showed remarkable interaction with RmAChE1 active site residues with docking scores of -9.11 to -8.71 while phytol and dehydrodigallic acid from Tamarix aphylla showed comparable docking scores of -7.17 and -7.14 respectively against Rhipicephalus microplus acetylcholinesterase protein. Based on obtained result, we believe that Berberium lyceum and Tamarixa aphylla bioactive components could be potential candidates in the control and management of Rhipicephalus microplus and should be studied further as a supplement or replacement for synthetic acaricides.
... The evidences in this study confirm the applicability of GIS as an ecological modeling tool employed for monitoring and evaluation of vector population. This presentation further bear similarities with the reports of Kalluri et al., (2007) in their surveillance of arthropod vector-borne infectious diseases using remote sensing techniques; Tran et al., (2013) in presenting geographical information system-based multi criteria evaluation to map areas at risk for Rift Valley vector-borne transmission in Italy and El-Zeiny and Sowilem (2016b),who revealed the area under risk of mosquito transmitted diseases, using remote sensing and field surveys. ...
The role of remote sensing and geographic information system (GIS) techniques is fast gaining prominence in the monitoring of vectors and infectious disease spread. Mosquitoes are important vectors of several diseases of humans across the world. In order to better understand some ecological aspects linking vegetation dynamics and vector population, we examined the spatial and temporal distribution of flora and malaria vector
within university of Uyo town campus using GIS based techniques. The results showed that the flora and vector population varied significantly (P<0.05) between the studied locations per time within the campus. During the first week, the least mean (5.25) abundance of the vector was recorded at point 1 while the highest (28.5) was recorded at point 3. During the second week, the least mean (11.25) abundance of the vector was recorded at point 1 while the highest (29.25) was recorded at point 3. For the third week, the least mean (28.0) abundance of the vector was recorded at point 4 while the highest (58.25) was still recorded at point 3. During the fourth week, the least mean (14.25) abundance of the vector was recorded at point 4 while the highest (43.0) was recorded at point 3. On the
other hand, the vegetation comprised of 16 plants species (mostly herbs and grasses) from 11 families. Eleusine indica was the most frequently (75%) encountered species. Conclusively, patterns of variation in mosquito population were sensitive to vegetation dynamics in studied sites within the campus. These observations have application in ecology and public health.
... The evidences in this study confirm the applicability of GIS as an ecological modeling tool employed for monitoring and evaluation of vector population. This presentation further bear similarities with the reports of Kalluri et al., (2007) in their surveillance of arthropod vector-borne infectious diseases using remote sensing techniques; Tran et al., (2013) in presenting geographical information system-based multi criteria evaluation to map areas at risk for Rift Valley vector-borne transmission in Italy and El-Zeiny and Sowilem (2016b),who revealed the area under risk of mosquito transmitted diseases, using remote sensing and field surveys. ...
The role of remote sensing and geographic information system (GIS) techniques is fast gaining prominence in the monitoring of vectors and infectious disease spread. Mosquitoes are important vectors of several diseases of humans across the world. In order to better understand some ecological aspects linking vegetation dynamics and vector population, we examined the spatial and temporal distribution of flora and malaria vector within university of Uyo town campus using GIS based techniques. The results showed that the flora and vector population varied significantly (P<0.05) between the studied locations per time within the campus. During the first week, the least mean (5.25) abundance of the vector was recorded at point 1 while the highest (28.5) was recorded at point 3. During the second week, the least mean (11.25) abundance of the vector was recorded at point 1 while the highest (29.25) was recorded at point 3. For the third week, the least mean (28.0) abundance of the vector was recorded at point 4 while the highest (58.25) was still recorded at point 3. During the fourth week, the least mean (14.25) abundance of the vector was recorded at point 4 while the highest (43.0) was recorded at point 3. On the other hand, the vegetation comprised of 16 plants species (mostly herbs and grasses) from 11 families. Eleusine indica was the most frequently (75%) encountered species. Conclusively, patterns of variation in mosquito population were sensitive to vegetation dynamics in studied sites within the campus. These observations have application in ecology and public health. [Oboho, DE., Egwali, EC., Akpan, AU., Abai, AB., Mbong, EO., George, U. U. GIS-based Modeling of Mosquitoes Population Dynamics in relation to Vegetation Distribution within University of Uyo Town Campus, Uyo, Akwa Ibom State, Nigeria. J. Am Sci 2021;17(6):66-76].
... The biochemical results in Table ( (Ammar et al.,2012, Tran et al.,2013, Elhawary et al.,2020. ...
Mosquito larvae and their predators were surveyed from different breeding sites in El-Fayoum Governorate. The physiochemical characters of water and environmental factors that effect on mosquito larvae were studied. Biochemical and toxicological effects of the two photosensitizing compounds; eosin yellow lactone and phloxine B (xanthene dye) were evaluated against the third instar larvae of the most dominant mosquito species and their predators. The surveyed results revealed the occurrence of six mosquito species in the study area: one aedine, Aedes caspius, two anopheline, Anopheles pharoensis, An. sergenti, and three culicines, Culex pipien, Cx. antennatus, and Culiseta longiareolata. The most dominant species was Cx. pipiens with a total number of 3571 larvae followed by Ae. caspius and An. phareonsis with a total number of 670, 452 collected larvae, respectively. The two commonly collected predators were Pantala flavescens (Odonata) and Caenis macrura (Ephemeroptera) naiads. The results explained that both eosin yellow and phloxine B can be used as larvicide. However, eosin was more efficient than phloxine against Cx. pipiens with LC50 equal to (0.025 and 0.053 ppm) and An. pharoensis (0.023 and 0.016 ppm, respectively. On the other hand, the phloxine was more effective than eosin against Ae. caspius (0.016 and 0.024 ppm, respectively. Also, the results investigated that phloxine was more efficient than eosin against Cx. pipiens in dark and there was a significant difference between their toxicity in sunlight and in the absence of direct light. In addition, phloxine was less toxic against P. flavescens than eosin with LC50 of 1.822 and 1.044 ppm, respectively) and the mayfly (C. macrura) was more sensitive to the both photosensitizers with LC50 equal to 0.003 and 0.006 ppm for eosin and phloxine, respectively. The biochemical studies indicated the increasing in the levels of glutathione S-transferase after treatment with eosin and phloxine and there is a significant decrease in peroxidase levels after treatment with both eosin and phloxine.
... Se considera que la mayoría de las enfermedades infecciosas están limitadas espacialmente por la presencia del transmisor, cuya abundancia y supervivencia son influenciadas por las condiciones ambientales y la presencia de fuentes de alimentación (17) . Una herramienta que facilita el estudio de la distribución de vectores y estas variables es mediante el uso de los Sistemas de Información Geográfica (SIG) (18,19,20) . ...
Desmodus rotundus es transmisor de enfermedades zoonóticas y emergentes a los humanos y al ganado, como el caso de la rabia. La mayoría de las enfermedades infecciosas están limitadas espacialmente por la presencia del transmisor, cuya abundancia y supervivencia son influenciadas por las condiciones ambientales y la presencia de fuentes de alimentación. Una herramienta que facilita su estudio es el uso de los Sistemas de Información Geográfica. El objetivo de este estudio fue analizar la interacción de las poblaciones de murciélagos hematófagos y humanos, a través de la elaboración de un modelo probable de dispersión del D. rotundus basado en refugios conocidos y diferentes variables medioambientales, además de analizar la relación entre refugios identificados durante tres años y su cercanía con asentamientos humanos, como un proceso de coexistencia. El estudio se llevó a cabo en el estado de San Luis Potosí del año 2014 al 2016. Se identificaron un total de 180 refugios de D. rotundus distribuidos hacia la zona de la Huasteca, el 80 % de éstos fueron construidos por el hombre y el 57 % se encontraron habitados. Se calculó un buffer de 5 km a la redonda a partir de la ubicación de cada refugio, encontrando en su interior un total de 976 comunidades rurales y 15 ciudades, con 337,836 habitantes. La distancia media de los refugios hasta el primer asentamiento humano fue de 518.65 ± 11.33 m. Es necesario continuar estudiando la asociación entre la urbanización y el surgimiento de zoonosis, a través del entendimiento de las interacciones entre animales silvestres-ganadería - humanos.
... In the study area, it is observed that Cx. pipiens was present with high density and collected from stagnant polluted drains associated with human activities. This is compatible with [39,40]. Most polluted breeding sites urge the spread of more culicines while these sites don't favor anopheline proliferation [41]. ...
El-Fayoum governorate has unique characteristics which induces mosquito proliferation and thus increased the risk arisen from diseases transmission. Present study explores the role of remote sensing and GIS modeling integrated with field survey for mapping mosquito breeding sites and the areas under risk of diseases transmission in El-Fayoum governorate. Entomological surveys were conducted for a total number of 40 accessible breeding sites during the period 12-16 November 2017. A calibrated Landsat OLI image, synchronized with the field trip, was processed to produce Normalized Difference Vegetation Index (NDVI), Normalized Difference Moisture Index (NDMI), and Land Surface Temperature (LST). A cartographic GIS model was generated to predict breeding sites in the whole governorate and to assess the potential risk. The main filarial disease vector ( Culex pipiens ) was abundant at Atsa district, while Malaria vectors ( Anopheles sergentii and Anopheles multicolor ) were mainly distributed in El-Fayoum and Youssef El-Seddiq districts. Means levels of NDVI, NDMI and LST at breeding habitats were recorded; 0.18, 0.08 and 21.75° C, respectively. Results of the model showed that the highest predicted risk area was reported at Atsa district (94.4 km ² ) and Yousef El-Sediq (81.8 km ² ) while the lowest prediction was observed at Abshawai district (35.9 km ² ). It can be concluded that Atsa, Yousef El-Sedik and El-Fayoum districts are more vulnerable to Malaria and Filaria diseases outbreaks, thus precaution and pest control methods must be applied to mitigate the possible risks.
... It was observed that the most preferred habitat types of Cx. pipiens was unused irrigation water basin followed by polluted drainage canals. This is compatible with Amr et al. (1997), Al-Khalili et al. (1999), Knio et al. (2005), Ammar et al. (2012) and Tran et al. (2013). A significant difference was recorded in Cx. pipiens presence in the different aquatic habitats. ...
Suez Canal Zone has an old history of diseases transmitted by mosquito such as Malaria, Lymphatic filariasis, West Nile virus and Rift Valley Fever virus. Water quality of mosquito breeding habitat represents an essential determinant of whether female mosquitoes will deposit their eggs and whether the resulting stages will complete their developmental process or not. Therefore, the objective of this study is to assess physical, chemical and spectral properties of mosquito breeding habitats in the Suez Canal Zone using hyperspectral data and spectral analyses. Fifty-two different sites were sampled, during February and April 2016, for mosquito larvae and were characterized based on water temperature, pH, Oxidation-Reduction Potential (ORP), Electrical Conductivity (EC), Turbidity, Chlorophyll, Dissolved oxygen (HDO), Crude Oil (CO), Salinity, and Organic Matter (OM). Data were statistically assessed by one-way ANOVA. Hyperion image and ASD Field Spectroradiometer were processed to generate an innovative spectral library for the investigated mosquito breeding habitats. Mosquito larvae were identified as Culex (3 spp.), Anopheles (1 sp.), Ochlerotatus (2 spp.) and Culiseta (1 sp.) at seven different habitats. Analyses showed that the spectral reflectance patterns were specific for each mosquito breeding habitat corresponding to the variability of water quality. Most of habitats reported high levels of total dissolved and suspended solids such as Turbidity, EC, and OM (i.e. >535.93 NTU, >16,642.05 µS/cm, and >38.31 mg/l, respectively). It can be concluded that hyperspectral data analyses help to give more feasible assessment of mosquito breeding habitats which should widely be utilized.
... The biology of some of the species also favours the transportation. For example, eggs of some strains of Ae. albopictus are able to survive prolonged periods without water showing a true biological diapause (Tran et al., 2013). This feature makes this species an excellent candidate for being transported by different commodities such as used tyres, as well as 'lucky bamboo' (Dracaena sanderiana; Dracaenaceae) and Bromeliaceae plants (Schaffner, 2003;Scholte et al., 2008;Scholte et al., 2012). ...
Rift Valley fever (RVF) is a vector‐borne disease transmitted by a broad spectrum of mosquito species, especially Aedes and Culex genus, to animals (domestic and wild ruminants and camels) and humans. Rift Valley fever is endemic in sub‐Saharan Africa and in the Arabian Peninsula, with periodic epidemics characterised by 5–15 years of inter‐epizootic periods. In the last two decades, RVF was notified in new African regions (e.g. Sahel), RVF epidemics occurred more frequently and low‐level enzootic virus circulation has been demonstrated in livestock in various areas. Recent outbreaks in a French overseas department and some seropositive cases detected in Turkey, Tunisia and Libya raised the attention of the EU for a possible incursion into neighbouring countries. The movement of live animals is the most important pathway for RVF spread from the African endemic areas to North Africa and the Middle East. The movement of infected animals and infected vectors when shipped by flights, containers or road transport is considered as other plausible pathways of introduction into Europe. The overall risk of introduction of RVF into EU through the movement of infected animals is very low in all the EU regions and in all MSs (less than one epidemic every 500 years), given the strict EU animal import policy. The same level of risk of introduction in all the EU regions was estimated also considering the movement of infected vectors, with the highest level for Belgium, Greece, Malta, the Netherlands (one epidemic every 228–700 years), mainly linked to the number of connections by air and sea transports with African RVF infected countries. Although the EU territory does not seem to be directly exposed to an imminent risk of RVFV introduction, the risk of further spread into countries neighbouring the EU and the risks of possible introduction of infected vectors, suggest that EU authorities need to strengthen their surveillance and response capacities, as well as the collaboration with North African and Middle Eastern countries.
... Serological evidence of RVFV circulation in Turkey is concerning and serves as a warning for possible incursion into Europe 7 . However, serological surveys in Europe suggest absence of the virus 8,9 and modelling indicates that the risk of introduction and large scale spread is low 10 ...
Rift Valley fever (RVF) is a mosquito-borne viral disease, principally of ruminants, that is endemic to Africa. The causative Phlebovirus, Rift Valley fever virus (RVFV), has a broad host range and, as such, also infects humans to cause primarily a self-limiting febrile illness. A small number of human cases will also develop severe complications, including haemorrhagic fever, encephalitis and visual impairment. In parts of Africa, it is a major disease of domestic ruminants, causing epidemics of abortion and mortality. It infects and can be transmitted by a broad range of mosquitos, with those of the genus Aedes and Culex thought to be the major vectors. Therefore, the virus has the potential to become established beyond Africa, including in Australia, where competent vector hosts are endemic. Vaccines for humans have not yet been developed to the commercial stage. This review examines the threat of this virus, with particular reference to Australia, and assesses gaps in our knowledge that may benefit from research focus.
... Although MCDA techniques have found wide application in several areas over the last few decades such as land suitability analysis and risk evaluation, their use is still limited and relatively recent in public health fields (Hongoh et al. 2011). In public health and epidemiological research, studies have used MCDA to study a compilation of decision problems including assessing vulnerabilities to infectious diseases (Vinhaes et al. 2014;Tran et al. 2013;de Oliveira et al. 2015) and prioritization of health intervention to infectious diseases (Aenishaenslin et al. 2013). Currently, one of the emerging application areas under public health relates to climate change and health. ...
Globally, climate change is impacting the incidence and distribution of climate-sensitive infectious diseases (CSIDs). The effects of climate change on infectious diseases are an important public health concern and necessitate effective prioritizing of resources for optimal responses, especially for the developing economies context where basic health services and capacities are challenged. To develop a coherent response to the potential incidence of climate-related outbreaks, and to longer-term altering disease patterns, there is the need for improved information upon which to base the mainstreaming of climate change into health planning. An essential way through which such information can be generated is prioritizing disease risks vis-à-vis public health threats under climate change. Using Ghana as a case study, a multicriteria evaluation approach was used to assess CSIDs that present the greatest risks and threats to public health under climate change based on a set of disease prioritization criteria. Expert opinion, morbidity data on CSIDs, and data from literature were utilized to undertake the disease prioritization. From the assessment, it emerged that epidemic-prone CSIDs (diarrhea, cholera, and meningitis) pose the greatest risks to public health. This prioritization provides a glimpse of the risks and threats that prevailing CSIDs would pose to public health under climate change. Further, it provides a preliminary model that can guide public health decisions in Ghana and other similar contexts in the developing world.
... Such models have also been employed to predict the likely range of infectious diseases, such as Ebola in Africa [25]. Environmental modelling has been used in Europe to predict the impact of climate change [8,26], as well as areas at higher risk of RVFV transmission at a country level including Italy and Spain [27,28]. This approach can be used to inform surveillance and outbreak management. ...
Vector borne diseases are a continuing global threat to both human and animal health. The ability of vectors such as mosquitos to cover large distances and cross country borders undetected provide an ever-present threat of pathogen spread. Many diseases can infect multiple vector species, such that even if the climate is not hospitable for an invasive species, indigenous species may be susceptible and capable of transmission such that one incursion event could lead to disease establishment in these species. Here we present a consensus modelling methodology to estimate the habitat suitability for presence of mosquito species in the UK deemed competent for Rift Valley fever virus (RVF) and demonstrate its application in an assessment of the relative risk of establishment of RVF virus in the UK livestock population. The consensus model utilises observed UK mosquito surveillance data, along with climatic and geographic prediction variables, to inform six independent species distribution models; the results of which are combined to produce a single prediction map. As a livestock host is needed to transmit RVF, we then combine the consensus model output with existing maps of sheep and cattle density to predict the areas of the UK where disease is most likely to establish in local mosquito populations. The model results suggest areas of high suitability for RVF competent mosquito species across the length and breadth of the UK. Notable areas of high suitability were the South West of England and coastal areas of Wales, the latter of which was subsequently predicted to be at higher risk for establishment of RVF due to higher livestock densities. This study demonstrates the applicability of outputs of species distribution models to help predict hot-spots for risk of disease establishment. While there is still uncertainty associated with the outputs we believe that the predictions are an improvement on just using the raw presence points from a database alone. The outputs can also be used as part of a multidisciplinary approach to inform risk based disease surveillance activities.
... In conclusion, the knowledge-driven approach proposed in this work to map the areas suitable for PPR occurrence and spread in Eastern Africa and Union of the Comoros provide valuable tools for several purposes: (i) to integrate the available knowledge about the disease; (ii) to provide suitability maps at regional scale using free geographic data. Applied in different geographical and epidemiological contexts (33,34,36,59,60), such an approach allows straightforward and easy updating of maps for users by including more precise geographic data, newly described risk factors, by modifying the weights of each factor, or by comparing scenarios of transmission. Another perspective of this work deals with the combination of the produced PPR suitability maps with modeling approaches accounting for temporal variability and transmission processes (28), in order to provide recommendations for vaccination strategies. ...
Peste des petits ruminants virus (PPRV), responsible for peste des petits ruminants (PPR), is widely circulating in Africa and Asia. The disease is a huge burden for the economy and development of the affected countries. In Eastern Africa, the disease is considered endemic. Because of the geographic proximity and existing trade between eastern African countries and the Comoros archipelago, the latter is at risk of introduction and spread, and the first PPR outbreaks occurred in the Union of the Comoros in 2012. The objective of this study was to map the areas suitable for PPR occurrence and spread in the Union of the Comoros and four eastern African countries, namely Ethiopia, Uganda, Kenya, and Tanzania. A Geographic Information System (GIS)-based Multicriteria Evaluation (MCE) was developed. Risk factors for PPR occurrence and spread, and their relative importance, were identified using literature review and expert-based knowledge. Corresponding geographic data were collected, standardized, and combined based on a weighted linear combination to obtain PPR suitability maps. The accuracy of the maps was assessed using outbreak data from the EMPRES database and a ROC curve analysis. Our model showed an excellent ability to distinguish between absence and presence of outbreaks in Eastern Africa (AUC = 0.907; 95% CI [0.820–0.994]), and a very good performance in the Union of the Comoros (AUC = 0.889, 95% CI: [0.694–1]). These results highlight the efficiency of the GIS-MCE method, which can be applied at different geographic scales: continental, national and local. The resulting maps provide decision support tools for implementation of disease surveillance and control measures, thus contributing to the PPR eradication goal of OIE and FAO by 2030.
... Distribution models of RVFV vectors around the Mediterranean Basin have been developed [9], and risk maps for identifying suitable areas for Rift Valley fever emergence are also available for the Maghreb region [126], Egypt [127], Spain [128], and Italy [129]. Potential hotspots have been identified in northern Africa, from Morocco to Libya [126], and include farming areas and desert oases, especially those located close to water bodies and animal facilities. ...
Background The Mediterranean Basin is historically a hotspot for trade, transport, and migration. As a result, countries surrounding the Mediterranean Sea share common public health threats. Among them are vector-borne diseases, and in particular, mosquito-borne viral diseases are prime candidates as (re)emerging diseases and are likely to spread across the area. Improving preparedness and response capacities to these threats at the regional level is therefore a major issue. The implementation of entomological surveillance is, in particular, of utmost importance. Guidance in designing entomological surveillance systems is critical, and these systems may pursue different specific objectives depending on the disease. The purpose of the proposed review is to draw up guidelines for designing effective and sustainable entomological surveillance systems in order to improve preparedness and response. However, we make it clear that there is no universal surveillance system, so the thinking behind harmonisation is to define evidence-based standards in order to promote best practises, identify the most appropriate surveillance activities, and optimise the use of resources. Such guidance is aimed at policymakers and diverse stakeholders and is intended to be used as a framework for the implementation of entomological surveillance programmes. It will also be useful to collaborate and share information with health professionals involved in other areas of disease surveillance. Medical entomologists and vector control professionals will be able to refer to this report to advocate for tailored entomological surveillance strategies. The main threats targeted in this review are the vectors of dengue virus, chikungunya virus, Zika virus, West Nile virus, and Rift Valley fever virus. The vectors of all these arboviruses are mosquitoes. Methods Current knowledge on vector surveillance in the Mediterranean area is reviewed. The analysis was carried out by a collaboration of the medical entomology experts in the region, all of whom belong to the MediLabSecure network, which is currently funded by the European Union and represents an international effort encompassing 19 countries in the Mediterranean and Black Sea region. Findings Robust surveillance systems are required to address the globalisation of emerging arboviruses. The prevention and management of mosquito-borne viral diseases must be addressed in the prism of a One Health strategy that includes entomological surveillance as an integral part of the policy. Entomological surveillance systems should be designed according to the entomological and epidemiological context and must have well-defined objectives in order to effect a tailored and graduated response. We therefore rely on different scenarios according to different entomological and epidemiological contexts and set out detailed objectives of surveillance. The development of multidisciplinary networks involving both academics and public authorities will provide resources to address these health challenges by promoting good practises in surveillance (identification of surveillance aims, design of surveillance systems, data collection, dissemination of surveillance results, evaluation of surveillance activities) and through the sharing of effective knowledge and information. These networks will also contribute to capacity building and stronger collaborations between sectors at both the local and regional levels. Finally, concrete guidance is offered on the vector of the main arbovirus based on the current situation in the area.
... Distribution models of RVFV vectors around the Mediterranean Basin have been developed [9], and risk maps for identifying suitable areas for Rift Valley fever emergence are also available for the Maghreb region [126], Egypt [127], Spain [128], and Italy [129]. Potential hotspots have been identified in northern Africa, from Morocco to Libya [126], and include farming areas and desert oases, especially those located close to water bodies and animal facilities. ...
Background
The Mediterranean Basin is historically a hotspot for trade, transport, and migration. As a result, countries surrounding the Mediterranean Sea share common public health threats. Among them are vector-borne diseases, and in particular, mosquito-borne viral diseases are prime candidates as (re)emerging diseases and are likely to spread across the area. Improving preparedness and response capacities to these threats at the regional level is therefore a major issue.
The implementation of entomological surveillance is, in particular, of utmost importance. Guidance in designing entomological surveillance systems is critical, and these systems may pursue different specific objectives depending on the disease.
The purpose of the proposed review is to draw up guidelines for designing effective and sustainable entomological surveillance systems in order to improve preparedness and response. However, we make it clear that there is no universal surveillance system, so the thinking behind harmonisation is to define evidence-based standards in order to promote best practises, identify the most appropriate surveillance activities, and optimise the use of resources.
Such guidance is aimed at policymakers and diverse stakeholders and is intended to be used as a framework for the implementation of entomological surveillance programmes. It will also be useful to collaborate and share information with health professionals involved in other areas of disease surveillance. Medical entomologists and vector control professionals will be able to refer to this report to advocate for tailored entomological surveillance strategies.
The main threats targeted in this review are the vectors of dengue virus, chikungunya virus, Zika virus, West Nile virus, and Rift Valley fever virus. The vectors of all these arboviruses are mosquitoes.
Methods
Current knowledge on vector surveillance in the Mediterranean area is reviewed. The analysis was carried out by a collaboration of the medical entomology experts in the region, all of whom belong to the MediLabSecure network, which is currently funded by the European Union and represents an international effort encompassing 19 countries in the Mediterranean and Black Sea region.
Findings
Robust surveillance systems are required to address the globalisation of emerging arboviruses. The prevention and management of mosquito-borne viral diseases must be addressed in the prism of a One Health strategy that includes entomological surveillance as an integral part of the policy. Entomological surveillance systems should be designed according to the entomological and epidemiological context and must have well-defined objectives in order to effect a tailored and graduated response. We therefore rely on different scenarios according to different entomological and epidemiological contexts and set out detailed objectives of surveillance. The development of multidisciplinary networks involving both academics and public authorities will provide resources to address these health challenges by promoting good practises in surveillance (identification of surveillance aims, design of surveillance systems, data collection, dissemination of surveillance results, evaluation of surveillance activities) and through the sharing of effective knowledge and information. These networks will also contribute to capacity building and stronger collaborations between sectors at both the local and regional levels. Finally, concrete guidance is offered on the vector of the main arbovirus based on the current situation in the area.
... El análisis multicriterio integrado a las herramientas de Sistemas de Información Geográfica (SIG) supone una importante herramienta para la toma de decisión, teniendo en cuenta la dimensión espacial 10 que, desde los años 90 se utiliza para la generación de mapas de riesgo 11 . Aunque en el área de salud esta metodología no había sido implementada hasta hace pocos años 12 , actualmente se utiliza junto con las herramientas SIG en la evaluación del riesgo de enfermedades transmitidas por vectores [13][14][15] . Este estudio tiene como objetivo identificar las zonas de riesgo para la proliferación del flebótomo en El Salvador. ...
Objetivo. Identificar las zonas de riesgo para la proliferación del flebótomo en El Salvador. Metodología. Estudio descriptivo para identificación del riesgo de proliferación de flebótomos en El Salvador, a partir del análisis multicriterio de factores ambientales y sociales. Se evaluó la importancia de los factores ambientales y sociales relacionados con la proliferación del flebótomo a través de un panel de expertos y análisis multicriterio, con el cual, se otorgó un peso para definir las zonas de riesgo. Resultados. El mapa de uso de suelo y altitud, muestran un riesgo alto en la mayor parte del país, sin embargo, la altitud, muestra las zonas montañosas con un riesgo medio. La densidad canina muestra un riesgo alto en la mayor parte del país, principalmente en la zona occidente y centro. Los mapas finales con la combinación de factores ambientales y sociales, muestran una concentración del nivel de riesgo medio en la mayor parte del país. Conclusiones. Se identificó un riesgo medio de proliferación del flebótomo en la mayor parte de El Salvador. Los factores ambientales y sociales que representan mayor riesgo fueron, el uso de suelo, altitud y la densidad canina. A pesar de que en algunas zonas del país el riesgo es bajo, existen las condiciones para la proliferación del flebótomo. Alerta Año 2018, Vol. 1 No. 2: 25-36 Palabras claves: Flebótomo, leishmaniasis, análisis multicriterio, factores de riesgo, El Salvador
... Nevertheless, in our case the bivariate output was sufficient, in order to identify potential sampling area. MCDA/MCE methods are used in a wide variety of research fields (Malczewski, 2006) including the health and epidemiology (Thompson and Etter, 2015) and also particularly vector-borne diseases (Tran et al., 2013;Rousseau et al., 2017;Vial et al., 2017) in last few years. ...
Research projects in the field of eco-epidemiology of tick-borne diseases often require extensive sampling of
arthropod vectors in the field. The aim of our study was to use geographical information systems (GIS) to select
appropriate sampling sites of Ixodes ricinus ticks in central European habitat for further ecological studies of
vector-borne pathogens (tick-borne encephalitis virus and Borrelia burgdorferi sensu lato). The model area was
the Czech-German borderland (the region of South Bohemia and two regions in Germany: the Upper Palatinate
and Lower Bavaria) where numerous human tick-borne encephalitis cases are reported annually. We prepared
the sampling site design as a multi-criteria evaluation (MCE) task. In the GIS environment, we conducted MCE
with a set of environmental, socio-economic and epidemiological data (altitude, vegetation cover, number of
tick-borne encephalitis cases recorded in the past, tourist activity). The MCE classified the surveyed area into two
classes: suitable for tick collection and unsuitable for tick collection. Subsequently, 50 tick sampling sites were
randomly selected in the suitable area: 30 in South Bohemia (Czech Republic) and 20 in the Upper Palatinate and
Lower Bavaria regions (Bavaria, Germany). The sampling sites were identified and surveyed in the field. The
presence of ticks was confirmed by flagging at each of the selected plots. The described MCE system represents a
versatile tool for semi-randomized design of tick sampling sites for research projects in the field of tick-borne
pathogen ecology as well as for tick-borne pathogen surveillance programs run by local health authorities.
... The application of geostatistical techniques to identify spatial heterogeneities in disease distributions, patterns and trends as well as forecasting for epidemic preparedness planning had been demonstrated in studies by 21 and 22 inter alia. The theory behind incorporation of RS data in disease mapping was based on the established association between environmental conditions and some of the disease causing vectors (Tran et al., 2013;Hassan et al., 1998;Dlamini et al., 2015). For instance, some studies have demonstrated the association between radiation reflectance as measured by satellites and certain land cover types which have been used as environmental proxies for measurement of presence of a disease and its vectors (Garni et al., 2014). ...
High resolution remotely sensed (RS) data products remain of interest in disease mapping studies. However, previous usage of such satellite-derived products had been limited by high costs. There is also unprecedented space activity characterized by prolific satellite launches for various purposes, the chief of which being land cover observation. Therefore, there is need for information availability on the type of data products obtainable from the captured satellite images in order to facilitate access and utilization. Clearly, the remote sensing landscape is changing with the advent of Unmanned Aerial Vehicle/drones and spatially explicit images being captured at relatively low costs. We conducted a review to find out which RS data products were accessible for disease mapping and epidemiology. Our aim was to document RS data products for disease mapping and to propose other such products that could be incorporated in disease mapping and epidemiology studies. In view of the fact that RS data products are rapidly evolving, image data of higher spatial and temporal resolutions in near-real time are already available to aid disease mapping. We presented a catalogue of indices from ecological studies that could be used as variables in disease mapping and epidemiology. Remotely sensed data products related to climate, meteorology, land use/cover, cartography and urban mapping are explored as potential indices for disease mapping. There remains a substantial amount of work to be conducted on the evaluation and validation of some of the indices presented in this study. Conversely, synergies between remote sensing experts and epidemiologists could be useful in the uptake and testing of some of the proposed RS data products presented in this work.
... Cx. pipiens has a preference for living near areas of high human population density, and breeding in the artificial containers abundant in close proximity to human settlements [9,10] or polluted pools of water associated with human activities [11,12,13,14] . The species also feeds opportunistically from a wide variety of blood hosts [8,15] , and is active nearly year round [13] . ...
Background: Lymphatic filariasis (LF) is focally endemic in Egypt where the female mosquito, Culex pipiens, is responsible for its transmission. The WHO developed a plan for elimination that is based on selective diagnosis to identify endemic areas followed by repeated, annual cycles of mass drug administration (MDA) of antifilarial medications.
... The most recent outbreak was in the Republic of Niger in October 2016 with a case-fatality rate of 31% 19 . It is predicted that it is just a matter of time until RVFV will spread to other parts of the world since Aedes and Culex mosquitoes, the most common vectors for RVFV, are present globally [20][21][22] . Previously we have presented the antiviral activity of benzavir-2 against HAdV, HSV-1 and HSV-2 infection in vitro 13,15 , all of them are DNA viruses that replicate in the nucleus. ...
Rift Valley fever virus (RVFV) is a mosquito-borne hemorrhagic fever virus affecting both humans and animals with severe morbidity and mortality and is classified as a potential bioterror agent due to the possible aerosol transmission. At present there is no human vaccine or antiviral therapy available. Thus, there is a great need to develop new antivirals for treatment of RVFV infections. Benzavir-2 was previously identified as potent inhibitor of human adenovirus, herpes simplex virus type 1, and type 2. Here we assess the anti-RVFV activity of benzavir-2 together with four structural analogs and determine pre-clinical pharmacokinetic parameters of benzavir-2. In vitro, benzavir-2 efficiently inhibited RVFV infection, viral RNA production and production of progeny viruses. In vitro, benzavir-2 displayed satisfactory solubility, good permeability and metabolic stability. In mice, benzavir-2 displayed oral bioavailability with adequate maximum serum concentration. Oral administration of benzavir-2 formulated in peanut butter pellets gave high systemic exposure without any observed toxicity in mice. To summarize, our data demonstrated potent anti-RVFV activity of benzavir-2 in vitro together with a promising pre-clinical pharmacokinetic profile. This data support further exploration of the antiviral activity of benzavir-2 in in vivo efficacy models that may lead to further drug development for human use.
... Bahgat et al. [13] and Abdel-Hamid et al. [15]. It was present with high density and collected from stagnant polluted drains associated with human activities; this is compatible with Amr et al. [26], Al-Khalili et al. [27], Knio et al. [28], Ammar et al. [29] and Tran et al. [30]. Also, Oringanje et al. [31] stated that most polluted breeding sites urge the spread of more culicines while these sites don't favor for anopheline proliferation. ...
Mosquito-borne diseases have a great impact on human and animal health throughout the world, including Egypt. A survey was conducted at Suez Canal Zone for 8 months, prolonged from November 2014 till April 2016 to identify the mosquito larvae and to investigate the different breeding habitats preferences of mosquito's larvae. Larvae were collected using a standard dipping with a small ladle. A total of 14806 mosquito larvae were collected from 7 different breeding habitats and found belonging to 5 genera and 10 species; Culex pipiens L. Culex perexiguus Theobald, Culex (Barraudius) pusillus Macquart, Anopheles (Cellia) multicolor Cambouliu, Anopheles (Anopheles) tenebrosus Dönitiz, Anopheles (Cellia) pharonsis Theobald, Culiseta longiareolata (Macquart), Ochlerotatus detritus Haliday, Ochlerotatus caspius (Pallas) and Uranotaenia unguiculata Edwards. Out of these, 5 species are considered as high potential vector of diseases in Egypt. Results indicated that Cx. pipiens is the most common vector prevalent in all months representing 66.90% (n=9905 larvae) of total collection, followed by Cx. perexiguus 10.06% (n=1490 larvae). Different habitats of Suez Canal area are environmentally suitable for mosquito breeding and therefore the probability of emergence/re-emergence of the mosquito-transmitted diseases becomes enhanced. So, the present study provides the baseline information for decision makers to take necessary optimal control strategies to mitigate mosquito nuisance, proliferation rate and the areas under risk of potential diseases transmission.
... Previous suitability maps of Ae. albopictus have often been built based on SDMs including climate variables as predictors, mainly temperatures (e.g., the mean temperature of the coldest month, the mean temperature of the warmest quarter), but also precipitations (e.g., annual precipitation, precipitation in spring or summer) [12,15]. By contrast, LULC has been only marginally considered as a predictor of Ae. albopictus distribution, even though Ae. albopictus population is strongly associated with urbanized areas [4,10,[16][17][18][19][20][21][22][23]. ...
Given the growing risk of arbovirus outbreaks in Europe, there is a clear need to better describe the distribution of invasive mosquito species such as Aedes albopictus. Current challenges consist in simulating Ae. albopictus abundance, rather than its presence, and mapping its simulated abundance at a local scale to better assess the transmission risk of mosquito-borne pathogens and optimize mosquito control strategy. During 2014–2015, we sampled adult mosquitoes using 72 BG-Sentinel traps per year in the provinces of Belluno and Trento, Italy. We found that the sum of Ae. albopictus females collected during eight trap nights from June to September was positively related to the mean temperature of the warmest quarter and the percentage of artificial areas in a 250 m buffer around the sampling locations. Maps of Ae. albopictus abundance simulated from the most parsimonious model in the study area showed the largest populations in highly artificial areas with the highest summer temperatures, but with a high uncertainty due to the variability of the trapping collections. Vector abundance maps at a local scale should be promoted to support stakeholders and policy-makers in optimizing vector surveillance and control.
... Critical stages for pathogen emergence are introduction, establishment and spread [21]. Potential routes of entry of RVFV into Europe and the USA have been identified [22][23][24] and the risk of establishment into North Africa [25], Italy [26], the Netherlands [27] and Spain [28] reviewed. The conclusions collectively identify a need to determine competence in local vectors to accurately evaluate risks, and guide control and surveillance activities [23,24]. ...
Rift Valley fever virus (RVFV) is a mosquito-borne arbovirus causing severe disease in humans and ruminants. Spread of RVFV out of Africa has raised concerns that it could emerge in Europe or the USA. Virus persistence is dependent on successful infection of, replication in, and transmission to susceptible vertebrate and invertebrate hosts, modulated by virus-host and vector-virus interactions. The principal accepted theory for the long-term maintenance of RVFV involves vertical transmission (VT) of virus to mosquito progeny, with the virus surviving long inter-epizootic periods within the egg. This VT hypothesis, however, is yet to be comprehensively proven. Here, evidence for and against the VT of RVFV is reviewed along with the identification of factors limiting its detection in natural and experimental data. The observations of VT for other arboviruses in the genera Alphavirus, Flavivirus and Orthobunyavirus are discussed within the context of RVFV. The review concludes that VT of RVFV is likely but that current data are insufficient to irrefutably prove this hypothesis.
... The results of surveys showed that Culex pipiens was the most common species in the study area, representing 65.22% (8220 larvae) of the total collection. This species is widespread in most localities; it favors living close to residential areas with high density and breeding in the artificial containers abundant in close proximity to human settlements (Kalluri et al., 2007;Tran, et al., 2013) or polluted pools of water associated with human activities (Amr et al., 1997;Al-Khalili, 1999;Knio, 2005;Ammar et al., 2012). The second most common species was Ochlerotatus detritus representing 13.86% (1747 larvae). ...
Present study aims to identify environmental characteristics associated with mosquito proliferation sites at Suez Canal zone, Egypt using remote sensing, field surveys and laboratory analyses of mosquito larvae and breeding water. Six field surveys, during the period Nov.2014-Apri.2016, were conducted since 130 different localities were visited to characterize mosquito habitats and identify mosquito larval species. Also, 26 representative breeding sites were sampled on Feb. 2016 since 9 different water characteristics were analyzed according to the standard method. Likewise, 6 Landsat images (Nov. 2014, Jan., Apr., Oct. 2015, Feb. and Apr. 2016), at same time of the field surveys, were processed to produce LULC, TC, NDVI, NDMI and LST to characterize mosquito breeding sites. LULC and TC maps showed the suitability of different habitats for mosquito breeding. The produced LULC classes are; desert (54 %), agriculture (19 %), fish farms (9 %), water (7 %), sabkha (6 %), urban (4 %) and bare land (1 %). Results of surveys showed that the main vector of Filariasis (Culex pipiens) was the most common species in the study area; 65.22% (8220 larvae of the total collection). It favors living close to residential areas with high density and breeding in the artificial containers or contaminated pools of water associated with human activities. Highest density of mosquito larvae was reported during Apr. 2016 and characterized by NDVI-0.07 to 0.56, NDMI-0.05 to 0.34 and LST 24.2 to 38.4º C which represents the most optimum conditions for mosquito proliferation in Suez Canal zone. Water characteristics of mosquito breeding sites showed that mosquito can proliferate in a wide range of water properties; clean, contaminated, fresh, saline, neutral and alkaline water which magnifies the risk of mosquito vector-diseases. It could be concluded that remotely sensed data integrated with field surveys provide excellent description for spatial and environmental characteristics of mosquito breeding habitats.
... The most common two species detected were Culex pipiens and Ochlerotatus detritus recording 362 larvae (52%) and 244 larvae (35%), respectively (Table 2, Fig. 5). It was found that Culex pipiens prefers sites of high human population densities and breed in artificial containers close to human settlements (Kalluri et al., 2007;Tran et al., 2013) or contaminated ponds (Amr et al., 1997;Al-Khalili et al., 1999;Knio et al., 2005;Ammar et al., 2012). This indicates to the presence of the main filariasis vector in most of the breeding habitats surveyed (Harb et al., 1993). ...
Egypt is currently witnessing a number of mega projects, along the axis of Suez Canal, which consequently have a great effect on environment and its biological components including mosquito vectors of diseases. This study is an attempt to explore the use and efficiency of integrated remote sensing-GIS techniques and field surveys for detection of mosquito breeding habitats at Suez Canal Zone. Remote sensing and field surveys provided the necessary verified ground truth information to the present study. A corrected Landsat8 image, acquired in Jan. 2015, was utilized to produce NDVI, NDMI and LST to identify environmental variables associated with mosquitoes breeding habitats. Concurrently, a GIS model was developed to predict probable mosquito habitats and areas under environmental risk of diseases transmission. Results revealed that Culex pipiens and Ochlerotatus detritus are the most abundant species in Suez Canal Zone recording total number of 362 larvae (51.86%) and 244 larvae (34.96%), respectively. The model predicted that Ismailia is the most subjected Suez Canal Governorate to mosquito borne diseases. It recorded the maximum levels of high risk, risk and vulnerable areas to mosquito proliferation; 6.06 km² (64.26%), 954.65 km² (54.58%) and 152.87 km² (80.09%), respectively. The developed prediction model achieved an accuracy of 80.95% and increased to 100% at sites where predicted larval habitats were ascertained by in-situ checks.
... MCDA has been used in studies seeking to assess the suitability of areas for the occurrence of Rift Valley fever 9,10 and African swine fever 9 in Africa and HPAI H5N1 in Asia 8 . MCDA methods have also been applied in disease-free areas to map the suitability for the emergence of Rift Valley fever in Europe 10,11 . Contrary to statistical models which require reliable disease data for the output variable, spatial MCDA approaches are based on decision rules derived from existing knowledge and applied to a set of predictor factors to identify areas potentially suitable for disease 12 . ...
The Highly Pathogenic Avian Influenza H5N1 (HPAI) virus is now considered endemic in several Asian countries. In Cambodia, the virus has been circulating in the poultry population since 2004, with a dramatic effect on farmers' livelihoods and public health. In Thailand, surveillance and control are still important to prevent any new H5N1 incursion. Risk mapping can contribute effectively to disease surveillance and control systems, but is a very challenging task in the absence of reliable disease data. In this work, we used spatial multicriteria decision analysis (MCDA) to produce risk maps for HPAI H5N1 in poultry. We aimed to i) evaluate the performance of the MCDA approach to predict areas suitable for H5N1 based on a dataset from Thailand, comparing the predictive capacities of two sources of a priori knowledge (literature and experts), and ii) apply the best method to produce a risk map for H5N1 in poultry in Cambodia. Our results showed that the expert-based model had a very high predictive capacity in Thailand (AUC = 0.97). Applied in Cambodia, MCDA mapping made it possible to identify hotspots suitable for HPAI H5N1 in the Tonlé Sap watershed, around the cities of Battambang and Kampong Cham, and along the Vietnamese border.
Rift Valley fever (RVF) is a zoonotic vector-borne disease mainly transmitted by mosquitoes, and present in Africa, the Arabian Peninsula, and the Indian Ocean. The endemic situation in Mauritania, and the recent outbreaks in Libya have raised concerns about the potential spread of the virus in the Mediterranean Basin, where competent mosquitoes are present. Because vector abundance is one of the drivers of RVF virus (RVFV) transmission, knowledge on species distributions and population dynamics is needed to implement entomological surveillance and to assess the risk of viral circulation. Here, we adapted a modeling framework of mosquito population dynamics to five species considered as possible RVFV vectors in the western Mediterranean Basin ( Aedes caspius, Aedes detritus, Aedes vexans, Culex pipiens and Culex theileri ). The mechanistic model used a daily time step and a 0.1° x 0.1° spatial resolution and was based on meteorological data along with published vector distribution maps. We gathered mosquito trapping data from Spain, France, Italy and Morocco to calibrate the model and to evaluate its predictions. The temporal correlation between predicted abundance and observational data was satisfactory. Goodness-of-fit was better for Aedes species, thus offering the means to target the area of interest for the surveillance of Ae. caspius , a highly competent mosquito species.
The sudden increase of infectious disease occurrences in a specified location and time is called a disease outbreak. The impact could affect, in the least case, the daily life of the population in the collapse of the country’s economic and demographic structure. Geospatial technologies have been an important tool in analyzing and making informed decisions to manage public health since the seventeenth century. In recent years, the GIS system’s functional capabilities have been tremendously developed that help the decision-makers in identifying the geographical factors, temporal spread, and velocity of the disease, model the data using mathematical algorithms for predictive analysis, and visualize them in real time through the use of connected devices. Waterborne diseases are transmitted by consuming contaminated water (WHO). In the year 2012, WHO estimated that low- and middle-income countries have recorded 842,000 deaths per year, including 361,000 in children under the age of five. In India, The Ministry of Health and Family Welfare has launched the Integrated Disease Surveillance Program (IDSP) to report all the disease outbreaks across the country since 2011. The study used IDSP disease outbreak weekly reports from 2011 to 2020 and the Census of India—2011 data for the analysis. The IDSP report covers most of the waterborne disease outbreaks across the country at a village and district level with how they are managed and reported with their local causes. The voluminous data (2011–2020) is compiled and attributed in the GIS database. The spatial statistics of the data reveal the hot and cold spots spatially across the country, which are associated with the rainfall pattern of India and other local phenomena. Getis–Ord Gi* statistic is used seasonal and annual data of the outbreaks; the Z-and P-values highlight the high and low clusters, which represents the context of neighboring attributes the study visualizes the outbreak hot spots along the east coast soon after the monsoon month gets over similar pattern is also found in the west coast of India. The spatial pattern and temporal sequencing of waterborne diseases with the use of geospatial technologies and geostatistical applications would help the governments to control and alleviate the severity and occurrence of the diseases.KeywordsGeostatisticsGetis–Ord GiWaterborne diseasesOutbreakClusters
Abstract
The Rift Valley fever virus (RVFV) is an emerging high-priority pathogen endemic in Africa with pandemic potential. There is no specific treatment or approved antiviral drugs for the RVFV. We previously developed a cell-based high-throughput assay to screen small molecules targeting the RVFV and identified a potential effective antiviral compound (1-N-(2-(biphenyl-4-yloxy)ethyl)propane-1,3-diamine) as a lead compound. Here, we investigated how structural modifications of the lead compound affected the biological properties and the antiviral effect against the RVFV. We found that the length of the 2-(3-aminopropylamino)ethyl chain of the compound was important for the compound to retain its antiviral activity. The antiviral activity was similar when the 2-(3-aminopropylamino)ethyl chain was replaced with a butyl piperazine chain. However, we could improve the cytotoxicity profile of the lead compound by changing the phenyl piperazine linker from the para-position (compound 9a) to the meta-position (compound 13a). Results from time-of-addition studies suggested that compound 13a might be active during virus post-entry and/or the replication phase of the virus life cycle and seemed to affect the K+ channel. The modifications improved the properties of our lead compound, and our data suggest that 13a is a promising candidate to evaluate further as a therapeutic agent for RVFV infection.
Diptera عائلة من Culicidae التعرف ويمكن يقارب الذي الصغير حجمه خالل من البعود على 3-9 ملم، أرجل و األجنحة، من احد و وزوج ً طويال ا ً خرطوم البعود أنثى فم اء أجز وتشكل ورفيعة، طويلة ، لالمتصا اإلناث عن الذكور تختلف أكثر من البعود يعتبر الجلد. لثقب مناسبة غير فم اء أجز و استشعار قرون وجود في ً ا خطر انات الحيو في العالم، تنتقل التي اد األمر بسبب وذلك ا، ً سنوي شخص مليون من يقرب ما وفاة في يسبب حيث بينها من يا، المالر ال وغيرها. اء الصفر الحمى و النيل غرب فيروس عالج الحالي الوقت في يوجد محدد ً ا تصنيف يجعل مما منها، الوقاية و البعود يق طر عن المنقولة اد األمر على ة للسيطر ولقاح اسة الدر هذه هدفت اد. األمر هذه مكافحة في ً مهما وتحديدها البعود اع أنو إلى اع أنو وتحديد تصنيف بمنطقة المنازل داخل من المجمع البعود اتة، صبر ليبيا. غرب شمال الب البعود عينات جمع تم الغ نوفمبر من الممتدة اسة الدر مدة خالل الشفط يق طر عن 2017 اير فبر إلى 2018 ، العينات عدد المدة هذه خالل المجمعة 254 عينة ، بنسبة ذكر احدة و بعوضه المجمعة العينات شملت حيث (0.4)% 253 بنسبة أنثي (99.6)% ، جنسين في المدروسة العينات ـت وتمثل genera البعود ـن م ـا: هم ـنس ج Culex ـسبة بن (99.6 ـنس وج)% Culiseta بنسبة (0.4)% ، ـاس ـ أجن ـت تح اثنان و subgenera ـي: ـ ه Culex %(ـسبة ـ بن 99.6 و) Allotheobaldia بنسبة (0.4)% ، تصنيف وتم هما: نوعين إلى ين المذكور الجنسين وتمييز Culex pipiens بنسبة (99.6 و)% Culiseta longiareolata بنسبة (0.4 نوع وكان .)% Culex pipiens المنطقة في المنازل داخل السائد هو اسة. الدر
Influenza has been a growing concern for the public health decision makers/policy makers. Indeed, they are in need of a real geo-making tool for monitoring and surveillance. The chapter aims to introduce a novel spatiotemporal decision system based on multicriteria ranking method, information geographic system (GIS), and SEIRSW system for public health. The later was designed, implemented, and validated in previous research for influenza risk assessment. The authors highlight the use of PROMETHEE II ranking method of multi-criteria decision analysis in GIS that incorporates various factors to monitor and identify potential high-risk areas of seasonal influenza and disease mapping. Factors related to the risk of seasonal influenza are obtained from simulation system and constitute the input values of PROMETHEE II ranking method for the 26 communes of the city of Oran, Algeria. The proposed system has demonstrated analytical capabilities in targeting high-risk spots and influenza surveillance monitoring system and it can help public health policy makers prioritize in their response goals and evaluate control strategies.
Influenza has been a growing concern for the public health decision makers/policy makers. Indeed, they are in need of a real geo-making tool for monitoring and surveillance. The chapter aims to introduce a novel spatiotemporal decision system based on multicriteria ranking method, information geographic system (GIS), and SEIRSW system for public health. The later was designed, implemented, and validated in previous research for influenza risk assessment. The authors highlight the use of PROMETHEE II ranking method of multi-criteria decision analysis in GIS that incorporates various factors to monitor and identify potential high-risk areas of seasonal influenza and disease mapping. Factors related to the risk of seasonal influenza are obtained from simulation system and constitute the input values of PROMETHEE II ranking method for the 26 communes of the city of Oran, Algeria. The proposed system has demonstrated analytical capabilities in targeting high-risk spots and influenza surveillance monitoring system and it can help public health policy makers prioritize in their response goals and evaluate control strategies.
Rift Valley fever (RVF) is a mosquito‐borne zoonotic disease. Since its first outbreak in in 1930, RVF epidemics have caused huge economic losses and public health impacts in Africa. In 2000, RVF became a disease of global concern as it spread to the Arabian Peninsula. In our study, a Geographic Information System‐based risk assessment for the occurrence of Rift Valley fever in China was established by means of ecological niche modelling. Based on occurrence records (RVF records from FAO EMPRES‐i, vector records from literatures and GBIF) and high‐resolution environmental layers, the prediction maps of RVF occurrence probability and distribution of five potential RVF vectors in China were modelled using Maxent. An internal validation was adopted for model verification, and high AUC values were obtained (0.918 for RVF and 0.837~0.992 for vectors). By overlaying the RVF prediction map with the combined RVF vector prediction map using Fuzzy overlay tool (“AND” operator) of ArcMap 10.2, we got the first risk map of possible RVF vector transmission. This map was further overlaid with the latest livestock distribution map (“AND” operator) to generate the second risk map of possible RVF threat to domestic livestock. The southwest border provinces in China, Yunnan, Guangxi and Tibet, were predicted to have a high possibility of RVF occurrence. Conditions conducive to the local amplification of RVF also exist in these areas. Temperature seasonality, mean temperature of dry season and precipitation of the driest month were considered as key environmental variables for RVF and common environmental conditions were found conductive for vectors. It is suggested to establish proper surveillance systems in southwest border areas to minimize the possibility of RVF invasion. Our findings can serve as a valuable reference for prevention measures to be implemented.
La cysticercose, parasitose tropicale négligée due à Taenia solium et dont le cycle concerne l’Homme et le porc, est responsable de 50 000 décès chaque année, principalement dans les pays du Sud. Notre travail de thèse a tenté d’explorer la situation épidémiologique de cette maladie dans la population porcine de Madagascar et de comprendre les déterminants expliquant sa prévalence dans le contexte épidémiologique et économique du pays. Dans un premier temps, nos enquêtes de prévalence en abattoir ont permis d’estimer une prévalence apparente de 4.6% [4.2-5.0%] au niveau national et une prévalence corrigée de 21.03% [19.18-22.87%] en tenant en compte de la sensibilité de la méthode (inspection vétérinaire par observation macroscopique). Dans un second temps nous avons modélisé le lien environnement-animal-homme dans le contexte des Hautes-Terres de Madagascar où l’élevage porcin est semi-intensifié mais où la cysticercose porcine reste endémique. Notre modèle multi-agents, développé sous Cormas, nous a permis de modéliser les comportements simplifiés des acteurs humains et animaux ainsi que les processus sanitaires et environnementaux. Une analyse de sensibilité multivariée nous a aidé à mieux comprendre les réactions du modèle vis-à-vis des paramètres d’entrée employés. Il s’est révélé sensible principalement à des paramètres décrivant (i) l’exposition des animaux à des aliments contaminés par des œufs de T. solium, notamment par la distribution d’aliments non contrôlés par l’éleveur et l’accès à un environnement contaminé, et (ii) la capacité infectante des œufs de T. solium, leur excrétion et leur survie dans l’environnement. Cette démarche exploratoire nous a permis ainsi d’identifier les paramètres d’importance mettant en lumière les besoins de recherche à mener pour renforcer la vraisemblance des résultats du modèle et nous aider à tester l’impact des scénarios de lutte contre la cysticercose dans des bassins de production porcine représentatifs de la réalité du pays.
Background
Zoonotic diseases account for a substantial portion of infectious disease outbreaks and burden on public health programs to maintain surveillance and preventative measures. Taking advantage of new modeling approaches and data sources have become necessary in an interconnected global community. To facilitate data collection, analysis, and decision-making, the number of spatial decision support systems reported in the last 10 years has increased. This systematic review aims to describe characteristics of spatial decision support systems developed to assist public health officials in the management of zoonotic disease outbreaks.
Methods
A systematic search of the Google Scholar database was undertaken for published articles written between 2008 and 2018, with no language restriction. A manual search of titles and abstracts using Boolean logic and keyword search terms was undertaken using predefined inclusion and exclusion criteria. Data extraction included items such as spatial database management, visualizations, and report generation.
Results
For this review we screened 34 full text articles. Design and reporting quality were assessed, resulting in a final set of 12 articles which were evaluated on proposed interventions and identifying characteristics were described. Multisource data integration, and user centered design were inconsistently applied, though indicated diverse utilization of modeling techniques.
Conclusions
The characteristics, data sources, development and modeling techniques implemented in the design of recent SDSS that target zoonotic disease outbreak were described. There are still many challenges to address during the design process to effectively utilize the value of emerging data sources and modeling methods. In the future, development should adhere to comparable standards for functionality and system development such as user input for system requirements, and flexible interfaces to visualize data that exist on different scales.
PROSPERO registration number: CRD42018110466.
Electronic supplementary material
The online version of this article (10.1186/s12942-018-0157-5) contains supplementary material, which is available to authorized users.
During the last decade, West Nile virus (WNV) outbreaks have increased sharply in both horses and human in Europe. The aims of this study were to evaluate characteristics and spatio-temporal distribution of WNV outbreaks in horses in Spain between 2010 and 2016 in order to identify the environmental variables most associated with WNV occurrence and to generate high-resolution WNV suitability maps to inform risk-based surveillance strategies in this country. Between August 2010 and November 2016, a total of 403 WNV suspected cases were investigated, of which, 177 (43.9%) were laboratory confirmed. Mean values of morbidity, mortality and case fatality rates were 7.5%, 1.6% and 21.2%, respectively. The most common clinical symptoms were as follows: tiredness/apathy, recumbency, muscular tremor, ataxia, incoordination and hyperaesthesia. The outbreaks confirmed during the last 7 years, with detection of WNV RNA lineage 1 in 2010, 2012, 2013, 2015 and 2016, suggest an endemic circulation of the virus in Spain. The spatio-temporal distribution of WNV outbreaks in Spain was not homogeneous, as most of them (92.7%) were concentrated in western part of Andalusia (southern Spain) and significant clusters were detected in this region in two non-consecutive years. These findings were supported by the results of the space–time scan statistics permutation model. A presence-only MaxEnt ecological niche model was used to generate a suitability map for WNV occurrence in Andalusia. The most important predictors selected by the Ecological Niche Modeling were as follows: mean annual temperature (49.5% contribution), presence of Culex pipiens (19.5% contribution), mean annual precipitation (16.1% contribution) and distance to Ramsar wetlands (14.9% contribution). Our results constitute an important step for understanding WNV emergence and spread in Spain and will provide valuable information for the development of more cost-effective surveillance and control programmes and improve the protection of horse and human populations in WNV-endemic areas.
Background: A cross sectional study to establish the levels of heavy metals and other potentially harmful elements (PHEs)present in samples obtained from selected open waste water channels in Nairobi industrial area (Kenya) was carried out. The waste water channels selected were those near the factories or those directly discharging from factories. The samples collected included mosquitoes (larvae and adults), waste water, green algae, and soil. Unmaintained open waste water channels are among the man-made features that enhance the breeding of urban mosquitoes because they tend to have overgrown vegetation and trapped solid wastes which slow or inhibit the waste water flow. Different mosquito species have previously transmitted arboviruses including those responsible for dangerous fevers such as West Nile, Rift Valley, Zika, Dengue, Yellow, and Chikungunya among others in different parts of the world. The study area (Nairobi industrial area) neighbours several densely populated informal human settlements. This paper specifically reports on composition and distribution of mosquito species obtained from the study area.
Methods: The fourth instars mosquito larvae were collected from waste water channels using the standard dipping method. Adult mosquitoes were trapped using the center for disease control and prevention (CDC) light traps. Purposive random sampling for mosquito adults and larvae was carried out in industrial premises and waste water channels respectively at seven locations. This involved selecting sampling sites from which mosquito samples were likely to be obtained. The mosquitoes were then microscopically identified using taxonomic keys for the Ethiopian and East African region.
Results: Out of 2,926 adult mosquitoes trapped, 12 species were identified including Cx. pipiens (95%); Cx. vansomereni (2.6%); Cx. zombaensis (1.4%); Cx. univittatus (0.34%); Cx. theileri (0.21%); Ae. aegpti (0.14%); An. maculipalpis (0.03%); An. squamosus (0.03%) and other culicid species (0.20%). Of these adult mosquitoes, 94% (2753/2926) were females and 6% (173/2926) were males giving a male: female ratio of 1: 16 when using CDC traps. Of the 4,679 mosquito larvae scooped from the waste water channels, 4 species were identified including Cx. pipiens (99.34%); Cx. vansomereni (0.51%); Toxorhynchites brevipalpis (0.13%) and Aedes mosquito (0.02%).
Conclusion: The majority of mosquito species obtained were culicid, Culex pipiens for both adults and larvae. A few Anopheles and Aedes populations were obtained. Unmaintained open waste water channels seen\med to enhance the breeding of urban mosquitoes in the study area. The ecology of these mosquitoes should be studied further to enhance surveillance and control in order to minimize the risk of mosquito borne viral infections or any other re-emerging mosquito-borne infections to the residents of Nairobi, in particular those living in the informal settlements near Nairobi industrial area, Kenya.
Keywords: urban, mosquitoes, Culex pipiens, waste water, industrial area, Nairobi
Suez Canal area is characterized by a unique nature therefore various species of mosquitoes are spread in the area. Present paper aims at mapping and classifying the area under environmental risk of mosquito proliferation and diseases transmission at Suez Canal Zone using Landsat OLI data and GIS. To fulfil this objective, 6 field trips in the period from Nov.2014 to Apr.2016, were conducted to collect mosquito larvae and characterize breeding sites. Six calibrated Landsat-8 images were processed to characterize mosquitoes breeding sites and therefore map the area under environmental risk of mosquito proliferation. Considering the degree of mosquito proliferation, the study area was categorized into four levels of risk; high risk, risk, vulnerable and non-infected. Results of surveys showed that the main vector of Filarasis (Culex pipiens) was the most abundant species in Suez Canal Zone. The produced risk map showed that the total high risk area occupies 59.16 km 2 (1 %), risk area 2026.37 km 2 (27 %), vulnerable 497.5 km 2 (7 %) and non-infected 4940.43 km 2 (65%) throughout Suez Canal Zone. Majority of the study area is located in the non-infected area which is concentrated in eastern and western deserts which are not inhabited. The high percent of the infected area is concentrated in several parts of Ismailia Governorate. The produced risk map is necessary requirement for decision makers to initiate mosquito control strategies and management programs. To assess the produced map, more than 120 different localities were visited. It could be concluded that Landsat-8 data and GIS techniques have proved high efficiency in mapping and classifying the area under risk of mosquito spread out particularly in inaccessible regions.
Suez Canal area is characterized by a unique nature therefore various species of mosquitoes are spread in the area. Present paper aims at mapping and classifying the area under environmental risk of mosquito proliferation and diseases transmission at Suez Canal Zone using Landsat OLI data and GIS. To fulfil this objective, 6 field trips in the period from Nov.2014 to Apr.2016, were conducted to collect mosquito larvae and characterize breeding sites. Six calibrated Landsat-8 images were processed to characterize mosquitoes breeding sites and therefore map the area under environmental risk of mosquito proliferation. Considering the degree of mosquito proliferation, the study area was categorized into four levels of risk; high risk, risk, vulnerable and non-infected. Results of surveys showed that the main vector of Filarasis (Culex pipiens) was the most abundant species in Suez Canal Zone. The produced risk map showed that the total high risk area occupies 59.16 km 2 (1 %), risk area 2026.37 km 2 (27 %), vulnerable 497.5 km 2 (7 %) and non-infected 4940.43 km 2 (65%) throughout Suez Canal Zone. Majority of the study area is located in the non-infected area which is concentrated in eastern and western deserts which are not inhabited. The high percent of the infected area is concentrated in several parts of Ismailia Governorate. The produced risk map is necessary requirement for decision makers to initiate mosquito control strategies and management programs. To assess the produced map, more than 120 different localities were visited. It could be concluded that Landsat-8 data and GIS techniques have proved high efficiency in mapping and classifying the area under risk of mosquito spread out particularly in inaccessible regions.
Epizootic haemorrhagic disease (EHD) is an infectious non-contagious viral disease transmitted by Culicoides, which affects wild and domestic ruminants. The disease has never been reported in Europe, however recently outbreaks of EHD occurred in the Mediterranean Basin. Consequently, the risk that Epizootic haemorrhagic disease virus (EHDV) might spread in Italy cannot be ignored. The aim of this study was to evaluate the risk of EHDV transmission in Italy, in case of introduction, through indigenous potential vectors. In Italy, the most spread and abundant Culicoides species associated to livestock are Culicoides imicola and the members of the Obsoletus complex. Culicoides imicola is a competent vector of EHDV, whereas the vector status of the Obsoletus complex has not been assessed yet. Thus, its oral susceptibility to EHDV was here preliminary evaluated. To evaluate the risk of EHDV transmission a geographical information system-based Multi-Criteria Evaluation approach was adopted. Distribution of vector species and host density were used as predictors of potential suitable areas for EHDV transmission, in case of introduction in Italy. This study demonstrates that the whole peninsula is suitable for the disease, given the distribution and abundance of hosts and the competence of possible indigenous vectors.
Rift Valley fever (RVF) virus is an arbovirus in the _Bunyaviridae_ family that, from phylogenetic analysis, appears to have first emerged in the mid-19th century and was only identified at the beginning of the 1930s in the Rift Valley region of Kenya. Despite being an arbovirus with a relatively simple but temporally and geographically stable genome, this zoonotic virus has already demonstrated a real capacity for emerging in new territories, as exemplified by the outbreaks in Egypt (1977), Western Africa (1988) and the Arabian Peninsula (2000), or for re-emerging after long periods of silence as observed very recently in Kenya and South Africa. The presence of competent vectors in countries previously free of RVF, the high viral titres in viraemic animals and the global changes in climate, travel and trade all contribute to make this virus a threat that must not be neglected as the consequences of RVF are dramatic, both for human and animal health. In this review, we present the latest advances in RVF virus research. In spite of this renewed interest, aspects of the epidemiology of RVF virus are still not fully understood and safe, effective vaccines are still not freely available for protecting humans and livestock against the dramatic consequences of this virus.
The aim of the work was to (1) produce a map that shows the precise current distribution of Aedes albopictus in Europe; and (2) map the risk for establishment of Aedes albopictus in Europe, in the event of its introduction.
From this, it can be concluded that the temperate strains of Aedes albopictus are here to stay — and that they will spread. In addition, new populations may become established in other parts of Europe. Surveillance of the introduction and spread of this vector, in particular in areas at risk, is important in order to be prepared for the mosquito’s role in the transmission of diseases.
In order to prepare the maps presented in this technical report, a huge amount of work was carried out by collecting data from many entomologists all over Europe, resulting in a database containing an enormous amount of valuable information. Regular revision of this database would provide the possibility to easily update the Aedes albopictus distribution maps, providing relevant information for public health specialists.
The distribution maps show the areas for which no mosquito surveillance data are available, while the risk maps show which areas are suitable for the mosquito’s establishment in case it is introduced. This information should support entomologists and public health experts in their efforts to ensure preparedness for mosquito-borne diseases. Additionally needed information includes the surveillance of the introduction, possible establishment and spread of other potential disease vectors, such as Aedes aegypti.
There are still many unknowns with regard to European Aedes albopictus strains for different pathogens, and further research into this topic is required. More research is also needed on the development of adapted control measures to eradicate newly established mosquito colonies and to prevent the further spread of the mosquito.
Finally, in order to improve our understanding of mosquito introduction pathways and the evolution and adaptation of mosquito populations, further research is needed on the genetic homogeneity or heterogeneity of European mosquito populations.
West Nile fever (WNF) and Rift Valley fever (RVF) are emerging diseases causing epidemics outside their natural range of distribution. West Nile virus (WNV) circulates widely and harmlessly in the old world among birds as amplifying hosts, and horses and humans as accidental dead-end hosts. Rift Valley fever virus (RVFV) re-emerges periodically in Africa causing massive outbreaks. In the Maghreb, eco-climatic and entomologic conditions are favourable for WNV and RVFV emergence. Both viruses are transmitted by mosquitoes belonging to the Culex pipiens complex. We evaluated the ability of different populations of Cx. pipiens from North Africa to transmit WNV and the avirulent RVFV Clone 13 strain. Mosquitoes collected in Algeria, Morocco, and Tunisia during the summer 2010 were experimentally infected with WNV and RVFV Clone 13 strain at titers of 10(7.8) and 10(8.5) plaque forming units/mL, respectively. Disseminated infection and transmission rates were estimated 14-21 days following the exposure to the infectious blood-meal. We show that 14 days after exposure to WNV, all mosquito st developed a high disseminated infection and were able to excrete infectious saliva. However, only 69.2% of mosquito strains developed a disseminated infection with RVFV Clone 13 strain, and among them, 77.8% were able to deliver virus through saliva. Thus, Cx. pipiens from the Maghreb are efficient experimental vectors to transmit WNV and to a lesser extent, RVFV Clone 13 strain. The epidemiologic importance of our findings should be considered in the light of other parameters related to mosquito ecology and biology.
There has been growing interest in Europe in recent years in the establishment and spread of invasive mosquitoes, notably the incursion of Aedes albopictus through the international trade in used tires and lucky bamboo, with onward spread within Europe through ground transport. More recently, five other non-European aedine mosquito species have been found in Europe, and in some cases populations have established locally and are spreading. Concerns have been raised about the involvement of these mosquito species in transmission cycles of pathogens of public health importance, and these concerns were borne out following the outbreak of chikungunya fever in Italy in 2007, and subsequent autochthonous cases of dengue fever in France and Croatia in 2010. This article reviews current understanding of all exotic (five introduced invasive and one intercepted) aedine species in Europe, highlighting the known import pathways, biotic and abiotic constraints for establishment, control strategies, and public health significance, and encourages Europe-wide surveillance for invasive mosquitoes.
The complex epidemiology of vector-borne diseases creates significant challenges in the design and delivery of prevention and control strategies, especially in light of rapid social and environmental changes. Spatial models for predicting disease risk based on environmental factors such as climate and landscape have been developed for a number of important vector-borne diseases. The resulting risk maps have proven value for highlighting areas for targeting public health programs. However, these methods generally only offer technical information on the spatial distribution of disease risk itself, which may be incomplete for making decisions in a complex situation. In prioritizing surveillance and intervention strategies, decision-makers often also need to consider spatially explicit information on other important dimensions, such as the regional specificity of public acceptance, population vulnerability, resource availability, intervention effectiveness, and land use. There is a need for a unified strategy for supporting public health decision making that integrates available data for assessing spatially explicit disease risk, with other criteria, to implement effective prevention and control strategies. Multi-criteria decision analysis (MCDA) is a decision support tool that allows for the consideration of diverse quantitative and qualitative criteria using both data-driven and qualitative indicators for evaluating alternative strategies with transparency and stakeholder participation. Here we propose a MCDA-based approach to the development of geospatial models and spatially explicit decision support tools for the management of vector-borne diseases. We describe the conceptual framework that MCDA offers as well as technical considerations, approaches to implementation and expected outcomes. We conclude that MCDA is a powerful tool that offers tremendous potential for use in public health decision-making in general and vector-borne disease management in particular.
TO THE EDITOR: Different arboviral diseases have expanded their geographic range in recent times. Of them, Rift Valley fever, West Nile fever, and African horse sickness are of particular concern. They are endemic in sub-Saharan Africa but occasionally spread beyond this area. Trade and transport of animals and animal products, along with wildlife movements, are considered the driving factors in the spread of these pathogens.
Vector-borne diseases are among those most sensitive to climate because the ecology of vectors and the development rate of pathogens within them are highly dependent on environmental conditions. Bluetongue (BT), a recently emerged arboviral disease of ruminants in Europe, is often cited as an illustration of climate's impact on disease emergence, although no study has yet tested this association. Here, we develop a framework to quantitatively evaluate the effects of climate on BT's emergence in Europe by integrating high-resolution climate observations and model simulations within a mechanistic model of BT transmission risk. We demonstrate that a climate-driven model explains, in both space and time, many aspects of BT's recent emergence and spread, including the 2006 BT outbreak in northwest Europe which occurred in the year of highest projected risk since at least 1960. Furthermore, the model provides mechanistic insight into BT's emergence, suggesting that the drivers of emergence across Europe differ between the South and the North. Driven by simulated future climate from an ensemble of 11 regional climate models, the model projects increase in the future risk of BT emergence across most of Europe with uncertainty in rate but not in trend. The framework described here is adaptable and applicable to other diseases, where the link between climate and disease transmission risk can be quantified, permitting the evaluation of scale and uncertainty in climate change's impact on the future of such diseases.
The present work evaluates the use of species distribution model (SDM) algorithms to classify high densities of small container-breeding Aedes mosquitoes (Diptera: Culicidae) on a fine scale in the Bermuda Islands. Weekly ovitrap data collected by the Department of Health, Bermuda for the years 2006 and 2007 were used for the models. The models evaluated included the algorithms Bioclim, Domain, GARP (genetic algorithm for rule-set prediction), logistic regression and MaxEnt (maximum entropy). Models were evaluated according to performance and robustness. The area under the receiver operating characteristic curve was used to evaluate each model's performance, and robustness was assessed according to the spatial correlation between classification risks for the two datasets. Relative to the other algorithms, logistic regression was the best and MaxEnt the second best model for classifying high-risk areas. We describe the importance of covariables for these two models and discuss the utility of SDMs in vector control efforts and the potential for the development of scripts that automate the task of creating risk assessment maps.
Rift Valley fever(RVF) virus is an arbovirus in the Bunyaviridae family that, from phylogenetic analysis, appears to have first emerged in the mid-19th century and was only identified at the beginning of the 1930's in the Rift Valley region of Kenya. Despite being an arbovirus with a relatively simple but temporally and geographically stable genome, this zoonotic virus has already demonstrated a real capacity for emerging in new territories, as exemplified by the outbreaks in Egypt (1977), Western Africa (1988) and the Arabian Peninsula (2000), or for re-emerging after long periods of silence as observed very recently in Kenya and South Africa. The presence of competent vectors in countries previously free of RVF, the high viral titres in viraemic animals and the global changes in climate, travel and trade all contribute to make this virus a threat that must not be neglected as the consequences of RVF are dramatic, both for human and animal health. In this review, we present the latest advances in RVF virus research. In spite of this renewed interest, aspects of the epidemiology of RVF virus are still not fully understood and safe, effective vaccines are still not freely available for protecting humans and livestock against the dramatic consequences of this virus.
To determine which arthropods should be targeted for control should Rift Valley fever virus (RVFV) be detected in North America, we evaluated Culex erraticus (Dyar and Knab), Culex erythrothorax Dyar, Culex nigripalpus Theobald, Culex pipiens L., Culex quinquefasciatus Say, Culex tarsalis Coquillett, Aedes dorsalis (Wiedemann), Aedes vexans (Meigen), Anopheles quadrimaculatus Say, and Culicoides sonorensis Wirth and Jones from the western, midwestern, and southern United States for their ability to transmit RVFV. Female mosquitoes were allowed to feed on adult hamsters inoculated with RVFV, after which engorged mosquitoes were incubated for 7-21 d at 260C, then allowed to refeed on susceptible hamsters, and tested to determine infection, dissemination, and transmission rates. Other specimens were inoculated intrathoracically, held for 7 d, and then allowed to feed on a susceptible hamster to check for a salivary gland barrier. When exposed to hamsters with viremias > or =10(8.8) plaque-forming units/ml blood, Cx. tarsalis transmitted RVFV efficiently (infection rate = 93%, dissemination rate = 56%, and estimated transmission rate = 52%). In contrast, when exposed to the same virus dose, none of the other species tested transmitted RVFV efficiently. Estimated transmission rates for Cx. erythrothorax, Cx. pipiens, Cx. erraticus, and Ae. dorsalis were 10, 8, 4, and 2%, respectively, and for the remaining species were < or = 1%. With the exception of Cx. tarsalis and Cx. pipiens, all species tested had moderate to major salivary gland barriers. None of the C. sonorensis became infected and none of the An. quadrimaculatus tested transmitted RVFV by bite, even after intrathoracic inoculation, indicating that these species would not be competent vectors of RVFV. Although Ae. vexans from Florida and Louisiana were relatively efficient vectors of RVFV, specimens of this species captured in Colorado or California were virtually incompetent, illustrating the need to evaluate local population for their ability to transmit a pathogen. In addition to laboratory vector competence, factors such as seasonal density, host feeding preference, longevity, and foraging behavior should be considered when determining the potential role that these species could play in RVFV transmission.
In the last 30 years several cases of West Nile (WN) virus infection were reported in horses and humans in Europe and in the Mediterranean Basin. Most of them were determined by strains of the Lineage 1 included in the European Mediterranean/Kenyan cluster. Strains of this cluster are characterised by a moderate pathogenicity for horses and humans and limited or no pathogenicity for birds. In recent years, however, WN cases determined by strains grouped in the Israeli/American cluster of Lineage 1 or in the lineage 2 have been reported in Hungary and Austria. The role of migrating birds in introducing new viruses to Europe has been often demonstrated. The migratory birds, which may be infected in their African wintering places, carry the virus northward to European sites during spring migrations. In the past, the virus introduction determined occasional cases of WN. In the recent years, new epidemiological scenarios are developing. In few occasions it has been evidenced the capability of WNV strains of overwintering by using local birds and mosquitoes. Species of Culex amongst mosquitoes and magpies (Pica pica), carrion crows (Corvus corone) and rock pigeons (Columba livia) amongst resident birds are the most probable species involved in this hypothetical WND endemic cycle.
The eastern focus of the current outbreak of bluetongue (BT) in the Mediterranean Basin commenced in late 1998, infecting Turkey and some of the eastern islands of Greece. In the summer of 1999 it moved to continental Greece and for the first time to Bulgaria. By the late summer of 2000, BT spread progressively through Greece and to the Balkan states. The BT virus (BTV) serotypes involved were BTV-4, BTV-9 and BTV-16. The west-central focus of the outbreak, involving BTV-2, appeared in Tunisia in December 1999 and the following summer also in Algeria. In August 2000, BTV-2 was reported for the first time in Italy (in Sardinia) and soon thereafter in France (Corsica) and in Spain (the Balearic Isles). In the autumn of 2000, a second serotype (BTV-9) emerged in southern peninsular Italy. Eventually this incursion of virus into the central Mediterranean region resulted in the largest epidemic of BT ever to affect Europe. Some features of this epidemic differ significantly from those observed previously, namely: a) its deep penetration northwards (reaching 44 degrees N both in Italy and in the Balkans) b) its persistence across four seasons in various zones of Italy and the Balkans, implying that BT could become endemic over a wide geographic area c) its successful invasion of areas separated from previously infected ones by fairly large distances (Sardinia, Sicily, Calabria, and the Balearic islands). The pattern of the spread of BT across Italy, before the introduction of vaccination, is described. The possible role of climate, soil and insect vectors on the incidence of the disease, and the overwintering of the virus, are discussed. Some hypotheses on the possible origins and modes of introduction of BTV into Italy are postulated.
West Nile virus (WNV) is neuropathogenic for birds, horses and humans and is maintained in natural cycles between birds and mosquitoes, particularly the Culex genus; horses and humans are considered to be incidental hosts. A surveillance plan was implemented in Italy in 1998, following a limited outbreak of WNV equine encephalomyelitis and a WNV outbreak in France very close to the Italian border. This plan to assess the risks of the virus being introduced again included entomological surveillance performed in 15 study areas considered 'at risk' of WNV introduction in the country. Entomological surveys conducted in Italy from 2003 to 2007 resulted in the capture of a total of 28,798 mosquitoes, of which there were 14,765 adults and 14,033 larvae belonging to 22 species. According to the literature, eight of the species identified have been found to be naturally infected with WNV or were successfully infected in the laboratory in some parts of Europe and in the United States, namely: Aedes albopictus (Skuse, 1897) (= Stegomiya albopicta), Aedes vexans (Meigen, 1830), Anopheles maculipennis Meigen, 1818, Coquillettidia richiardii (Ficalbi, 1889), Culex modestus Ficalbi, 1889, Culex pipiens Linnaeus, 1758, Culex theileri Theobald, 1903 and Ochlerotatus caspius (Pallas, 1771) (= Aedes caspius).
Rift Valley fever (RVF) is a severe mosquito-borne disease affecting humans and domestic ruminants, caused by a Phlebovirus (Bunyaviridae). It is widespread in Africa and has recently spread to Yemen and Saudi Arabia. RVF epidemics are more and more frequent in Africa and the Middle East, probably in relation with climatic changes (episodes of heavy rainfall in eastern and southern Africa), as well as intensified livestock trade. The probability of introduction and large-scale spread of RVF in Europe is very low, but localized RVF outbreaks may occur in humid areas with a large population of ruminants. Should this happen, human cases would probably occur in exposed individuals: farmers, veterinarians, slaughterhouse employees etc. Surveillance and diagnostic methods are available, but control tools are limited: vector control is difficult to implement, and vaccines are only available for ruminants, with either a limited efficacy (inactivated vaccines) or a residual pathogenic effect. The best strategy to protect Europe and the rest of the world against RVF is to develop more efficient surveillance and control tools and to implement coordinated regional monitoring and control programmes.
An outbreak of Plasmodium falciparum malaria occurred in Tinzaouatine in southern Algeria in 2007. The likely vector, Anopheles gambiae mosquitoes, had not been detected in Algeria. Genes for resistance to chloroquine were detected in the parasite. The outbreak shows the potential for an increase in malaria vectors in Algeria.
The rapid spread of West Nile viral activity across North America since its discovery in 1999 illustrates the potential for an exotic arbovirus to be introduced and widely established across North America. Rift Valley fever virus (RVFV) has been responsible for large outbreaks in Africa that have resulted in hundreds of thousands of human infections and major economic disruption due to loss of livestock and to trade restrictions. However, little is known about the potential for North American mosquitoes to transmit this virus should it be introduced into North America. Therefore, we evaluated selected mosquito species from the southeastern United States for their ability to serve as potential vectors for RVFV. Mosquitoes were fed on adult hamsters inoculated 1 day previously with RVFV. These mosquitoes were tested for infection and ability to transmit RVFV after incubation at 26 degrees C for 7-21 days. None of the species tested (Aedes taeniorhynchus, Ae. vexans, Culex erraticus, Cx. nigripalpus, Cx. quinquefasciatus, and Cx. salinarius) were efficient vectors after they fed on hamsters with viremias ranging from 10(4.1) to 10(6.9) plaque-forming units (PFU)/ml. However, Ae. taeniorhynchus, Ae. vexans, and Cx. erraticus all developed disseminated infections after they fed on hamsters with viremias between 10(8.5) and 10(10.2) PFU/ml, and both Ae. vexans and Cx. erraticus transmitted RVFV by bite. These studies illustrate the need to identify the ability of individual mosquito species to transmit RVFV so that appropriate decisions can be made concerning the application of control measures during an outbreak.
Rift Valley fever (RVF), which was enzootic in Sudan in 1976 and epidemic in Egypt in 1977-78, may have been introduced into Egypt from Sudan via sheep transported along Lake Nasser. A hypothesis is presented which describes sheep transport from holding areas in north-central Sudan, where RVF was epizootic, to live animal markets in southern Egypt. Travel time from north-central Sudan to the Aswan area was less than 5 days, approximating the incubation period of RVF virus in sheep. Reintroduction of RVF or other diseases from Sudan into Egypt will be facilitated by the construction of new roads linking the two countries.
West Nile virus causes sporadic cases and outbreaks of human and equine disease in Europe (western Mediterranean and southern Russia in 1962-64, Belarus and Ukraine in the 1970s and 1980s, Romania in 1996-97, Czechland in 1997, and Italy in 1998). Environmental factors, including human activities, that enhance population densities of vector mosquitoes (heavy rains followed by floods, irrigation, higher than usual temperature, or formation of ecologic niches that enable mass breeding of mosquitoes) could increase the incidence of West Nile fever.
In 1993, Rift Valley fever (RVF) virus reappeared in Egypt. We determined the prevalence and feeding patterns of mosquitoes in 5 villages where the virus was active. Of 10 species recovered, Aedes caspius (Pallas), Culex pipiens L., Cx. antennatus (Becker), and Cx. perexiguus Theobald constituted 99% of > 35,000 mosquitoes captured in dry ice-baited CDC light traps. Ae. caspius was most prevalent, except at Nag' El Hagar where it was replaced by Cx. perexiguus. Cx. pipiens ranked 2nd, except at Nag' El Ghuneimiya, where it was replaced by Cx. antennatus. Most blood meals analyzed by an enzyme-linked immunosorbent assay reacted to > or = 1 antiserum. Cx. pipiens was mainly anthropophagic, and therefore may have been the main vector of RVF virus among humans. Ae. caspius feeds were chiefly from humans, bovines, and equines. Cx. antennatus and Cx. perexiguus fed generally on bovines. Mixed blood meals from humans and RVF virus susceptible animals were identified in the predominant mosquitoes. Prevalence and host selection, as well as predicted probability for a blood meal being interrupted, indicated that Ae. caspius may have served as a bridge vector between humans and bovines in 4 of the villages. Cx. perexiguus may have played this role at Nag' El Hagar. Because potential vectors are abundant, susceptible domestic animals are associated closely with humans, and surveillance of imported livestock is not systematic, we conclude that RVF virus sporadically will recur in Egypt.
Attempts were made to isolate virus from wild caught mosquitoes during the 1977 and 1978 Rift Valley fever (RVF) epizootics in Egypt. Over 95% of the 55,126 mosquitoes collected from epizootic areas in the Nile Delta and Valley were Culex pipiens. Two strains of RVF virus were isolated from unengorged female C. pipiens taken in 1978. Laboratory-reared C. pipiens originating from a population sample from the Nile Delta epizootic area transmitted RVF virus. The infection rate of mosquitoes that fed on viremic hamsters was 86.7%; the transmission rate was 40.0% (46.2% based only on infected mosquitoes). From these results, it is suggested that C. pipiens was a vector of RVF virus during the 1977–1978 epizootics in Egypt.
In the last 30 years several cases of West Nile (WN) virus infection were reported in horses and humans in Europe and in the Mediterranean Basin. Most of them were determined by strains of the Lineage 1 included in the European Mediterranean/Kenyan cluster. Strains of this cluster are characterised by a moderate pathogenicity for horses and humans and limited or no pathogenicity for birds. In recent years, however, WN cases determined by strains grouped in the Israeli/American cluster of Lineage 1 or in the lineage 2 have been reported in Hungary and Austria. The role of migrating birds in introducing new viruses to Europe has been often demonstrated. The migratory birds, which may be infected in their African wintering places, carry the virus northward to European sites during spring migrations. In the past, the virus introduction determined occasional cases of WN. In the recent years, new epidemiological scenarios are developing. In few occasions it has been evidenced the capability of WNV strains of overwintering by using local birds and mosquitoes. Species of Culex amongst mosquitoes and magpies (Pica pica), carrion crows (Corvus corone) and rock pigeons (Columba livia) amongst resident birds are the most probable species involved in this hypothetical WND endemic cycle.
In the last 30 years several cases of West Nile (WN) virus infection were reported in horses and humans in Europe and in the Mediterranean Basin. Most of them were determined by strains of the Lineage 1 included in the European Mediterranean/Kenyan cluster. Strains of this cluster are characterised by a moderate pathogenicity for horses and humans and limited or no pathogenicity for birds. In recent years, however, WN cases determined by strains grouped in the Israeli/American cluster of Lineage 1 or in the lineage 2 have been reported in Hungary and Austria. The role of migrating birds in introducing new viruses to Europe has been often demonstrated. The migratory birds, which may be infected in their African wintering places, carry the virus northward to European sites during spring migrations. In the past, the virus introduction determined occasional cases of WN. In the recent years, new epidemiological scenarios are developing. In few occasions it has been evidenced the capability of WNV strains of overwintering by using local birds and mosquitoes. Species of Culex amongst mosquitoes and magpies (Pica pica), carrion crows (Corvus corone) and rock pigeons (Columba livia) amongst resident birds are the most probable species involved in this hypothetical WND endemic cycle.
A computational model is a representation of some physical or other system of interest, first expressed mathematically and then implemented in the form of a computer program; it may be viewed as a function of inputs that, when evaluated, produces outputs. Motivation for this article comes from computational models that are deterministic, complicated enough to make classical mathematical analysis impractical and that have a moderate-to-large number of inputs. The problem of designing computational experiments to determine which inputs have important effects on an output is considered. The proposed experimental plans are composed of individually randomized one-factor-at-a-time designs, and data analysis is based on the resulting random sample of observed elementary effects, those changes in an output due solely to changes in a particular input. Advantages of this approach include a lack of reliance on assumptions of relative sparsity of important inputs, monotonicity of outputs with respect to inputs, or ad...
The Rift Valley fever virus (RVFV) is a threat that must not be neglected, as the consequences of RVFV are dramatic, both for human and animal health. This virus is a zoonotic virus that already has demonstrated a real capacity for re-emerging after long periods of silence, as observed in Barkedji (Senegal, West Africa) in 2002. In this article we present the 2nd emergence in Barkedji after the 1st manifestation in 1993, and for the 1st time the circulation of RVFV during 2 consecutive years among mosquito populations in Senegal. As part of the entomological surveillance program undertaken since 1990 to detect circulation of the RVFV in Barkedji, 108,336 mosquitoes belonging to 34 species and 5 genera were collected in 2002-2003. Aedes vexans and Culex poicilipes, previously known to be vectors of RVFV in Senegal, comprised 88.7% of the total collection. In 2002, Ae. vexans was the most abundant mosquito, followed by Cx. poicilipes; the opposite situation was observed in 2003. In 2002, 29 and 10 RVFV isolates were obtained from Cx. poicilipes (minimum infection rate [MIR] = 0.13%) and Ae. vexans (MIR = 0.02%) pools, respectively and the MIR for the 2 species were significantly different (chi2 = 34.65; df = 1, P < 0.001). In 2003, 7 RVFV strains were isolated from Cx. poicilipes (3, MIR = 0.03), Mansonia africana (2, MIR = 0.08), Ae. fowleri (1), and Ma. uniformis (1, MIR = 0.05). The 3 latter species were found to be associated with RVFV for the 1st time in Senegal. A significant decrease in MIR was observed from 2002 to 2003 (chi2 6.28; df = 1, P = 0.01) for Cx. poicilipes, the only species involved in the transmission during the 2 sampling years.
A computational model is a representation of some physical or other system of interest, first expressed mathematically and then implemented in the form of a computer program; it may be viewed as a function of inputs that, when evaluated, produces outputs. Motivation for this article comes from computational models that are deterministic, complicated enough to make classical mathematical analysis impractical and that have a moderate-to-large number of inputs. The problem of designing computational experiments to determine which inputs have important effects on an output is considered. The proposed experimental plans are composed of individually randomized one-factor-at-a-time designs, and data analysis is based on the resulting random sample of observed elementary effects, those changes in an output due solely to changes in a particular input. Advantages of this approach include a lack of reliance on assumptions of relative sparsity of important inputs, monotonicity of outputs with respect to inputs, or adequacy of a low-order polynomial as an approximation to the computational model.
The increasing concern about vector-borne diseases such as West Nile disease in northern Italy motivated our analysis of data on the mosquito fauna and the seasonal and daily flight patterns collected in 1998 in the Po Valley. Collections were performed once a week from May to November, with human landing collections and CO(2) traps. Culex pipiens was present from July to October and showed a clearly unimodal nocturnal flight habit. Culex modestus appeared in July-August and showed a bimodal flight pattern, (main peak during the evening and a minor one in the morning). Aedes caspius was present from May to November (highest densities in July-August) and showed a bimodal flight pattern with a major crepuscular peak and a minor dawn peak in the morning. Aedes detritus was the most abundant species in May, with a crepuscular sharply bimodal flight pattern, particularly according to human landing collections. Sunset and sunrise time, in combination with the solar phase (that determines daylight duration and its trend of changing) were the main factors affecting flight behavior. Temperature, relative humidity, and wind speed differently affected the flight behavior of mosquito females according to the species.
A review is presented of all aspects of adult mosquito dispersal, encompassing transportation of mosquitoes by ships, airplanes and trains, long distance wind-assisted dispersal, and much shorter almost daily flights that mosquitoes make to locate mates, blood sources, nectar, oviposition sites, and resting sites. The many definitions and concepts of animal migration are debated, and instances of so-called mosquito migration, that is long distance wind-assisted flights, and the ecological advantages and disadvantages of such journeys are examined. It is concluded that there is little evidence that mosquitoes make purposeful long distance flights that can be classified zoologically as migration. It is argued that it is better to regard all mosquito flights as dispersal. Host orientation cues are not discussed, but the contentious idea of a memorized home range between feeding and oviposition sites is presented.
Sensitivity analysis screening methods aim to isolate the most important factors in experiments involving a large number of significant factors and interactions.This paper extends the one-factor-at-a-time screening method proposed by Morris. The new method, in addition to the `overall' sensitivity measures already provided by the traditional Morris method, offers estimates of the two-factor interaction effects. The number of model evaluations required is O(k2), where k is the number of model input factors.The efficient sampling strategy in the parameter space is based on concepts of graph theory and on the solution of the `handcuffed prisoner problem'.
This paper is concerned with developing a framework for GIS-based multicriteria group decision-making using the fuzzy majority approach. The procedure for solving a spatial group decision-making problem involves two stages. First, each decision-maker solves the problem individually. Second, the individual solutions are aggregated to obtain a group solution. The first stage is operationalized by a linguistic quantifier-guided ordered weighted averaging (OWA) procedure to create individual decision-maker’s solution maps. Then the individual maps are combined using the fuzzy majority procedure to generate the group solution map which synthesizes the majority of the decision-makers’ preferences. The paper provides an illustrative example of the fuzzy majority method for a land suitability problem. It also demonstrates the implementation of the framework within the ArcGIS environment.
The rapid spread of West Nile viral activity across North America since its discovery in 1999 illustrates the potential for an exotic arbovirus to be introduced and become widely established across North America. Rift Valley fever virus (RVFV) has been responsible for large outbreaks in Africa that have resulted in hundreds of thousands of human infections and major economic disruption due to loss of livestock and to trade restrictions. However, little is known about the potential for mosquitoes in Canada to transmit this virus, should it be introduced into North America. Therefore, we evaluated mosquito species captured near Winnipeg, Manitoba, Canada, for their ability to serve as potential vectors for RVFV. Mosquitoes were exposed to RVFV by allowing them to feed on adult hamsters inoculated the previous day with RVFV. These mosquitoes were tested for infection, dissemination, and the ability to transmit RVFV after incubation at 25 degrees C for 14-18 days. Based on the detection of virus in saliva collected in capillary tubes, individual Culex tarsalis, Aedes sticticus, and Coquillettidia perturbans were able to transmit RVFV under laboratory conditions. These preliminary results suggest that these 3 species may be able to transmit RVFV, should this virus be introduced into Canada.
Rift Valley fever (RVF) is a mosquito-borne viral zoonosis of increasing global importance. Occurring since 1930 across Africa, it was detected for the first time in Saudi Arabia and Yemen in September 2000, leading to human deaths and major losses in livestock populations. Assuming the virus has not survived in Yemen or has been circulating at a low level, authors qualitatively assessed the likelihood of "re-introduction" of RVF into Yemen through the legal importation of small ruminants from the Horn of Africa. The overall probability of introduction was assessed very low to medium, increasing during festival periods and higher when considering a direct transmission exposure as compared to a vectorial transmission exposure. The uncertainty was considered to be medium underlining important gaps in information that need to be fulfilled in the region. Options to reduce the risk are proposed and discussed, including possible improvements of the current Yemeni quarantine system.
Epidemiological factors related to the introduction, spread and maintenance of Rift Valley fever (RVF) virus were studied
during the 1977–1978 epizootic in Egypt. Culex pipiens is the most ubiquitous and prevalent mosquito species in the Nile Valley and Delta. Isolation of RVF virus from unengorged
C. pipiens, and demonstration of laboratory transmission of the virus by this species, strongly implicate it as the chief vector in
Egypt. Virus transmission to man also occurs by contamination when handling infected meat and by inhaling natural virus aerosols.
Wild rodents apparently do not serve as RVF virus reservoirs. Domestic sheep, cattle, buffaloes, camels, goats, donkeys and
dogs act as amplifying hosts. Over 30% of the camels sampled at the southern border of Egypt were serologically positive for
antibodies to RVF virus and it appears likely that the virus was introduced into Egypt, either by these animals or by other
vehicles from the south.
Seven species of mosquito among the fauna of Southern Africa were tested for their ability to transmit Rift Valley fever virus. Anopheles coustani, Aedes lineatopenis and Aedes circumluteolus were readily infected by high doses of virus but attempts at transmission of virus failed. These were regarded as inconclusive because only a small number of mosquitoes was fed. Culex theileri, Culex zombaensis, Culex neavei and Eretmapodites quinquevittatus all successfully transmitted virus at varying degrees of efficiency. Culex theileri was the most efficient vector and 92 to 100% of females of this species were infected by 6.5-8.5 log LD 50 of virus and 11 out of 20 mosquitoes transmitted virus. Seventy five per cent of Culex zombaensis were infected by 5.8 log LD 50 of virus and at least 2 out of 5 mosquitoes transmitted virus. Between 31 and 69% of Culex neavei were infected by 6.6-8.5 log LD 50 of virus and about 3 out of 22 mosquitoes transmitted virus. The poorest vector was Eretmapodites quinquevittatus which was readily infected but only about one out of 22 mosquitoes transmitted virus. Attempts to demonstrate transovarian transmission of virus with this species failed.
Attempts to isolate Rift Valley fever virus from wild-caught hematophagous flies were made over an 8-yr period in the coastal lowlands of Natal, where the virus causes enzootic infection of cattle, and on infected farms in the inland plateau region of South Africa during epizootics in 1974/1975. In Natal the virus was not isolated from 71,561 mosquitoes, 10,514 Culicoides spp., or from fewer numbers of simuliid, phlebotomine and tabanid flies. On the plateau there were 12 isolations from Culex theileri and 6 from 3 other mosquito species. There were no isolations from 12,368 Culicoides spp., and smaller numbers of simuliids, tabanids and Stomoxys flies. In laboratory transmission tests the virus was transmitted by 7 mosquito species: Cx. theileri, Cx. univittatus, Cx. quinquefasciatus, Aedes Juppi, Ae. lineatopennis, Ae. aegypti and Eretmapodites quinquevittatus. Two mosquito species, Ae. caballus and Cx. rubinotus, became infected but failed to transmit by bite. Cx. theileri was shown to be the most efficient vector. The tick, Ornithodoros savignyi, failed to become infected or to transmit virus by bite. It is concluded that Cx. theileri is the main epizootic vector among sheep and cattle on the plateau, where it probably causes some human infection. In the same region Ae. juppi and Ae. lineatopennis are believed to act as vectors of lesser importance. Failure to isolate the virus from mosquitoes in enzootic foci in Natal is in accordance with previously observed low isolation rates from mosquitoes in such localities. It is concluded that there is no definitive evidence to indicate that mosquitoes are concerned in viral maintenance.
Following ingestion of 10(4.2) to 10(7.2) plaque-forming units (PFU) of Rift Valley fever (RVF) virus, 662 of 850 female Culex pipiens (78%) became infected. Those mosquitoes that became infected separated into two distinct groups: 1) those with a nondisseminated infection limited to the gut, and 2) those with a disseminated infection. The former group contained a median of 10(3.2) PFU, while those females with a disseminated infection contained a median of 10(5.5) PFU. Only those females with a disseminated infection were capable of transmitting virus by bite to a susceptible hamster. This is consistent with a mesenteronal escape barrier to viral dissemination. Following intrathoracic inoculation of RVF virus, all females developed a disseminated infection (26/26) and successfully transmitted virus by bite (49/49) if allowed to feed on a susceptible hamster or suckling mouse. Examination of legs and bodies separately provided a rapid and efficient method of determining dissemination status.
The influence on malaria incidence in Algeria of anophelism in the oases and construction of a trans-Saharan highway is discussed. The few remaining cases of malaria in Algeria are of Plasmodium vivax, a parasite absent from tropical West Africa where P. falciparum, now eradicated from the Mediterranean Basin, predominates. Epidemics arising from imported falciparum malaria are considered to be unlikely in Algeria north of the desert, but some oases are at risk. More precise estimates of the probabilities of outbreaks in these oases require analyses of their populations of Anopheles sergentii s.l., a taxon comprising vector and nonvector forms, and also establishment of the northerly limits of the distributions in Niger of A. arabiensis and A. gambiae.
Attempts were made to isolate virus from wild caught mosquitoes during the 1977 and 1978 Rift Valley fever (RVF) epizootics in Egypt. Over 95% of the 55,126 mosquitoes collected from epizootic areas in the Nile Delta and Valley were Culex pipiens. Two strains of RVF virus were isolated from unengorged female C. pipiens taken in 1978. Laboratory-reared C. pipiens originating from a population sample from the Nile Delta epizootic area transmitted RVF virus. The infection rate of mosquitoes that fed on viremic hamsters was 86.7%; the transmission rate was 40.0% (46.2% based only on infected mosquitoes). From these results, it is suggested that C. pipiens was a vector of RVF virus during the 1977-1978 epizootics in Egypt.
Thirteen strains of Rift Valley fever virus were isolated from Aedes vexans and Ae. ochraceus mosquitoes collected in October and November 1993 in northern Senegal. Entomologic and serologic data show that the risk of a new epizootic is increasing in this region.
Reintroduction of Rift Valley fever (RVF) into Egypt in 1993 raised concerns about the potential for Egyptian mosquitoes to transmit the virus. We evaluated the ability of Aedes caspius, Culex pipiens, Cx. antennatus, Cx. perexiguus, Cx. poicilipes, and Anopheles pharoensis collected in the Aswan area and Cx. pipiens collected in the Nile Delta to transmit RVF virus. All mosquito species tested were susceptible to RVF virus infection, with An. pharoensis and Ae. caspius being the most sensitive to infection. However, none of 12 An. pharoensis, including 10 with a disseminated infection, transmitted RVF virus by bite. In contrast, nearly all Cx. pipiens (87%, n = 15) and Cx. perexiguus (90%, n = 10) with a disseminated infection transmitted virus. Overall transmission rates for mosquitoes exposed to hamsters with a viremia > or = 10(7) plaque-forming units/ml were Ae. caspius, 20% (n = 5); Cx. pipiens, 7% (n = 102); Cx. antennatus, 7% (n = 30); Cx. perexiguus, 11% (n = 9); and An. pharoensis, 0% (n = 7). Based on abundance, susceptibility to infection, ability to transmit virus, and feeding behavior, Ae. caspius appeared to be the most efficient vector of the Egyptian mosquitoes evaluated. While less susceptible than Ae. caspius, Cx. pipiens, Cx. antennatus, and Cx. perexiguus were also potential vectors during this RVF outbreak in Egypt.
In two areas of Senegal where previous evidence of Rift Valley fever (RVF) virus circulation was detected, Barkedji in the Sahelian bioclimatic zone and Kedougou in the Sudano-Guinean zone, a longitudinal study of the enzootic maintenance of RVF virus was undertaken from 1991 to 1993. Mosquitoes, sand flies, and ticks were collected and domestic ungulates were monitored with serologic surveys. Rift Valley fever virus was not isolated in Kedougou. In Barkedji, RVF virus was isolated from Aedes vexans and Ae. ochraceus mosquitoes collected in traps near ground pools and cattle droves and from one health sheep. Sand flies were not involved in the maintenance cycle. Seroconversions were recorded in three (1.9%) of 160 monitored sheep and goats. The interepizootic vectors appeared to belong to the Aedes subgenus Neomelaniconion in East Africa, and to the subgenus Aedimorphus in West Africa. Epizootics in East Africa are associated with an increase in rainfall. However, factors associated with epizootics remain unknown for West Africa.
Surveillance for mosquito-borne viruses was conducted in Barkedji area from 1990 to 1995, following an outbreak of Rift Valley fever (RVF) virus in southern Mauritania. Mosquitoes, sand flies, and midges were collected from human bait and trapped by solid-state U.S. Army battery-powered CDC miniature light traps baited with dry ice or animals (sheep or chickens) at four ponds. Overall, 237,091 male and female mosquitoes representing 52 species in eight genera, 214,967 Phlebotomine sand flies, and 2,527 Culicoides were collected, identified, and tested for arboviruses in 9,490 pools (7,050 pools of female and 331 of male mosquitoes, 2,059 pools of sand flies and 50 pools of Culicoides). Viruses isolated included one Alphavirus, Babanki (BBK); six Flaviviruses, Bagaza (BAG), Ar D 65239, Wesselsbron (WSL), West Nile (WN), Koutango (KOU), Saboya (SAB); two Bunyavirus, Bunyamwera (BUN) and Ngari (NRI); two Phleboviruses, Rift Valley fever (RVF) and Gabek Forest (GF); one Orbivirus, Ar D 66707 (Sanar); one Rhabdovirus, Chandipura (CHP); and one unclassified virus, Ar D 95537. Based on repeated isolations, high field infection rates and abundance, Culex appeared to be the vectors of BAG, BBK, Ar D 65239 (BAG-like), and WN viruses, Ae. vexans and Ae. ochraceus of RVF virus, Mansonia of WN and BAG viruses, Mimomyia of WN and BAG viruses, and Phlebotomine of SAB, CHP, Ar D 95537, and GF viruses. Our data indicate that RVF virus circulated repeatedly in the Barkedji area.