[Show abstract][Hide abstract] ABSTRACT: Background:
Divergent selection can be a major driver of ecological speciation. In insects of medical importance, understanding the speciation process is both of academic interest and public health importance. In the West Nile virus vector Culex pipiens, intraspecific pipiens and molestus forms vary in ecological and physiological traits. Populations of each form appear to share recent common ancestry but patterns of genetic differentiation across the genome remain unknown. Here, we undertook an AFLP genome scan on samples collected from both sympatric and allopatric populations from Europe and the USA to quantify the extent of genomic differentiation between the two forms.
The forms were clearly differentiated but each exhibited major population sub-structuring between continents. Divergence between pipiens and molestus forms from USA was higher than in both inter- and intra-continental comparisons with European samples. The proportion of outlier loci between pipiens and molestus (≈3 %) was low but consistent in both continents, and similar to those observed between sibling species of other mosquito species which exhibit contemporary gene flow. Only two of the outlier loci were shared between inter-form comparisons made within Europe and USA.
This study supports the molestus and pipiens status as distinct evolutionary entities with low genomic divergence. The low number of shared divergent loci between continents suggests a relatively limited number of genomic regions determining key typological traits likely to be driving incipient speciation and/or adaptation of molestus to anthropogenic habitats.
[Show abstract][Hide abstract] ABSTRACT: The ability to effectively modify behaviours is increasingly relevant to attain and maintain a good health status. Current behaviour-change models and theories present two main approaches for (healthier) decision-making: one analytical/logical, and one experiential/emotional/intuitive. Therefore, to achieve an integral and dynamic understanding of the public perceptions both approaches should be considered: community surveys should measure cognitive understanding of health-risk contexts, and also explore how past experiences affect this understanding. In 2011, community perceptions regarding domestic source reduction were assessed in Madeira Island͘. After Madeira's first dengue outbreak (2012) a unique opportunity to compare perceptions before and after the outbreak-experience occurred. This was the aim of this study, which constituted the first report on the effect of an outbreak experience on community perceptions regarding a specific vector-borne disease. A cross-sectional survey was performed within female residents at the most aegypti-infested areas. Perceptions regarding domestic source reduction were assessed according to the Essential Perception (EP)-analysis tool. A matching process paired individuals from studies performed before and after the outbreak, ensuring homogeneity in six determinant variables. After the outbreak, there were more female residents who assimilated the concepts considered to be essential to understand the proposed behaviour. Nevertheless, no significant difference was observed in the number of female residents who achieved the defined 'minimal understanding''. Moreover, most of the population (95.5%) still believed at least in one of the identified myths. After the outbreak some myths disappeared and others appeared. The present study quantified and explored how the experience of an outbreak influenced the perception regarding a dengue-preventive behaviour. The outbreak experience surprisingly led to the appearance of new myths within the population, apart from the expected increase of relevant concepts' assimilation. Monitoring public perceptions is therefore crucial to make preventing dengue campaigns updated and worthy.
[Show abstract][Hide abstract] ABSTRACT: The recent emergence in Europe of invasive mosquitoes and mosquito-borne disease associated with both invasive and native mosquito species has prompted intensified mosquito vector research in most European countries. Central to the efforts are mosquito monitoring and surveillance activities in order to assess the current species occurrence, distribution and, when possible, abundance, in order to permit the early detection of invasive species and the spread of competent vectors. As active mosquito collection, e.g. by trapping adults, dipping preimaginal developmental stages or ovitrapping, is usually cost-, time- and labour-intensive and can cover only small parts of a country, passive data collection approaches are gradually being integrated into monitoring programmes. Thus, scientists in several EU member states have recently initiated programmes for mosquito data collection and analysis that make use of sources other than targeted mosquito collection. While some of them extract mosquito distribution data from zoological databases established in other contexts, community-based approaches built upon the recognition, reporting, collection and submission of mosquito specimens by citizens are becoming more and more popular and increasingly support scientific research. Based on such reports and submissions, new populations, extended or new distribution areas and temporal activity patterns of invasive and native mosquito species were found. In all cases, extensive media work and communication with the participating individuals or groups was fundamental for success. The presented projects demonstrate that passive approaches are powerful tools to survey the mosquito fauna in order to supplement active mosquito surveillance strategies and render them more focused. Their ability to continuously produce biological data permits the early recognition of changes in the mosquito fauna that may have an impact on biting nuisance and the risk of pathogen transmission associated with mosquitoes. International coordination to explore synergies and increase efficiency of passive surveillance programmes across borders needs to be established.
Full-text · Article · Jan 2015 · Parasites & Vectors
[Show abstract][Hide abstract] ABSTRACT: Dengue virus (DENV) is the arbovirus with the widest impact on human health. Although its dispersal is partially conditioned by environmental constraints that limit the distribution of its main vector (Aedes aegypti), DENV has been spreading geographically in recent times, but mostly afflicting tropical and subtropical regions. With no prophylactic vaccine or specific therapeutics available, vector control remains the best alternative to restrain its circulation. Moreover, the establishment of thriving vector populations in peri urban environments brings humans and viruses together, opening the possibility for the occurrence of unexpected outbreaks. Europe is no exception: such was the case of Madeira in 2012. In addition to its impact on the health of the local population, health services, and economy, this outbreak revealed how difficult it may be to control the circulation of pathogenic arboviruses, especially taking into consideration that Europe is already partially colonized by another DENV vector, Aedes albopictus.
No preview · Article · Nov 2014 · Expert Review of Anti-infective Therapy
[Show abstract][Hide abstract] ABSTRACT: O Aedes aegypti é o principal vetor da dengue em todo o mundo. Por causa da natureza doméstica deste mosquito, a importância relativa do Macroclima na modelação da sua distribuição tem sido um assunto controverso. Neste trabalho capturaram-se as condições macroclimáticas dos locais ocupados pelo A. aegypti no século passado e avaliou se a capacidade desta informação para prever a distribuição observada da espécie. Também foi projetada a distribuição futura da espécie (2010-2039) sob dois cenários de mudança climática. Os resultados indicam que o macroclima é em grande parte responsável pela definição do limite de alcance máximo do A. Aegypti, e continuará a ser no futuro.
Paralelamente, muita da variedade da espécie em regiões temperadas e subtropicais é sustentada pelos ambientes artificiais. Globalmente, estas análises sugerem que, se os ambientes domésticos normalmente explorados por esta espécie estiverem disponíveis, a sua distribuição pode expandir-se consideravelmente num futuro próximo.
[Show abstract][Hide abstract] ABSTRACT: The malaria vector Anopheles arabiensis exhibits greater behavioural and ecological plasticity than the other major vectors of the Anopheles gambiae complex, which presents challenges for major control methods. This study reports for the first time the presence of An. arabiensis in Antula, a suburb of Bissau city, the capital of Guinea Bissau, where high levels of hybridization between Anopheles coluzzii and An. gambiae have been reported. Given that previous surveys in the area, based on indoor collections, did not sample An. arabiensis, the possibility of a recently introduced exophilic population was investigated.
Larval and adult mosquito collections were carried out in Antula at the end of the rainy season of 2010. Anopheles gambiae species composition, determined by rDNA-IGS and SINE200X6.1 markers, was compared with four previously collected samples dating back to 1993. Analysis of ten microsatellites was used to estimate levels of genetic diversity, relatedness and to investigate demographic stability.
Anopheles arabiensis comprised 54.0% of larvae and 25.6% of adults collected in 2010, but was absent in all previous collections, a highly unlikely observation by chance if the population was stable. This species had the lowest levels of genetic diversity, highest relatedness and, along with An. gambiae, exhibited evidence of a recent population expansion.
Results point to the presence of a previously undetected outdoor population of An. arabiensis in Antula, which appears to have expanded recently, highlighting the importance of complementing indoor-based mosquito collections with sampling methods targeting outdoor adults and immature stages for a more complete assessment of mosquito biodiversity. A change in temporal dynamics in the species complex composition was also detected. Coupled with previous evidence of asymmetric introgression from An. coluzzii to An. gambiae, this suggests that the study area may be subject to ecological changes with a potential impact on both the genetics of these species and on malaria transmission.
[Show abstract][Hide abstract] ABSTRACT: Dengue is a vector-borne disease and 40% of world population is at risk.
Dengue transcends international borders and can be found in tropical and
subtropical regions around the world, predominantly in urban and semi-urban
areas. A model for dengue disease transmission, composed by mutually-exclusive
compartments representing the human and vector dynamics, is presented in this
study. The data is from Madeira, a Portuguese island, where an unprecedented
outbreak was detected on October 2012. The aim of this work is to simulate the
repercussions of the control measures in the fight of the disease.
[Show abstract][Hide abstract] ABSTRACT: In 2005, The Institute of Hygiene and Tropical Medicine received from the Natural History Museum of Madeira a sample of mosquitoes collected in the island, following complaints of the local inhabitants about a highly nuisance mosquito. These mosquitoes were identified as Aedes aegypti, the first report of this important arbovirus vector in the island. After this report, it took less than 8 years until a Dengue epidemic occurred in the island. The first cases were detected in October 2012 and the epidemic lasted for 20 weeks counting over 2,000 reported cases with no fatalities. Since 2009, IHMT has been participating in the monitoring of A. aegypti in Madeira. Studies involve monitoring of mosquito dispersal and abundance, bioecological characterizations, insecticide resistance profiling and genetic analyses. Here we present an update of the ongoing studies, with emphasis on the levels of insecticide resistance and its mechanisms, and molecular genetic analysis aiming at establishing the origin of this mosquito population. Insecticide susceptibility assays have shown a highly resistant A. aegypti population with mortality rates below 80% for pyrethroid and organochlorine (DDT) insecticides. Genetic analysis of the voltage-gated sodium channel gene revealed a high frequency of the knockdown resistance (kdr) associated mutation F1534C. An additional mutation, V1016I, was also detected at frequencies up to 23%. Phylogenetic analysis based on mtDNA genes suggest a South American origin for this vector population, possibly from Brazil or Venezuela, two countries with important migrant flows with Madeira island.
[Show abstract][Hide abstract] ABSTRACT: Aedes aegypti is the most important mosquito vector of dengue and yellow fever, two of the most significant mosquito-borne viral diseases in the world. Due to the lack of antiviral therapy or vaccination, reducing dengue transmission depends only on mosquito control. In the archipelago of Cape Verde (West Africa) in November 2009 a dengue epidemic was declared with more than 20,000 people affected, 174 hemorrhagic fever cases and six deaths. The presence of Ae. aegypti in the archipelago was reported since 1931. In this study we aim to clarify the origins and population history of Ae. aegypti in Cape Verde by analyzing the variability of the mitochondrial gene NADH dehydrogenase subunit 4 (ND4). We analyzed 42 mosquitoes from three islands (Santiago, Brava and Fogo) collected before and after the dengue outbreak (2007/2010). ND4 sequences of 360bp revealed seven haplotypes, three of which are Cape Verde specific (haplotype diversity =0.637 and nucleotide diversity =0.002). All haplotypes were closely related and formed a star-like structure typical of expanded populations. In a comparison with 194 published haplotypes (including 6 African Aedes sp. outgroups), sequences from Cape Verde occurred in a basal clade mainly associated with West African mosquito populations. Our results suggest a high genetic diversity and a West African origin for this insular mosquito population. We found no evidence of new recent founder events that could be associated with the unique dengue outbreak in 2009.
[Show abstract][Hide abstract] ABSTRACT: Background: Aedes aegypti is the mosquito vector of dengue, the most significant mosquito-borne viral diseases in the world. Due to the lack of antiviral therapy or vaccination, reducing dengue transmission depends only on mosquito control. In the archipelago of Cape Verde (West Africa) in November 2009 a dengue epidemic was declared with more than 20000 people affected and six deaths. The presence of A. aegypti in the archipelago was reported since 1931.
Objectives: To evaluate the genetic variability and effective population size of A. aegypti populations from Cape Verde before and after the dengue outbreak.
Methods: We analysed two mosquito samples from Santiago island collected before and after the dengue outbreak (N=47 in 2007 and N=24 in 2010, respectively) and genotyped them for 14 microsatellites. Parameters of genetic diversity and population differentiation were assessed with the softwares Genepop and Arlequin 3.5. NeEstimator and Bottleneck softwares were used to estimate effective population size (Ne) and detect population changes, respectively. We also used a Bayesian clustering method (software Structure) to evaluate patterns of population structure.
Results: Mean over loci allelic richness and expected heterozygosity was 5 and 0.7, respectively in both temporal samples. Ne was smaller in 2010 (Ne=16) than in 2007 (Ne=8), and we detected a bottleneck effect in 2010. The two samples were significantly differentiated, and Bayesian clustering analysis detected two clusters (k=2) corresponding to each temporal sample.
Conclusion: We have found comparable levels of genetic diversity between collection years, within the range of values for other African populations. However, there was significant inter-temporal genetic differentiation associated with a signal of population bottleneck and a reduction in effective population size. Results will be discussed with respect to the epidemiology of dengue and control efforts in the archipelago.
[Show abstract][Hide abstract] ABSTRACT: Aedes aegypti is the main vector of dengue and a number of other diseases worldwide. Because of the domestic nature of this mosquito, the relative importance of macroclimate in shaping its distribution has been a controversial issue. We have captured here the worldwide macroclimatic conditions occupied by A. aegypti in the last century. We assessed the ability of this information to predict the species' observed distribution using supra-continental spatially-uncorrelated data. We further projected the distribution of the colonized climates in the near future (2010-2039) under two climate-change scenarios. Our results indicate that the macroclimate is largely responsible for setting the maximum range limit of A. aegypti worldwide and that in the near future, relatively wide areas beyond this limit will receive macroclimates previously occupied by the species. By comparing our projections, with those from a previous model based strictly on species-climate relationships (i.e., excluding human influence), we also found support for the hypothesis that much of the species' range in temperate and subtropical regions is being sustained by artificial environments. Altogether, these findings suggest that, if the domestic environments commonly exploited by this species are available in the newly suitable areas, its distribution may expand considerably in the near future.
[Show abstract][Hide abstract] ABSTRACT: Malaria was endemic in Europe for more than two millennia until its eradication inthe1970s. Recent autochthonous cases registered in Greece have increased the awareness regarding the threat of malaria re-emergence in Southern Europe. Currently, the presence of competent vectors, suitable environmental conditions and the evidences of a changing climate may increase the widespread re-emergence of malaria in Southern Europe.
This work focused on determining the current relationships between environmental factors and the density of the former malaria vector Anopheles atroparvus in Portugal, a previously endemic country. Adult females were sampled and vector density was estimated in 22 sites in Southern Portugal between 2001 and 2010 and related with land cover and satellite-derived air temperature and vegetation indices. The relationship between vector density and local larval habitat, temperature and, in a broader sense, to environmental suitability, was assessed using a statistical modelling approach.
Results showed that present environmental conditions are suitable for vector development at high densities and the spatial and temporal patterns closely resemble the ones registered in the past endemic period. The use of satellite-derived data, together with statistical models, allowed the extrapolation of suitable environmental conditions for vector development from site-level to the Portuguese main land territory.This work also improved the baseline knowledge needed to understand the potential impacts of future environmental changes on vector density and, indirectly, on the risk of malaria re-emergence.
Full-text · Article · Feb 2014 · Remote Sensing of Environment
[Show abstract][Hide abstract] ABSTRACT: Community participation is mandatory in the prevention of Dengue outbreaks. Taking public views into account is crucial to guide more effective planning and quicker community participation in preventing campaigns. This study aims to assess community perceptions of Madeira population in order to explore their involvement in the A. aegypti's control and reinforce health-educational planning. Due to the lack of accurate methodologies for measuring perception, a new tool to assess the community's perceptions was built.
A cross-sectional survey was performed in the Island's aegypti-infested area, exploring residents' perceptions regarding most critical community behaviour: aegypti-source reduction and their domestic aegypti-breeding sites. A novel tool defining five essential topics which underlie the source reduction's awareness and accession was built, herein called Essential-Perception (EP) analysis.
Of 1276 individuals, 1182 completed the questionnaire (92 . 6%). EP-Score analysis revealed that community's perceptions were scarce, inconsistent and possibly incorrect. Most of the population (99 . 6%) did not completely understood the five essential topics explored. An average of 54 . 2% of residents only partially understood each essential topic, revealing inconsistencies in their understanding. Each resident apparently believed in an average of four false assumptions/myths. Significant association (p[modifier letter left arrowhead]0.001) was found between both the EP-Score level and the domestic presence of breeding sites, supporting the validity of this EP-analysis. Aedes aegypti's breeding sites, consisting of decor/leisure containers, presented an atypical pattern of infestation comparing with dengue prone regions.
The studied population was not prepared for being fully engaged in dengue prevention. Evidences suggest that EP-methodology was efficient and accurate in assessing the community perception and its compliance to practices. Moreover, it suggested a list of myths that could persist in the community. This is the first study reporting an aegypti-entomological pattern and community's perception in a developed dengue-prone region. Tailored messages considering findings of this study are recommended to be used in future campaigns in order to more effectively impact the community perception and behaviour.
Full-text · Article · Jan 2014 · BMC Public Health