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The ecology of ticks and epidemiology of tick-borne viral diseases
Abstract
A number of tick-borne diseases of humans have increased in incidence and geographic range over the past few decades, and there is concern that they will pose an even greater threat to public health in future. Although global warming is often cited as the underlying mechanism favoring the spread of tick-borne diseases, climate is just one of many factors that determine which tick species are found in a given geographic region, their population density, the likelihood that they will be infected with microbes pathogenic for humans and the frequency of tick-human contact. This article provides basic information needed for microbiologists to understand the many factors that affect the geographic range and population density of ticks and the risk of human exposure to infected ticks. It first briefly summarizes the life cycle and basic ecology of ticks and how ticks and vertebrate hosts interact, then reviews current understanding of the role of climate, sociodemographic factors, agricultural development and changes in human behavior that affect the incidence of tick-borne diseases. These concepts are then illustrated in specific discussions of tick-borne encephalitis and Crimean-Congo hemorrhagic fever.
... There were different correlations between incidence rates and lowest winter temperature in previous study [8]. Medium cold days (from -10 to -7ºC) had a positive correlation with TBE incidence, while on the contrary, very cold days (<-10ºC) might protect underground ticks [11] and had a negative coefficient. Ticks tend to live in highly humid environment [6]. ...
... Ticks tend to live in highly humid environment [6]. Studies proved that precipitation, relative humidity [5], and air saturation deficit [12] characterizing the degree of water loss in the environment could affect tick mortality [11]. Except for seasonal temperature change above [8], short-term (daily) temperature and perception showed a positive relationship with incidence rates [13]. ...
... It has been studied that low temperature in winter might lead to the death of hibernating ticks. However, the long-term snow cover caused by low temperature can protect the underground ticks [11], so with the increase of the lowest temperature, the snow melted and killed a large number of ticks, as warm spring went by, led to a negative correlation between minimum temperature and incidence. The significant effect of the minimum temperature on the incidence rate mainly appeared in 2000 when the annual minimum temperature was lower than -10ºC in 86.25% of Russia's regions. ...
... Humans are the dead-end host of TBEV [3]. In Europe, the Ixodes ricinus (IR) tick is the main vector for the transmission of TBEV [4]. IR ticks are prevalent throughout Europe, from Ireland in the west to the Urals in the east, and from northern Sweden to north Africa [5]. ...
... The life cycle of ticks is affected by the microclimate, host factors, and seasonal variation. During colder seasons, the activity and development of the two common species of ticks are limited [4]. Ticks become active during vegetation seasons, with adequate levels of humidity and elevated temperatures. ...
Tick-borne encephalitis is a neuroinfection caused by the Tick-Borne Encephalitis Virus. It is transmitted primarily by tick bite and rarely because of consuming raw milk. It has been discovered in the 1930s. The disease covers the Euro-Asia region which also known as the tick-borne encephalitis belt. It is prevalent in most parts of Europe. The top affected parts of Europe include Southern Germany, Switzerland, the Czech Republic, Austria, Slovakia, Hungary, the Baltic countries, Slovenia, Poland, parts of Scandinavia, and European Russia. Since 2000, in Europe the total number of confirmed cases reported to the European CDC was 51,519. There were signs of decreasing number of cases in 2014 and 2015 however after 2015 a steadily increasing number of cases with involvement of countries which had no history of tick-borne encephalitis. Within Europe, from 1950 to 2006 ticks were prevalent between 600 to 2000 meters above sea level of altitude. The determinant factors for the spread of tick-borne encephalitis are host population size, weather, movement of hosts, altitude, and local regulations on socio-economic dynamics of the local and travelling people around the foci areas. The mean incidence rate of tick-borne encephalitis since 2000 to 2019 in Europe was 3.27 while the age adjusted mean incidence rate was 2.19 per 100,000 population size. The recent increase is mainly associated with human activity as a dominant factor since there are new foci areas with no significant climate change. This review used several articles and data sources from the European Center for Diseases Prevention and Control and Polish National Public Health Institute to examine the trend of TBE across Europe and in Poland in particular.
... Increasingly relevant are vector-borne zoonotic infections, of which the most important in the Northern hemisphere are caused by tick-borne pathogens (TBPs) (Jones et al., 2008;Rizzoli et al., 2011;Medlock et al., 2013;Sykes and Makiello 2017;Petrulionienė et al., 2020). Ticks are obligate parasites that require blood meals from vertebrate hosts for development and reproduction (Randolph, 2004;Estrada-Peña and De La Fuente, 2014). Consequently, the hosts affect the abundance of the ticks and contribute to TBPs circulation, ultimately affecting the risks that TBPs pose to humans (Randolph, 2004). ...
... The tick Ixodes ricinus is the most important vector of TBPs in Europe (Jore et al., 2011;Jaenson et al., 2012;Medlock et al., 2013;Laaksonen et al., 2017Laaksonen et al., , 2018Kjaer et al., 2019). Ixodes ricinus quests for hosts on the vegetation, with larvae, nymphs and adult females feeding mostly on small-, medium-and large-sized animals, respectively (Randolph, 2004;Francischetti et al., 2009;Mannelli et al., 2012;Estrada-Peña and De La Fuente, 2014). Females require sufficiently large blood meals, typically from a medium-or large-sized animal, to reproduce. ...
... For this reason, effective surveillance for monitoring those tick-borne pathogens affecting humans and other animals is needed (Parola & Raoult, 2001). It is worth noting that most studies on questing ticks to date were performed in woodland areas far away from the major population centres; in consequence, the detection of high prevalences in ticks from these areas does not always involve a real risk of infection for humans and domestic animals (Estrada-Peña & de la Fuente, 2014). Previous studies on questing ticks collected from the vegetation in urban and suburban areas reported a high risk of acquiring tick-borne pathogens in cities where micromammals and birds may play an important role in the maintenance of tick populations (Hansford et al., 2022); this could be related to the high density of these animals in urban areas when compared to natural areas as they have few or no natural predators in urban areas (Estrada-Peña et al., 2017). ...
... in questing ticks (Estrada-Peña & de la Fuente, 2014). ...
To identify the questing tick populations in urban and suburban areas from the city of Lugo (NW Spain), ticks were collected monthly by flagging. The presence of Borrelia spp., Rickettsia spp. and Anaplasma phagocytophilum also was determined by polymerase chain reaction (PCR) and sequence analysis. Overall, 342 questing ticks were collected; the tick abundance was higher in suburban (95.9%) than in urban areas (4.1%). Ixodes frontalis was the most abundant (86.5%); 88.5% were larvae, 11.1% nymphs and 0.3% adults. All development stages of I. ricinus (7.3%) and adults of Rhipicephalus sanguineus sensu lato (5.8%) and Dermacentor reticulatus (0.3%) were found. Rickettsia spp. (31.9%) was more prevalent than Borrelia spp. (2.7%); no ticks were positive to A. phagocytophilum. Six Rickettsia species were identified (R. slovaca, R. monacensis, R. massiliae, R. raoultii, R. sibirica subsp. mongolitimonae and R. aeschielmanii); Candidatus Rickettsia rioja and two novel Rickettsia species also were detected. In addition, Borrelia turdi (1.8%) and B. valaisiana (0.9%) were identified in Ixodes ticks. This is the first report of R. slovaca in R. sanguineus s.l. and of R. monacensis, R. raoultii, R. slovaca, R. sibirica subsp. mongolitimonae and Ca. R. rioja in I. frontalis. Since most of the pathogens detected are zoonotic, their presence in these areas may have implications for public health.
... In tropical and subtropical regions, R. microplus tick infestation is predominant [25]. Based on the cytochrome C oxidase subunit (cox), R. microplus species complex has been grouped into five distinct geographical clusters; clade A includes ticks from Africa, Asia, and South America, clade B includes ticks from southern China and northern India, clade C includes ticks from Pakistan, Myanmar, Malaysia, Bangladesh, and India, and Rhipicephalus australis and Rhipicephalus annulatus [25][26][27][28]. ...
... In tropical and subtropical regions, R. microplus tick infestation is predominant [25]. Based on the cytochrome C oxidase subunit (cox), R. microplus species complex has been grouped into five distinct geographical clusters; clade A includes ticks from Africa, Asia, and South America, clade B includes ticks from southern China and northern India, clade C includes ticks from Pakistan, Myanmar, Malaysia, Bangladesh, and India, and Rhipicephalus australis and Rhipicephalus annulatus [25][26][27][28]. Pakistan is a subtropical country where more than 70% of the rural population is directly or indirectly dependent upon livestock and contribute approximately 60.07% and 11.53% to agriculture and gross domestic product values, respectively [28][29][30]. ...
Rhipicephalus microplus tick highly affects the veterinary sector throughout the world. Different tick control methods have been adopted, and the identification of tick-derived highly immuno-genic sequences for the development of an anti-tick vaccine has emerged as a successful alter-nate. This study aimed to characterize immunogenic sequences from R. microplus ticks prevalent in Pakistan. Ticks collected in the field were morphologically identified and subjected to DNA and RNA extraction. Ticks were molecularly identified based on the partial mitochondrial cyto-chrome C oxidase subunit (cox) sequence and screened for piroplasms (Theileria/Babesia spp.), Rick-ettsia spp., and Anaplasma spp. PCR-based pathogens-free R. microplus-derived cDNA was used for the amplification of full-length cysteine protease inhibitor (cystatin 2b), cathepsin L-like cysteine proteinase (cathepsin-L), glutathione S-transferase (GST), ferritin 1, 60S acidic ribosomal protein (P0), aquaporin 2, ATAQ, and R. microplus 05 antigen (Rm05Uy) coding sequences. The cox se-quence revealed 100% identity with the nucleotide sequences of Pakistan's formerly reported R. microplus, and full-length immunogenic sequences revealed maximum identities to the most similar sequences reported from India, China, Cuba, USA, Brazil, Egypt, Mexico, Israel, and Uruguay. Low nonsynonymous polymorphisms were observed in ATAQ (1.5%), cathepsin-L (0.6%), and aquaporin 2 (0.4%) sequences compared to the homologous sequences from Mexico, India, and the USA, respectively. Based on the cox sequence, R. microplus was phylogenetically assembled in clade C, which includes R. microplus from Pakistan, Myanmar, Malaysia, Thailand, Bangladesh, and India. In the phylogenetic trees, the cystatin 2b, cathepsin-L, ferritin 1, and aq-uaporin 2 sequences were clustered with the most similar available sequences of R. microplus, P0 with R. microplus, R. sanguineus and R. haemaphysaloides, and GST, ATAQ, and Rm05Uy with R. mi-croplus and R. annulatus. This is the first report on the molecular characterization of clade C R. microplus-derived immunogenic sequences.
... Urbanization can impact the abundance and distribution of ticks by altering the availability of suitable hosts or by changing the external environment used by ticks when off-host, where they may spend up to 99% of their lifespan (40). Moreover, for a population of ticks to be maintained at a site over time, suitable hosts for all life stages must be present in an environment that also supports off-host behaviors like questing (40,41). In this study, we found that rodents, and S. muelleri in particular, appear to be suitable hosts for both the larval and nymph stages of all three genera of ticks across the landscape; however, adult ticks were found relatively infrequently, particularly in the urban location. ...
... As in many Southeast Asian cities, green spaces across Kuching are heavily utilized by residents for recreational and other activities and are often considered to be clean, healthy urban environments (45). However, the results of this study suggest that these activities may pose underappreciated public health risks akin to those associated with the transmission of Lyme disease in temperate urban green spaces (23,41). We suggest that effective public health messaging could inform residents of tropical cities about the potential risks posed by ticks in urban green spaces and encourage the use of insect repellants and other preventative measures. ...
Urbanization is rapidly transforming much of Southeast Asia, altering the structure and function of the landscape, as well as the frequency and intensity of the interactions between people, animals, and the environment. In this study, we explored the impact of urbanization on zoonotic disease risk by simultaneously characterizing changes in the ecology of animal reservoirs (rodents), ectoparasite vectors (ticks), and pathogens across a gradient of urbanization in Kuching, a city in Malaysian Borneo. We sampled 863 rodents across rural, developing, and urban locations and found that rodent species diversity decreased with increasing urbanization—from 10 species in the rural location to 4 in the rural location. Notably, two species appeared to thrive in urban areas, as follows: the invasive urban exploiter Rattus rattus ( n = 375) and the native urban adapter Sundamys muelleri ( n = 331). R. rattus was strongly associated with built infrastructure across the gradient and carried a high diversity of pathogens, including multihost zoonoses capable of environmental transmission (e.g., Leptospira spp.). In contrast, S. muelleri was restricted to green patches where it was found at high densities and was strongly associated with the presence of ticks, including the medically important genera Amblyomma , Haemaphysalis , and Ixodes . Our analyses reveal that zoonotic disease risk is elevated and heterogeneously distributed in urban environments and highlight the potential for targeted risk reduction through pest management and public health messaging.
... Vector-borne and zoonotic infections are emerging threats to public health [1]. Tick-borne pathogens (TBP) are maintained at the interface between tick vectors and a large variety of vertebrate hosts permitting ticks to feed and complete their life cycles [2]. Transmission to humans occur by tick-bites on specific occasions, and understanding and quantifying this transmission risk is necessary to control diseases. ...
... The phenology of ticks in the Central Great Plains is likely influenced by an interplay of factors, including temperature, humidity, vegetation type, and host availability [10], given the region's distinctive blend of grasslands, forests, and agricultural landscapes. Different tick species' seasonal prevalence, abundance, and distribution, on these landscapes might offer important clues to their ecological preferences, and likely responses to change in climate conditions [11]. Since ticks are dependent on vertebrate hosts for survival and reproduction, their phenology is also closely linked to the actions and life cycles of their hosts [12]. ...
The states of Kansas and Oklahoma, in the central Great Plains, lie at the western periphery of the geographic distributions of several tick species. As the focus of most research on ticks and tick-borne diseases has been on Lyme disease which commonly occurs in areas to the north and east, the ticks of this region have seen little research attention. Here, we report on the phenology and activity patterns shown by tick species observed at 10 sites across the two states and explore factors associated with abundance of all and life specific individuals of the dominant species. Ticks were collected in 2020–2022 using dragging, flagging and carbon-dioxide trapping techniques, designed to detect questing ticks. The dominant species was A. americanum (24098, 97%) followed by Dermacentor variabilis (370, 2%), D. albipictus (271, 1%), Ixodes scapularis (91, <1%) and A. maculatum (38, <1%). Amblyomma americanum, A. maculatum and D. variabilis were active in Spring and Summer, while D. albipictus and I. scapularis were active in Fall and Winter. Factors associated with numbers of individuals of A. americanum included day of year, habitat, and latitude. Similar associations were observed when abundance was examined by life-stage. Overall, the picture is one of broadly distributed tick species that shows seasonal limitations in the timing of their questing activity.
... In the tropical and subtropical regions, ticks are vectors for multiple pathogens that cause diseases in animals and humans (Balinandi et al. 2020;Estrada-Peña and De La Fuente 2014). With the increasing trade of livestock among African countries Extended author information available on the last page of the article Content courtesy of Springer Nature, terms of use apply. ...
Ticks are important disease vectors affecting animal health and causing substantial economic loss, especially in the tropics and subtropics. To examine the tick burden of cattle and associated risk factors for tick infestation, ticks were collected from 388 cattle within five regions in Ghana. Most of the cattle were males (50.3%) and generally older than 3 years (65%). Of the animals sampled, 2187 ticks were collected with a mean tick burden of 5.6 ticks per cattle, and the average tick burden on the udder/scrotum being significantly higher than in the anal region (Generalized Linear Mix Model [GLMM], p = 0.01197). The tick species identified were predominantly Amblyomma variegatum (42.6%) and Hyalomma rufipes (26.2%). High proportions of cattle examined were found to have A. variegatum infesting the udder/scrotum. Furthermore, H. rufipes infested mostly the anal region compared to other examined body parts (OR 14.8, 95% CI 8.6–25.4, p < 0.001). Using the GLMM, tick abundance was found to be significantly higher in cattle older than 3 years. The tick burden in the udder/scrotum was higher than that from the chest and leg/thigh of the cattle (GLMM, p < 0.05). The tick burden at the anal region was also significantly higher than the leg/thigh and chest. This study indicates that the preferred attachment sites of ticks on cattle are species-dependent and effective treatment with acaricides should take into consideration the udder/scrotum and anal regions as well as prioritizing older cattle.
... Classically, CCHFV has been identi ed in Africa, Asia and Europe in territories located south of the 50th North parallel and in areas inhabited by its main vector [7][8][9] . It is absent only in North America, South America, and Australia. ...
Purpose
Crimean-Congo haemorrhagic fever (CCHF) is a tick-borne disease caused by CCHF virus (CCHFV). CCHF is an emerging infectious disease. Recently, the disease has been described in humans in Spain. Most cases have been described in the central-western area of the Iberian Peninsula. This study aimed to evaluate the seroprevalence of anti-CCHFV antibodies in humans in this endemic area of Spain.
Methods
Study was conducted to estimate the seroprevalence of anti-CCHFV antibodies among patients referred to a hospital located in the central-western area of Spain, an endemic area for CCHFV of Spain. Patients were recruited from April 1, 2023, to June 30, 2023. A commercial ELISA was used to detect anti-CCHFV serum antibodies.
Principal findings
We screened 658 samples from 370 (56.2%) men, with a mean (±SD) age of 58.6 years (± 14.3). Of these, 4 were IgG positive, representing an IgG seropositivity of 0.6% (95% CI, 0.01-1.19). None of these four patients recalled having a clinical picture that strongly suggested CCHF. The incidence of CCHF in the Bejar area was 33.2 cases per 100,000 inhabitants.
Conclusions
Our results suggest active circulation of the virus in humans in western Spain. More extensive clinical and epidemiological studies are needed. Although the risk is considered low, clinicians should be alert to the possibility of new CCHF cases, given the high pathogenicity of CCHFV and the risk of transmission. A detailed medical history of each patient is critical for rapid diagnosis, appropriate adoption of therapeutic measures and timely control of the infection.
... a re-emerging viral disease with increasing epidemic magnitude and spread [12]. Although ticks of the genus Hyalomma are the principal vectors of CCHFV [4], members of the genera Amblyomma and Rhipicephalus have also been implicated as important vectors for this virus [1,29]. ...
Sampled ticks were screened for Crimean-Congo haemorrhagic fever virus (CCHFV) using an assay that targets the nucleoprotein gene region of the S segment, a conserved region of the CCHFV genome. Minimum infection rates of 0.34% and 0.10% were obtained when testing pools of Hyalomma rufipes and Amblyomma variegatum, respectively. Next-generation sequencing and phylogenetic analysis showed that the S and L segments of the CCHFV isolate clustered with those of similar isolates of genotype III. However, analysis of the M segment showed that reassortment had occurred, causing this segment to cluster with those of isolates of genotype I, providing the first evidence of such an occurrence in Ghana.
... Over the past few decades, many tick-borne diseases (TBD) have increased in incidence and geographical range due to the geographic expansion of their tick vectors [2]. This may be related to changes in climate, human activities, animal migration, and agricultural development that affect tick population and ecology [2,[7][8][9]. ...
Background: Tick-borne diseases (TBD) are considered neglected diseases in Thailand with disease burden likely underestimated. To assess risk for emerging TBD in Thailand, the seasonality of questing tick and pathogen prevalence were studied in Khao Yai National Park, a top tourist destination.
Methods: During 2019, questing ticks around tourist attractions were systematically collected bimonthly and analyzed for Rickettsia and Anaplasmataceae bacterial species by polymerase chain reaction and DNA sequencing.
Results: Larvae and nymphs of questing ticks peaked in Khao Yai National Park during the late rainy-winter season, though no specific trends were observed in adult ticks. Winter (November to February) was the highest risk for human tick-bites due to higher numbers of both ticks and visitors. Of the total 5916 ticks analyzed (651 pools), Anaplasma phagocytophilum, Neoehrlichia mikurensis, Ehrlichia ewingii, and Ehrlichia chaffeensis were detected at low rates (≤0.05%). There was a higher prevalence of human rickettsioses (0.2-7%) in ticks surveyed with Rickettsia tamurae, Rickettsia raoultii, and Rickettsia montana the major species. Amblyomma ticks had the highest prevalence of Rickettsia (85%, 35/44 Amblyomma adults), in which only R. tamurae and R. raoultii were found in Amblyomma with mixed species infections common. We report the first detection of R. africae-like and N. mikurensis in Ixodes granulatus adults in Thailand, suggesting I. granulatus as a potential vector for these pathogens.
Conclusion: This study demonstrated the risk of emerging TBD in Thailand and underscores the need for tick-bite prevention among tourists in Thailand.
... Reservoir hosts of TBEV are small rodents (genera Myodes and Apodemus), and TBEV can be transmitted from infected ticks to vertebrate hosts during feeding [11]. Horizontal transmission by co-feeding can also transmit the virus, but the role of accidental hosts, such as large vertebrates and humans, in virus transmission between ticks is considered insignificant [12,13]. Humans can be infected with TBEV through tick bites or ingesting unpasteurized raw milk and dairy products from infected animals [14,15]. ...
Ticks are important vectors of the tick-borne encephalitis virus (TBEV). In Kyrgyzstan, the livestock farming trade and nomadic lifestyle enable tick-borne diseases to be imported from neighboring countries, but there are few relevant studies. In this study, we collected 40 ticks from cattle in Kyrgyzstan. Molecular marker analysis identified the ticks as Ixodes persulcatus (97.5%; n = 39) and Haemaphysalis punctata (2.5%; n = 1). Real-time PCR screening revealed two ticks to be positive for TBEV, but only one tick was amplified using nested PCR targeting the TBEV envelope (E) and non-structure 5 (NS5) gene. The obtained sequences belonged to the TBEV Siberian subtype and phylogenetic tree analysis results confirmed that the virus was related to the Bosnia strain. We also performed next-generation sequencing, which confirmed the TBEV Siberian subtype. Continuous research and surveillance of TBEV in Kyrgyzstan are required to provide further information on tick-borne diseases.
... Complex interactions between humans, environmental conditions, and biological factors make the management of these diseases challenging [8]. Also, these factors infuence the tick burden on hosts [9], thus afecting the efcacy of tick control [10,11]. With the level of tick infestation in animals serving as a focal point for controlling tick-borne diseases [7], it is essential to determine the animal hosts that are mostly infested [12] and their preferred resting sites on livestock. ...
The ability of ticks to adapt to different ecological zones, coupled with the spread of infectious pathogens negatively affects livestock production and thus, there is a need for better control strategies. However, control measures within a geographical region can only be effective if there is available information on tick population dynamics and ecology. This study focused on ticks infesting livestock in the Kassena-Nankana Districts of the Upper East Region of Ghana. The ticks were morphologically identified, variables such as season, animal host, and predilection sites were recorded, and the data were analyzed using STATA version 13. Out of 448 livestock examined, tick infestation in cattle was (78.60%), followed by sheep (25%) and goats (5.88%). A total of 1,550 ticks including nymphs (303) and adults (1,247) were collected. Adult ticks were found to be significantly associated with season (), with a high burden in the wet season. The nymph burden and body parts of livestock hosts were significantly associated with more nymphs collected from male animals than females (p < 0.001). Three genera of ticks, Amblyomma (62.97%), Hyalomma (18.71%), and Rhipicephalus (18.32%) were morphologically identified with the most predominant tick species recorded as Amblyomma variegatum (62.97%). Matured A. variegatum was sampled primarily in the wet season with their predilection site as the udder/scrotum (p < 0.001). However, adult Hyalomma truncatum was observed to have a significant association with the anal region (p < 0.001). Findings from this study are essential for formulating tick control measures to prevent the spread of infectious pathogens.
... In this study, we used a novel improved methodology and allowed different modeling settings to construct the habitat suitability model for H. marginatum based on calibration and evaluation of our models using several updated variables that previously were not used. Although our continental-scale predictions provide valuable insights into the distribution of H. marginatum, it is crucial to investigate the species' interactions with microclimate and the influence of host availability on its response to prevailing climatic conditions [85]. ...
Crimean-Congo haemorrhagic fever (CCHF) is the most widely distributed tick-borne viral disease in humans and is caused by the Crimean-Congo haemorrhagic fever virus (CCHFV). The virus has a broader distribution, expanding from western China and South Asia to the Middle East, southeast Europe, and Africa. The historical known distribution of the CCHFV vector Hyalomma marginatum in Europe includes most of the Mediterranean and the Balkan countries, Ukraine, and southern Russia. Further expansion of its potential distribution may have occurred in and out of the Mediterranean region. This study updated the distributional map of the principal vector of CCHFV, H . marginatum , in the Old World using an ecological niche modeling approach based on occurrence records from the Global Biodiversity Information Facility (GBIF) and a set of covariates. The model predicted higher suitability of H . marginatum occurrences in diverse regions of Africa and Asia. Furthermore, the model estimated the environmental suitability of H . marginatum across Europe. On a continental scale, the model anticipated a widespread potential distribution encompassing the southern, western, central, and eastern parts of Europe, reaching as far north as the southern regions of Scandinavian countries. The distribution of H . marginatum also covered countries across Central Europe where the species is not autochthonous. All models were statistically robust and performed better than random expectations (p < 0.001). Based on the model results, climatic conditions could hamper the successful overwintering of H . marginatum and their survival as adults in many regions of the Old World. Regular updates of the models are still required to continually assess the areas at risk using up-to-date occurrence and climatic data in present-day and future conditions.
... is a tickborne Orthonairovirus that causes a potentially fatal hemorrhagic systemic disease in humans, Crimean-Congo hemorrhagic fever (CCHF). The virus is sustained in the ecosystem through wild and domestic animals, which act as tick amplification hosts and are asymptomatic (1). CCHF has recently increased in Africa and is emerging in new regions (2). ...
Serosurvey results for Crimean-Congo hemorrhagic fever virus antibodies in dromedary camels in Algeria indicate that the pathogen is circulating endemically in desertic areas, despite the hostile environment. Thus, dromedaries are suitable sentinels for detecting human risk for Crimean-Congo hemorrhagic fever in desertic areas
... Ticks are blood-feeding parasites that need one or more hosts to go through their life cycle. They spend a significant portion of their lives away from hosts, and during this time, environmental factors have a significant impact on their population dynamics [45]. The climate is one of the major factors affecting ticks, particularly the microclimate, which directly affects ticks more than the macroclimate. ...
Crimean–Congo hemorrhagic fever (CCHF) typically spreads through ticks and is categorized as a viral hemorrhagic fever. CCHF is a fatal endemic disease in Iraq, and it has been reported sporadically since its first report in 1979. Recent outbreaks during 2021–2023 and their fatal consequences captured the interest of this study. CCHF is a tick-borne disease that represents a major challenge to the public health, social, and economic sectors. The geographical distribution of CCHF is closely linked with Hyalomma vector tick distribution. Therefore, predicting and mapping the spatial distribution of the disease vector in relation to relevant environmental factors provides invaluable information for establishing an early warning system based on which preventive measures can be taken to minimize the spread and, hence, the fatal consequences of CCHF. To achieve this, this study incorporates geospatial techniques and maximum entropy modeling (Maxent) to assess the habitat suitability of the Hyalomma vector and to identify the key environmental drivers contributing to its spatial distribution in Iraq. Utilizing the area under the ROC curve (AUC) as the performance metric, the model evaluation yielded successful results in predicting habitat suitability for Hyalomma vector ticks in Iraq. The AUC attained an average score of 0.885 with a regularization multiplier (β) set at 1. The Hyalomma ticks’ suitable habitat distribution within the study area covers a fraction of the total land, at approximately 51% (225,665 km2) of the entire 441,724 km2 region. Among these suitable areas, 41.57% (183,631 km2) were classified as lowly suitable, 8.61% (38,039 km2) as moderately suitable, and 0.9% (3994 km2) as highly suitable. Several factors have significantly influenced Hyalomma vector tick distribution in Iraq. These include land cover (accounting for 50.8%), elevation (contributing 30.4%), NDVI (5.7%), temperature seasonality (4.7%), precipitation seasonality (3.3%), sheep density (2.3%), goat density (2.2%), and the mean diurnal range (0.5%). The findings of this study could have significant implications for establishing a strategic early warning system and taking preventive measures beforehand to minimize and control Crimean–Congo haemorrhagic fever in Iraq and similar ecoregions in the Middle East. As a primary precaution, this study recommends focusing on highly suitable areas (3994 km2) in the southern part of Iraq for management and preventive actions.
... Even in the absence of viremic hosts, there are other mechanisms that may explain the maintenance of CCHFV foci. Tick co-feeding allows the transmission of the virus present in the saliva of an infected tick to uninfected ticks feeding nearby [38]. This mechanism has been thoroughly explored for tick-borne encephalitis virus [39,40], but its J o u r n a l P r e -p r o o f Journal Pre-proof importance for CCHFV transmission remains to be determined [8]. ...
Identifying the role that host species play in pathogen transmission and maintenance is crucial for disease control, but it is a difficult task, in particular for vector-borne and multi-host pathogens, and especially when wildlife species are involved. This is the case for a Crimean-Congo hemorrhagic fever virus (CCHFV) hotspot in north-eastern Spain, where Iberian ibex (Capra pyrenaica) and wild boar (Sus scrofa) are involved, but their roles in disease transmission are unclear. In this context, we studied the dynamics of CCHFV transmission in these two species during the collapse of an Iberian ibex population due to a sarcoptic mange outbreak. We carried out a repeated cross-sectional study measuring the trends of CCHFV seroprevalence in Iberian ibex and wild boar and their abundances. In addition, we identified the tick species present in this area on the vegetation and on wild boars, and evaluated relevant meteorological factors. Results show that while the trends in CCHFV seroprevalence in Iberian Ibex and density of wild boars remained constant (p = 1.0 and p = 0.8, respectively), both the trends in Iberian ibex census and CCHFV seroprevalence in wild boars decreased significantly (p = 0.003 and p = 0.0001, respectively), and were correlated (Spearman's rank, 0.02 < p-adjusted<0.05). The correlation between the patterns of reduction of Iberian ibex abundance and the decrease of seroprevalence in wild boars suggests some sort of shared transmission cycle between the two species. Data from tick species in the area suggest a possible role of Rhipicephalus bursa in CCHFV transmission. The dynamics of CCHFV were unlikely caused by changes in meteorological variables such as temperature or water vapor pressure deficit. Further studies will be needed to confirm these hypotheses.
... It's hard to think about CCHFV without taking ticks and vertebrate hosts into account. Some species of vectors may have a restricted host range in a given area (such as H. dromedarii for dromedary camels and H. aegyptium for Testudo species tortoises), this is often only the case at the local level (Široký et al., 2007;McCoy et al., 2013;Estrada-Peña and de la Fuente, 2014). ...
Arthropod-borne infections, known as vector-borne diseases, are a significant threat to both humans and animals. These diseases are transmitted to humans and animals through the bites of infected arthropods. In the last half century, there have been a number of unexpected viral outbreaks in Middle Eastern countries. Recently, Iraq has witnessed an outbreak of the Crimean-Congo Hemorrhagic Fever virus with high morbidity and mortality rates in humans. However, very little is known about the prevalence and distribution of CCHFV in Iraq, and therefore, it is impossible to quantify the risk of infection.
CCHFV is transmitted to humans through the bite of infected ticks. However, transmission can also occur through contact with the blood or tissues of infected animals during slaughter or through contact with contaminated objects or surfaces. Accidental crushing of infected ticks can also release the virus and lead to transmission. In addition, healthcare workers and family members caring for infected individuals are at risk of infection through exposure to contaminated body fluids and aerosols.
There are still many unknowns about the role that vertebrates play in the upkeep and spread of CCHFV. Critical information for our comprehension of CCHFV ecology may be gleaned through experimental studies conducted on wild animals and cattle. Therefore, the purpose of this review is to draw attention to current studies and publications that shed light on the intricate dynamic between CCHFV, vector, and host and demonstrate how biosurveillance at each stage aids in our knowledge of disease transmission, risk, and future research prospects.
... A number of tick-borne diseases in humans have increased their incidence and geographic range over the past few decades, and there is concern that they will pose an even greater threat to public health in the future. 1 Various health agencies and institutions are currently working on the design of health promotion strategies that involve educational interventions, primarily aimed at informing communities about the importance of addressing the risk factors associated with tick borne disease (TBD) s in order to promote self-care. [2][3][4] One TBD of epidemiological importance for public health in tropical and subtropical regions, given its re-emergence, is Rickettsiosis, which involves vectors such as fleas, lice and ticks. ...
Background:
It is important to work on designs of health promotion strategies that involve educational interventions about the risk factors associated to TB-rickettsiosis (Tick-Borne rickettsiosis). Children's drawings provide a window into their thoughts and feelings. The aim was to analyze children's risk perceptions regarding by the presence of ticks in a rural community in southeast Mexico.
Methods:
The main framework used was a social cognitive perspective under the Health Belief Model. Study was carried out in rural elementary schools and included a drawing contest. A total of 224 children (8-12 years old) participated. Drawings were coded and classified; descriptive trend analysis was performed using counts and percentages. The qualitative data was analyzed by researcher experts in TB- rickettsiosis and using Atlas ti V.8.
Results:
Results are presented in seven categories that consider environmental elements, actors, and cognitive aspects. The environmental context, 99.1% of the drawings represent sites outside the home (92% include vegetation with the presence of ticks in their immediate external environment). In the actors' category, 69.6% included people carrying out activities (prevention and risk). As for the cognitive aspects, 70% included domestic pets and 13.4% farmyards animals.
Conclusion:
The children expressed their ideas about risk factors and preventive measures against TB-rickettsiosis with a self-care approach. They acquired knowledge about preventive strategies and clinical symptoms. It is necessary to evaluate what happens after an intervention and how they implement in their lives what they have learned.
... Klitgaard et al. [51] reported that the infection rates of Anaplasma, Rickettsia, and Borrelia in adults (52.2%) were 2.7 times higher than those of nymphs (19.1%) collected by flagging in Denmark. Considering the transstadial transmission of various TBPs throughout the life stages of ticks, this is a reasonable result, as adults have one to two times more opportunities to acquire pathogens by means of blood feeding from different hosts infected with pathogens than nymphs [52,53]. ...
Tick-borne pathogens (TBPs), transmitted by the bites of ticks, are of great medical and veterinary importance. They include bacteria, viruses, and protozoan parasites. To provide fundamental data on the risk of tick contact and public health strategies, we aimed to perform a molecular investigation on four tick-borne bacterial pathogens in ticks collected from humans across the Republic of Korea (ROK) in 2021. In total, 117 ticks were collected, including Haemaphysalis longicornis (56.4%), Amblyomma testudinarium (26.5%), Ixodes nipponensis (8.5%), H. flava (5.1%), and I. persulcatus (0.9%). Among the ticks, 20.5% (24/117) contained tick-borne bacterial pathogens, with infection rates of 17.9% for Rickettsia (Candidatus Rickettsia jingxinensis, R. tamurae, R. monacensis, and Candidatus Rickettsia tarasevichiae), 2.5% for Anaplasma (A. phagocytophilum, A. capra, and A. bovis), and 0.9% for Ehrlichia (Ehrlichia sp.). Additionally, the co-detection rate for R. monacensis and A. phagocytophilum was 0.9%. To our knowledge, this is the first report of A. capra and A. bovis detection in ticks collected from humans in the ROK. This study contributes to the understanding of the potential risk of tick contact and provides fundamental data for establishing a public health strategy for tick-borne disease management in the ROK.
... Incidence of TBE has been increasing globally during the last decades 2,4 and since 2012, the European Centre for Disease Prevention and Control (ECDC) has included TBE in the list of notifiable diseases in the European Union 7 . The increase in TBE incidence is likely due to several factors such as changes in climate 8,9 and changes in the availability of tick host species 10,11 , which all impact tick life cycle and thus tick distribution, abundance, and seasonality 11,12 . In Europe, I. ricinus has expanded its geographical range northwards and to higher altitudes 9,11,[13][14][15] , whereas I. persulcatus, previously limited to eastern Europe and northern Asia, has expanded westward to Finland and northern Sweden [16][17][18] . ...
Incidence of tick-borne encephalitis (TBE) has increased during the last years in Scandinavia, but the underlying mechanism is not understood. TBE human case data reported between 2010 and 2021 were aggregated into postal codes within Örebro County, south-central Sweden, along with tick abundance and environmental data to analyse spatial patterns and identify drivers of TBE. We identified a substantial and continuing increase of TBE incidence in Örebro County during the study period. Spatial cluster analyses showed significant hotspots (higher number of cases than expected) in the southern and northern parts of Örebro County, whereas a cold spot (lower number of cases than expected) was found in the central part comprising Örebro municipality. Generalised linear models showed that the risk of acquiring TBE increased by 12.5% and 72.3% for every percent increase in relative humidity and proportion of wetland forest, respectively, whereas the risk decreased by 52.8% for every degree Celsius increase in annual temperature range. However, models had relatively low goodness of fit (R² < 0.27). Results suggest that TBE in Örebro County is spatially clustered, however variables used in this study, i.e., climatic variables, forest cover, water, tick abundance, sheep as indicator species, alone do not explain this pattern.
... De los 4347 reportes, el 64,8 % provenían de hombres y el 35,2 % de mujeres, siendo similares a los ya obtenidos en 2003 (Fernández, 2003) y entre 2014(Vieira et al., 2022. Las picaduras en el grupo de edad +55 se redujeron en 2020, debido a la pandemia y a las posibles medidas de prevención adoptadas por este grupo de edad (Águila-Gordo et al., 2021). ...
Las garrapatas son ectoparásitos hematófagos de gran importancia a nivel mundial debido a su capacidad de transmitir agentes patógenos. En 2020, se produjo una pandemia mundial de SARS-CoV-2 que alteró el comportamiento humano y los ecosistemas de las garrapatas. El objetivo principal del trabajo es el estudio de la distribución de las garrapatas extraídas a personas en Castilla y León durante la pandemia de SARS-CoV-2 y su comparación con el año anterior y posterior. Se recibieron 5010 garrapatas extraídas a personas en los servicios de salud de la comunidad durante 2019, 2020 y 2021. En el laboratorio se procedió a su identificación y recogida de datos epidemiológicos del paciente picado para la posterior elaboración de una base de datos. Se realizó un análisis descriptivo de la comparación entre los periodos prepandemia, pandemia y postpandemia según variables divididas en tres clases: grupos poblacionales, especie de garrapata y distribución geográfica y temporal. De los resultados obtenidos en esta comparación se puede concluir que, mientras algunas variables se mantuvieron estables, la pandemia provocó alteraciones en el número de picaduras reportadas, en su distribución temporal y de especie y en la distribución de las picaduras en algunos grupos poblacionales.
... In some species (e.g., Rhipicephalus (Boophilus) microplus Canestrini or Hyalomma marginatum Koch), feeding placement is facilitated by the emission of aggregation and sexual recognition pheromones (Diehl et al., 1982;Estrada-Peña & de la Fuente, 2014), the reason why congregations of these ticks often appear on hosts. However, there are no descriptions of any pheromone types in H. lusitanicum (Lighton & Fielden, 1995;Ouhelli, 1994;Starkoff, 1958). ...
In the Mediterranean basin, the tick species Hyalomma lusitanicum Koch stands out among other species of the Hyalomma genus due to its wide distribution, and there is great concern about its potential role as a vector and/or reservoir and its continuous expansion to new areas because of climate warming and human and other animal movements. This review aims to consolidate all the information on H. lusitanicum, including taxonomy and evolution, morphological and molecular identification, life cycle, sampling methods, rearing under laboratory conditions, ecology, hosts, geographical distribution, seasonality, vector role and control methods. The availability of adequate data is extremely relevant to the development of appropriate control strategies in areas where this tick is currently distributed as well as in new areas where it could become established in the near future.
... In contrast to WNV and USUV, TBEV is mainly transmitted by hard ticks, and small rodents are the main reservoir [55][56][57]. In Germany, the life cycle of TBEV is maintained by the early developmental stages of castor bean tick (Ixodes ricinus) which pick up the virus from reservoir hosts on so-called natural foci [58]. During the next blood meal as nymphs or adults, these ticks infect birds, larger mammals, and humans [59]. ...
Since 2018, autochthonous West Nile virus (WNV) infections have been regularly reported in eastern–central Germany. While clinically apparent infections in humans and horses are not frequent, seroprevalence studies in horses may allow the tracing of WNV and related flaviviruses transmission, such as tick-borne encephalitis virus (TBEV) and Usutu virus (USUV), and consequently help to estimate the risk of human infections. Hence, the aim of our study was to follow the seropositive ratio against these three viruses in horses in Saxony, Saxony Anhalt, and Brandenburg and to describe their geographic distribution for the year 2021. In early 2022, i.e., before the virus transmission season, sera from 1232 unvaccinated horses were tested using a competitive pan-flavivirus ELISA (cELISA). In order to estimate the true seropositive ratio of infection with WNV, TBEV, and USUV for 2021, positive and equivocal results were confirmed by a virus neutralization test (VNT). In addition, possible risk factors for seropositivity using questionnaires were analyzed using logistic regression based on questionnaires similar to our previous study from 2020. In total, 125 horse sera reacted positive in the cELISA. Based on the VNT, 40 sera showed neutralizing antibodies against WNV, 69 against TBEV, and 5 against USUV. Three sera showed antibodies against more than one virus, and eight were negative based on the VNT. The overall seropositive ratio was 3.3% (95% CI: 2.38–4.40) for WNV, 5.6% (95% CI: 4.44–7.04) for TBEV, and 0.4% (95% CI: 0.14–0.98) for USUV infections. While age and number of horses on the holding were factors predicting TBEV seropositivity, no risk factors were discovered for WNV seropositivity. We conclude that horses are useful sentinels to determine the flavivirus circulation in eastern–central Germany, as long as they are not vaccinated against WNV.
... Ixodes-suvun puutiaiset käyttävät ravintonaan isäntäeläimensä verta, ja ne ovat merkittäviä taudinkantajia toimien vektorina lukuisille taudinaiheuttajille (Hillyard 1996;Parola & Raoult 2001;Dantas-Torres ym. 2012;Estrada-Peña & de la Fuente 2014;Rizzoli ym. 2014;Sormunen ym. ...
Hard ticks (Acari: Ixodidae) and tick-borne diseases are considered as a threat in several parts of Europe. In Finland, both Ixodes ricinus and Ixodes persulcatus have shifted northwards in recent decades, and they have become more abundant at the same time. This is thought to be due to global climate change and its effect directly on ticks or indirectly on their host animals. This review focuses on the factors that affect both tick activity and survival, and the factors that influence the life cycle of ticks. Both presence and availability of host animals and microclimatic conditions are factors that affect tick occurrence in any given area. For example, high temperatures or low humidity force the species to seek shelter from cooler and more humid microhabitats, as ticks are sensitive to desiccation. However, tick distribution is associated with a complex combination of environmental and climatic factors.
... In addition, the unknown health repercussions and lack of control methods for newly emerging TBDs generate human anxiety [6]. The geographic range of zoonotic TBDs is expanding and infection rates could increase in the future [7]. ...
... In addition, the unknown health repercussions and lack of control methods for newly emerging TBDs generate human anxiety [6]. The geographic range of zoonotic TBDs is expanding and infection rates could increase in the future [7]. ...
Ticks are obligatory hematophagous ectoparasites and vectors of many animal and human pathogens. Chemosensation plays a significant role in tick communication with their environment, including seeking out blood meal hosts. Studies on the structure and function of Haller’s organ and its components have improved our understanding regarding tick olfaction and its chemical ecology. Compared with the knowledge on insect olfaction, less is known about the molecular basis of olfaction in ticks. This review focused on the chemosensory-related candidate molecules likely involved in tick olfaction. Members of the ionotropic receptor family and a new class of odorant-binding proteins are now known to be involved in tick olfaction, which appear to differ from that of insects. These candidate molecules are more closely related to those of mites and spiders than to other arthropods. The amino acid sequences of candidate niemann–pick type C2 and microplusin-like proteins in ticks exhibit features indicating their potential role as binding proteins. In the future, more comprehensive pertinent research considering the existing shortcomings will be required to fully understand the molecular basis of tick olfactory chemoreception. This information may contribute to the development of new molecular-based control mechanisms to reduce tick populations and related disease transmission.
... This could result in widespread mixing of viral lineages leading to the emergence of novel variants [15]. The patterns of tick-host-virus interrelationships are changing due to changes in population densities of ticks, hosts, and other environmental factors [22]. An understanding of the epidemiology of tick-borne viral diseases, tick vector competence, and transmission dynamics in tick vectors is important for designing tick management strategies and curtailing the spread of viral infections. ...
Background and Aim: Viruses are important components of the microbiome of ticks. Ticks are capable of transmitting
several serious viral diseases to humans and animals. Hitherto, the composition of viral communities in Hyalomma
dromedarii ticks associated with camels in the United Arab Emirates (UAE) remains unexplored. This study aimed to
characterize the RNA virome diversity in male and female H. dromedarii ticks collected from camels in Al Ain, UAE.
Materials and Methods: We collected ticks, extracted, and sequenced RNA, using Illumina (NovaSeq 6000) and Oxford
Nanopore (MinION).
Results: From the total generated sequencing reads, 180,559 (~0.35%) and 197,801 (~0.34%) reads were identified as
virus-related reads in male and female tick samples, respectively. Taxonomic assignment of the viral sequencing reads
was accomplished based on bioinformatic analyses. Further, viral reads were classified into 39 viral families. Poxiviridae,
Phycodnaviridae, Phenuiviridae, Mimiviridae, and Polydnaviridae were the most abundant families in the tick viromes.
Notably, we assembled the genomes of three RNA viruses, which were placed by phylogenetic analyses in clades that
included the Bole tick virus.
Conclusion: Overall, this study attempts to elucidate the RNA virome of ticks associated with camels in the UAE and the
results obtained from this study improve the knowledge of the diversity of viruses in H. dromedarii ticks.
... Incidence of TBE has been increasing globally during the last decades 2,4 and since 2012, the European Centre for Disease Prevention and Control (ECDC) included TBE in the list of noti able diseases in the European Union 7 . The increase in TBE incidence is likely due to several factors such as changes in climate 8, 9 , as well as changes in the availability of tick host species 10,11 , which all impact tick life cycle and thus tick distribution 11,12 . In Europe, I. ricinus has expanded its geographical range northwards and to higher altitudes 9,11,[13][14][15] . ...
Incidence of tick-borne encephalitis (TBE) has increased during the last years in Scandinavia, but the underlying mechanism is not understood. TBE human case data reported between 2010 and 2021 (N = 81) was aggregated into postal codes within Örebro County, south-central Sweden, along with tick abundance and environmental data to analyse spatial patterns and drivers of TBE. We identified a substantial and continuing increase of human TBE incidence in Örebro County during the study period. Although the spatial pattern varied between years, spatial cluster analyses showed significant hotspots (higher number of cases than expected) in the southern and northern parts of Örebro County, whereas a cold spot (lower number of cases than expected) was found in the central part comprising Örebro municipality. Generalised linear models showed that the risk for residents of acquiring TBE increased by approximately 141% for every percent increase in the proportion of wetland forest, however models had relatively low goodness of fit (R ² < 0.25). Results suggest that incidence of TBE in Örebro County is spatially clustered, however variables used in this study, i.e., forest cover, water, tick abundance, sheep as indicator species, alone do not explain these patterns.
... These shifts may increase the risk of tick bites, leading to subsequent pathogen exposure and disease development in companion animals [1]. Some tick species, such as Ixodes scapularis and Dermacentor variabilis, are vectors of several disease-causing pathogens in humans and animals [2][3][4]. In Canada, serum antibodies to Borrelia burgdorferi, a bacterial spirochete that is transmitted by I. scapularis and causes Lyme disease, have been consistently identified in dogs, particularly in central and eastern provinces [1,[4][5][6]. ...
Due to recent climatic and land use changes, Canada has experienced changes in tick populations, leading to an increased risk of tick bites and tick-borne pathogen exposure, especially in eastern Canada. Preventative recommendations for companion animals from veterinary professionals include regular use of tick prevention products and tick checks. Tick checks, specifically, should target regions of an animal's body which are deemed to be high risk for tick attachment. However, tick species-specific infestation patterns on dogs and cats are largely understudied, and additional research is needed to help guide targeted tick checks. The objective of this study was to identify tick species-specific infestation patterns on dogs and cats. Ticks were collected for one year (April 2019 -March 2020) from 94 veterinary clinics across Canada as part of the Canadian Pet Tick Survey. All ticks were identified to species, and data on the location of tick attachment were ascertained with each submission. To examine the association between location of attachment (outcome) and tick species (explanatory variable), specifically Ixodes scapularis and Dermacentor variabilis, mixed effects univariable models were built. Two thousand three hundred and six submissions were received from 1925 dogs and 381 cats across Canada. Of these submissions, 1377 comprised Ixodes scapularis, and 620 comprised Dermacentor variabilis. Clear tick species-specific infestation patterns for dogs were present, with I. scapularis being significantly more likely to be found on the shoulders, and D. variabilis more likely to be found on the ears and neck. Dermacentor variabilis was more likely to be found on the cranial aspect of cats' limbs, compared to I. scapularis. Up-to-date information on infestation patterns can be used to inform veterinary professionals and pet owners of common attachment sites based on established ticks in their region and thus conduct targeted tick checks.
... In recent years, the epidemiology of CCHFV has changed; climate change has been identified as one of the factors driving the circulation of the virus. CCH-FV has been identified in Africa, Asia, and Europe, in territories located south of the 50th North parallel, the area inhabited by its main vector (6)(7)(8). CCHFV has caused major outbreaks in eastern Europe (9). In turn, CCHF is considered endemic in areas of southwestern Europe. ...
Crimean-Congo hemorrhagic fever (CCHF) is a viral infectious disease for which distribution of the main vector, Hyalomma spp. ticks, is expanding. We analyzed all 10 cases of CCHF diagnosed in Spain during 2013-2021; case-patient median age was 56.5 years, and 7 were men. We identified CCHF virus genotypes III and V. Six case-patients acquired the infection in urban areas. Sixty percent of patients were infected in summer and 40% in spring. Two patients met criteria for hemophagocytic syndrome. Seven patients survived. The epidemiologic pattern of CCHF in Spain is based on occasional cases with an elevated mortality rate. Genotype III and, to a less extent also genotype V, CCHF circulates in humans in a common geographic area in Spain. Those data suggest that the expansion pathways are complex and may change over time. Physicians should remain alert to the possibility of new CCHF cases.
... Tick populations are growing, and tick-borne diseases (TBD) are considered more prevalent, drawing the attention of a broader range of public health professionals 2 . Argasidae, or soft ticks, and Ixodidae, or the hard ticks, are the two primary families 3 . The Ixodidae family is classified into seven genera 4 . ...
... Despite this shortfall, this study was still able to identify broad trends in seasonal differences, which are in line with other published results (Buczek et al., 2014;Hansford et al., 2017;Heylen et al., 2019;Kowalec et al., 2017;Marchant et al., 2017;Oechslin et al., 2017). Although the risk of tick-borne diseases can be estimated using various metrics such as nymph density, pathogen prevalence or the density of infected nymphs (Estrada-Peña and De La Fuente, 2014;Gilbert, 2021;Kilpatrick et al., 2017), the lack of collection of tick-bite data, Lyme borreliosis case data or human usage of urban patches during this study limits these results. Understanding how members of the public move through urban green space, their activities within them, and any subsequent tick bites or Lyme borreliosis cases could enhance current estimates of risk. ...
Understanding the effects of local habitat and wider landscape connectivity factors on tick presence, nymph density and Borrelia species (spp.) prevalence in the tick population is important for identifying the public health risk from Lyme borreliosis. This multi-city study collected data in three southern England cities (Bath, Bristol, and Southampton) during spring, summer, and autumn in 2017. Focusing specifically on urban green space used for recreation which were clearly in urbanised areas, 72 locations were sampled. Additionally, geospatial datasets on urban green space coverage within 250 m and 1 km of sampling points, as well as distance to woodland were incorporated into statistical models. Distance to woodland was negatively associated with tick presence and nymph density, particularly during spring and summer. Furthermore, we observed an interaction effect between habitat and season for tick presence and nymph density, with woodland habitat having greater tick presence and nymph density during spring. Borrelia spp. infected Ixodes ricinus were found in woodland, woodland edge and under canopy habitats in Bath and Southampton. Overall Borrelia spp. prevalence in nymphs was 2.8%, similar to wider UK studies assessing prevalence in Ixodes ricinus in rural areas. Bird-related Borrelia genospecies dominated across sites, suggesting bird reservoir hosts may be important in urban green space settings for feeding and infecting ticks. Whilst overall density of infected nymphs across the three cities was low (0.03 per 100 m²), risk should be further investigated by incorporating data on tick bites acquired in urban settings, and subsequent Lyme borreliosis transmission.
... Among these, the Ixodidae is the most diverse, abundant, and dominant tick family from a One Health significance (Tsatsaris et al., 2016). The prevalence of tick-borne diseases (TBDs) has increased recently because of several biotic and abiotic factors (Estrada-Peña and de la Fuente, 2014Fuente, , 2018Estrada-Peña et al., 2017;Martina et al., 2017). Thus, ticks are among the major contributing factors to lowered production and mortality, and are the basic reason for economic losses in livestock around the globe (Grisi et al., 2014). ...
Autobiographical scientometrics studies of established scientists are rare but may contribute to
guidance for young researchers. This study covered my 40-years career in Life Sciences and Biomedicine by
focusing on bibliometric analysis of scientific publications and other papers and patents. Data included 811
papers published in international journals and book chapters and 6 books edited. Total citations for these
publications are 44923 with author’s 98 H-index and 521 i10-index according to the Google scholar profile.
Correlation was not found between citations and the number of publications per research area, journal H-
index or journal impact factor (IF). Data included 36 patents in the areas of pharmaceutical, transgenesis,
vaccine, formulation, probiotic and diagnostic. Three of these patents resulted in products registered and
commercialized. Students are highlighted as key components of research with 36 Ph.D. thesis supervised and
6 thesis under supervision. Lessons from this study contributing to guidance for young scientists include that
quality of research is the priority together with productivity but considering what, when and where to publish
not only based on journal IF, H-index and quartile (Q).Inter- and multi-disciplinary international
collaborations in research and co-authorship in review and method papers contribute to research quality and
to advance in scientific career. Projects leading to patent applications and products improve scientific and
social impact of research. Additionally, communication of results in social media is important to promote
research and scientific career, and exploration of other areas such as humanities, art and music contributes to
inspiration and imaginative research approaches.
Background
Forest cover has undergone significant changes, which have accelerated over recent decades. Acari vectors such as ticks and chigger mites are intricately linked to forest ecosystems because of the suitable hosts and microclimates they provide. However, the implications of forest cover change and dynamics on acari vectors and their pathogens remain poorly understood. This study aims to investigate the impacts of forest dynamics on the risk of acari-borne diseases worldwide through a comprehensive review of the literature.
Methods
We conducted a scoping review following the PRISMA Method to retrieve citations related to forest dynamics and acari-borne diseases. Eligibility criteria were predefined and relevant data were extracted from selected articles. The analysis employed a descriptive approach and thematic narrative synthesis.
Results
Our review reveals that the influence of forest dynamics on acari-borne diseases and related vectors was predominantly discussed within a Western context, particularly with regard to Ixodes ticks and Lyme disease. Four types of forest dynamics have been identified in the literature: deforestation, fragmentation, conversion and reforestation. However, there was no consensus on the impacts of those dynamics on the vectors and their associated pathogens. Studies have reported conflicting findings including: protective or risk effects, nonlinear relationships, dependent effects influenced by additional factors altering relationships or nonsignificant effects. Those outcomes had been reported across different forest dynamics and various locations. Although, there is limited empirical evidence on tropical contexts as well as for reforestation and conversion dynamics, making it difficult to draw conclusions regarding pathogen and vector trends. Differences in results trends emerge when comparing the entire article sample (n = 111) to empirical studies (n = 73), with literature reviews often overestimating the dilution effect observed in empirical research. Finally, our review identifies a notable absence of studies on scrub typhus disease in the context of forest dynamics.
Conclusions
This scoping review offers a novel and comprehensive overview of global literature on the impacts of forest dynamics on acari vectors and the infectious agents they transmit. It highlights research gaps and the need for future research targeting specific forest dynamics, particularly chigger mite vectors in a tropical context.
The geographic range of tick populations has expanded in Canada due to climate warming and the associated poleward range shifts of their vertebrate hosts. Abiotic factors, such as temperature, precipitation, and snow, are known to directly affect tick abundance. Yet, biotic factors, such as the abundance and diversity of mammal hosts, may also alter tick abundance and consequent tick-borne disease risk. Here, we incorporated host surveillance data with high-resolution environmental data to evaluate the combined impact of abiotic and biotic factors on questing Ixodes scapularis abundance in Ontario and Quebec, Canada. High-resolution abiotic factors were derived from remote sensing satellites and meteorological towers, while biotic factors related to mammal hosts were derived from active surveillance data that we collected in the field. Generalized additive models were used to determine the relative importance of abiotic and biotic factors on questing I. scapularis abundance. Combinations of abiotic and biotic factors were identified as important drivers of abundances of questing I. scapularis. Positive and negative linear relationships were found for questing I. scapularis abundance with monthly mean precipitation and accumulated snow, but no effect was found for the relative abundance of white-footed mice. Positive relationships were also identified between questing I. scapularis abundance with monthly mean precipitation and mammal species richness. Therefore, future studies that assess I. scapularis should incorporate host surveillance data with high-resolution environmental factors to determine the key drivers impacting the abundance and geographic spread of tick populations and tick-borne pathogens.
Disease ecologists commonly use abiotic factors (e.g. temperature and moisture) or measures of biodiversity (e.g. species richness) to predict Lyme disease transmission patterns, but variance in infection probability among individuals within a population is poorly understood. Most studies assume intraspecific consistency, but recent evidence suggests that individual traits, such as animal personality, may drive differences in encounter rates with infected vectors and pathogen transmission probabilities through differential space use and microhabitat selection, leading to intraspecific variation in infection probability. In addition, because vectors and hosts are nonrandomly distributed across a landscape, land-use changes that modify key habitat features—such as forest management practices—may substantially alter associations between individual traits and infection probability. To address these gaps in our knowledge, we used a large-scale capture–mark–recapture study targeting Peromyscus mice in Maine, United States, to test whether personality drives probability of Borrelia burgdorferi infection in hosts within managed forest compartments with different silvicultural treatments. Specifically, we tested effects of individual phenotypic traits (physical and behavioral) and environmental traits (microhabitat and forest type) on infection probability within 2 species: P. leucopus and P. maniculatus. We found evidence that boldness negatively influences infection probability in P. maniculatus, and that body mass positively influences infection probability in both species. We found no effect of mouse density, microhabitat, or forest type in our analyses. These results suggest that personalities vary in their functional contributions to the natural cycle of B. burgdorferi, and that broader integration of behavioral diversity in disease ecology studies may aid in identifying key transmission zones for this rapidly expanding vector-borne zoonosis.
Ixodid ticks are distributed across all countries of the Western Balkans, with a high diversity of species. Many of these species serve as vectors of pathogens of veterinary and medical importance. Given the scattered data from Western Balkan countries, we have conducted a comprehensive review of available literature, including some historical data, with the aim to compile information about all recorded tick species and associated zoonotic pathogens in this region. Based on the collected data, the tick fauna of the Western Balkans encompasses 32 tick species belonging to five genera: Ixodes, Haemaphysalis, Dermacentor, Rhipicephalus and Hyalomma. A range of pathogens responsible for human diseases has also been documented, including viruses, bacteria and parasites. In this review, we emphasize the necessity for integrated surveillance and reporting, urging authorities to foster research by providing financial support. Additionally, international and interdisciplinary collaborations should be encouraged that include the exchange of expertise, experiences and resources. The present collaborative effort can effectively address gaps in our knowledge of ticks and tick-borne diseases.
Graphical Abstract
This study examined ticks infesting ruminants and tick-borne pathogens (TBPs) they are carrying using polymerase chain reaction (PCR) and sequencing analysis. A total of 964 ticks were collected from cattle (n=202), goats (n=63) and sheep (n=16) in 11 districts of Malawi. Stereomicroscope and taxonomical keys were used to morphologically identify the ticks to species level, and PCR by amplifying and sequencing 12S rRNA and cytochrome c oxidase subunit I ( COI ) genes were used to confirm the species. PCR assays with species-specific primers were used to screen TBPs. The identified tick species were Rhipicephalus microplus (30.5%), R. appendiculatus (23.3%), R. decoloratus (13.2%), R. evertsi (9.8%), Hyalomma rufipes (7.5%), Amblyomma variegatum (6.3%), R. sanguineus (3.6%), H. truncatum (2.8%), R. simus (2.0%), R. pravus (0.6%), and R. annulatus (0.4%). Out of the total ticks, 37.0% were infected with at least one TBP, with Theileria parva making the majority (34.7%), followed by Anaplasma marginale (17.4%), Babesia bigemina (14.9%), A. ovis (11.2%), Ehrlichia ruminantium (9.2%) , T. mutans (8.4%), B. bovis (2.2%) and A. bovis (2.0%). The present study reveals critical data on the distribution of tick species infesting ruminants in Malawi and TBPs they are carrying. Moreover, this study has pioneered genetic characterization of ruminant ticks in Malawi and overall data will contribute to formulation of improved ticks and TBPs control approaches.
Ticks are vectors for transmitting tick-borne pathogens (TBPs) in animals and humans. Therefore, tick identification is necessary to understand the distribution of tick species and the pathogens they carry. Unfortunately, data on dog ticks and the TBPs they harbor in Malawi are incomplete. This study aimed to identify dog ticks and the TBPs they transmit in Malawi. One hundred thirty-two ticks were collected from 87 apparently healthy but infested domestic dogs in four districts of Malawi, which were pooled into 128 tick samples. The ticks were morphologically identified under a stereomicroscope using identification keys, and species identification was authenticated by polymerase chain reaction (PCR) through the amplification and sequencing of 12S rRNA and cytochrome c oxidase subunit I (CO1) genes. The tick species identified were Rhipicephalus sanguineus sensu lato (58.3%), Haemaphysalis elliptica (32.6%), and Hyalomma truncatum (9.1%). Screening for TBPs using species-specific PCR assays revealed that 48.4% of the ticks were infected with at least one TBP. The TBP detection rates were 13.3% for Anaplasma platys, 10.2% for Babesia rossi, 8.6% for B. vogeli, 6.3% for Ehrlichia canis, 3.9% for A. phagocytophilum, 3.1% for B. gibsoni, 2.3% for B. canis and 0.8% for Hepatozoon canis. Co-infections of up to three pathogens were observed in 48.4% of the positive samples. This is the first study to identify dog ticks and the TBPs they harbor in Malawi. These findings provide the basis for understanding dog tick distribution and pathogens they carry in Malawi. This study necessitates the examination of ticks from more study locations to have a better picture of tick challenge, and the development of ticks and tick-borne disease control methods in Malawi.
Severe fever with thrombocytopenia syndrome (SFTS) is an emerging infectious disease with increasing incidence and geographic extent. The extent to which global climate change affects the incidence of SFTS disease remains obscure. We use an integrated multi-model, multi-scenario framework to assess the impact of global climate change on SFTS disease in China. The spatial distribution of habitat suitability for the tick Haemaphysalis longicornis was predicted by applying a boosted regression tree model under four alternative climate change scenarios (RCP2.6, RCP4.5, RCP6.0, and RCP8.5) for the periods 2030-2039, 2050-2059, and 2080-2089. We incorporate the SFTS cases in the mainland of China from 2010 to 2019 with environmental variables and the projected distribution of H. longicornis into a generalized additive model to explore the current and future spatiotemporal dynamics of SFTS. Our results demonstrate an expanded geographic distribution of H. longicornis toward Northern and Northwestern China, showing a more pronounced change under the RCP8.5 scenario. In contrast, the environmental suitability of H. longicornis is predicted to be reduced in Central and Eastern China. The SFTS incidence in three time periods (2030-2039, 2050-2059, and 2080-2089) is predicted to be increased as compared to the 2010s in the context of various RCPs. A heterogeneous trend across provinces, however, was observed, when an increased incidence in Liaoning and Shandong provinces, while decreased incidence in Henan province is predicted. Notably, we predict possible outbreaks in Xinjiang and Yunnan in the future, where only sporadic cases have been reported previously. These findings highlight the need for tick control and population awareness of SFTS in endemic regions, and enhanced monitoring in potential risk areas.
Background:
Powassan virus (POWV) is an emerging arthropod-borne flavivirus, transmitted by Ixodes spp ticks, which has been associated with neuroinvasive disease and poor outcomes.
Methods:
A retrospective study was conducted at Mayo Clinic from 2013 to 2022. We included clinical and epidemiological data of probable and confirmed neuroinvasive POWV cases.
Results:
Sixteen patients with neuroinvasive POWV were identified with a median age of 63.2 years and 62.5% were male. Six patients presented with rhombencephalitis, four with isolated meningitis, three with meningoencephalitis, two with meningoencephalomyelitis, and one with opsoclonus myoclonus syndrome. A median time of 18 days was observed between symptom onset and diagnosis. Cerebrospinal fluid analysis showed lymphocytic pleocytosis with elevated protein and normal glucose in the majority of patients. Mortality within 90 days occurred in three cases (18.8%), and residual neurological deficits were seen in eight (72.7%) survivors.
Conclusions:
To our knowledge, this is the largest case series of patients with neuroinvasive POWV infection. We highlight the importance of a high clinical suspicion among patients that live in or travel to high-risk areas during the spring to fall months. Our data show high morbidity and mortality among patients with neuroinvasive disease.
The Crimean-Congo haemorrhagic fever virus (CCHFV) is an arbovirus that is spread by ticks. Transmission with this virus has been documented in the Crimean Peninsula. Currently, the World Health Organization (WHO) has designated “CCHF” as the highest priority disease for public health study and growth. It was transmitted through blood or any other bodily substance. The danger of this virus re-emerging over decades is increasing, as is the risk of it expanding to new areas. Scientists had little knowledge of the CCHF virus-host cell response. Climate has an impact on the outcome of this contagious illness. Treatment for confirmed instances of CCHF includes symptom management as well as general supportive treatment. According to some research, nucleoprotein activity was investigated for innate defence. The Notch signalling pathway was downregulated during CCHF virus infection, suggesting that it, along with virus-host contact, plays a role in the early phases of viral replication. miRNAs are also receiving similar focus. One of the current efforts is the development of a CCHF-specific target product profiles (TPP) as part of WHO’s roadmap. There are no authorized antiviral treatments due to a lack of data; successful study with therapeutic approaches would only be feasible if entire endemic nations collaborated to produce fruitful results.
Crimean-Congo haemorrhagic fever (CCHF) is a re-emerging viral haemorrhagic fever causing outbreaks in Iran in the last 15 years. In this systematic review and meta-analysis, the status of Crimean-Congo haemorrhagic fever virus (CCHFV) in ticks would be evaluated. PubMed, Google Scholar and Web of Science were searched for peer-reviewed original papers published between 2000 and 1 July 2022. We included papers that evaluated the prevalence of CCHFV in individual ticks using reverse transcription polymerase chain reaction (RT-PCR). The pooled prevalence of CCHFV was 6.0% (95% confidence interval [CI]: 4.5-7.9%), with heterogeneity (I2 = 82.706; P < 0.0001). The prevalence of CCHFV was higher related to regions with above sea level of 1001-1500 m (6.4%; 95% CI: 4.3-9.5%), an average temperature of ≤15 °C (8.3%; 95% CI: 5.6-12.0%), latitude of ≥36° (8.1%; 95% CI: 5.2-12.3%), an annual rainfall of 101-300 mm (9.8%; 95% CI: 6.1-15.4%) and humidity of ≥61% (10.2%; 95% CI: 5.1-19.3%). Due to the importance of CCHF, it is better to do new epidemiologic studies on ticks by related organizations and adjacent regions of some provinces in which human cases have been previously reported.
Ticks are important vectors in human and veterinary medicine. This article describes the most important tick-borne zoonotic diseases in animals and humans,
as well as some biological, ecological, and public health aspects to provide the reader a multidisciplinary perspective.
Crimean–Congo Hemorrhagic Fever (CCHF) is one of the most important vector-borne diseases of zoonotic potential that can be acquired following the bite of the Hyalomma species of ticks. It is a highly prevalent disease in Asia and the Middle East. The risk factors of this disease are contact with infected tissue, blood, patient, or livestock in the acute viremic phase, infected tick bites, or the manual removal of ticks. The disease is clinically described as progressive hemorrhages, fever, and pain in musculature. Biochemical tests reveal elevated levels of creatinine phosphokinase, alanine transaminase, aspartate aminotransferase, and lactate dehydrogenase. Clotting time is prolonged in pro-thrombin tests, and pathogenesis is mostly related to the disruption of the epithelium during viral replication and indirectly by secreting cytotoxic molecules. These molecules cause endothelial activation and result in the loss of function. Supportive therapy is given through blood or plasma infusions to treat or manage the patients. According to the most advanced studies, CCHF can be treated by Ribavirin, which is an antiviral drug that shows excellent results in preventing the disease. Health-care staff are more prone to infection. The hemorrhagic phase represents a high risk for accidental exposures. This literature review presents a comprehensive overview of the viral epidemiology, zoonotic perspectives, and significant risk factors of CCHF in various Middle East and Asian countries. Furthermore, the pathophysiology and preventive strategies of CCHF have also been discussed as well as legislation and policies regarding public outreach programs, research, and development aimed at infection prevention and control that are required at a global level.
Climatic and land use changes have contributed to substantial changes in the abundance, distribution, and activity patterns of ticks in Canada, which have led to an increased risk of tick bites and tick-borne pathogen exposure for companion animals. The objectives of this study were to describe current spatial and temporal patterns of Ixodes spp. on companion animals in Canada and explore the association between tick bites and dog and cat demographic factors. Ticks were collected for one year (April 2019 – March 2020) from 94 veterinary clinics. Included with each submission was a short questionnaire containing owner-reported information on travel history, date of removal and suspected location of tick acquisition, and animal-specific demographic factors. Ticks were identified morphologically using a stereomicroscope, standard keys, and through PCR analyses. Mixed effect multivariable logistic regression models were built to explore the association between an Ixodes scapularis bite and animal demographic factors; veterinary clinic was included as a random effect. Approximately 2300 submissions were received from clinics across Canada, totalling 4425 ticks. The most common Ixodes spp. was I. scapularis (n = 2168), followed by Ixodes pacificus (n = 172) and Ixodes cookei (n = 155). Ixodes scapularis were well distributed in regions across central and eastern Canada. Ixodes cookei was found in eastern Canada, with the greatest numbers from Quebec and New Brunswick. Ixodes pacificus submissions were restricted to British Columbia. Across eastern Canada, dogs of the herding, mixed breed (large and small), sporting, working, terrier, and toy breed groups, and spayed cats were all found to have higher odds of acquiring I. scapularis, compared to other tick species. For the dog model, significant interactions were found between predictor variables age and sex. Regional information on tick distribution, seasonality, and risk factors for acquisition contribute to evidence-based veterinary practices for tick and tick-borne disease control in Canada.
This work is intended as a consensus list of valid tick names, following recent revisionary studies, wherein we recognize 896 species of ticks in 3 families. The Nuttalliellidae is monotypic, containing the single entity Nuttalliella namaqua. The Argasidae consists of 193 species, but there is widespread disagreement concerning the genera in this family, and fully 133 argasids will have to be further studied before any consensus can be reached on the issue of genus-level classification. The Ixodidae comprises 702 species in 14 genera: Amblyomma (130 species, of which 17 were formerly included in Aponomma, a genus that is still considered valid by some authors), Anomalohimalaya (3), Bothriocroton (7, all previously included in Aponomma), Cosmiomma (1), Cornupalpatum (1), Compluriscutula (1), Dermacentor (34, including the single member of the former genus Anocentor, which is still considered valid by some authors), Haemaphysalis (166), Hyalomma (27), Ixodes (243), Margaropus (3), Nosomma (2), Rhipicentor (2) and Rhipicephalus (82, including 5 species from the former genus Boophilus, which is still considered valid by some authors). We regard six names as invalid: Amblyomma laticaudae Warburton, 1933 is a synonym of Amblyomma nitidum Hirst & Hirst, 1910; Bothriocroton decorosum (Koch, 1867) is a synonym of B. undatum (Fabricius, 1775); Haemaphysalis vietnamensis Hoogstraal & Wilson, 1966 is a synonym of H. colasbelcouri (Santos Dias, 1958); Haemaphysalis xinjiangensis Teng, 1980 is a synonym of H. danieli Č erný & Hoogstraal, 1977; Hyalomma erythraeum Tonelli-Rondelli, 1932 is a synonym of H. impeltatum Schulze and Schlottke, 1930 and Rhipicephalus hoogstraali Kolonin, 2009 was not described according to the rules of the International Code of Zoological Nomenclature.
Viruses transmitted by tick bites remain a health problem in many parts of the world. Several events that occurred during the final decades of the twentieth century and the beginning of the twenty-first
century suggest a rise of tick-borne viral infections worldwide. These events include recent national and regional epidemics of known diseases such as tick-borne encephalitis (TBE) in Central and Eastern Europe, Kyasanur forest disease (KFD) in Karnataka state in India,
and Crimean–Congo hemorrhagic fever (CCHF) in northern Turkey and the southwestern regions of the Russian Federation. Some of them, like TBE, may be also transmitted by milk intake, while others, like CCHF, may be transmitted to humans at abattoirs. We want to review here some findings relating climate and the behavior in nature of important tick-transmitted viruses, like the etiologic agents of TBE and CCHF. Our specific point in this review is that climate may be probably behind some of the recent (re) emergence of the reported active foci of the disease, driving the dynamics and the abundance patterns of ticks. However, a note of caution is issued about the lack of suitable data on the dynamics of the hosts and about the changes that climate may operate in social habits, which are difficult to quantify. The
effects of climate on tick-transmitted viruses are indirect and difficult to quantify. A simple approach might not be enough to capture the many levels at which climate operates driving these infections. Of course this is not the first time the topic has been reviewed. We will also summarize some findings related to other tick-transmitted viruses as associated with human disease.
The area under the receiver operating characteristic (ROC) curve, known as the AUC, is currently considered to be the standard method to assess the accuracy of predictive distribution models. It avoids the supposed subjectivity in the threshold selection process, when continuous probability derived scores are converted to a binary presence–absence variable, by summarizing overall model performance over all possible thresholds. In this manuscript we review some of the features of this measure and bring into question its reliability as a comparative measure of accuracy between model results. We do not recommend using AUC for five reasons: (1) it ignores the predicted probability values and the goodness-of-fit of the model; (2) it summarises the test performance over regions of the ROC space in which one would rarely operate; (3) it weights omission and commission errors equally; (4) it does not give information about the spatial distribution of model errors; and, most importantly, (5) the total extent to which models are carried out highly influences the rate of well-predicted absences and the AUC scores.
INTRODUCTION Saliva-assisted transmission (SAT) is the indirect promotion of arthropod-borne pathogen transmission via the actions of arthropod saliva molecules on the vertebrate host. This phenomenon has been reported for most blood-feeding arthropods that transmit disease causing agents via their saliva, but the greatest number of examples has been recorded in ticks. The skin site where ticks feed is highly modified by the pharmacologically active molecules secreted in tick saliva. For pathogens, it is an ecologically privileged niche they can exploit. Here we review evidence for SAT and consider candidates for SAT factors among the tick pharmacopoeia of antihaemostatic, anti-inflammatory and immunomodulatory molecules. SAT factors appear to differ for different pathogens and tick vector species, and possibly even depend on the vertebrate host species on which a tick feeds. Most probably, SAT is mediated by a suite of molecules that act together to overcome the redundancy in host response mechanisms. The quest to identify the tick molecules that mediate SAT is an exciting one, offering new insights into host inflammatory and immune mechanisms, and novel ways of controlling ticks and tick-borne diseases. TICK–HOST–PATHOGEN INTERACTIONS The relationships between tick-borne pathogens, their tick vectors and diverse vertebrate hosts, can be represented by a triangle of parasitic interactions (Fig. 10). The interactions are between (i) pathogen–tick, (ii) pathogen–host and (iii) tick–host. In (i) the pathogen interacts with its vector, infecting and replicating within tick cells or extracellular spaces (including those of the gut, haemocoel and salivary glands).
After massive proliferation over the last decade, distribution modelling (DM) – research with the purpose of modelling the distribution of observable objects of a specific type – has grown into an independent branch of ecological science. There is consensus that this new discipline needs a stronger theoretical foundation. I describe DM as an inductive scientific process with 12 steps, organised into three composite steps: ecological model, data model, and statistical model. Step 8, modelling of the overall ecological response, places DM unambiguously among gradient analysis techniques and motivates for a gradient analytic (GA) perspective on DM. DM terminology is reviewed and revised accordingly.
Three fundamental insights of the GA perspective are described: (1) that external ‘factors’ do not influence the species one by one, but act on the species in concert; (2) that a few major complex-gradients normally account for most of the variation in species composition that can be explained environmentally; and (3) that species occur within a restricted interval along each major complex-gradient. These insights are developed into a theoretical platform for DM. General patterns of species performance variation along environmental complex-gradients and the structuring processes responsible for these patterns are reviewed. Three categories of ecoclines, i.e., gradients of variation in species composition and the environment, are recognised: regional ecoclines, local ecoclines, and condition or impact ecoclines. Causes and implications of the unimodal shape of species’ responses to environmental complex-gradients are reviewed. Structuring processes are divided into three categories: limited physiological tolerance, interspecific interactions, and demographic processes. Relationships between categories of ecoclines, the processes responsible for variation in species performance along them, and the spatial and temporal scale intervals in which variation is large, are reviewed.
The GA perspective forms the basis for discussions of important steps in the DM process. Initially, the controversial concepts of the habitat and the niche are reviewed and their role in the ecological model (Step 1) discussed. I conclude that neither of these concepts are necessary, nor useful, for DM. As an alternative to conceptual models based upon the niche concept, I propose a new conceptual modelling framework for DM, the HED framework, which is rooted in the gradient analytic perspective. I show how this new framework can be used, in initial phases of a DM study to formulate a meta-model for factors that influence distributions, and in the analytic phase to guide important choices of methods and options and to assist interpretation of modelling results. Important data model issues are: collection of data for the modelled target and preparation of raw response variables (Steps 2 and 6); collection of explanatory data (Step 3); conceptualisation of the study area (Step 4); collection of data for calibration and evaluation (Step 9); and transformation of explanatory variables to derived variables subjected to DM (Step 5,ii). Important statistical model issues are: statistical model formulation, i.e. choice of method (Step 7,i) and model specification (Step 7,ii); model selection and internal assessment of model performance (Steps 8,i and 8,ii); and model evaluation (Step 10). Two points are emphasised: (1) that modelling purpose should inform choice of methods and options; and (2) the importance of an independently collected presence/absence data set, which can be used to calibrate, evaluate and iteratively improve models.
Finally I list seven challenges of particular importance for progress in DM: (1) that more knowledge of patterns of natural variation is needed; (2) that a better mechanistic understanding of causes of patterns of natural variation is needed; (3) that the availability of relevant rasterised explanatory variables needs to be improved; (4) that more studies of patterns at local and micro spatial scales, in addition to multiple-scale studies using DM methods, are needed; (5) that evaluation by independent data should be established as a standard in DM; (6) that further insights into statistical modelling methods and their options, with particular reference to appropriateness for different types of data and DM purposes, are needed; and (7) that DM methods should be incorporated in studies with a broader scope. I conclude that there are considerable potentials for improvement of DM methods and practice. Increased return from DM in terms of contributions that improve our understanding of patterns of natural variation and their causes, should be expected.
1. Over the past two decades, Ixodes scapularis, the primary tick vector of the Lyme disease pathogen Borrelia burgdorferi in North America has expanded its range northward from the USA to colonize new regions in southern Canada. We have previously projected range increases for I. scapularis based on temperature suitability, but to what extent this is matched by actual tick range expansion is unknown.
2. Since 1990, I. scapularis ticks have been collected across Canada offering a unique opportunity to track the range expansion of an arthropod vector. We used these data to model time-to-establishment for tick populations across Canada to identify factors influencing the rate of spread.
3. Our results point to both long-distance dispersal of ticks by migratory birds and local dispersal by resident hosts as important potential mechanisms underlying patterns of tick range expansion.
4. Temperature (accumulated degree days > 0 °C) was the most important determinant of environmental suitability for tick population establishment, suggesting that climate warming may facilitate range expansion.
5. Model projections suggest that I. scapularis range will expand c. 46 km year−1 in the coming decade, with climate warming expected to increase the rate of spread. This expansion is likely to result in a substantial increase in human Lyme disease risk, with the proportion of the human population of eastern Canada inhabiting areas with established tick populations increasing from 18% in 2010 to over 80% by 2020.
6. This first empirical model of I. scapularis invasion supports theoretical range projections based on climate suitability and provides a unique data-driven estimate of the speed of northward range expansion for I. scapularis at the continental scale.
7. Synthesis and applications. By tracking I. scapularis invasion in Canada over the past two decades, we show that I. scapularis is rapidly expanding its range and is likely to colonize the most densely populated areas of southern Canada in the coming decade. These projections suggest that prompt action is necessary to prepare the Canadian public for a likely epidemic of Lyme disease, with emphasis on focusing surveillance activities to confirm the locations of emerging Lyme disease risk.
Abrupt collapse of the tropical rainforest biome (Coal Forests) drove rapid diversificationof Carboniferous tetrapods (amphibians and reptiles) in Euramerica. This finding is based onanalysis of global and alpha diversity databases in a precise geologic context. From Visean toMoscovian time, both diversity measures steadily increased, but following rainforest collapsein earliest Kasimovian time (ca. 305 Ma), tetrapod extinction rate peaked, alpha diversityimploded, and endemism developed for the first time. Analysis of ecological diversity showsthat rainforest collapse was also accompanied by acquisition of new feeding strategies (preda-tors, herbivores), consistent with tetrapod adaptation to the effects of habitat fragmentationand resource restriction. Effects on amphibians were particularly devastating, while amniotes(‘reptiles’) fared better, being ecologically adapted to the drier conditions that followed. Ourresults demonstrate, for the first time, that Coal Forest fragmentation influenced profoundlythe ecology and evolution of terrestrial fauna in tropical Euramerica, and illustrate the tightcoupling that existed between vegetation, climate, and trophic webs.
Crimean-Congo hemorrhagic fever virus (CCHFV) is one of the most geographically widespread arboviruses and causes a severe hemorrhagic syndrome in humans. The virus circulates in nature in a vertebrate-tick cycle and ticks of the genus Hyalomma are the main vectors and reservoirs. Although the tick vector plays a central role in the maintenance and transmission of CCHFV in nature, comparatively little is known of CCHFV-tick interactions. This is mostly due to the fact that establishing tick colonies is laborious, and working with CCHFV requires a biosafety level 4 laboratory (BSL4) in many countries. Nonetheless, an in vivo transmission model is essential to understand the epidemiology of the transmission cycle of CCHFV. In addition, important parameters such as vectorial capacity of tick species, levels of infection in the host necessary to infect the tick, and aspects of virus transmission by tick bite including the influence of tick saliva, cannot be investigated any other way. Here, we evaluate the influence of different laboratory animal species as hosts supporting the life cycle of Hyalomma marginatum, a two-host tick. Rabbits were considered the host of choice for the maintenance of the uninfected colonies due to high larval attachment rates, shorter larval-nymphal feeding times, higher nymphal molting rates, high egg hatching rates, and higher conversion efficiency index (CEI). Furthermore, we describe the successful establishment of an in vivo transmission model for CCHFV in a BSL4 biocontainment setting using interferon knockout mice. This will give us a new tool to study the transmission and interaction of CCHFV with its tick vector.
Interest in tick-transmitted pathogens has experienced an upsurge in the past few decades. Routine application of tools for the detection of fragments of foreign DNA in ticks, together with a high degree of interest in the quantification of disease risk for humans, has led to a marked increase in the number of reports on the eco-epidemiology of tick-borne diseases. However, procedural errors continue to accumulate in the scientific literature, resulting in misleading information. For example, unreliable identification of ticks and pathogens, erroneous interpretations of short-term field studies, and the hasty acceptance of some tick species as vectors have led to ambiguities regarding the vector role of these arthropods. In this review, we focus on the ecological features driving the life cycle of ticks and the resulting effects on the eco-epidemiology of tick-transmitted pathogens. We review the factors affecting field collections of ticks, and we describe the biologically and ecologically appropriate procedures for describing tick host-seeking activity and its correlation with environmental traits. We detail the climatic variables that have biological importance on ticks and explain how they should be properly measured and analyzed. We also provide evidence to critically reject the use of some environmental traits that are being increasingly reported as the drivers of the behavior of ticks. With the aim of standardization, we propose unambiguous definitions of the status of hosts and ticks regarding their ability to maintain and spread a given pathogen. We also describe laboratory procedures and standards for evaluating the vectorial capacity of a tick or the reservoir role of a host. This approach should provide a coherent framework for the reporting of research findings concerning ticks and tick-borne diseases.
Utilitarian arguments concerning the value of biodiversity often include the benefits of animals, plants, and microbes as sources of medicines and as laboratory models of disease. The concept that species diversity per se may influence risk of exposure to disease has not been well developed, however. We present a conceptual model of how high species richness and evenness in communities of terrestrial vertebrates may reduce risk of exposure to Lyme disease, a spirochetal ( Borrelia burgdorferi) disease transmitted by ixodid tick vectors. Many ticks never become infected because some hosts are highly inefficient at transmitting spirochete infections to feeding ticks. In North America, the most competent reservoir host for the Lyme disease agent is the white-footed mouse ( Peromyscus leucopus), a species that is widespread and locally abundant. We suggest that increases in species diversity within host communities may dilute the power of white-footed mice to infect ticks by causing more ticks to feed on inefficient disease reservoirs. High species diversity therefore is expected to result in lower prevalence of infection in ticks and consequently in lower risk of human exposure to Lyme disease. Analyses of states and multistate regions along the east coast of the United States demonstrated significant negative correlations between species richness of terrestrial small mammals (orders Rodentia, Insectivora, and Lagomorpha), a key group of hosts for ticks, and per capita numbers of reported Lyme disease cases, which supports our “dilution effect” hypothesis. We contrasted these findings to what might be expected when vectors acquire disease agents efficiently from many hosts, in which case infection prevalence of ticks may increase with increasing diversity hosts. A positive correlation between per capita Lyme disease cases and species richness of ground-dwelling birds supported this hypothesis, which we call the “rescue effect.” The reservoir competence of hosts within vertebrate communities and the degree of specialization by ticks on particular hosts will strongly influence the relationship between species diversity and the risk of exposure to the many vector-borne diseases that plague humans.
Resumen: Argumentos utilitarios relacionados con el valor de la biodiversidad frecuentemente incluyen los beneficios de animales, plantas y microbios como recursos para medicinas y como modelos de enfermedades en laboratorio. Sin embargo, la idea de que la diversidad de especies por sí misma puede influenciar el riesgo de exposición a enfermedades no ha sido bien desarrollada. Presentamos un modelo conceptual de cómo la riqueza de especies y la uniformidad en comunidades de vertebrados terrestres puede reducir el riesgo de exposición a la enfermedad de Lyme, una enfermedad causada por una espiroqueta ( Borrelia burgdorferi) y transmitida por una garrapata ixódida. Muchas garrapatas nunca son infectadas debido a que los huéspedes son altamente ineficientes en la transmisión de espiroquetas a las garrapatas que se alimentan de ellos. En Norte América, el huésped reservorio más competente del agente de la enfermedad de Lyme es el ratón de patas blancas ( Peromyscus leucopus), una especie de amplia dispersión y localmente abundante. Sugerimos que los incrementos en la diversidad de especies dentro de las comunidades de huéspedes pueden diluir el potencial de infección de las garrapatas por el ratón de patas blancas al ocasionar que más garrapatas se alimenten de reservorios ineficientes en la transmisión de la enfermedad. Por lo tanto, se esperaría que una alta diversidad de especies resulte en una prevalencia de infección de garrapatas reducida y, por lo tanto, en una disminución del riesgo de exposición de humanos a la enfermedad de Lyme. Un análisis por estado y de varios estados a lo largo de la costa este de los Estados Unidos demostró correlaciones significativamente negativas entre la riqueza de especies de mamíferos terrestres pequeños (órdenes Rodentia, Insectivora, y Lagomorfa), un grupo clave de huéspedes para garrapatas, y los números per capita de casos de la enfermedad de Lyme reportados, lo cual apoya nuestra hipótesis de efecto de dilución. Contrastamos estos resultados con lo que se podría esperar cuando los vectores adquieren eficientemente agentes de la enfermedad de muchos huéspedes, caso en el cual, una alta diversidad causaría la prevalencia de infección de garrapatas permaneciendo alta aún cuando la diversidad de huéspedes disminuyera. Una correlación positiva entre los casos de la enfermedad de Lyme per capita y la riqueza de especies de aves residentes del suelo apoya esta hipótesis, que hemos llamado efecto de rescate. La capacidad de reservorio de huéspedes dentro de las comunidades de vertebrados y el grado de especialización de las garrapatas en huéspedes particulares, influenciaría fuertemente la relación entre la diversidad de especies y el riesgo de exposición a muchas de las enfermedades transmitidas por vectores que infectan a humanos.
This article explores the intersection of theatre performance and the dissemination of health research. A collaboration between health scientists and theatre artists to develop After the Crash, a play about brain injury based on health research knowledge, highlights differing methodological approaches and expectations of the ultimate theatrical outcome. Specifically, this article discusses how performed representation of the body contributes to the dissemination of health research through the lens of After the Crash. This relationship is explored in two ways: first, how embodied performance strays from traditional science-based dissemination methods; and second, the use of abstract movement in the context of a theatrical performance to reflect scientific health-based research. Future directions are also discussed to continue to draw parameters around the formal connection between theatre performance and health research. Résumé Cet article explore l'intersection entre la performance théâtrale et la dissémination de la recherche sur la santé. Une collaboration entre les scientifiques de la santé et les artistes théâtraux pour développer After the Crash (Après l'accident), une pièce sur les lesions cérébrales basée sur la connaissance actuelle en santé, met l'accent sur les différentes approches méthodologiques et les attentes des résultats théâtraux ultimes. En particulier, cet article discute de la façon dont la représentation par le comédien du corps contribue à la dissémination de la recherche sur la santé à travers le prisme de After the Crash. Cette relation est explorée sous deux aspects : d'abord, la façon dont la performance physique s'éloigne des méthodes de dissémination traditionnelle basées sur la science ; et ensuite, l'utilisation du mouvement abstrait dans le contexte d'une performance théâtrale pour refléter la recherche scientifique basée sur la santé. Les directions futures sont également discutées pour continuer à tracer des paramètres autour de la connexion formelle entre la performance théâtrale et la recherche sur la santé. Resumen Este artículo examina la intersección de la actuación teatral y la difusión de la investigación sanitaria. Una cooperación entre científicos sanitarios y artistas teatrales para desarrollar 'After the Crash' (Después del accidente), una obra dramática sobre lesiones cerebrales basada en los conocimientos derivados de la investigación sanitaria, destaca los enfoques metodológicos y expectativas discrepantes del resultado teatral fundamental. En particular, este artículo estudia como la representación interpretada del cuerpo contribuye a la difusión de la investigación sanitaria a través de la lente de 'After the Crash'. Esta relación se estudia de dos formas: primero, como se aparta la actuación corporizada de los métodos de diffusion tradicionales basados en la
Tick-borne encephalitis (TBE) is a virus infection which sometimes causes human disease. The TBE virus is found in ticks and certain vertebrate tick hosts in restricted endemic localities termed TBE foci. The formation of natural foci is a combination of several factors: the vectors, a suitable and numerous enough number of hosts and in a habitat with suitable vegetation and climate. The present study investigated the influence of deer on the incidence of tick-borne encephalitis. We were able to obtain data from deer culls. Using this data, the abundance of deer was estimated and temporal and spatial analysis was performed. The abundance of deer has increased in the past decades, as well as the incidence of tick-borne encephalitis. Temporal analysis confirmed a correlation between red deer abundance and tick-borne encephalitis occurrence. Additionally, spatial analysis established, that in areas with high incidence of tick-borne encephalitis red deer density is higher, compared to areas with no or few human cases of tick-borne encephalitis. However, such correlation could not be confirmed between roe deer density and the incidence of tick-borne encephalitis. This is presumably due to roe deer density being above a certain threshold so that availability of tick reproduction hosts has no apparent effect on ticks' host finding and consequently may not be possible to correlate with incidence of human TBE.
Background
The dominant, cell surface lipophosphoglycan (LPG) of Leishmania is a multifunctional molecule involved in the interaction with vertebrate and invertebrate hosts. Although the role of LPG on infection has been extensively studied, it is not known if LPG interspecies variations contribute to the different immunopathologies of leishmaniases. To investigate the issue of interspecies polymorphisms, two Leishmania species from the New World that express structural variations of side chains of LPG repeat units were examined. In this context, the procyclic form of L. braziliensis LPG (strain M2903), is devoid of side chains, while the L. infantum LPG (strain BH46) has up to three glucoses residues in the repeat units.
Methods
Mice peritoneal macrophages from Balb/c, C57BL/6 and knock-out (TLR2 −/−, TLR4 −/−) were primed with IFN-γ and stimulated with purified LPG from both species. Nitric oxide and cytokine production, MAPKs (ERK, p38 and JNK) and NF-kB activation were evaluated.
Results
Macrophages stimulated with L. braziliensis LPG, had a higher TNF-α, IL-1β, IL-6 and NO production than those stimulated with that of L. infantum. Furthermore, the LPGs from the two species resulted in differential kinetics of signaling via MAPK activation. L. infantum LPG exhibited a gradual activation profile, whereas L. braziliensis LPG showed a sharp but transient activation. L. braziliensis LPG was able to activate NF-kB.
Conclusion
These data suggest that two biochemically distinct LPGs were able to differentially modulate macrophage functions.
No-analog communities (communities that are compositionally unlike any found today) occurred frequently in the past and will develop in the greenhouse world of the future. The well documented no-analog plant communities of late-glacial North America are closely linked to "novel" climates also lacking modern analogs, characterized by high seasonality of temperature. In climate simulations for the Intergovernmental Panel on Climate Change A2 and B1 emission scenarios, novel climates arise by 2100 AD, primarily in tropical and subtropical regions. These future novel climates are wanner than any present climates globally, with spatially variable shifts in precipitation, and increase the risk of species reshuffling into future no-analog communities and other ecological surprises. Most ecological models are at least partially parameterized from modern observations and so may fail to accurately predict ecological responses to these novel climates. There is an urgent need to test the robustness of ecological models to climate conditions outside modern experience.
Hosts species for multi-host pathogens show considerable variation in the species' reservoir competence, which is usually used to measure species' potential to maintain and transmit these pathogens. Although accumulating research has proposed a trade-off between life-history strategies and immune defences, only a few studies extended this to host species' reservoir competence. Using a phylogenetic comparative approach, we studied the relationships between some species' life-history traits and reservoir competence in three emerging infectious vector-borne disease systems, namely Lyme disease, West Nile Encephalitis (WNE) and Eastern Equine Encephalitis (EEE). The results showed that interspecific variation in reservoir competence could be partly explained by the species' life histories. Species with larger body mass (for hosts of Lyme disease and WNE) or smaller clutch size (for hosts of EEE) had a higher reservoir competence. Given that both larger body mass and smaller clutch size were linked to higher extinction risk of local populations, our study suggests that with decreasing biodiversity, species with a higher reservoir competence are more likely to remain in the community, and thereby increase the risk of transmitting these pathogens, which might be a possible mechanism underlying the dilution effect.
Many factors are involved in determining the latitudinal and altitudinal spread of the important tick vector Ixodes ricinus (Acari: Ixodidae) in Europe, as well as in changes in the distribution within its prior endemic zones. This paper builds on published literature and unpublished expert opinion from the VBORNET network with the aim of reviewing the evidence for these changes in Europe and discusses the many climatic, ecological, landscape and anthropogenic drivers. These can be divided into those directly related to climatic change, contributing to an expansion in the tick's geographic range at extremes of altitude in central Europe, and at extremes of latitude in Scandinavia; those related to changes in the distribution of tick hosts, particularly roe deer and other cervids; other ecological changes such as habitat connectivity and changes in land management; and finally, anthropogenically induced changes. These factors are strongly interlinked and often not well quantified. Although a change in climate plays an important role in certain geographic regions, for much of Europe it is non-climatic factors that are becoming increasingly important. How we manage habitats on a landscape scale, and the changes in the distribution and abundance of tick hosts are important considerations during our assessment and management of the public health risks associated with ticks and tick-borne disease issues in 21st century Europe. Better understanding and mapping of the spread of I. ricinus (and changes in its abundance) is, however, essential to assess the risk of the spread of infections transmitted by this vector species. Enhanced tick surveillance with harmonized approaches for comparison of data enabling the follow-up of trends at EU level will improve the messages on risk related to tick-borne diseases to policy makers, other stake holders and to the general public.
Background
Crimean-Congo Haemorrhagic Fever (CCHF) is a zoonotic viral disease transmitted by ixodid tick bites, mainly of Hyalomma spp., or through contact with blood/tissues from infected people or animals. CCHF is endemic in the Balkan area, including Bulgaria, where it causes both sporadic cases and community outbreaks.
Methods
We described trends of CCHF in Bulgaria between 1997 and 2009 and investigated the associations between CCHF incidence and a selection of environmental factors using a zero-inflated modelling approach.
Results
A total of 159 CCHF cases (38 women and 121 men) were identified between 1997 and 2009. The incidence was 0.13 cases per 100,000 population/year with a fatality rate of 26%. An epidemic peak was detected close to the Turkish border in the summer of 2002. Most cases were reported between April and September. Increasing mean temperature, Normalized Difference Vegetation Index (NDVI), savannah-type land coverage or habitat fragmentation increased significantly the incidence of CCHF in the CCHF-affected areas. Similar to that observed in Turkey, we found that areas with warmer temperatures in the autumn prior to the case-reporting year had an increased probability of reporting zero CCHF cases.
Conclusions
We identified environmental correlates of CCHF incidence in Bulgaria that may support the prospective implementation of public health interventions.
Crimean-Congo hemorrhagic fever (CCHF) is an increasing health concern in Turkey since 2002. There were also some recent human cases from the South Marmara region of Turkey; thus, a tick survey was performed, and possible vector tick species for the CCHF virus were determined in the region. A total of 740 adult ticks were collected from infested livestock from five locations: Çanakkale-Biga, Bursa-Orhaneli, Bursa-Keles, Balıkesir and Bilecik. Total of 11 tick species from the genera Hyalomma, Rhipicephalus, Dermacentor, Ixodes and Haemaphysalis were identified. Rhipicephalus ticks were dominant in the region; the most frequently observed tick species was R. turanicus, (53.1 %), and only 15.4 % of the identified ticks were H. marginatum. The occurrence of H. rufipes infestation in the region fort he first time. A total of 73 pools of adult ticks were tested with both an antigen-detecting ELISA and RT real-time PCR (RT rt PCR). The presence of the CCHF virus was demonstrated in 9 (12.3 %) of the tested tick pools. Although seven of the tick pools were positive for the CCHF virus with both of the methods, one pool was positive only with RT rt PCR and the other pool was only positive with the ELISA. Positive results were obtained from ticks collected from cattle, sheep and goats from two locations, Bursa-Orhaneli and Bilecik. The CCHF virus was detected in R. turanicus (n = 3), R. bursa (n = 2), H. marginatum (n = 2) and D. marginatus (n = 2) ticks. The results of this study confirm the presence of the CCHF virus and present preliminary data on the vector tick species in the southern Marmara region of Turkey.
Recent reviews have argued that disease control is among the ecosystem services yielded by biodiversity. Lyme disease (LD) is commonly cited as the best example of the 'diluting' effect of biodiversity on disease transmission, but many studies document the opposite relationship, showing that human LD risk can increase with forestation. Here, we unify these divergent perspectives and find strong evidence for a positive link between biodiversity and LD at broad spatial scales (urban to suburban to rural) and equivocal evidence for a negative link between biodiversity and LD at varying levels of biodiversity within forests. This finding suggests that, across zoonotic disease agents, the biodiversity-disease relationship is scale dependent and complex.
Crimean-Congo haemorrhagic fever (CCHF) is a viral haemorrhagic fever caused by the CCHF virus. It is mainly trans-mitted to humans and animals by ticks. In recent y, large numbers of livestock have been transported across the border areas of Ardabil Province resulting in an outbreak of CCHF in the adjacent districts. A comprehensive study was carried out to assess the epidemiological aspects of the disease in this province. In the study area, 130 ticks were collected from randomly selected villages and classified into 9 species of hard tick and 2 species of soft tick. All ticks were analyzed for the presence of CCHF virus genome using gel-based and real-time reverse transcriptase polymerase chain reactions (RT-PCR). The results showed CCHF infection in almost 28% of ticks collectively. Also, of 56 livestock sera, around 39% were IgG-positive. The presence of anti-CCHF virus IgG antibodies and the CCHF virus genome in ticks points to a great hidden threat of an outbreak in these districts. Those in high-risk professions in this province should be informed and trained on the risk of CCHF with urgency.
Tick-borne encephalitis (TBE) is endemic to Europe and medically highly significant. This study, focused on Poland, investigated individual risk factors for TBE symptomatic infection.
In a nation-wide population-based case-control study, of the 351 TBE cases reported to local health departments in Poland in 2009, 178 were included in the analysis. For controls, of 2704 subjects (matched to cases by age, sex, district of residence) selected at random from the national population register, two were interviewed for each case and a total of 327 were suitable for the analysis. Questionnaires yielded information on potential exposure to ticks during the six weeks (maximum incubation period) preceding disease onset in each case. Independent associations between disease and socio-economic factors and occupational or recreational exposure were assessed by conditional logistic regression, stratified according to residence in known endemic and non-endemic areas. Adjusted population attributable fractions (PAF) were computed for significant variables. In endemic areas, highest TBE risk was associated with spending ≥10 hours/week in mixed forests and harvesting forest foods (adjusted odds ratio 19.19 [95% CI: 1.72-214.32]; PAF 0.127 [0.064-0.193]), being unemployed (11.51 [2.84-46.59]; 0.109 [0.046-0.174]), or employed as a forester (8.96 [1.58-50.77]; 0.053 [0.011-0.100]) or non-specialized worker (5.39 [2.21-13.16]; 0.202 [0.090-0.282]). Other activities (swimming, camping and travel to non-endemic regions) reduced risk. Outside TBE endemic areas, risk was greater for those who spent ≥10 hours/week on recreation in mixed forests (7.18 [1.90-27.08]; 0.191 [0.065-0.304]) and visited known TBE endemic areas (4.65 [0.59-36.50]; 0.058 [-0.007-0.144]), while travel to other non-endemic areas reduced risk.
These socio-economic factors and associated human activities identified as risk factors for symptomatic TBE in Poland are consistent with results from previous correlational studies across eastern Europe, and allow public health interventions to be targeted at particularly vulnerable sections of the population.
The ecological relationships found to exist between tick vectors and pathogens in their zootic cycle can profoundly influence patterns of transmission and disease for humans and domestic animals. This book examines the ecological parameters affecting the conservation and regulation of tick-borne zoonoses as well as the geographic and seasonal distributions of those infections. Written by an eminent authority on the subject, the book will be sought after by students and researchers in ecology, invertebrate zoology, parasitology, entomology, public health, and epidemiology.
Crimean-Congo hemorrhagic fever (CCHF) is a tick-borne disease associated with severe hemorrhagic manifestations. CCHF has been referred to as the Asian Ebola. However, in fact, the disease is one of the most widely distributed tick-borne diseases in the world, occurring in Africa, Asia, Europe, and the Middle East. This volume covers major aspects of this important disease and the virus which causes it. Chapters are written by leading experts in their fields and detail historical, public health, epidemiological, and clinical aspects of CCHF and the genetics and molecular biology of the virus. Additional chapters focus on disease control, tick vectors and infection among animals, both natural and experimental. This book will be of interest to virologists, microbiologists, medical entomologists, infectious disease physicians, epidemiologists, public health specialists, veterinary scientists, public health policy makers, journalists, and medical educators.
The nymphal and adult life stages of the tick Ixodes pacificus Cooley & Kohls are the primary vectors of the causative agent(s) of Lyme disease in the far-western United States. In contrast to I. pacificus adults, data on the extent of spatial and temporal variation in the density of the nymphal stage have been scarce. Therefore, we compared the density of I. pacificus nymphs from 1997 to 1999 at a small rural community at high risk for Lyme disease (CHR) and the University of California Hopland Research and Extension Center (HREC), Mendocino County, CA, I. pacificus nymphs were collected readily by drag sampling in leaf litter but not from low vegetation. The mean number of questing nymphs per 100 m2 in leaf/fir-needle litter areas from late April to early June differed significantly among years at both the CHR and the HREC. Climatic data from the HREC suggested that yearly nymphal densities in this area may be positively correlated with the amount of rainfall and negatively correlated with maximum temperatures from March to May. Further, nymphal density was two to four times higher at the CHR than the HREC in all 3 yr. Yearly mean nymphal density generally differed two- to four-fold (HREC) and 10- to 20-fold (CHR) among individual sampling areas. Also, two- to three-fold differences in mean nymphal density were frequently observed between continuous litter and litter edges bordering on other habitats within sampling areas at the HREC, and between sampling areas <100 m apart at the CHR. The distributions of nymphs within individual areas were generally aggregated at both the HREC and the CHR, at the 15-m sampling transect scale we used. Environmental factors with some potential to predict the density of I. pacificus nymphs at different spatial scales included climatic conditions, topographic exposure, and presence of habitat edges or logs. However, stepwise multiple regression analysis revealed that only 6.2-18.0% (HREC) or 14.9-27.9% (CHR) of the yearly variation in nymphal densities was explained by the abiotic or biotic traits measured in this study, at the 15-m transect scale. Thus, other abiotic or biotic traits that we did not examine (e.g., local densities of tick hosts) must account for most of the spatial variation in nymphal density.
This work is intended as a consensus list of valid tick names, following recent revisionary studies, wherein we recognize 896 species of ticks in 3 families. The Nuttalliellidae is monotypic, containing the single entity Nuttalliella namaqua. The Argasidae consists of 193 species, but there is widespread disagreement concerning the genera in this family, and fully 133 argasids will have to be further studied before any consensus can be reached on the issue of genus-level classification. The Ixodidae comprises 702 species in 14 genera: Amblyomma (130 species, of which 17 were formerly included in Aponomma, a genus that is still considered valid by some authors), Anomalohimalaya (3), Bothriocroton (7, all previously included in Aponomma), Cosmiomma (1), Cornupalpatum (1), Compluriscutula (1), Dermacentor (34, including the single member of the former genus Anocentor, which is still considered valid by some authors), Haemaphysalis (166), Hyalomma (27), Ixodes (243), Margaropus (3), Nosomma (2), Rhipicentor (2) and Rhipicephalus (82, including 5 species from the former genus Boophilus, which is still considered valid by some authors). We regard six names as invalid: Amblyomma laticaudae Warburton, 1933 is a synonym of Amblyomma nitidum Hirst & Hirst, 1910; Bothriocroton decorosum (Koch, 1867) is a synonym of B. undatum (Fabricius, 1775); Haemaphysalis vietnamensis Hoogstraal & Wilson, 1966 is a synonym of H. colasbelcouri (Santos Dias, 1958); Haemaphysalis xinjiangensis Teng, 1980 is a synonym of H. danieli Cerný & Hoogstraal, 1977; Hyalomma erythraeum Tonelli-Rondelli, 1932 is a synonym of H. impeltatum Schulze and Schlottke, 1930 and Rhipicephalus hoogstraali Kolonin, 2009 was not described according to the rules of the International Code of Zoological Nomenclature.
Modelling the environmental niche and spatial distribution of pathogen-transmitting arthropods involves various quality and methodological concerns related to using climate data to capture the environmental niche. This study tested the potential of MODIS remotely sensed and interpolated gridded covariates to estimate the climate niche of the medically important ticks Ixodes ricinus and Hyalomma marginatum. We also assessed model inflation resulting from spatial autocorrelation (SA) and collinearity (CO) of covariates used as time series of data (monthly values of variables), principal components analysis (PCA), and a discrete Fourier transformation. Performance of the models was measured using area under the curve (AUC), autocorrelation by Moran's I, and collinearity by the variance inflation factor (VIF).
The covariate spatial resolution slightly affected the final AUC. Consistently, models for H. marginatum performed better than models for I. ricinus, likely because of a species-derived rather than covariate effect because the former occupies a more limited niche. Monthly series of interpolated climate always better captured the climate niche of the ticks, but the SA was around 2 times higher and the maximum VIF between covariates around 30 times higher in interpolated than in MODIS-derived covariates. Interpolated or remotely sensed monthly series of covariates always had higher SA and CO than their transformations by PCA or Fourier. Regarding the effects of background point selection on AUC, we found that selection based on a set of rules for the distance to the core distribution and the heterogeneity of the landscape influenced model outcomes. The best selection relied on a random selection of points as close as possible to the target organism area of distribution, but effects are variable according to the species modelled.
Testing for effects of SA and CO is necessary before incorporating these covariates into algorithms building a climate envelope. Results support a higher SA and CO in an interpolated climate dataset than in remotely sensed covariates. Satellite-derived information has fewer drawbacks compared to interpolated climate for modelling tick relationships with environmental niche. Removal of SA and CO by a harmonic regression seems most promising because it retains both biological and statistical meaning.
Aim
When faced with dichotomous events, such as the presence or absence of a species, discrimination capacity (the ability to separate the instances of presence from the instances of absence) is usually the only characteristic that is assessed in the evaluation of the performance of predictive models. Although neglected, calibration or reliability (how well the estimated probability of presence represents the observed proportion of presences) is another aspect of the performance of predictive models that provides important information. In this study, we explore how changes in the distribution of the probability of presence make discrimination capacity a context‐dependent characteristic of models. For the first time, we explain the implications that ignoring the context dependence of discrimination can have in the interpretation of species distribution models.
Innovation
In this paper we corroborate that, under a uniform distribution of the estimated probability of presence, a well‐calibrated model will not attain high discrimination power and the value of the area under the curve will be 0.83. Under non‐uniform distributions of the probability of presence, simulations show that a well‐calibrated model can attain a broad range of discrimination values. These results illustrate that discrimination is a context‐dependent property, i.e. it gives information about the performance of a certain algorithm in a certain data population.
Main conclusions
In species distribution modelling, the discrimination capacity of a model is only meaningful for a certain species in a given geographic area and temporal snapshot. This is because the representativeness of the environmental domain changes with the geographical and temporal context, which unavoidably entails changes in the distribution of the probability of presence. Comparative studies that intend to generalize their results only based on the discrimination capacity of models may not be broadly extrapolated. Assessment of calibration is especially recommended when the models are intended to be transferred in time or space.
The area under the receiver operating characteristic (ROC) curve, known as the AUC, is currently considered to be the standard method to assess the accuracy of predictive distribution models. It avoids the supposed subjectivity in the threshold selection process, when continuous probability derived scores are converted to a binary presence-absence variable, by summarizing overall model performance over all possible thresholds. In this manuscript we review some of the features of this measure and bring into question its reliability as a comparative measure of accuracy between model results. We do not recommend using AUC for five reasons: (1) it ignores the predicted probability values and the goodness-of-fit of the model; (2) it summarises the test performance over regions of the ROC space in which one would rarely operate; (3) it weights omission and commission errors equally; (4) it does not give information about the spatial distribution of model errors; and, most importantly, (5) the total extent to which models are carried out highly influences the rate of well-predicted absences and the AUC scores.
The presence of Crimean-Congo hemorrhagic fever virus (CCHFV) in Iran was first identified in studies of livestock sera and ticks in the 1970s, but the first human infection was not diagnosed until 1999. Since that time, the number of cases of CCHF in Iran has markedly increased. Through January 2012, articles in the published literature have reported a total of 870 confirmed cases, with 126 deaths, for a case fatality rate (CFR) of 17.6%. The disease has been seen in 26 of the country's 31 provinces, with the greatest number of cases in Sistan and Baluchestan, Isfahan, Fars, Tehran, Khorasan, and Khuzestan provinces. The increase in CCHF in Iran has paralleled that in neighboring Turkey, though the number of cases in Turkey has been much larger, with an overall CFR of around 5%. In this article, we review the features of CCHF in Iran, including its history, epidemiology, animal and tick reservoirs, current surveillance and control programs, diagnostic methods, clinical features and experience with ribavirin therapy, and consider possible explanations for the difference in the CFR of CCHF between Iran and Turkey. The emergence of CCHF in Iran calls for countermeasures at many levels to protect the population, but also provides opportunities for studying the epidemiology, diagnosis and management of the disease.
The habitat mosaic was used to quantify connectivity between patches of different tick density of the notorious tick species Ixodes ricinus in an attempt to determine the cause of variations in tick abundance among apparently homogeneous sites in northern Spain. The analysis revealed that patches with high tick abundance are “stepping-stone” territories that, when removed from the landscape, cause large changes in connectivity. Sites with medium tick abundance do not cause such a critical transition in connectivity. Patches with low tick abundance, but optimal abiotic conditions for survival, are located within the minimum cost corridors network joining the patches, while those sites where the tick has been intermittently collected are located at variable distances from this network. Sites where the tick is consistently absent, but where the habitat is predicted to be suitable (old, heterogeneous forests of Quercus spp.) for the tick, are very separated from this main network of connections. These results suggest that tick distribution in a zone is highly affected not only by abiotic variables (vegetation and weather) but also by host movements. Dispersal of the tick is a function of how the hosts perceive the habitat, and the habitat's permeability to host movement. Permanent tick populations seem to be supported by the existence of these critical, high density patches, located at significant places within the habitat network.
A stage-structured Leslie matrix model of a partial, discrete population of Ixodes ricinus (Linnaeus) (Ixodida: Ixodidae) ticks was developed to elucidate the impact of climate trends on the distribution and phenology of this species in the western Palaearctic. The model calculates development and mortality rates for each instar and evaluates recruitment rates based on the development of the tick population. The model captures the changes in development and mortality rates, providing a coherent index of performance correlated with the tick's geographic range. Maximum development rates are recorded for latitudes south of 36 °N and are spatially correlated with sites of maximum temperature, highest saturation deficit and highest mortality. The maximum available developmental time (the total annual time during which temperature allows development) for I. ricinus in the western Palaearctic is < 45% of the total year. North of 60 °N, available developmental time decreases sharply to only 15% of the year. The latitudinal boundary at which survival rates sharply drop is 43-46 °N, clearly delimiting the classically recognized extent of the main tick populations. The pattern of activity for larval-nymphal synchrony shows a clear west-east pattern. The model demonstrates the impact of climate according to tick stage and geographic location, and provides a practical framework for testing how the tick's lifecycle is affected by climate change.
Abstract Babesiosis is an emerging arthropod-borne infection that has been increasing in incidence for the last decade in the northeastern United States. Babesiosis may share features of its landscape epidemiology with other arthropod-borne infections transmitted by the same tick vectors in similar geographic spaces. This study examined 11 years of surveillance data in New York State to measure the relationship between forest fragmentation and the incidence of human babesiosis. Adjusted Poisson models showed that increasing edges of contact between forested land and developed land, as measured by their shared perimeters, was associated with a higher incidence of babesiosis cases (incident rate ratio [IRR]=1.015, 95% confidence interval [CI] 1.01-1.02; p<0.001), even after controlling for the total developed land area and forest density, and temperature and precipitation. Each 10-km increase in perimeter contact between forested land and developed land per county was associated with a 1.5% increase in babesiosis risk. Higher temperature was also strongly associated with increasing babesiosis risk (IRR=1.18, 95% CI 1.10-1.27; p<0.001), wherein each degree Celsius increase was associated with an 18% increase in babesiosis risk. While direct causal conclusions cannot be drawn from these data, these findings do identify a potentially important signal in the epidemiology of babesiosis and suggest that the underlying physical landscape may play a role in shaping points of contact between humans and tick vectors and the subsequent transmission of Babesia microti.
This book contains 12 chapters. The first chapter outlines the historical and clinical aspects of Lyme borreliosis including descriptions of the disease in humans and domestic animals, and of diagnosis and treatment. The second chapter deals with ecological methods and terminology and chapters 3-5 describe the biology of the spirochaetes and their behaviour in vectors and vertebrates. The next 4 chapters (6-9) concern the ecology of Borrelia burgdorferi in Europe, Russia, South East Asia and North America, and the last 3 chapters (10-12) deal with the application of the biological and ecological attributes of the pathogens to disease epidemiology, vaccine development and ecological management of Lyme borreliosis.
The nymphal and adult life stages of the tick Ixodes pacificus Cooley & Kohls are the primary vectors of the causative agent(s) of Lyme disease in the far-western United States. In contrast to I. pacificus adults, data on the extent of spatial and temporal variation in the density of the nymphal stage have been scarce. Therefore, we compared the density of I. pacificus nymphs from 1997 to 1999 at a small rural community at high risk for Lyme disease (CHR) and the University of California Hopland Research and Extension Center (HREC), Mendocino County, CA, I. pacificus nymphs were collected readily by drag sampling in leaf litter but not from low vegetation. The mean number of questing nymphs per 100 m2 in leaf/fir-needle litter areas from late April to early June differed significantly among years at both the CHR and the HREC. Climatic data from the HREC suggested that yearly nymphal densities in this area may be positively correlated with the amount of rainfall and negatively correlated with maximum temperatures from March to May. Further, nymphal density was two to four times higher at the CHR than the HREC in all 3 yr. Yearly mean nymphal density generally differed two- to four-fold (HREC) and 10- to 20-fold (CHR) among individual sampling areas. Also, two- to three-fold differences in mean nymphal density were frequently observed between continuous litter and litter edges bordering on other habitats within sampling areas at the HREC, and between sampling areas <100 m apart at the CHR. The distributions of nymphs within individual areas were generally aggregated at both the HREC and the CHR, at the 15-m sampling transect scale we used. Environmental factors with some potential to predict the density of I. pacificus nymphs at different spatial scales included climatic conditions, topographic exposure, and presence of habitat edges or logs. However, stepwise multiple regression analysis revealed that only 6.2–18.0% (HREC) or 14.9–27.9% (CHR) of the yearly variation in nymphal densities was explained by the abiotic or biotic traits measured in this study, at the 15-m transect scale. Thus, other abiotic or biotic traits that we did not examine (e.g., local densities of tick hosts) must account for most of the spatial variation in nymphal density.
Aims:
To produce a spatial risk map regarding spread of Crimean-Congo haemorrhagic fever virus (CCHFV) in the western Palearctic by linking a process-driven model of the main tick vector, Hyalomma marginatum, to a Next Generation Matrix.
Methods and results:
Process-driven model was composed of deterministic equations that simulate developmental and mortality rates of different tick stages by using temperature and atmospheric water vapour data. The model used climate data at 10-day intervals at a spatial resolution of 10 min over western Palearctic. The model estimated the basic reproduction number, R0, for CCHFV transmission by H. marginatum ticks and evaluated how changes in temperature and biological parameters may alter the geographical range of CCHFV. In particular, variation in the rate of transovarial transmission of CCHFV in the tick produced the greatest change in CCHFV circulation in the tick population. Parameters affecting the rates of tick bite, non-systemic transmission and efficiency of tick-to-tick transmission had little effect on R0. Temperature changes that affect tick development, survival and activity rates increased the suitable area for CCHFV transmission at higher latitudes in the western Palearctic.
Conclusions:
Non-systemic transmission had little impact on virus transmission under all scenarios. In the area studied, increase of temperature has no impact on the routes of transmission of CCHFV. However, climate conditions favouring tick survival, which increase infected adult tick populations, together with large numbers of hosts for adults were predicted as the most likely scenario for the spread of the virus in the studied area.
Significance and impact of the study:
The proposed framework is able to capture the dynamics and the relative contribution of the different routes (hosts, ticks) in the transmission and spread of an important pathogen affecting human health. The high contribution of the transovarial transmission route makes the process highly dependent upon suitable hosts for adult ticks, like large domestic and wild ungulates. Climate seems to have a very reduced effect on such spread.
The major surface protein (MSP) 1a of the ehrlichial cattle pathogen Anaplasma marginale, encoded by the single-copy gene msp1α, has been shown to have a neutralization-sensitive epitope and to be an adhesin for bovine erythrocytes and tick cells. msp1α has been found to be a stable genetic marker for the identification of geographic isolates of A. marginale throughout development in acutely and persistently infected cattle and in ticks. The molecular weight of MSP1a varies among geographic isolates of A. marginale because of a varying number of tandemly repeated peptides of 28–29 amino acids. Variation in the sequence of the tandem repeats occurs within and among isolates, and may have resulted from evolutionary pressures exerted by ligand–receptor and host–parasite interactions. These repeated sequences include markers for tick transmissibility that may be important in the identification of ehrlichial pathogens because they may influence control strategies and the design of subunit vaccines.