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Flyingfoxes (Pteropus spp.) face several conservation threats in Southeast Asia. They are considered to be the main reservoir of the Nipah virus (NiV), which has caused more than 500 human cases since its emergence in Malaysia and Bangladesh. Though NiV circulation has been documented in flying foxes in Cambodia and Thai¬land, little is known in Southeast Asia about the risk of transmission of NiV to domestic animals and Humans. To better assess the risk of emergence of NiV in Cambodia while taking into account the conservation threats to flying foxes, we implemented a multidisciplinary study involving researchers (in ecology,epidemiology, virology, genetics, anthropology and modelling),conservationists and local and national authorities. We monitored the population dynamics and the diet of a colony of Lyle's flying fox(Pteropus lylei) as well as the circulation of NiV in the urine of these bats. We investigated the perception of the bats by local communities and their practices regarding bats (such as hunting, collecting guano, harvesting fruits, harvesting and drinking palm juice). We studied the bat / human interface by deploying GPS collars on 14 bats. Our results showed seasonal patterns in both population dynamics and virus circulation, allowing us to identi¬fy a period when local communities' practices may put them at a higher risk of infection. The telemetry study revealed areas with increased potential contacts between humans and bats. Interviews showed limited conflicts between bats and humans and the absence of perceived risk by local communities. An integrative model is being developed and participatory approaches are being used to transfer knowledge about the risk of emergence and ecosystem services associated with the flying foxes, in order to advocate the use of prevention measures conciliating public health and conservation. (Texte intégral)

The impact on human and horse health of West Nile fever (WNF) recently and dramatically increased in Europe and neighboring countries. Involving several mosquito and wild bird species, WNF epidemiology is complex. Despite the implementation of surveillance systems in several countries of concern, and due to a lack of knowledge, outbreak occurrence remains unpredictable. Statistical models may help identifying transmission risk factors. When spatialized, they provide tools to identify areas that are suitable for West Nile virus transmission. Mathematical models may be used to improve our understanding of epidemiological process involved, to evaluate the impact of environmental changes or test the efficiency of control measures. We propose a systematic literature review of publications aiming at modeling the processes involved in WNF transmission in the Mediterranean Basin. The relevance of the corresponding models as predictive tools for risk mapping, early warning and for the design of surveillance systems in a changing environment is analyzed.

Rift Valley fever (RVF) is a severe mosquito-borne disease that is caused by a Phlebovirus (Bunyaviridae) and affects domestic ruminants and humans. Recently, its distribution widened, threatening Europe. The probability of the introduction and large-scale spread of Rift Valley fever virus (RVFV) in Europe is low, but localized RVF outbreaks may occur in areas where populations of ruminants and potential vectors are present. In this study, we assumed the introduction of the virus into Italy and focused on the risk of vector-borne transmission of RVFV to three main European potential hosts (cattle, sheep and goats). Five main potential mosquito vectors belonging to the Culex and Aedes genera that are present in Italy were identified in a literature review. We first modelled the geographical distribution of these five species based on expert knowledge and using land cover as a proxy of mosquito presence. The mosquito distribution maps were compared with field mosquito collections from Italy to validate the model. Next, the risk of RVFV transmission was modelled using a multicriteria evaluation (MCE) approach, integrating expert knowledge and the results of a literature review on host sensitivity and vector competence, feeding behaviour and abundance. A sensitivity analysis was performed to assess the robustness of the results with respect to expert choices. The resulting maps include (i) five maps of the vector distribution, (ii) a map of suitable areas for vector-borne transmission of RVFV and (iii) a map of the risk of RVFV vector-borne transmission to sensitive hosts given a viral introduction. Good agreement was found between the modelled presence probability and the observed presence or absence of each vector species. The resulting RVF risk map highlighted strong spatial heterogeneity and could be used to target surveillance. In conclusion, the geographical information system (GIS)-based MCE served as a valuable framework and a flexible tool for mapping the areas at risk of a pathogen that is currently absent from a region.

The Highly Pathogenic Avian Influenza H5N1 (HPAI) virus is now considered endemic in several Asian countries. In Cambodia, the virus has been circulating in the poultry population since 2004, with a dramatic effect on farmers’ livelihoods and public health. In Thailand, surveillance and control are still important to prevent any new H5N1 incursion. Risk mapping can contribute effectively to disease surveillance and control systems, but is a very challenging task in the absence of reliable disease data. In this work, we used spatial multicriteria decision analysis (MCDA) to produce risk maps for HPAI H5N1 in poultry. We aimed to i) evaluate the performance of the MCDA approach to predict areas suitable for H5N1 based on a dataset from Thailand, comparing the predictive capacities of two sources of a priori knowledge (literature and experts), and ii) apply the best method to produce a risk map for H5N1 in poultry in Cambodia. Our results showed that the expert-based model had a very high predictive capacity in Thailand (AUC = 0.97). Applied in Cambodia, MCDA mapping made it possible to identify hotspots suitable for HPAI H5N1 in the Tonlé Sap watershed, around the cities of Battambang and Kampong Cham, and along the Vietnamese border.

Background Rift Valley fever (RVF) is a vector-borne disease affecting ruminants and humans. Madagascar was heavily affected by RVF in 2008–2009, with evidence of a large and heterogeneous spread of the disease. The identification of at-risk environments is essential to optimize the available resources by targeting RVF surveillance in Madagascar. Herein, the objectives of our study were: (i) to identify the environmental factors and areas favorable to RVF transmission to both cattle and human and (ii) to identify human behaviors favoring human infections in Malagasy contexts. Methodology/Principal Findings First, we characterized the environments of Malagasy communes using a Multiple Factor Analysis (MFA). Then, we analyzed cattle and human serological data collected at national level using Generalized Linear Mixed Models, with the individual serological status (cattle or human) as the response, and MFA factors, as well as other potential risk factors (cattle density, human behavior) as explanatory variables. Cattle and human seroprevalence rates were positively associated to humid environments (p, Author Summary Rift Valley fever virus (RVFV) is a pathogen that causes a vector-borne tropical disease. The disease affects ruminants and humans and severely impacts the health and economy of affected countries. Madagascar was heavily affected by Rift Valley fever (RVF) in 2008–2009, with evidence of a large and heterogeneous spread of the disease. Our study aims at identifying environmental and human-related risk factors for RVFV transmission. First, we characterized Malagasy environments according to their putative influence on RVFV mosquito density and population dynamics. Then we statistically analyzed cattle and human serological data collected at a national level with the individual serological status as response, and Malagasy environments previously characterized by climatic and landscape variables as well as other potential risk factors as explanatory variables. Our results identified humid environments of the western, north-western and eastern parts of the island as risky areas. The identification of at-risk environments is essential to focus veterinary surveillance and control of RVFV.

West Nile disease, caused by the West Nile virus (WNV), is a mosquito-borne zoonotic disease affecting humans and horses that involves wild birds as amplifying hosts. The mechanisms of WNV transmission remain unclear in Europe where the occurrence of outbreaks has dramatically increased in recent years. We used a dataset on the competence, distribution, abundance, diversity and dispersal of wild bird hosts and mosquito vectors to test alternative hypotheses concerning the transmission of WNV in Southern France. We modelled the successive processes of introduction, amplification, dispersal and spillover of WNV to incidental hosts based on host–vector contact rates on various land cover types and over four seasons. We evaluated the relative importance of the mechanisms tested using two independent serological datasets of WNV antibodies collected in wild birds and horses. We found that the same transmission processes (seasonal virus introduction by migratory birds, Culex modestus mosquitoes as amplifying vectors, heterogeneity in avian host competence, absence of ‘dilution effect’) best explain the spatial variations in WNV seroprevalence in the two serological datasets. Our results provide new insights on the pathways of WNV introduction, amplification and spillover and the contribution of bird and mosquito species to WNV transmission in Southern France. Electronic supplementary material The online version of this article (doi:10.1007/s10393-017-1249-6) contains supplementary material, which is available to authorized users.

Background West Nile virus (WNV) is transmitted by mosquitoes in both urban as well as in rural environments and can be pathogenic in birds, horses and humans. Extrinsic factors such as temperature and land use are determinants of WNV outbreaks in Europe, along with intrinsic factors of the vector and virus. Methods With a multivariate model for WNV transmission we computed the probability of WNV infection in 2014, with July 2014 temperature anomalies. We applied the July temperature anomalies under the balanced A1B climate change scenario (mix of all energy sources, fossil and non-fossil) for 2025 and 2050 to model and project the risk of WNV infection in the future. Since asymptomatic infections are common in humans (which can result in the contamination of the donated blood) we estimated the predictive prevalence of WNV infections in the blood donor population. Results External validation of the probability model with 2014 cases indicated good prediction, based on an Area Under Curve (AUC) of 0.871 (SD = 0.032), on the Receiver Operating Characteristic Curve (ROC). The climate change projections for 2025 reveal a higher probability of WNV infection particularly at the edges of the current transmission areas (for example in Eastern Croatia, Northeastern and Northwestern Turkey) and an even further expansion in 2050. The prevalence of infection in (blood donor) populations in the outbreak-affected districts is expected to expand in the future. Conclusions Predictive modelling of environmental and climatic drivers of WNV can be a valuable tool for public health practice. It can help delineate districts at risk for future transmission. These areas can be subjected to integrated disease and vector surveillance, outreach to the public and health care providers, implementation of personal protective measures, screening of blood donors, and vector abatement activities. Electronic supplementary material The online version of this article (doi:10.1186/s12940-016-0105-4) contains supplementary material, which is available to authorized users.

Detail of the ordinary differential equation system. (PDF 139 kb)

Mapping flooding extent method. Figure in Additional file 2. Maps of Modified Normalized Difference Water Index (MNDWI) derived from MODIS imagery at different dates corresponding to the study period. (PDF 3185 kb)

Rift Valley fever (RVF), a mosquito-borne disease affecting ruminants and humans, is one of the most important viral zoonoses in Africa. The objective of the present study was to develop a geographic knowledge-based method to map the areas suitable for RVF amplification and RVF spread in four East African countries, namely, Kenya, Tanzania, Uganda and Ethiopia, and to assess the predictive accuracy of the model using livestock outbreak data from Kenya and Tanzania. Risk factors and their relative importance regarding RVF amplification and spread were identified from a literature review. A numerical weight was calculated for each risk factor using an analytical hierarchy process. The corresponding geographic data were collected, standardized and combined based on a weighted linear combination to produce maps of the suitability for RVF transmission. The accuracy of the resulting maps was assessed using RVF outbreak locations in livestock reported in Kenya and Tanzania between 1998 and 2012 and the ROC curve analysis. Our results confirmed the capacity of the geographic information system-based multi-criteria evaluation method to synthesize available scientific knowledge and to accurately map (AUC = 0.786; 95% CI [0.730–0.842]) the spatial heterogeneity of RVF suitability in East Africa. This approach provides users with a straightforward and easy update of the maps according to data availability or the further development of scientific knowledge., Author Summary Rift Valley fever (RVF) is a zoonotic disease affecting ruminants and humans. It occurs mostly in Africa, causing human deaths and important economic losses in the livestock sector. The RVF virus (RVFV) is transmitted from ruminant to ruminant by mosquitoes. Different climatic, environmental, and socio-economic factors may impact the transmission of the virus. Our work uses all current available knowledge on the epidemiology of the disease and geographic data to map areas suitable for RVFV. The study area includes four East African countries: Kenya, Tanzania, Uganda, three countries which have been historically affected by RVF, and Ethiopia, where the disease has never been reported but which shares borders with infected countries. The resulting maps are compared with the locations of outbreaks reported in livestock. Our results demonstrate the capacity of the spatial multi-criteria evaluation method to map with accuracy the areas suitable for RVF occurrence. Thus, the method we developed provides users with risk maps that could be used for early warning detection and implementation of control measures.

International audience; Infectious diseases are caused by a pathogenic microorganism (virus, bacterium, parasite or fungus) and have a significant impact on public and animal health. In public health, they are one of the leading causes of death and are priorities in the poorest countries. In animal health, they can be devastating and radical measures are taken to prevent them from spreading. Infectious diseases therefore have major economic consequences, in terms of both healthcare and livestock production losses. In recent decades, we have seen the emergence of a significant number of infectious diseases, such as chikungunya, avian influenza and Ebola. These diseases have spread around the world all the more dramatically due to the rapid movement of populations and goods. The majority of pathogenic agents responsible for these emergences are zoonotic (transmitted from animals to humans or vice versa). There has also been a significant increase in vector-borne diseases – that is diseases whose pathogenic agent is transmitted through the intermediary of a vector. Vectors are arthropods (e.g. mosquitoes, fleas, sand flies and reduviid bugs) and acarids (e.g. ticks). One example is the mosquito Aedes albopictus, more commonly known as the “tiger mosquito”, which is a vector for the chikungunya and dengue viruses. The geographical distribution of this mosquito is increasing year by year. This species was responsible for the first indigenous cases of chikungunya in France in 2010.

(Published: 17 February 2016) Citation: Infection Ecology and Epidemiology 2016, 6: 30978 - http://dx.doi.org/10.3402/iee.v6.30978

To establish how the conversion of natural habitats for agricultural purposes may impact the distribution of hantaviruses in Southeast Asia, we tested how habitat structure affects hantavirus infection prevalence of common murine rodents that inhabit human-dominated landscapes in this region. For this, we used geo-referenced data of rodents analysed for hantavirus infection and land cover maps produced for the seven study sites in Thailand, Cambodia and Lao PDR where they were collected. Rodents were tested by serological methods that detect several hantaviruses, including pathogenic ones. Rodents with a seropositive status were more likely to be found near to agriculture on steep land, and also in environments with a high proportion of agriculture on steep land. These results suggest that in Southeast Asia, hantaviruses, which are often associated with generalist rodent species with a preference for agricultural land, may benefit from land conversion to agriculture.

SUMMARYLeptospirosis incidence has increased markedly since 1995 in Thailand, with the eastern and northern parts being the most affected regions, particularly during flooding events. Here, we attempt to overview the evolution of human prevalence during the past decade and identify the environmental factors that correlate with the incidence of leptospirosis and the clinical incidence in humans. We used an extensive survey of Leptospira infection in rodents conducted in 2008 and 2009 and the human incidence of the disease from 2003 to 2012 in 168 villages of two districts of Nan province in Northern Thailand. Using an ad-hoc developed land-use cover implemented in a geographical information system we showed that humans and rodents were not infected in the same environment/habitat in the land-use cover. High village prevalence was observed in open habitat near rivers for the whole decade, or in 2008–2009 mostly in rice fields prone to flooding, whereas infected rodents (2008–2009) were observed in patchy habitat with high forest cover, mostly situated on sloping ground areas. We also investigated the potential effects of public health campaigns conducted after the dramatic flood event of 2006. We showed that, before 2006, human incidence in villages was explained by the population size of the village according to the environmental source of infection of this disease, while as a result of the campaigns, human incidence in villages after 2006 appeared independent of their population size. This study confirms the role of the environment and particularly land use, in the transmission of bacteria, emphasized by the effects of the provincial public health campaigns on the epidemiological pattern of incidence, and questions the role of rodents as reservoirs.

Serological analysis (Sampling strategy, laboratory analysis and results). (PDF 71 kb)

Vector-borne diseases are among those most sensitive to climate because the ecology of vectors and the development rate of pathogens within them are highly dependent on environmental conditions. Bluetongue (BT), a recently emerged arboviral disease of ruminants in Europe, is often cited as an illustration of climate's impact on disease emergence, although no study has yet tested this association. Here, we develop a framework to quantitatively evaluate the effects of climate on BT's emergence in Europe by integrating high-resolution climate observations and model simulations within a mechanistic model of BT transmission risk. We demonstrate that a climate-driven model explains, in both space and time, many aspects of BT's recent emergence and spread, including the 2006 BT outbreak in northwest Europe which occurred in the year of highest projected risk since at least 1960. Furthermore, the model provides mechanistic insight into BT's emergence, suggesting that the drivers of emergence across Europe differ between the South and the North. Driven by simulated future climate from an ensemble of 11 regional climate models, the model projects increase in the future risk of BT emergence across most of Europe with uncertainty in rate but not in trend. The framework described here is adaptable and applicable to other diseases, where the link between climate and disease transmission risk can be quantified, permitting the evaluation of scale and uncertainty in climate change's impact on the future of such diseases.

Aliment Pharmacol Ther 2011; 34: 454–461 Summary Background In end-stage renal disease (ESRD) patients, hepatitis C virus (HCV) eradication improves patient and graft survival. Aim To determine optimal use of erythropoietin (EPO) and ribavirin, to compare ribavirin concentrations with those of HCV patients having normal renal function and to evaluate sustained virological response (SVR) in a prospective observatory of ESRD candidates for renal transplantation. Methods Thirty-two naive patients were treated with Peg-IFN-α2a and ribavirin. Two different schedules of ribavirin and EPO administration were used: starting ribavirin at 600 mg per week and adapting EPO when haemoglobin (Hb) fell below 10 g/dL (adaptive strategy) or starting ribavirin at 1000 mg per week while increasing EPO from the start of treatment (preventive strategy). Results Patients treated with the adaptive strategy had lower median Hb levels (9.6 vs. 10.9 g/dL, P = 0.02) and more frequent median Hb levels below 10 g/dL (58 vs. 5%, P = 0.0007) despite lower median ribavirin doses (105 vs. 142 mg/day, P

A case-control study at both village and farm levels was designed to investigate risk factors for highly pathogenic avian influenza H5N1 during the 2007 outbreaks in one province of Northern Vietnam. Data related to human and natural environments, and poultry production systems were collected for 19 case and 38 unmatched control villages and 19 pairs of matched farms. Our results confirmed the role of poultry movements and trading activities. In particular, our models found that higher number of broiler flocks in the village increased the risk (OR=1.49, 95% CI: 1.12-1.96), as well as the village having at least one poultry trader (OR=11.53, 95% CI: 1.34-98.86). To a lesser extent, in one of our two models, we also identified that increased density of ponds and streams, commonly used for waterfowl production, and greater number of duck flocks in the village also increased the risk. The higher percentage of households keeping poultry, as an indicator of households keeping backyard poultry in our study population, was a protective factor (OR=0.95, 95% CI: 0.91-0.98). At the farm level, three risk factors at the 5% level of type I error were identified by univariate analysis: a greater total number of birds (P=0.006), increase in the number of flocks having access to water (P=0.027) and a greater number of broiler flocks in the farm (P=0.049). Effect of vaccination implementation (date and doses) was difficult to investigate because of a poor recording system. Some protective or risk factors with limited effect may not have been identified owing to our limited sample size. Nevertheless, our results provide a better understanding of local transmission mechanisms of HPAI H5N1 in one province of the Red River Delta region in Vietnam and highlight the need to reduce at-risk trading and production practices.

SUMMARYIn 2005, a serological study was carried out on horses in five ecologically contrasted zones of the Senegal River basin (Senegal) to assess West Nile virus (WNV) transmission and investigate underlying environmental risk factors. In each study zone, horses were randomly selected and blood samples taken. A land-cover map of the five study areas was built using two satellite ETM+ images. Blood samples were screened by ELISA for anti-WNV IgM and IgG and positive samples were confirmed by seroneutralization. Environmental data were analysed using a principal components analysis. The overall IgG seroprevalence rate was 85% (n=367; 95% CI 0·81–0·89). The proximity to sea water, flooded banks and salted mudflats were identified as protective factors. These environmental components are unfavourable to the presence of Culex mosquitoes suggesting that in Senegal, the distribution of the vector species is more limiting for WNV transmission than for the hosts' distribution.

[Departement_IRSTEA]Territoires [TR1_IRSTEA]SYNERGIE; Remote sensing methods for locating and monitoring temporary ponds over large areas in arid lands were tested on a study site in Northern Senegal. Three main results are presented, validated with field data and intended to highlight different spectral, spatial and temporal characteristics of the methods: (1) Among several water indices tested, two Middle Infrared-based indices (MNDWIModified Normalized Difference Water Index and NDWI1Normalized Difference Water Index) are found to be most efficient; (2) an objective method is given prescribing the necessary sensor spatial resolution in terms of minimal detected pond area; and (3) the potential of multi-temporal MODIS imagery for tracking the filling phases of small ponds is illustrated. These results should assist in epidemiological studies of vector-borne diseases that develop around these ponds, but also more generally for land and water management and preservation of threatened ecosystems in arid areas.

Diseases transmitted by insect vectors have a major impact on human and animal health, as well as on the economy of societies. Because of their modes of transmission, these vector-borne diseases-zoonotic or not-are particularly sensitive to climate change. The climate and its variations determine, sometimes substantially, the presence of vectors at a given place, as well as their density and capacity to transmit diseases. The climate also has an influence on the presence and density of animals and humans, in addition to the survival capacities of pathogens in a given environment. All of the components, conditions and processes necessary for the transmission of these diseases form a complex dynamic system whose behaviour, under the influence of the climate and other environmental variables, will determine whether or not transmission will occur. Experimental and epidemiological studies are carried out in laboratory and field conditions to gain greater insight into the underlying biological processes and measure the impact of climate parameters on these processes. Mathematical modelling is used to represent these systems and simulate their behaviour under different environmental conditions. This major tool sheds light on the biological phenomena involved in the transmission of given pathogens, while also simulating, over a more or less long time scale, spatiotemporal variations in the intensity of this transmission so as to be able to tailor control strategies against these diseases.

International audience; This review aims to synthesise knowledge regarding the taxonomy of South-east Asian murine rodents and the challenges associated with the identification of habitat preferences and associated rodent-borne diseases. Recent studies concerning the Rattini tribe have identified unclear species boundaries that would benefit from further investigation. The development of barcoding may allow more accurate identification of rodents, specifically for complex species. However, knowledge on the distribution and habitat specialisations of many common murine rodents is still scarce, particularly regarding the specific habitat preferences of most synanthropic rodent species (Rattus tanezumi or Rattus exulans). Several studies have analysed the prevalence of major rodent-borne diseases in South-east Asia and it appears that the greatest risk of rodent zoonoses are in the lowland rain-fed and irrigated landscapes, generally in and around rice fields.

International audience; An accurate understanding and prediction of mosquito population dynamics are needed to identify areas where there is a high risk of mosquito-borne disease spread and persistence. Simulation tools are relevant for supporting decision-makers in the surveillance of vector populations, as models of vector population dynamics provide predictions of the greatest risk periods for vector abundance, which can be particularly helpful in areas with a highly variable environment. We present a generic weather-driven model of mosquito population dynamics, which was applied to one species of each of the genera Anopheles, Culex, and Aedes, located in the same area and thus affected by similar weather conditions. The predicted population dynamics of Anopheles hyrcanus, Culex pipiens, and Aedes caspius were not similar. An. hyrcanus was abundant in late summer. Cx. pipiens was less abundant but throughout the summer. The abundance of both species showed a single large peak with few variations between years. The population dynamics of Ae. caspius showed large intra- and inter-annual variations due to pulsed egg hatching. Predictions of the model were compared to longitudinal data on host-seeking adult females. Data were previously obtained using CDC-light traps baited with carbon dioxide dry ice in 2005 at two sites (Marais du Viguerat and Tour Carbonnière) in a favourable temperate wetland of southern France (Camargue). The observed and predicted periods of maximal abundance for An. hyrcanus and Cx. pipiens tallied very well. Pearson's coefficients for these two species were over 75% for both species. The model also reproduced the major trends in the intra-annual fluctuations of Ae. caspius population dynamics, with peaks occurring in early summer and following the autumn rainfall events. Few individuals of this species were trapped so the comparison of predicted and observed dynamics was not relevant. A global sensitivity analysis of the species-specific models enabled us to identify the parameters most influencing the maximal abundance of mosquitoes. These key parameters were almost similar between species, but not with the same contributions. The emergence of adult mosquitoes was identified as a key process in the population dynamics of all of the three species considered here. Parameters associated with adult emergence therefore need to be precisely known to achieve accurate predictions. Our model is a flexible and efficient tool that predicts mosquito abundance based on local environmental factors. It is useful to and already used by a mosquito surveillance manager in France.

International audience; While the effects of deforestation and habitat fragmentation on parasite prevalence or richness are well investigated, host–parasite networks are still understudied despite their importance in understanding the mechanisms of these major disturbances. Because fragmentation may negatively impact species occupancy, abundance and co‐occurrence, we predict a link between spatiotemporal changes in habitat and the architecture of host–parasite networks. For this, we used an extensive data set on 16 rodent species and 29 helminth species from seven localities of South‐East Asia. We analysed the effects of rapid deforestation on connectance and modularity of helminth–parasite networks. We estimated both the degree of fragmentation and the rate of deforestation through the development of land uses and their changes through the last 20 to 30 years in order to take into account the dynamics of habitat fragmentation in our statistical analyses. We found that rapid fragmentation does not affect helminth species richness per se but impacts host–parasite interactions as the rodent–helminth network becomes less connected and more modular. Our results suggest that parasite sharing among host species may become more difficult to maintain with the increase of habitat disturbance.

A model for the spatial and temporal dynamics of dengue fever is proposed in this article. The vector population dynamics is derived from a diffusion equation that is based on environmental parameters at the scale of a remote-sensing image. Vectors and hosts populations are then classically divided into compartments corresponding to their respective disease status. The transmission processes between hosts and vectors are described by a set of differential equations. The link between the vector population diffusion model and the compartmental model enables one to describe both the spatial and temporal dynamics of the disease. Simulations in artificial and actual landscapes show the advantage of using remotely sensed and complementary meteorological data for modelling in a realistic way the geographic spread of a vector-borne disease such as dengue fever.

A model for the spatial and temporal dynamics of dengue fever is proposed in this article. The vector population dynamics is derived from a diffusion equation that is based on environmental parameters at the scale of a remote-sensing image. Vectors and hosts populations are then classically divided into compartments corresponding to their respective disease status. The transmission processes between hosts and vectors are described by a set of differential equations. The link between the vector population diffusion model and the compartmental model enables one to describe both the spatial and temporal dynamics of the disease. Simulations in artificial and actual landscapes show the advantage of using remotely sensed and complementary meteorological data for modelling in a realistic way the geographic spread of a vector-borne disease such as dengue fever.

International audience; Reports of atypical human cases of Trypanosoma lewisi or T. lewisi-like and Trypanosoma evansi infections have increased in South-East Asia, urging to investigate the possible links between humans, animal reservoirs and habitats. We tested how habitat structure affects the infection by Trypanosoma species of common murine rodents, inhabiting human-dominated landscapes in South East Asia. For this, we used geo-referenced data of rodents investigated for Trypanosoma infection and land cover maps produced for seven study sites in Thailand, Cambodia and Lao PDR. High prevalence of infection by T. lewisi was observed in rodents living near human settlement and in areas with high cover of built-up habitat, while the infection of rodents by T. evansi was explained by increased landscape patchiness and high cover of rain-fed agriculture lands. These results suggest a likely role of wild rodents as reservoir and possible source of atypical human infection by animal trypanosomes.

Background West Nile virus (WNV) is a mosquito-borne pathogen of global public health importance. Transmission of WNV is determined by abiotic and biotic factors. The objective of this study was to examine environmental variables as predictors of WNV risk in Europe and neighboring countries, considering the anomalies of remotely sensed water and vegetation indices and of temperature at the locations of West Nile fever (WNF) outbreaks reported in humans between 2002 and 2013. Methods The status of infection by WNV in relationship to environmental and climatic risk factors was analyzed at the district level using logistic regression models. Temperature, remotely sensed Normalized Difference Vegetation Index (NDVI) and Modified Normalized Difference Water Index (MNDWI) anomalies, as well as population, birds’ migratory routes, and presence of wetlands were considered as explanatory variables. Results The anomalies of temperature in July, of MNDWI in early June, the presence of wetlands, the location under migratory routes, and the occurrence of a WNF outbreak the previous year were identified as risk factors. The best statistical model according to the Akaike Information Criterion was used to map WNF risk areas in 2012 and 2013. Model validations showed a good level of prediction: area under Receiver Operator Characteristic curve = 0.854 (95% Confidence Interval 0.850-0.856) for internal validation and 0.819 (95% Confidence Interval 0.814-0.823) (2012) and 0.853 (95% Confidence Interval 0.850-0.855) (2013) for external validations, respectively. Conclusions WNF incidence is increasing in Europe and WNV is expanding into new areas where it had never been observed before. Our model can be used to direct surveillance activities and public health interventions for the upcoming WNF season.

International audience; Ghardaia, central Algeria, experienced a major outbreak of cutaneous leishmaniasis (CL) in 2005. Two Leishmania species occur in this region: Leishmania major (MON-25) and Leishmania killicki (MON-301). The two species are transmitted respectively by the sandflies Phlebotomus papatasi and Phlebotomus sergenti and probably involve rodent reservoirs with different ecologies, suggesting distinct epidemiological patterns and distribution areas. The aims of this study were to establish risk maps for each Leishmania species in Ghardaia, taking into account the specificities of their vectors and reservoirs biotopes, using land cover and topographical characteristics derived from remote sensing imagery. Using expert and bibliographic knowledge, habitats of vectors and reservoirs were mapped. Hazard maps, defined as areas of presence of both vectors and reservoirs, were then combined with vulnerability maps, defined as areas with human presence, to map the risk of CL occurrence due to each species. The vector habitat maps and risk maps were validated using available entomological data and epidemiological data. The results showed that remote sensing analysis can be used to map and differentiate risk areas for the two species causing CL and identify palm groves and areas bordering the river crossing the city as areas at risk of CL due to L. major, whereas more limited rocky hills on the outskirts of the city are identified as areas at risk of CL due to L. killicki. In the current context of urban development in Ghardaia, this study provides useful information for the local authorities on the respective risk areas for CL caused by both parasites, in order to take prevention and control measures to prevent future CL outbreaks.

International audience; We modelled the ecoclimatic niche of Culicoides imicola, a major arthropod vector of midge-borne viral pathogens affecting ruminants and equids, at fine scale and on a global extent, so as to provide insight into current and future risks of disease epizootics, and increase current knowledge of the species' ecology. Based on the known distribution and ecology of C. imicola, the species' response to monthly climatic conditions was characterised using CLIMEX with 109 spatial resolution climatic datasets. The species' climatic niche was projected worldwide and under future climatic scenarios. The validated model highlights the role of irrigation in supporting the occurrence of C. imicola in arid regions. In Europe, the modelled potential distribution of C. imicola extended further West than its reported distribution, raising questions regarding ongoing process of colonization and non-climatic habitat factors. The CLIMEX model highlighted similar ecological niches for C. imicola and the Australasian C. brevitarsis raising questions on biogeography and biosecurity. Under the climate change scenarios considered, its' modelled potential distribution could expand northward in the Northern hemisphere, whereas in Africa its range may contract in the future. The biosecurity risks from bluetongue and African horse sickness viruses need to be re-evaluated in regions where the vector's niche is suitable. Under a warmer climate, the risk of vector-borne epizootic pathogens such as bluetongue and African horse sickness viruses are likely to increase as the climate suitability for C.imicola shifts poleward, especially in Western Europe.

Rift valley fever (RVF) is an arboviral disease produced by a bunyavirus belonging to the genus Phlebovirus. Several species of Aedes and Culex are the vectors of this virus that affects sheep, goats, buffalos, cattle, camels and human beings. The human disease is well known, especially during periods of intense epizootic activity. The initial description of the disease dates back to 1930, when animals and human outbreaks appeared on a farm in Lake Naivasha, in the Great Rift Valley of Kenya. Until 2000, this disease was only described in Africa, and then outbreaks were also declared in the Kingdom of Saudi Arabia (2000-2001 and 2004) and in Yemen (2000-2001). Animal and human cases were recorded. This work presents a retrospective summary of the data collected on animal RVF cases during this epidemic in Yemen. Results from several RVF surveys were gathered from the Yemeni vet services and FAO experts. Geographical data (topographic maps and data freely available on internet) were used for the location of outbreaks. After cleaning and standardization of location names, all the data were introduced into a GIS database. The spatial distribution of outbreaks was then studied at two scales: at the national level and at a local scale in the particular area of Wadi Mawr in the Tihama plain, Western coast of Yemen.

Background: Predicting habitats prone to favor disease transmission is challenging due to confounding information on habitats, reservoirs, and diseases. Comparative analysis, which aims at investigating ecological and evolutionary patterns among species, is a tool that may help. The emergence of zoonotic pathogens is a major health concern and is closely linked to habitat modifications by human activities. Risk assessment requires a better knowledge of the interactions between hosts, parasites, and the landscape.Methods: We used information from a field spatial study that investigated the distribution of murid rodents, in various habitats of three countries in Southeast Asia, in combination with their status of infection by 10 taxa of microparasites obtained from the literature. Microparasite species richness was calculated by rodent species on 20,272 rodents of 13 species. Regression tree models and generalized linear models were used to explain microparasite diversity by the average distance between the trapping site and five categories of land cover: forest, steep agriculture land, flat agriculture land, water, and built-up surfaces. Another variable taken into account was the slope. Results: We found that microparasite diversity was positively associated with flat agriculture land, in this context mainly rice fields, and negatively associated with slope. Microparasite diversity decreased sharply a 100 m or less from flat agriculture land.Conclusion: We conclude that there is high microparasite circulation in rodents of flooded farmlands, meaning possibly a higher risk of disease for human inhabitants. Keywords: rodent-borne diseases; landscape; transmission ecology; comparative analysis(Published: 8 April 2013)Citation: Infection Ecology and Epidemiology 2013, 3: 20178 - http://dx.doi.org/10.3402/iee.v3i0.20178

International audience; The mosquito Aedes (Stegomyia) albopictus (Skuse) (Diptera: Culicidae) is an invasive species which has colonized Southern Europe in the last two decades. As it is a competent vector for several arboviruses, its spread is of increasing public health concern, and there is a need for appropriate monitoring tools. In this paper, we have developed a modelling approach to predict mosquito abundance over time, and identify the main determinants of mosquito population dynamics. The model is temperature-and rainfall-driven, takes into account egg diapause during unfavourable periods, and was used to model the population dynamics of Ae. albopictus in the French Riviera since 2008. Entomological collections of egg stage from six locations in Nice conurbation were used for model validation. We performed a sensitivity analysis to identify the key parameters of the mosquito population dynamics. Results showed that the model correctly predicted entomological field data (Pearson r correlation coefficient values range from 0.73 to 0.93). The model's main control points were related to adult's mortality rates, the carrying capacity in pupae of the environment, and the beginning of the unfavourable period. The proposed model can be efficiently used as a tool to predict Ae. albopictus population dynamics, and to assess the efficiency of different control strategies.

The ability of livestock to breed, grow, and lactate to their maximal genetic potential, and their capacity to maintain health is affected by climatic features. Climate affects animals both indirectly and directly. Indirect effects include those that climate exerts on grassland and crops, and on water availability. Additionally, climate may also affect survival of pathogens and/or their vectors, which may cause risks for health in animal and human populations. Analysis of meteorological and entomological data indicate that climate has favored invasion of Culicoides imicola into new regions of the Mediterranean basin where it was previously absent. The meteorological complex has not been studied precisely to determine the optimal combination for normal physiological functions and behavioral actions, health, welfare, and maximal performance of livestock. An index for measurements of environmental warmth and its direct effects in livestock is the Temperature Humidity Index (THI). The THI combines values of temperature and humidity and has been widely used as a bioclimatic indicator of thermal stress in livestock. Studies carried out within the CIRCE project permitted to characterize the Mediterranean basin in terms of THI and to establish its strong heterogeneity even if most of the area is at risk of heat stress for farm animals during summer. The same studies also indicated that the area will be also subjected to warming and extreme climate events, which may aggravate the consequences of hot weather in livestock. Comprehensive frameworks need to be developed to identify and target adaptation options that are appropriate for specific contexts.

Introduction: Dynamics of most of vector-borne diseases are strongly linked to global and local environmental changes. Landscape changes are indicators of human activities or natural processes that are likely to modify the ecology of the diseases. Here, a landscape approach developed at a local scale is proposed for extracting mosquito favourable biotopes, and for testing ecological parameters when identifying risk areas of Rift Valley fever (RVF) transmission. The study was carried out around Barkedji village, Ferlo region, Senegal. Methods: In order to test whether pond characteristics may influence the density and the dispersal behaviour of RVF vectors, and thus the spatial variation in RVFV transmission, we used a very high spatial resolution remote sensing image (2.4 m resolution) provided by the Quickbird sensor to produce a detailed land-cover map of the study area. Based on knowledge of vector and disease ecology, seven landscape attributes were defined at the pond level and computed from the land-cover map. Then, the relationships between landscape attributes and RVF serologic incidence rates in small ruminants were analyzed through a beta-binomial regression. Finally, the best statistical model according to the Akaike Information Criterion corrected for small samples (AICC), was used to map areas at risk for RVF. Results: Among the derived landscape variables, the vegetation density index (VDI) computed within a 500 m buffer around ponds was positively correlated with serologic incidence (p

Rift Valley fever (RVF) is a vector-borne disease affecting ruminants and humans. Madagascar was heavily affected by RVF in 2008-2009, with evidence of a large and heterogeneous spread of the disease. The identification of at-risk environments is essential to optimize the available resources by targeting RVF surveillance in Madagascar. Herein, the objectives of our study were: (i) to identify the environmental factors and areas favorable to RVF transmission to both cattle and human and (ii) to identify human behaviors favoring human infections in Malagasy contexts.First, we characterized the environments of Malagasy communes using a Multiple Factor Analysis (MFA). Then, we analyzed cattle and human serological data collected at national level using Generalized Linear Mixed Models, with the individual serological status (cattle or human) as the response, and MFA factors, as well as other potential risk factors (cattle density, human behavior) as explanatory variables. Cattle and human seroprevalence rates were positively associated to humid environments (p0.001). Areas with high cattle density were at risk (p0.01; OR = 2.6). Furthermore, our analysis showed that frequent contact with raw milk contributed to explain human infection (OR = 1.6). Finally, our study highlighted the eastern-coast, western and north-western parts as high-risk areas for RVF transmission in cattle.Our integrated approach analyzing environmental, cattle and human datasets allow us to bring new insight on RVF transmission patterns in Madagascar. The association between cattle seroprevalence, humid environments and high cattle density suggests that concomitant vectorial and direct transmissions are critical to maintain RVF enzootic transmission. Additionally, in the at-risk humid environment of the western, north-western and the eastern-coast areas, suitable to Culex and Anopheles mosquitoes, vectorial transmission probably occurs in both cattle and human. The relative contribution of vectorial or direct transmissions could be further assessed by mathematic modelling.

Biting midges of the genus Culicoides (Diptera: Ceratopogonidae) are small hematophagous dipterans responsible for transmitting major viruses to livestock such as African horse sickness virus in equids, and pizootic haemorrhagic disease and bluetongue viruses (BTV) in ruminants. Between 1998 and 2005, BTV outbreaks occurred into many countries around the Mediterranean basin associated with the northward extension of C. imicola, which colonized new Mediterranean territories in the past decades due to the global increase of temperatures. In August 2006, BTV serotype 8 (BTV-8) was unexpectedly introduced in the Netherlands and was intensively transmitted by autochthonous Palaearctic Culicoides species, leading in 2007 and 2008 to a major sanitary crisis in whole continental Europe with huge economic losses due to animal movement restrictions. This chapter presents a synthesis of the data gathered through the different entomological surveillance networks implemented in France since 2000 when C. imicola was recorded for the first time in France. These networks aimed at first to monitor the spread and establishment of the invasive C. imicola and then from 2006 onwards, to study the diversity and dynamics of autochthonous Culicoides species. The data collected enable to describe for the first time the spread of C. imicola into French mainland, propose an updated list of Culicoides species for France, describe the Culicoides species distribution and seasonal dynamics, and report assays to identify BTV in field-collected Culicoides during outbreaks. (Texte intégral)

International audience; As mosquitoes are vectors of major pathogens worldwide, the control of mosquito populations is one way to fight vector-borne diseases. The objectives of our study were to develop a tool to predict mosquito abundance over time, identify the main determinants of mosquito population dynamics, and assess mosquito control strategies. We developed a generic, mechanistic, climate-driven model of seasonal mosquito population dynamics that can be run over several years because it takes diapause into account. Both aquatic and adult stages are considered, resulting in 10 model compartments: eggs, larvae, and pupae for juveniles; emergent, nulliparous, and parous for adults, the latter two broken down into host-seeking, resting, and ovipositing adults. We then applied the model to Anopheles species of southern France, some of which (nulliparous adults) overwinter. We defined specific transition functions and parameter values for these species and this geographical area based on a literature review. Our model correctly predicted entomological field data. Control points in the model were related to mortality rates of adults, the sex-ratio at emergence, parameters related to development functions and the number of eggs laid by females. Lastly, we used our model to compare the efficiency of mosquito control strategies targeting larvae. We found that a larvicide spraying at regular time intervals acted as a preventive measure against mosquito emergence, and that such a strategy was more efficient than spraying only when the abundance of host-seeking females reached a given threshold. The proposed model can be applied easily to other mosquito species and geographic areas by adapting transition functions and parameter values

Despite considerable effort for surveillance of wild birds for avian influenza viruses (AIVs), empirical investigations of ecological drivers of AIV prevalence in wild birds are still scarce. Here we used a continental-scale dataset, collected in tropical wetlands of 15 African countries, to test the relative roles of a range of ecological factors on patterns of AIV prevalence in wildfowl. Seasonal and geographical variations in prevalence were positively related to the local density of the wildfowl community and to the wintering period of Eurasian migratory birds in Africa. The predominant influence of wildfowl density with no influence of climatic conditions suggests, in contrast to temperate regions, a predominant role for inter-individual transmission rather than transmission via long-lived virus persisting in the environment. Higher prevalences were found in Anas species than in non- Anas species even when we account for differences in their foraging behaviour (primarily dabbling or not) or their geographical origin (Eurasian or Afro-tropical), suggesting the existence of intrinsic differences between wildfowl taxonomic groups in receptivity to infection. Birds were found infected as often in oropharyngeal as in cloacal samples, but rarely for both types of sample concurrently, indicating that both respiratory and digestive tracts may be important for AIV replication.

Background West Nile virus (WNV) is a widespread pathogen maintained in an enzootic cycle between mosquitoes and birds with occasional spill-over into dead-end hosts such as horses and humans. Migratory birds are believed to play an important role in its dissemination from and to the Palaearctic area, as well as its local dispersion between wintering sites. The Djoudj Park, located in Senegal, is a major wintering site for birds migrating from Europe during the study period (Sept. 2008- Jan. 2009). In this work, we studied the seasonal feeding behaviour dynamics of the potential WNV mosquito vectors at the border of the Djoudj Park, using a reference trapping method (CDC light CO2-baited traps) and two host-specific methods (horse- and pigeon-baited traps). Blood meals of engorged females were analysed to determine their origin. Results Results indicated that Culex tritaeniorhynchus and Cx. neavei may play a key role in the WNV transmission dynamics, the latter being the best candidate bridging-vector species between mammals and birds. Moreover, the attractiveness of pigeon- and horse-baited traps for Cx. neavei and Cx. tritaeniorhynchus varied with time. Finally, Cx. tritaeniorhynchus was only active when the night temperature was above 20°C, whereas Cx. neavei was active throughout the observation period. Conclusions Cx. neavei and Cx. tritaeniorhynchus are the main candidate vectors for the transmission of WNV in the area. The changes in host attractiveness might be related to variable densities of the migratory birds during the trapping period. We discuss the importance of these results on the risk of WNV transmission in horses and humans.

Malaria resurgence risk in Morocco depends, among other factors, on environmental changes as well as the introduction of parasite carriers. The aim of this paper is to analyze the receptivity of the Loukkos area, large wetlands in Northern Morocco, to quantify and to map malaria transmission risk in this region using biological and environmental data. This risk was assessed on entomological risk basis and was mapped using environmental markers derived from satellite imagery. Maps showing spatial and temporal variations of entomological risk for Plasmodium vivax and P. falciparum were produced. Results showed this risk to be highly seasonal and much higher in rice fields than in swamps. This risk is lower for Afrotropical P. falciparum strains because of the low infectivity of Anopheles labranchiae, principal malaria vector in Morocco. However, it is very high for P. vivax mainly during summer corresponding to the rice cultivation period. Although the entomological risk is high in Loukkos region, malaria resurgence risk remains very low, because of the low vulnerability of the area.

National audience

Rift Valley fever (RVF) is a major vector-borne zoonosis first identified on the African continent in the early 1900s. In 2000, RVF was reported for the first time in Yemen. In this study, we provide a descriptive analysis of the period 1999-2007 in Yemen, taking into account the environmental and socioeconomic factors likely to have been involved in the emergence of RVF in the country. We characterize each year in the study period by the environmental conditions (linked to vegetation indexes), the festival calendar, and economic data. We then use a principal component analysis to synthesize the different variables, assess whether the year 2000 was atypical compared with other years in the study period, and, if that was the case, in what respect. Our results show that 2000 presented above-normal vegetation index values, which reflect important precipitation, for both the two rainy seasons (the first between March and May; the second between July and October). These environmental conditions, ones favorable to mosquito vector populations, coincided that year with a late (March) starting date of the Eid al-Kabeer festival, which corresponds to a period with high host (cattle, sheep, goats) densities. According to these criteria, 2000 was an atypical year. These conclusions suggest that it is important to consider social variables in addition to environmental ones when assessing the risk of RVF emergence.

Background In this study, carried out in the Camargue region (France), we combined entomological data with geomatic and modelling tools to assess whether the location of breeding sites may explain the spatial distribution of adult mosquitoes. The species studied are important and competent disease vectors in Europe: Culex modestus Ficalbi and Cx. pipiens Linnaeus (West Nile virus), Anopheles atroparvus Van Thiel, a former Plasmodium vector, and An. melanoon Hackett, competent to transmit Plasmodium. Using a logistic regression model, we first evaluated which land cover variables determined the presence of Culex and Anopheles larva. The resulting probability map of larval presence then was used to project the average probability of finding adults in a buffer area. This was compared to the actual number of adults collected, providing a quantitative assessment of adult dispersal ability for each species. Results The distribution of Cx. modestus and An. melanoon is mainly driven by the repartition of irrigated farm fields and reed beds, their specific breeding habitats. The presence of breeding sites explained the distribution of adults of both species. The buffer size, reflecting the adult dispersal ability, was 700 m for Cx. modestus and 1000 m for An. melanoon. The comparatively stronger correlation observed for Cx. modestus suggested that other factors may affect the distribution of adult An. melanoon. We did not find any association between Cx. pipiens larval presence and the biotope due to the species' ubiquist character. Conclusion By applying the same method to different species, we highlighted different strengths of association between land cover (irrigated farm fields and reed beds), larval presence and adult population distribution. This paper demonstrates the power of geomatic tools to quantify the spatial organization of mosquito populations, and allows a better understanding of links between landcover, breeding habitats, presence of immature mosquito populations and adult distributions for different species.

Landscape attributes influence spatial variations in disease risk or incidence. We present a review of the key findings from eight case studies that we conducted in Europe and West Africa on the impact of land changes on emerging or re-emerging vector-borne diseases and/or zoonoses. The case studies concern West Nile virus transmission in Senegal, tick-borne encephalitis incidence in Latvia, sandfly abundance in the French Pyrenees, Rift Valley Fever in the Ferlo (Senegal), West Nile Fever and the risk of malaria re-emergence in the Camargue, and rodent-borne Puumala hantavirus and Lyme borreliosis in Belgium., Journal Article, Research Support, Non-U.S. Gov't, info:eu-repo/semantics/published

A large number of diseases that affect humans and animals are influenced by environmental factors. For multi-host infectious diseases, various species might be involved in the transmission process and the circulation of the pathogenic agent might result from the occurrence of certain specific association(s) between host and vector species. The need to characterise multi-species assemblage requires the development of new methods to derive integrated environmental risk factors. We have given remote sensing an ecological application to study the potential distribution of West Nile virus (WNV) in the Rhone River delta in southern France. West Nile fever is a vector-borne disease transmitted in natural cycles between birds and mosquitoes. Satellite images were used to create an ecological map on land cover. Appropriate typology was employed for the description of both hosts and vectors distributions. A database including the probability of occurrence of bird and mosquito species in each landscape unit is linked to this ecological map. Spatial and temporal information on host and vector distribution is then integrated using geographic information systems. This integrative tool is designed to test some hypotheses on the epidemiological process of WNV and to identify environmental configurations and environmental changes likely to favour the emergence of WNV.

Landscape ecology is seldom used in epidemiology. The aim of this study is to assess the possible improvements that can be derived from the use of landscape approaches on several scales when exploring local differences in disease distribution, using bluetongue (BT) in Corsica as an example. The environment of BT-free and BT-infected sheep farms is described on a fine scale, using high resolution satellite images and a digital elevation model. Land-coverage is characterised by classifying the satellite image. Landscape metrics are calculated to quantify the number, diversity, length of edge and connectance of vegetation patches. The environment is described for three sizes of buffers around the farms. The models are tested with and without landscape metrics to see if such metrics improve the models. Internal and external validation of the models is performed and the relative impact of scale versus variables on the discriminatory ability of the models is explored. Results show that for all scales and irrespective of the number of parameters included, models with landscape metrics perform better than those without. The 1-km buffer model combines both the best scale of application and the best set of variables. It has a good discriminating ability and good sensitivity and specificity.

Background Canine leishmaniasis (CanL) is a zoonotic disease caused by Leishmania infantum, a Trypanosomatid protozoan transmitted by phlebotomine sandflies. Leishmaniasis is endemic in southern France, but the influences of environmental and climatic factors on its maintenance and emergence remain poorly understood. From a retrospective database, including all the studies reporting prevalence or incidence of CanL in France between 1965 and 2007, we performed a spatial analysis in order to i) map the reported cases in France, and ii) produce an environment-based map of the areas at risk for CanL. We performed a Principal Component Analysis (PCA) followed by a Hierarchical Ascendant Classification (HAC) to assess if the locations of CanL could be grouped according to environmental variables related to climate, forest cover, and human and dog densities. For each group, the potential distribution of CanL in France was mapped using a species niche modelling approach (Maxent model). Results Results revealed the existence of two spatial groups of CanL cases. The first group is located in the Cévennes region (southern Massif Central), at altitudes of 200-1000 m above sea level, characterized by relatively low winter temperatures (1.9°C average), 1042 mm average annual rainfall and much forest cover. The second group is located on the Mediterranean coastal plain, characterized by higher temperatures, lower rainfall and less forest cover. These two groups may correspond to the environments favoured by the two sandfly vectors in France, Phlebotomus ariasi and Phlebotomus perniciosus respectively. Our niche modelling of these two eco-epidemiological patterns was based on environmental variables and led to the first risk map for CanL in France. Conclusion Results show how an ecological approach can help to improve our understanding of the spatial distribution of CanL in France.

In the Ferlo Region in Senegal, livestock depend on temporary ponds for water but are exposed to the Rift Valley Fever (RVF), a disease transmitted to herds by mosquitoes which develop in these ponds. Mosquito abundance is related to the emptying and filling phases of the ponds, and in order to study the epidemiology of RVF, pond modelling is required. In the context of a data scarce region, a simple hydrologic model which makes use of remote sensing data was developed to simulate pond water dynamics from daily rainfall. Two sets of ponds were considered: those located in the main stream of the Ferlo Valley whose hydrological dynamics are essentially due to runoff, and the ponds located outside, which are smaller and whose filling mechanisms are mainly due to direct rainfall. Separate calibrations and validations were made for each set of ponds. Calibration was performed from daily field data (rainfall, water level) collected during the 2001 and 2002 rainy seasons and from three different sources of remote sensing data: 1) very high spatial resolution optical satellite images to access pond location and surface area at given dates, 2) Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) Digital Elevation Model (DEM) data to estimate pond catchment area and 3) Tropical Rainfall Measuring Mission (TRMM) data for rainfall estimates. The model was applied to all ponds of the study area, the results were validated and a sensitivity analysis was performed. Water height simulations using gauge rainfall as input were compared to water level measurements from four ponds and Nash coefficients >0.7 were obtained. Comparison with simulations using TRMM rainfall data gave mixed results, with poor water height simulations for the year 2001 and good estimations for the year 2002. A pond map derived from a Quickbird satellite image was used to assess model accuracy for simulating pond water areas for all the ponds of the study area. The validation showed that modelled water areas were mostly underestimated but significantly correlated, particularly for the larger ponds. The results of the sensitivity analysis showed that parameters relative to pond shape and catchment area estimation have less effects on model simulation than parameters relative to soil properties (rainfall threshold causing runoff in dry soils and the coefficient expressing soil moisture decrease with time) or the water loss coefficient. Overall, our results demonstrate the possibility of using a simple hydrologic model with remote sensing data to track pond water heights and water areas in a homogeneous arid area.