Rift Valley fever (RVF) is a mosquito-borne disease mostly affecting wild and domestic ruminants.... more Rift Valley fever (RVF) is a mosquito-borne disease mostly affecting wild and domestic ruminants. It is widespread in Africa, with spillovers in the Arab Peninsula and the southwestern Indian Ocean. Although RVF has been circulating in West Africa for more than 30 years, its epidemiology is still not clearly understood. In 2013, an RVF outbreak hit Senegal in new areas that weren’t ever affected before. To assess the extent of the spread of RVF virus, a national serological survey was implemented in young small ruminants (6–18 months old), between November 2014 and January 2015 (after the rainy season) in 139 villages. Additionally, the drivers of this spread were identified. For this purpose, we used a beta-binomial (BB) logistic regression model. An Integrated Nested Laplace Approximation (INLA) approach was used to fit the spatial model. Lower cumulative rainfall, and higher accessibility were both associated with a higher RVFV seroprevalence. The spatial patterns of fitted RVFV ...
Bluetongue virus (BTV) (Reoviridae: Orbivirus) is a good example of emerging arbovirus in Europe,... more Bluetongue virus (BTV) (Reoviridae: Orbivirus) is a good example of emerging arbovirus in Europe, with a little understanding of the disease epidemiology. This virus is transmitted by blood-sucking midges of the genus Culicoides (Diptera: Ceratopogonidae) to wild and domestic ruminants. In Europe, BT had been considered as an exotic disease until recently. In 1998, several BT incursions were observed in the western Mediterranean Basin in line with the northward progression of C. imicola populations, the main afrotropical vector. From August 2006, the emergence and transmission of BT serotype 8 in northern Europe, in areas where C. imicola was absent, revealed the importance of autochthonous Culicoides species and the urgent need to understand their vector role. The emergence and massive spread of bluetongue virus in western Europe during 2006-2008 had disastrous consequences for sheep and cattle production and confirmed the ability of Palaearctic Culicoides to transmit the virus. De...
a SAS Nevantropic, 16 bis av. du 14 juillet, 97300 Cayenne, French Guiana. b CIRAD (French Agricu... more a SAS Nevantropic, 16 bis av. du 14 juillet, 97300 Cayenne, French Guiana. b CIRAD (French Agricultural Research Center for Internationa l Development), Baillarguet Campus, 34398 Montpellie r Cedex. c UMR TETIS (Territories, Environment, Remote Sensing and Spatial Information Joint Research Unit), Maison de la Téléd étection, 500 rue J.-F. Breton, 34093 Montpellier C edex 5, France. d IRD (Institut de Recherche pour le Développement ), 34394 Montpellier Cedex 05, France. e ISRA/LNERV Route du front de terre, BP 2057, Dak ar-Hann, Sénégal.
Several animal or zoonotic emerging infectious disease (EID) events were recently caused by vecto... more Several animal or zoonotic emerging infectious disease (EID) events were recently caused by vector-borne pathogens, e.g. bluetongue virus (BTV) transmitted by biting midges which caused huge economic losses in western Europe between 2006 and 2009, and is still around, or tick-borne encephalitis in northern and central Europe, causing several thousands of clinical cases in humans. The effects of climate changes have been put forward to explain these EID events. Because the bio-ecological features of arthropod vectors make them highly sensitive to environmental conditions, vector-borne diseases are ideal candidates to assess the effect of climate changes on EID. The question was extensively studied these past years. For instance, the effects of climate on BTV's emergence in Europe were evaluated by integrating high-resolution climate observations and model simulations within a climate-driven, mechanistic transmission model of BTV. This model explained, in both space and time, many...
We have developed an explicit spatial and temporal model to predict the population dynamics and d... more We have developed an explicit spatial and temporal model to predict the population dynamics and dispersal of the two main mosquito vector species (Aedes vexans and Culex poicilipes) involved in Rift Valley fever virus (RVFV) transmission in Senegal (western Africa). Covering an area of 11x10 km around the village of Barkedji, and located in the Ferlo valley (Northern Senegal), the study area is characterized by a complex and dense network of water bodies and ponds that are filled by rainfall during the rainy season (from July to mid- October). These water bodies are known to be the principal mosquito breeding sites in the area. A spatial diffusion model (Raffy and Tran, 2005) is applied in combination with a vector population dynamic model (Soti et al., 2009), and which takes into account the hydrological conditions of the system (Soti et al., submitted). The vector population dynamic model has been more specifically derived from Porphyre et al. (2005). Daily mosquito abundance for ...
In the dominant livestock systems of Sahelian countries herds have to move across territories. Th... more In the dominant livestock systems of Sahelian countries herds have to move across territories. Their mobility is often a source of conflict with farmers in the areas crossed, and helps spread diseases such as Rift Valley Fever. Knowledge of the routes followed by herds is therefore core to guiding the implementation of preventive and control measures for transboundary animal diseases, land use planning and conflict management. However, the lack of quantitative data on livestock movements, together with the high temporal and spatial variability of herd movements, has so far hampered the production of fine resolution maps of animal movements. This paper proposes a general framework for mapping potential paths for livestock movements and identifying areas of high animal passage potential for those movements. The method consists in combining the information contained in livestock mobility networks with landscape connectivity, based on different mobility conductance layers. We illustrate...
In Senegal, the last epidemic of African horse sickness (AHS) occurred in 2007. The western part ... more In Senegal, the last epidemic of African horse sickness (AHS) occurred in 2007. The western part of the country (the Niayes area) concentrates modern farms with exotic horses of high value and was highly affected during the 2007 outbreak that has started in the area. Several studies were initiated in the Niayes area in order to better characterize Culicoides diversity, ecology and the impact of environmental and climatic data on dynamics of proven and suspected vectors. The aims of this study are to better understand the spatial distribution and diversity of Culicoides in Senegal and to map their abundance throughout the country. Culicoides data were obtained through a nationwide trapping campaign organized in 2012. Two successive collection nights were carried out in 96 sites in 12 (of 14) regions of Senegal at the end of the rainy season (between September and October) using OVI (Onderstepoort Veterinary Institute) light traps. Three different modeling approaches were compared: th...
Several epidemics caused by different bluetongue virus (BTV) serotypes occurred in European rumin... more Several epidemics caused by different bluetongue virus (BTV) serotypes occurred in European ruminants since the early 2000. Studies on the spatial distribution of these vector-borne infections and the main vector species highlighted contrasted eco-climatic regions characterized by different dominant vector species. However, little work was done regarding the factors associated with the velocity of these epidemics. In this study, we aimed to quantify and compare the velocity of BTV epidemic that have affected different European countries under contrasted eco-climatic conditions and to relate these estimates to spatial factors such as temperature and host density. We used the thin plate spline regression interpolation method in combination with trend surface analysis to quantify the local velocity of different epidemics that have affected France (BTV-8 2007-2008, BTV-1 2008-2009), Italy (BTV-1 2014), Andalusia in Spain (BTV-1 2007) and the Balkans (BTV-4 2014). We found significant di...
Demographic rates (i.e., fecundity, mortality, offtake and intake rates) are necessary for assess... more Demographic rates (i.e., fecundity, mortality, offtake and intake rates) are necessary for assessing animal productivity and modeling the dynamics of tropical livestock populations. These rates are estimated from data collected in the field. In developing countries, data collection and management is a tricky part of the studies. In that context, we present two standardized survey methods for ruminants and camels managed in extensive or semi-extensive farming systems. These methods can be adapted to many contexts (animal production and health, genetics or agricultural economy) and are provided with operational tools for data management and analysis. The first method, LASER, is based on longitudinal follow-up of herd with individual identification of the animals. Gold-standard of the on-farm methods, LASER is well adapted for accurate assessment of herd productivity and impact of new technologies (vaccine, reproduction,...). The second method, 12MO, is a rapid appraisal method based o...
Background In Senegal, the 2007 epidemic of African horse sickness (AHS) caused the death of 1,16... more Background In Senegal, the 2007 epidemic of African horse sickness (AHS) caused the death of 1,169 horses and considerable economic loss (Akakpo et al. 2011). The vectors responsible for biological transmission of the virus belong to the genus Culicoides (Diptera: Ceratopogonidae). In Senegal, studies on Culicoides are rare, out of date and did not specifically target the species in the vicinity of horses. Thus we initiated two studies in 2011 to better understand the dynamics and distribution of the Culicoides of Senegal and their involvement in the transmission of AHS virus (AHSV).
Rift Valley fever (RVF) is a mosquito-borne disease mostly affecting wild and domestic ruminants.... more Rift Valley fever (RVF) is a mosquito-borne disease mostly affecting wild and domestic ruminants. It is widespread in Africa, with spillovers in the Arab Peninsula and the southwestern Indian Ocean. Although RVF has been circulating in West Africa for more than 30 years, its epidemiology is still not clearly understood. In 2013, an RVF outbreak hit Senegal in new areas that weren’t ever affected before. To assess the extent of the spread of RVF virus, a national serological survey was implemented in young small ruminants (6–18 months old), between November 2014 and January 2015 (after the rainy season) in 139 villages. Additionally, the drivers of this spread were identified. For this purpose, we used a beta-binomial (BB) logistic regression model. An Integrated Nested Laplace Approximation (INLA) approach was used to fit the spatial model. Lower cumulative rainfall, and higher accessibility were both associated with a higher RVFV seroprevalence. The spatial patterns of fitted RVFV ...
Bluetongue virus (BTV) (Reoviridae: Orbivirus) is a good example of emerging arbovirus in Europe,... more Bluetongue virus (BTV) (Reoviridae: Orbivirus) is a good example of emerging arbovirus in Europe, with a little understanding of the disease epidemiology. This virus is transmitted by blood-sucking midges of the genus Culicoides (Diptera: Ceratopogonidae) to wild and domestic ruminants. In Europe, BT had been considered as an exotic disease until recently. In 1998, several BT incursions were observed in the western Mediterranean Basin in line with the northward progression of C. imicola populations, the main afrotropical vector. From August 2006, the emergence and transmission of BT serotype 8 in northern Europe, in areas where C. imicola was absent, revealed the importance of autochthonous Culicoides species and the urgent need to understand their vector role. The emergence and massive spread of bluetongue virus in western Europe during 2006-2008 had disastrous consequences for sheep and cattle production and confirmed the ability of Palaearctic Culicoides to transmit the virus. De...
a SAS Nevantropic, 16 bis av. du 14 juillet, 97300 Cayenne, French Guiana. b CIRAD (French Agricu... more a SAS Nevantropic, 16 bis av. du 14 juillet, 97300 Cayenne, French Guiana. b CIRAD (French Agricultural Research Center for Internationa l Development), Baillarguet Campus, 34398 Montpellie r Cedex. c UMR TETIS (Territories, Environment, Remote Sensing and Spatial Information Joint Research Unit), Maison de la Téléd étection, 500 rue J.-F. Breton, 34093 Montpellier C edex 5, France. d IRD (Institut de Recherche pour le Développement ), 34394 Montpellier Cedex 05, France. e ISRA/LNERV Route du front de terre, BP 2057, Dak ar-Hann, Sénégal.
Several animal or zoonotic emerging infectious disease (EID) events were recently caused by vecto... more Several animal or zoonotic emerging infectious disease (EID) events were recently caused by vector-borne pathogens, e.g. bluetongue virus (BTV) transmitted by biting midges which caused huge economic losses in western Europe between 2006 and 2009, and is still around, or tick-borne encephalitis in northern and central Europe, causing several thousands of clinical cases in humans. The effects of climate changes have been put forward to explain these EID events. Because the bio-ecological features of arthropod vectors make them highly sensitive to environmental conditions, vector-borne diseases are ideal candidates to assess the effect of climate changes on EID. The question was extensively studied these past years. For instance, the effects of climate on BTV's emergence in Europe were evaluated by integrating high-resolution climate observations and model simulations within a climate-driven, mechanistic transmission model of BTV. This model explained, in both space and time, many...
We have developed an explicit spatial and temporal model to predict the population dynamics and d... more We have developed an explicit spatial and temporal model to predict the population dynamics and dispersal of the two main mosquito vector species (Aedes vexans and Culex poicilipes) involved in Rift Valley fever virus (RVFV) transmission in Senegal (western Africa). Covering an area of 11x10 km around the village of Barkedji, and located in the Ferlo valley (Northern Senegal), the study area is characterized by a complex and dense network of water bodies and ponds that are filled by rainfall during the rainy season (from July to mid- October). These water bodies are known to be the principal mosquito breeding sites in the area. A spatial diffusion model (Raffy and Tran, 2005) is applied in combination with a vector population dynamic model (Soti et al., 2009), and which takes into account the hydrological conditions of the system (Soti et al., submitted). The vector population dynamic model has been more specifically derived from Porphyre et al. (2005). Daily mosquito abundance for ...
In the dominant livestock systems of Sahelian countries herds have to move across territories. Th... more In the dominant livestock systems of Sahelian countries herds have to move across territories. Their mobility is often a source of conflict with farmers in the areas crossed, and helps spread diseases such as Rift Valley Fever. Knowledge of the routes followed by herds is therefore core to guiding the implementation of preventive and control measures for transboundary animal diseases, land use planning and conflict management. However, the lack of quantitative data on livestock movements, together with the high temporal and spatial variability of herd movements, has so far hampered the production of fine resolution maps of animal movements. This paper proposes a general framework for mapping potential paths for livestock movements and identifying areas of high animal passage potential for those movements. The method consists in combining the information contained in livestock mobility networks with landscape connectivity, based on different mobility conductance layers. We illustrate...
In Senegal, the last epidemic of African horse sickness (AHS) occurred in 2007. The western part ... more In Senegal, the last epidemic of African horse sickness (AHS) occurred in 2007. The western part of the country (the Niayes area) concentrates modern farms with exotic horses of high value and was highly affected during the 2007 outbreak that has started in the area. Several studies were initiated in the Niayes area in order to better characterize Culicoides diversity, ecology and the impact of environmental and climatic data on dynamics of proven and suspected vectors. The aims of this study are to better understand the spatial distribution and diversity of Culicoides in Senegal and to map their abundance throughout the country. Culicoides data were obtained through a nationwide trapping campaign organized in 2012. Two successive collection nights were carried out in 96 sites in 12 (of 14) regions of Senegal at the end of the rainy season (between September and October) using OVI (Onderstepoort Veterinary Institute) light traps. Three different modeling approaches were compared: th...
Several epidemics caused by different bluetongue virus (BTV) serotypes occurred in European rumin... more Several epidemics caused by different bluetongue virus (BTV) serotypes occurred in European ruminants since the early 2000. Studies on the spatial distribution of these vector-borne infections and the main vector species highlighted contrasted eco-climatic regions characterized by different dominant vector species. However, little work was done regarding the factors associated with the velocity of these epidemics. In this study, we aimed to quantify and compare the velocity of BTV epidemic that have affected different European countries under contrasted eco-climatic conditions and to relate these estimates to spatial factors such as temperature and host density. We used the thin plate spline regression interpolation method in combination with trend surface analysis to quantify the local velocity of different epidemics that have affected France (BTV-8 2007-2008, BTV-1 2008-2009), Italy (BTV-1 2014), Andalusia in Spain (BTV-1 2007) and the Balkans (BTV-4 2014). We found significant di...
Demographic rates (i.e., fecundity, mortality, offtake and intake rates) are necessary for assess... more Demographic rates (i.e., fecundity, mortality, offtake and intake rates) are necessary for assessing animal productivity and modeling the dynamics of tropical livestock populations. These rates are estimated from data collected in the field. In developing countries, data collection and management is a tricky part of the studies. In that context, we present two standardized survey methods for ruminants and camels managed in extensive or semi-extensive farming systems. These methods can be adapted to many contexts (animal production and health, genetics or agricultural economy) and are provided with operational tools for data management and analysis. The first method, LASER, is based on longitudinal follow-up of herd with individual identification of the animals. Gold-standard of the on-farm methods, LASER is well adapted for accurate assessment of herd productivity and impact of new technologies (vaccine, reproduction,...). The second method, 12MO, is a rapid appraisal method based o...
Background In Senegal, the 2007 epidemic of African horse sickness (AHS) caused the death of 1,16... more Background In Senegal, the 2007 epidemic of African horse sickness (AHS) caused the death of 1,169 horses and considerable economic loss (Akakpo et al. 2011). The vectors responsible for biological transmission of the virus belong to the genus Culicoides (Diptera: Ceratopogonidae). In Senegal, studies on Culicoides are rare, out of date and did not specifically target the species in the vicinity of horses. Thus we initiated two studies in 2011 to better understand the dynamics and distribution of the Culicoides of Senegal and their involvement in the transmission of AHS virus (AHSV).
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Papers by Renaud Lancelot