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Rift Valley fever (RVF) is endemic in northern Senegal, a Sahelian area characterized by a temporary pond network that drive both RVF mosquito population dynamics and nomadic herd movements. To investigate the mechanisms that explain RVF recurrent circulation, we modelled a realistic epidemiological system at the pond level integrating vector population dynamics, resident and nomadic ruminant herd population dynamics, and nomadic herd movements recorded in Younoufere area. To calibrate the model, serological surveys were performed in 2015–2016 on both resident and nomadic domestic herds in the same area. Mosquito population dynamics were obtained from a published model trained in the same region. Model comparison techniques were used to compare five different scenarios of virus introduction by nomadic herds associated or not with vertical transmission in Aedes vexans. Our serological results confirmed a long lasting RVF endemicity in resident herds (IgG seroprevalence rate of 15.3%, n = 222), and provided the first estimation of RVF IgG seroprevalence in nomadic herds in West Africa (12.4%, n = 660). Multivariate analysis of serological data suggested an amplification of the transmission cycle during the rainy season with a peak of circulation at the end of that season. The best scenario of virus introduction combined yearly introductions of RVFV from 2008 to 2015 (the study period) by nomadic herds, with a proportion of viraemic individuals predicted to be larger in animals arriving during the 2nd half of the rainy season (3.4%). This result is coherent with the IgM prevalence rate (4%) found in nomadic herds sampled during the 2nd half of the rainy season. Although the existence of a vertical transmission mechanism in Aedes cannot be ruled out, our model demonstrates that nomadic movements are sufficient to account for this endemic circulation in northern Senegal., Author summary Rift Valley fever (RVF) is one of the most important vector borne disease in Africa, seriously affecting the health of domestic ruminants and humans and leading to severe economic consequences. This disease is endemic in northern Senegal, a Sahelian area characterized by a temporary pond network that drive both RVF mosquito population dynamics and nomadic herd movements. Two non-exclusive mechanisms may support this endemicity: recurrent introductions of the virus by nomadic animals, and vertical transmission of the virus (i.e. from infected female mosquito to eggs) in local Aedes populations. The authors followed resident and nomadic domestic herds for 1 year. They used the data thus obtained to model a realistic epidemiological system at the pond level integrating vector population dynamics, resident and nomadic ruminant herd population dynamics. They found that the best scenario explaining RVF remanence combined yearly introductions of RVFV by nomadic herds, with a viraemic proportion predicted to be larger in animals arriving during the 2nd half of the rainy season, which is consistent with an amplification of virus circulation in the area during the rainy season. Although the existence of a vertical transmission mechanism in Aedes cannot be ruled out, their results demonstrates that nomadic movements are sufficient to account for this endemic circulation in northern Senegal.

The geographical distribution and impact on animal and human health of both West Nile and Usutu viruses, two flaviviruses of the Japanese encephalitis complex, have been increasing during the past two decades. Both viruses circulate in Europe and Africa within a natural cycle between wild birds and mosquitoes, mainly from the Culex genus. We retrospectively analyzed sera from domestic and wild birds sampled in 2008 in two wetlands, namely the Inner Niger Delta, Mali, and the Lake Alaotra area, Madagascar. Sera were first tested using a commercial ID Screen West Nile Competition Multi-species ELISA kit. Then, positive sera and sera with insufficient volume for testing with ELISA were tested with a Microneutralization Test. In Mali, the observed seroprevalence in domestic birds was 28.5% [24.5; 32.8] 95%CI, 3.1 % [1.8; 5.2] 95%CI, 6.2% [3.4; 10.2] 95%CI and 9.8 % [7.3; 12.8] 95%CI, for West Nile virus (WNV), Usutu virus (USUV), undetermined flavivirus, and WNV/USUV respectively. Regarding domestic birds of Madagascar, the observed seroprevalence was 4.4 % [2.1; 7.9]95%CI for WNV, 0.9% [0.1; 3.1] 95%CI for USUV, 1.3% [0.5; 2.8] 95%CI for undetermined flavivirus, and null for WNV/USUV. Among the 150 wild birds sampled in Madagascar, two fulvous whistling-ducks (Dendrocygna bicolor) were positive for WNV and two for an undetermined flavivirus. One white-faced whistling-duck (Dendrocygna viduata) and one Hottentot teal (Spatula hottentota) were tested positive for USUV. African and European wetlands are linked by wild bird migrations. This first detection of USUV—as well as the confirmed circulation of WNV in domestic birds of two wetlands of Mali and Madagascar—emphasizes the need to improve the surveillance, knowledge of epidemiological patterns, and phylogenetic characteristics of flavivirus in Africa, particularly in areas prone to sustained, intense flavivirus transmission such as wetlands.

Purpose: Certain Palaearctic biting midges have been implicated as vectors of bluetongue virus in northern Europe. Separation of two species (Culicoides obsoletus and C. scoticus) is considered difficult morphologically, with females often grouped together in entomological studies. Species specific identification is desirable to assess their roles in disease transmission or measure abundance during arboviral outbreaks. Our aim is to investigate whether morphometric identification techniques can be applied to female C. obsoletus and C. scoticus individuals trapped in different geographical regions and time periods during the year. Methods: Using light-suction traps, female C. obsoletus and C. scoticus were sampled from two locations in the UK, France and Spain. A total of 759 individuals were identified with a molecular assay using the cytochrome oxidase I gene. Fifteen morphometric measurements were then taken from the head, wings and abdomen of slide-mounted specimens. Multivariate analyses investigated whether a combination of these could lead to accurate species identification. Results: Principal component analyses revealed that the length and width of the smaller and larger spermathecae, and the length of, and width between, the chitinous plates can differentiate the species. These are all abdominal characteristics. Seasonal and geographic variation was observed for head and wing measurements, but not for those from the abdomen. Conclusions: Our results suggest that female C. obsoletus and C. scoticus individuals can be separated under a stereomicroscope using abdominal measurements. Although we show that morphometrics can be used to differentiate the species, this can be time-consuming and we recommend undertaking this using standardized subsampling of large catches. Relevance: This work highlights a new morphometric method of discriminating two of the main vector species of bluetongue virus. Such separations generally rely on molecular techniques, which can be expensive. Morphometric identifications may prove useful in outbreak situations when they can be quickly undertaken on a subsample of individuals to determine the proportions of each species present. (Texte intégral)

Infectious causes of cattle abortions have significant impacts on livestock and people the health in developing countries. Adopting One Health principles for coordinated surveillance and simultaneous preventative actions in animal and human populations has proved to be efficient and cost-effective. However, wild ruminants can also be infected with the same abortive pathogens, which may considerably complicate the management strategies. We synthesise the results of several eco-epidemiology and ethno-veterinary studies carried out over the past decade in the Great Limpopo Transfrontier Conservation Area in Zimbabwe. Serological surveys indicated that Rift valley fever virus circulate in cattle and African buffalo populations, whereas brucellosis apparently infects only cattle. In areas where there was no physical barrier between cattle and wildlife, farmers interviewed perceived that the number of cattle abortions was higher, and the proportion of farmers perceiving wildlife as playing a role in livestock abortions was higher compared to other sites. Monitoring of movements of sympatric cattle and buffalo with GPS collars demonstrated seasonal home range overlap potentially resulting in interspecific transmission of brucellosis and RVF through aborted foetuses. Several management options are discussed including awareness campaigns, vaccination and other preventive actions to limit infective contacts between wildlife, livestock and people. (Texte intégral)

Rift Valley Fever (RVF) is an emerging disease threatening human and livestock health in Africa and the Middle-East. The role of wildlife in the maintenance and transmission of the virus at human/livestock/wildlife interfaces in Southern Africa remains unclear. In order to elucidate RVF epidemiology in the Great Limpopo (GLTFCA) and the Kavango-Zambezi (KAZATFCA), we combined preliminary data from serology, entomology, telemetry and field experiments in Zimbabwe. Methods: At each site, blood samples were taken between 2008 and 2011 from livestock and buffalo. The samples were tested with I-ELISA for RVF antibodies and the data analysed with Generalized Linear Model. Four mosquito trapping sessions were conducted at water holes used by livestock and/or wildlife. Potential contacts between wildlife and cattle were assessed using data of GPS collared cattle and buffalo published elsewhere. Bags of viscera were used as a proxy to estimate residence time of aborted fetus and potential infectious contacts between livestock and wild ruminants. Results: KAZATFCA serological results were all negative. In GLTFCA, the seroprevalence was 4.6% in cattle (27/587), 3% in small ruminants (2/66) and 6.8% in buffalo (14/205). The disease was endemic in livestock, with 2009 prevalence lower than 2008 (p=0.04). Buffalo prevalence was significantly higher in 2010 (p=0.05). Six species of mosquitoes were captured, including 3 potential RVF vectors: Culex quinquefasciatus, C. theileri trapped at both sites; Anopheles coustani identified in KAZATFCA only. Home ranges of sympatric cattle and buffalo overlapped, with significant differences in seasonality and frequency of indirect contacts across sites. Estimated residence time of aborted fetus ranged between a few hours and several days. Conclusions: These results indicate that RVF circulates in cattle and buffalo populations within the GLTFCA, with inter-annual and spatial variations, and that transmission between wild and domestic compartments may be due to both vectors and direct contacts Relevance: This innovative study combining different field data will contribute to improving zoonotic RVF at wild/domestic interfaces in Africa. (Texte intégral)

La maladie de Newcastle est une maladie virale des oiseaux, très contagieuse et présente partout dans le monde. Sa présentation clinique est variable. Elle se manifeste généralement par des signes respiratoires mais le tableau clinique peut être dominé par un abattement, des symptômes nerveux ou des diarrhées. Historiquement, la maladie a été découverte en Indonésie en 1926 (Kraneveld, 1926). Mais elle a tiré son nom de la ville de Newcastle-on-Tyne en Angleterre, où elle est apparue en 1927 (Doyle, 1927). Cette maladie constatée dans le monde entier, est actuellement maitrisée au Canada, aux Etats-Unis d'Amérique et dans certains pays de l'Europe occidentale. Elle persiste dans différentes régions d'Afrique, d'Asie et d'Amérique du Sud. Toutefois, étant donné que les oiseaux sauvages peuvent parfois être porteurs du virus sans contracter la maladie, des foyers peuvent apparaître partout où existent des élevages de volailles (OIE, 2016). A Madagascar, elle constitue la cause la plus importante des mortalités aviaires, notamment chez les animaux non vaccinés. De nombreuses mesures de lutte s'imposent pour une meilleure production avicole.

Purpose: In 2008-09, an outbreak of Rift Valley fever (RVF) virus occurred in Madagascar. Spatial heterogeneity in seroprevalence (SP) and case occurrence frequencies suggested that some areas are more favorable to RVF circulation. The objectives of our study were to identify environmental factors in favor to human and cattle infections; test the relevance of using local cattle infection as human infection predictor and give a new insight on the respective role of direct and vectorial transmission both in human and cattle. Methods: We used 2 independent cattle and human serological datasets originating from two national surveys (2009 and 2011-13). Multiple Factor Analysis (MFA) was used to characterize environments of the whole island in terms of climate and landscape. The datasets were analyzed independently using a generalized linear mixed model (GLMM) with the individual serological status- human or cattle- as the binomial response. Explicative variables were age and MFA factors for cattle model (M1) and age, gender, MFA factors and contact with ruminants and their product for human model (M2). Then human and cattle data were analyzed jointly by GLMM with the human individual status as binomial response. In addition to the previous explicative variables cattle SP predicted by M1 was used. Models accuracies were tested using ROC curve method. Results: Four MFA factors were selected. Age and factor4 - humid (irrigation, lake, marshland) environment - had a positive effect on SP of cattle and human living in rural areas (p