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ABSTRACT: Rift Valley fever is an acute, zoonotic viral disease of domestic ruminants, caused by a phlebovirus (Bunyaviridae family). A large outbreak occurred in Madagascar in 2008-2009. The goal of the present study was to evaluate the point prevalence of antibodies against Rift Valley Fever Virus (RVFV) in cattle in the Anjozorobe district, located in the wet and temperate highland region of Madagascar and yet heavily affected by the disease, and analyse environmental and trade factors potentially linked to RVFV transmission. A serological study was performed in 2009 in 894 bovines. For each bovine, the following variables were recorded: age, location of the night pen, minimum distance from the pen to the nearest water point and the forest, nearest water point type, and herd replacement practices. The serological data were analyzed using a generalized linear mixed model. The overall anti-RVFV IgG seroprevalence rate was 28% [CI95% 25-31]. Age was statistically linked to prevalence (p = 10(-4)), being consistent with a recurrent RVFV circulation. Distance from the night pen to the nearest water point was a protective factor (p = 5.10(-3)), which would be compatible with a substantial part of the virus transmission being carried out by nocturnal mosquito vectors. However, water point type did not influence the risk of infection: several mosquito species are probably involved. Cattle belonging to owners who purchase animals to renew the herd were significantly more likely to have seroconverted than others (p = 0.04): cattle trade may contribute to the introduction of the virus in this area. The minimum distance of the night pen to the forest was not linked to the prevalence. This is the first evidence of a recurrent transmission of RVFV in such an ecosystem that associates a wet, temperate climate, high altitude, paddy fields, and vicinity to a dense rain forest. Persistence mechanisms need to be further investigated.
PLoS Neglected Tropical Diseases 12/2011; 5(12):e1423. · 4.69 Impact Factor
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ABSTRACT: Current knowledge suggests that there is a low-level and recurrent circulation of West Nile virus (WNV) in Europe, with sporadic human and/or equines cases. However, recent events indicate that this picture is changing, raising the possibility that Europe could experience a modification in the virus' circulation patterns. We used an existing model of WNV circulation between Southern Europe and West Africa to estimate the sample size of equivalent West Nile surveillance systems, either passive (based upon horse populations and sentinel veterinarians) or active (sentinel horses, sentinel chickens, or WNV genome detection in trapped mosquito pools). The costs and calendar day of first detection of these different surveillance systems were compared under three different epidemiological scenarios: very low level circulation, low level recurrent circulation, and epidemic situation. The passive surveillance of 1000 horses by specialized veterinarian clinics appeared to be the most cost-effective system in the current European context, and estimated median dates of first detection appeared consistent with recent field observations. Our results can be used to optimize surveillance designs for different epidemiological requirements.
Vector borne and zoonotic diseases (Larchmont, N.Y.) 05/2011; 11(8):1085-91. · 2.61 Impact Factor
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ABSTRACT: West Nile fever epidemiology is complex, and the role of birds in the maintenance, amplification, and dissemination of the West Nile virus (WNV) remains partially unknown. In 2003, a serological study was performed in Senegal, where West Nile infection is considered endemic. The goal was to identify potential reservoirs of WNV among bird species present in the Ferlo area (northern Senegal) and the Senegal River Valley, and to screen the ecological factors possibly related to West Nile infection. Serological data were analyzed using a generalized linear model. Statistical association between ecological factors and the risk of infection were then modeled to derive a species-specific risk. A cross-validation was conducted. The overall observed prevalence rate was 5.5% (n = 422). Thirteen bird species were found positive, from which five were migrating: Lanius senator, Anthus trivialis, Hippolais opaca, Jynx torquilla, and Cercotrichas galactotes. The nesting type in resident birds was positively correlated with the risk of infection (odds ratio [OR] = 11, p = 0.0003); the gregariousness level of birds appeared as a protective factor (OR = 0.3, p = 0.01). The predicted prevalence varied between 1% and 39% for resident species and between 1% and 7% for migrating species. Results of model internal validation were satisfactory at the individual and species level. However, more field and experimental investigations are needed to confirm these preliminary results and help target the future research and surveillance in Senegal.
Vector borne and zoonotic diseases (Larchmont, N.Y.) 02/2009; 9(6):589-96. · 2.61 Impact Factor
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Emmanuel Albina,
Gilles Balança,
Emmanuel Camus,
Eric Cardinale,
Alexandre Caron, Véronique Chevalier,
Stéphane La Rocque,
Stéphanie Desvaux,
Nicolas Gaidet,
Guillaume Gerbier,
Flavie Goutard,
Renaud Lancelot,
Dominique Martinez,
François Monicat,
Vincent Porphyre,
Jean-François Renard,
Didier Richard,
François Roger,
Paulo Salgado,
Laurence Vial
edited by CIRAD, 01/2006: pages 64 p.; CIRAD., ISBN: 2876146304
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