Annelise Tran, Vladimir Grosbois, Jean-Pierre Ravalohery, Fanjasoa Rakotomanana, Jean-Michel Heraud, Soa Fy Andriamandimby, Christophe Rogier, Seta Andriamamonjy, Véronique Chevalier, Benoit Durand, Marie-Marie Olive, Animal et gestion intégrée des risques (UPR AGIRs), Centre de Coopération Internationale en Recherche Agronomique pour le Développement (Cirad), Unité de Virologie [Antananarivo, Madagascar] (IPM), Institut Pasteur de Madagascar, Réseau International des Instituts Pasteur (RIIP)-Réseau International des Instituts Pasteur (RIIP), Laboratoire de santé animale, sites de Maisons-Alfort et de Dozulé, Agence nationale de sécurité sanitaire de l'alimentation, de l'environnement et du travail (ANSES), Réseau International des Instituts Pasteur (RIIP), This study was supported in part by funds raised by (i) CIRAD (ii) the Centre National d'Etudes Spatiales (CNES, grant # 131163/00) (iii) the Institut Pasteur de Madagascar. Human field work was funded by the Institut Pasteur of Madagascar (Internal Project through the ZORA (ZOonoses, Rodent and Arboviruses) project and the Centers for Disease Control and Prevention (CDC, and Cooperative Agreement #U51/IP000327). Moreover, this material is based upon work supported by the U. S. Department of Homeland Security under the Center of Excellence of Emerging and Zoonotic Animal Diseases Grant Award Number 2010-ST061-AG0001. Cattle study was supported in part by funds raised by World Health Organization (WHO) and the Food and Agriculture Organization of the United Nations (FAO) through the Central Emergency Response Fund of the United Nations. The views and conclusions contained in this paper are those of the authors and should not be interpreted as necessarily representing the official policies, either explicit or implicit, of the U. S. Department of Homeland Security. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.
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.