title: Reconstruction of Rift Valley fever transmission dynamics in Madagascar: estimation of force of infection from seroprevalence surveys using Bayesian modelling.
abstract: The force of infection (FOI) is one of the key parameters describing the dynamics of transmission of vector-borne diseases. Following the occurrence of two major outbreaks of Rift Valley fever (RVF) in Madagascar in 1990-91 and 2008-09, recent studies suggest that the pattern of RVF virus (RVFV) transmission differed among the four main eco-regions (East, Highlands, North-West and South-West). Using Bayesian hierarchical models fitted to serological data from cattle of known age collected during two surveys (2008 and 2014), we estimated RVF FOI and described its variations over time and space in Madagascar. We show that the patterns of RVFV transmission strongly differed among the eco-regions. In the North-West and Highlands regions, these patterns were synchronous with a high intensity in mid-2007/mid-2008. In the East and South-West, the peaks of transmission were later, between mid-2008 and mid-2010. In the warm and humid northwestern eco-region favorable to mosquito populations, RVFV is probably transmitted all year-long at low-level during inter-epizootic period allowing its maintenance and being regularly introduced in the Highlands through ruminant trade. The RVF surveillance of animals of the northwestern region could be used as an early warning indicator of an increased risk of RVF outbreak in Madagascar.
authors.affiliation: CIRAD, Animal and Integrated Risk Management (AGIRs) Unit, Montpellier, France.|Institut Pasteur de Madagascar, Virology Unit, Antananarivo, Madagascar.
authors.forename: Marie-Marie
authors.initials: MM
authors.lastname: Olive
authors.affiliation: CIRAD, Animal and Integrated Risk Management (AGIRs) Unit, Montpellier, France.
authors.forename: Vladimir
authors.initials: V
authors.lastname: Grosbois
authors.affiliation: CIRAD, Animal and Integrated Risk Management (AGIRs) Unit, Montpellier, France.
authors.forename: Annelise
authors.initials: A
authors.lastname: Tran
authors.affiliation: Institut Pasteur de Madagascar, Virology Unit, Antananarivo, Madagascar.
authors.forename: Lalaina Arivony
authors.initials: LA
authors.lastname: Nomenjanahary
authors.affiliation: Institut Pasteur de Madagascar, Virology Unit, Antananarivo, Madagascar.
authors.forename: Mihaja
authors.initials: M
authors.lastname: Rakotoarinoro
authors.affiliation: Institut Pasteur de Madagascar, Virology Unit, Antananarivo, Madagascar.
authors.forename: Soa-Fy
authors.initials: SF
authors.lastname: Andriamandimby
authors.affiliation: Institut Pasteur de Madagascar, Direction, Madagascar.|Institute for Biomedical Research of the French Armed Forces (IRBA), Brétigny-Sur-Orge, France.|Unité de recherche sur les maladies infectieuses et tropicales émergentes (URMITE), Marseille, France.
authors.forename: Christophe
authors.initials: C
authors.lastname: Rogier
authors.affiliation: Institut Pasteur de Madagascar, Virology Unit, Antananarivo, Madagascar.
authors.forename: Jean-Michel
authors.initials: JM
authors.lastname: Heraud
authors.affiliation: CIRAD, Animal and Integrated Risk Management (AGIRs) Unit, Montpellier, France.
authors.forename: Veronique
authors.initials: V
authors.lastname: Chevalier
mesh_terms: D000818:Animals; D001499:Bayes Theorem; D002417:Cattle; D009033:Culicidae / Q000502:physiology; D004196:Disease Outbreaks; D008270:Madagascar / Q000453:epidemiology; D000072138:Mosquito Vectors / Q000254:growth & development / Q000821:virology; D012295:Rift Valley Fever / Q000453:epidemiology* / Q000473:pathology / Q000635:transmission; D012296:Rift Valley fever virus / Q000276:immunology / Q000472:pathogenicity; D016036:Seroepidemiologic Studies