title: Agro-environmental determinants of avian influenza circulation: a multisite study in Thailand, Vietnam and Madagascar.
abstract: Outbreaks of highly pathogenic avian influenza have occurred and have been studied in a variety of ecological systems. However, differences in the spatial resolution, geographical extent, units of analysis and risk factors examined in these studies prevent their quantitative comparison. This study aimed to develop a high-resolution, comparative study of a common set of agro-environmental determinants of avian influenza viruses (AIV) in domestic poultry in four different environments: (1) lower-Northern Thailand, where H5N1 circulated in 2004-2005, (2) the Red River Delta in Vietnam, where H5N1 is circulating widely, (3) the Vietnam highlands, where sporadic H5N1 outbreaks have occurred, and (4) the Lake Alaotra region in Madagascar, which features remarkable similarities with Asian agro-ecosystems and where low pathogenic avian influenza viruses have been found. We analyzed H5N1 outbreak data in Thailand in parallel with serological data collected on the H5 subtype in Vietnam and on low pathogenic AIV in Madagascar. Several agro-environmental covariates were examined: poultry densities, landscape dominated by rice cultivation, proximity to a water body or major road, and human population density. Relationships between covariates and AIV circulation were explored using spatial generalized linear models. We found that AIV prevalence was negatively associated with distance to the closest water body in the Red River Delta, Vietnam highlands and Madagascar. We also found a positive association between AIV and duck density in the Vietnam highlands and Thailand, and with rice landscapes in Thailand and Madagascar. Our findings confirm the important role of wetlands-rice-ducks ecosystems in the epidemiology of AI in diverse settings. Variables influencing circulation of the H5 subtype in Southeast Asia played a similar role for low pathogenic AIV in Madagascar, indicating that this area may be at risk if a highly virulent strain is introduced.
authors.affiliation: Centre de coopération internationale en recherche agronomique pour le développement (CIRAD), UR AGIRs, Montpellier, France; Université de Toulouse, INP-ENVT, UMR ENVT INRA 1225 IHAP, Toulouse, France.
authors.forename: Mathilde C
authors.initials: MC
authors.lastname: Paul
authors.affiliation: Biological Control and Spatial Ecology, Université Libre de Bruxelles, Brussels, Belgium; Fonds National de la Recherche Scientifique, Brussels, Belgium.
authors.forename: Marius
authors.initials: M
authors.lastname: Gilbert
authors.affiliation: Centre de coopération internationale en recherche agronomique pour le développement (CIRAD), UR AGIRs, Montpellier, France; Direction Régionale de l'Alimentation, de l'Agriculture et de la Forêt de Languedoc- Roussillon, Montpellier, France.
authors.forename: Stéphanie
authors.initials: S
authors.lastname: Desvaux
authors.affiliation: FOFIFA-DRZV, Antananarivo, Madagascar; Faculté de Médecine d'Antananarivo - Département Vétérinaire, Antananarivo, Madagascar.
authors.forename: Harena Rasamoelina
authors.initials: HR
authors.lastname: Andriamanivo
authors.affiliation: Centre de coopération internationale en recherche agronomique pour le développement (CIRAD), UR AGIRs, Montpellier, France.
authors.forename: Marisa
authors.initials: M
authors.lastname: Peyre
authors.affiliation: National Institute of Veterinary Research, Hanoi, Vietnam.
authors.forename: Nguyen Viet
authors.initials: NV
authors.lastname: Khong
authors.affiliation: Department of Livestock Development, Bangkok, Thailand.
authors.forename: Weerapong
authors.initials: W
authors.lastname: Thanapongtharm
authors.affiliation: Centre de coopération internationale en recherche agronomique pour le développement (CIRAD), UR AGIRs, Montpellier, France.
authors.forename: Véronique
authors.initials: V
authors.lastname: Chevalier
mesh_terms: D000383:Agriculture; D000818:Animals; D001717:Birds / Q000821:virology; D004777:Environment; D006801:Humans; D005585:Influenza in Birds / Q000453:epidemiology*; D008270:Madagascar / Q000453:epidemiology; D012307:Risk Factors; D062206:Spatial Analysis; D013785:Thailand; D014744:Vietnam / Q000453:epidemiology