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Master Thesis

Approche géographique du risque d'émergence de l'influenza aviaire à H5N1 au sein des élevages de volailles de Thaïlande

Abstract : The highly pathogenic avian influenza (HPAI) H5N1 virus remains a worldwide threat to human and animal health, while the mechanisms and factors explaining its epizootic emergence and re-emergence are largely unknown. Several past studies have analysed virus spread and have identified a few risk factors associated to disease occurrence globally, without focusing on emerging foci. In order to efficiently control the dissemination of the epizootics in poultry, the most important action consists now in the identification and characterization of emergence sites, including their environment and human contexts. Data from Thailand, a country that experienced significant epizootic waves and has recorded positive cases of HPAI since 2004, are used here to study the process of emergence through a spatial approach. This work completes the analyses conducted by Souris M. et al. in 2007-2008 with regard to randomness of spatial distribution of emergence foci. After data integration in a geographic information system, sites where epizootics originate are filtered from those to which virus subsequently spreads using screening procedures that involve date, location and geographical arrangement of epizootic cases. Discrimination of both groups of foci is analyzed for different combinations of time and distance, using geostatistical tests and several environmental factors. The most suitable combination for the identification of emergence sites is consequently determined. Distinguishing the process of emergence from the dissemination one allows us in a last stage to identify potential environmental or anthropogenic conditions that are specifically associated to an increasing risk of emergence, such as rice paddies localized along the Central plains of Thailand and which previously supported “free-grazing duck” activity. Although the potential of virus introduction by wild birds cannot be ignored in other contexts, our results suggest that poultry infection emergence is more likely associated with specific human (commercial and raising) practices. Finally, using spatio-temporal analysis and environmental factors for the characterization of emergence or reemergence sites appears to be a suitable approach to improve the statistical analysis on HPAI risk in the future.
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Master Thesis
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Victoria Corvest. Approche géographique du risque d'émergence de l'influenza aviaire à H5N1 au sein des élevages de volailles de Thaïlande. Géographie. 2008. ⟨dumas-01644493⟩

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