Highly pathogenic avian influenza risk, biosecurity and smallholder adversity

There is considerable global concern over the newly emergent H5N1 strain of avian influenza that has affected millions of domestic poultry flocks and resulted in more than 150 deaths in humans. There has been little analysis of the general assumption that smallholder backyard poultry flocks are inherently at higher risk of highly pathogenic avian influenza (HPAI) than confined and commercial scale operations. We utilized data from Thailand, collected in 2004, to test the relative risks of HPAI infection in poultry flocks, by species, type of operation, and geographic location. The results indicate that backyard flocks are at lower risk of HPAI infection compared to commercial scale operations of broiler or layer chickens or quail. These findings are plausible in terms of the opportunities for breach of biosecurity in commercial scale, industrial operations. Both experimental and observational studies in developed country settings have demonstrated the capacity of microbes to enter and leave these larger operations despite the implementation of standard biosecurity measures. Patterns of infection during 2002 Newcastle disease epidemic in Denmark proved further evidence to question that smallholder backyard flocks are at higher risk of epidemic diseases than commercial operations. These results should be considered by policy makers and public health officials when developing plans to control or prevent HPAI in order to limit avoidable adverse effects on the livelihood of smallholder poultry producers in developing countries.