Because the majority of HPAI outbreaks in Asia have been reported in smallholder 'backyard' flocks, there is an assumption these small flocks, with typical flock sizes of well under 50 birds, largely, but not exclusively kept for home consumption, have an inherently higher risk of contracting and thereby disseminating HPAI than larger market-oriented flocks maintained in poultry operations following the specialized, high-input production models of industrialized countries. This assumption was tested using HPAI reports from Cambodia, published data from the first 2004 HPAI epidemic and concurrent active surveillance programme in Thailand, and data collected in Viet Nam by the national animal health authorities during the second, third and fourth epidemic waves. In fact, the highest HPAI risk appeared to be associated with those producers best able to finance improved risk reduction measures themselves, i.e. the larger commercial poultry operations.
HPAI Research Brief No. 5, 2008. 4 pp.