Backyard Poultry Mortality Associated with Highly Pathogenic Avian Influenza (HPAI) H5N1 outbreaks in Nigeria

Backyard poultry farms infected with highly pathogenic avian influenza (HPAI) H5N1 virus in Nigeria between 2006 and 2008 were investigated for morbidity, mortality and Pathology. Affected farms raised local chickens, duck, turkey, guinea fowl and geese and were already confirmed to be infected with HPAI virus by virus isolation and reverse transcriptase polymerase chain reaction at the National Veterinary Research Institute, Vom Nigeria. Backyard local chickens recorded the highest number of death with 89.4% of the total flock size while the duck had the highest mortality rate at 87.1%. Mortality rate was least in guinea fowls (20.55%), and above average in geese (54.64%). For Pathology, submitted carcasses comprised of sixty (60) chickens, twenty-nine (29) ducks, thirty-seven (37) turkeys, fourteen (14) guinea fowls and twelve (12) geese which were examined for gross morphological changes and histopathology. Though lesions sparingly occurred in these village poultry, main pathologic findings were associated with the nervous, circulatory, respiratory, and gastro-intestinal systems and occasionally lesions were general unspecific and multi-systemic. It was observed that mortality rate was highest in duck, then chicken and turkey compared to guinea fowl and geese while lesions were milder and mortality were acute in these flocks.