Surveillance for avian influenza virus in captive wild birds and indigenous chickens in Nigeria

Several reports of avian influenza virus (AIV) have been made on commercial chickens and wild birds in sub-Saharan Africa, but there is paucity of information of AIV among captive wild birds and indigenous chickens. Blood samples were obtained randomly from captive wild birds and chickens. AIV nucleoprotein antibody detection involved the use of enzyme immunoassay (ELISA) and subsequent subtyping with H5 and H7 AIV antigens (haemagglutination inhibition). Four hundred birds belonging to nine families and 14 species were sampled, and overall prevalence of 23% (92/400) was obtained (captive wild birds (10.4%, 5/48), indigenous birds (47.3%, 87/184) and exotic commercial birds (0.0%, 0/168)). Twelve ELISA-positive birds (13.04%) were positive to H7 antigen. Univariate analysis indicated statistical significance of AIV prevalence in captive wild birds (p < 0.0001) and exotic birds (p < 0.0001) using indigenous chickens as reference. This study gave an evidence of exposure of captive wild birds and indigenous chickens to AIV in Nigeria. Scavenging activities common among indigenously raised chickens, unrestricted movement of nonflying wild birds within the captive complex and free access by migrating wild birds to captive wild birds and local chickens were likely factors observed to promote AIV transmission. Continuous surveillance can further highlight the roles played by these birds in the epidemiology of AIV.