Detection of avian Influenza virus H5N1 serotype in backyard poultry, wild and zoo birds in Pakistan

Highly pathogenic avian Influenza virus (HPAI) serotype H5N1 caused severe harm to the backyard poultry, wild and zoo birds along with commercial poultry population of Pakistan during 2006 to 2007. Outbreaks were evidenced by passive surveillance from 2000 samples analysed over a period of 3 years by virus isolation and identification using haemagglutination tests, serology and RT-PCR in domestic backyard poultry (50.6%), wild (4.76%) and exotic pet birds (29.46%) and illustrated an alarming situation for the villagers and the domestic poultry keepers. An overall prevalence of 50.60% was obtained and this virus also infected a number of zoo birds near the outbreak epicenters such as duck (2.1%), common goose (1.19%), turkey (1.49%), peafowl (0.89%), ostrich (0.29%) and falcon (0.29%) and constituted the main cause of severe mortality in scavenger (4.76%) and other wild birds (8.93%) near these epicenters. Considering virus isolation and identification as the reference method, the agreement scores with serology and RT-PCR were high (> 95%) but RT-PCR exhibited the lowest sensibility (72.92%). However, no sero-conversion against H5N1 virus was found by active surveillance in the Punjab province, emphasizing in this way the necessity for a continuous virological monitoring to avoid its spread in healthy populations of birds and human beings in close contact with infected birds.