Serological and Molecular Detection of Low Pathogenic Avian Influenza Subtype H9N2 in Commercial Poultry Flock in Kaduna and Kano State Nigeria

The poultry business in Nigeria has been severely affected by highly pathogenic avian influenza (HPAI), particularly the H5 variant. Unlike H5 and H7 subtypes, low pathogenic strains like the H9N2 are not notifiable to the OIE. However, in many instances in the West African sub-region, this strain poses a threat to chicken and turkey farming. In the present study, reports of mortality in commercial layer chicken with clinical indications and lesions of Newcastle disease and E. coli septicemia from two farms in Kano and Kaduna states. Ten tracheal, cloacal swabs, and blood samples were collected from moribund and dead birds on each of these farms and sent to the lab for analysis. Using the Enzyme Linked Immunosorbent Assay, antibodies against the H9 subtypes of the AIV were found in 85 percent (17/20) of the sera. Low pathogenic avian influenza subtype H9N2, Escherichia coli and Klebsiella spp were detected in six samples by RT- qPCR and Microbiology respectively as well as virus isolation in 9-11day old specific antibody negative embryonated chicken egg. Hyperaemia, oedema, necrosis and loss of cilia on the epithelial lining of the trachea with heterophils and lymphocytes infiltration of the lamina propria were observed in all the samples. These findings confirmed the presence and circulation of the low pathogenic subtype H9N2 in commercial layer flock; though the virus is biologically low pathogenic, co-infection with other pathogens could exacerbate infection and cause severe economic losses. We suggest that all subtypes of avian influenza virus be monitored at all times across the country.