Molecular Characterization of Avian Influenza H9N2 and H5N1 from Outbreak in a Backyard Layer Farm in Kaduna State, Nigeria

Abstract

Avian influenza viruses (AIVs) have been reported in Nigeria since 2006, and the co-circulation of high-pathogenic avian influenza H5N1 and low-pathogenic avian influenza H9N2 subtypes in poultry has been reported. These Avian Influenza virus subtypes could lead to severe economic losses to the poultry farmers and may force the farmers out of the poultry production leading to unemployment for the staff of the farm. The co-infection with both highly pathogenic (H5N1) and low pathogenic (H9N2) could lead to possible re-assortment and the production of novel strain that can be highly pathogenic to chicken and may have the capacity to infect humans and be transmitted from human to humans which may lead to a pandemic of influenza. The clinical signs observed were somnolence, marginal cyanosis of the combs, ruffled feathers, matted vent and whitish/yellowish diarrhoea; while the post mortem examinations revealed dehydrated carcass, multiple foci of petechial haemorrhages on the abdominal fats, congested and necrotic-friable liver, edematous and congested lungs, congested spleen with multiple foci of necrosis, hemorrhagic and misshaped ovarian follicles, egg yolk peritonitis, swollen and hemorrhagic kidneys, erosion of the proventricular mucosa, congested trachea with mucoid exudates, and sinusitis. The disease was diagnosed based on the clinical signs, post mortem findings, competitive Enzyme-Linked Immunosorbent Assays (ELISAs) and clade-specific RT-qPCR, for the detection of co-circulating highly pathogenic avian influenza virus H5N1 and low pathogenic H9N2. The result of all sera (5/5) tested for Antibodies against Avian influenza Nucleoprotein produced positive results while 80 % of sera (4/5) tested positive for the H9 subtype of AIV. Antibodies against the H5 and H7 subtypes were not detected. The results of RRT-PCR and RRTPCR/ H5 were positive for both tracheal and cloacal samples. RRT-PCR/ H7 & H9 yielded negative results.