Pathology and molecular detection of influenza A subtype H9N2 virus in commercial poultry in Nigeria, 2024.

Background: After the first Avian Influenza H5N1 outbreak in Nigerian poultry in 2006, subsequent waves of outbreaks occurred, causing substantial losses. Despite effective control measures by 2008, a resurgence in 2015 led to further losses and required depopulation efforts.

Aim: The aim of this study was to do pathology and molecular detection of influenza A subtype H9N2 virus in commercial poultry in Nigeria during 2024.

Methods: In February 2024, a poultry farmer reported high mortality in his mixed commercial poultry flock in Ibadan, Nigeria, submitting carcasses to the University of Ibadan's V.T.H. and the FAO Regional Laboratory at National Veterinary Research Institute (NVRI), Vom.

Results: Necropsy of nine Isa Brown layers and three Abor Acre broilers revealed cyanosis of comb and wattles, generalized petechial and ecchymotic hemorrhages including shank hemorrhages with sinusitis, pneumonia, and severe greenish fecal pasting also observed. At histopathology, denudation of the tracheal epithelia and parabronchial epithelial necrosis, obliteration, with airsac edema and emphysema were observed. At NVRI, qPCR detected an Influenza A H9N2 virus in several pooled organ samples of layers, and broilers and eliminating the avian infectious bronchitis and Newcastle disease viruses.

Conclusion: This is the first report of an H9N2 outbreak in commercial poultry in Southern Nigeria. The high pathogenicity shown in commercial poultry in this outbreak and the risk of dispersal of infected live poultry in Nigeria as previously seen in H5N1 require stakeholders' intervention.