Pathological Study of Avian Aspergillosis in Commercial Poultry Flocks in Enugu State, South East Nigeria

Avian aspergillosis caused by Aspergillus fumigatus is a fungal respiratory disease causing significant morbidity and mortality in young and immunocompromised poultry in Nigeria's South East geopolitical zone, particularly when mouldy litter or contaminated feed is used. This study investigated the gross and histopathological features of aspergillosis in commercial poultry flocks in Enugu State, from January to June 2023. Sixty chickens from five affected farms with clinical signs including respiratory distress, gasping, lethargy, and torticollis were necropsied. Tissue specimens from the lungs, air sacs, brain, and proventriculus were processed for histopathological analysis with haematoxylin and eosin, and Grocott-Gomori methenamine silver stain for fungal visualisation. Feed and litter samples were cultured for Aspergillus species. Aspergillus fumigatus was isolated from feed samples in 60 percent of affected farms. Gross lesions included caseous white-to-yellow nodular plaques throughout the lungs, air sacs, and occasionally in the brain. Microscopically, lesions revealed pyogranulomatous inflammation with septate branching hyphae, central caseous necrosis, and surrounding epithelioid macrophages and heterophils. Cerebral aspergillosis was documented in 13.3 percent of cases. These findings underscore the need for quality feed procurement, dry litter management, and antifungal prophylaxis in at-risk flocks. Keywords: aspergillosis, Aspergillus fumigatus, poultry, histopathology, Enugu