Gross and Microscopic Lesions of Newcastle Disease in Backyard Poultry in Zaria Metropolis, Kaduna State

Newcastle disease (ND) continues to be a major constraint to backyard poultry production in Nigeria's North West zone, causing significant mortality and economic losses among smallholder farmers. This descriptive study examined gross and microscopic lesions of Newcastle disease in chickens obtained from backyard flocks across Zaria metropolis, Kaduna State, from March to September 2023. A total of 85 chickens exhibiting clinical signs consistent with ND, including respiratory distress, nervous manifestations, and greenish diarrhoea, were euthanised and subjected to thorough post-mortem examination. Representative tissue samples from the trachea, proventriculus, caecal tonsils, brain, and intestines were processed for histopathological analysis using standard procedures. Gross findings included haemorrhagic proventricular erosions, caecal tonsil haemorrhages, petechiae on the intestinal serosa, and tracheal congestion. Microscopically, lymphocytic encephalitis with perivascular cuffing, necrosis of caecal tonsil lymphoid follicles, and catarrhal enteritis were prominent features. Lesion scores were significantly higher in unvaccinated flocks compared to vaccinated ones. The study highlights the inadequacy of vaccination coverage in backyard poultry systems within the study area. These observations are consistent with recently published reports on velogenic viscerotropic ND pathology in African village poultry. Improving vaccination delivery through community-based animal health workers and reducing the movement of birds during market days are critical interventions required to reduce disease burden. Keywords: Newcastle disease, histopathology, backyard poultry, Zaria, lesions