An Outbreak of Marek’s Disease in Adult Layer Chickens in Umuahia, Abia State, Nigeria

Between the months of May and August, 2014, a disease outbreak in two small poultry farms consisting of 600 and 550 Isa Brown layers both located in Umuahia, Abia state was reported to the Veterinary Teaching Hospital of Michael Okpara University of Agriculture Umudike. The two flocks, ages 31 and 41 weeks respectively, were vaccinated with MD vaccine mixed with gentamicine at day old. The clinical signs observed in the layers were paleness of the comb, emaciation, marked reduction in egg production, low morbidity and mortality rates of 4.7% and 2.3% in the first farm and 9.5% and 2.7% in the second farm. Postmortem revealed prominent neoplastic nodular lesions in their visceral organs. The histopathology of the affected organs of the birds showed highly pleomorphic lymphoid proliferation of the tissues. Based on the clinical signs, postmortem lesions and histopathology, the disease was diagnosed as acute Marek’s disease.