Lesions and Prevalence of Newcastle Disease in Chicken Presented for Necropsy at Faculty of Veterinary Medicine, Makerere University

Poultry diseases are among the major constraints of chicken production in Uganda of which Newcastle disease (ND) is still one of the most important devastating diseases of chicken. This study was conducted from October 2008 to March 2010 to identify and describe the lesions due to ND, determine its prevalence and relate the presence of the viral antigen in tissues to the lesions in the various organs of chicken presented for disease diagnosis in Department of Pathology, Faculty of veterinary Medicine, Makerere University. Chickens for necropsy in the study period were received from clients coming from the Central, Eastern and Western regions of Uganda. Necropsy was done on a total of 216 chicken carcasses; samples for histopathology were obtained from various organs and fixed in 10% buffered formalin. The fixed tissue samples were then trimmed and processed for histopathology. Then immunohistochemistry (IHC) was performed on 86 samples of formalin fixed, paraffin embedded tissue sections to confirm ND in which the presence of viral antigens in the target tissues were specifically detected as brown precipitates mainly in mononuclear phagocytic cells. Diagnosis based on clinical and pathological findings showed that coccidiosis was the most common condition encountered (25.0%), followed by ND (23.61%), helminthiasis (12.50%), pasteurelosis (6.02), salmonellosis (3.70%), infectious bursal disease (3.24%) and other non specific conditions constituted 25.93%. Of the 86 samples tendatiely diagnosed with NCD and tested for ND using IHC, 44 (51.16%) were found positive for the disease. In conclusion, Newcastle disease is still among the most prevalent diseases of chicken in the study area. Clinical – pathologic findings provided some bases for ND diagnosis but are less reliable method, therefore, a more sensitive and specific diagnostic tests such as IHC, RT-PCR, HI, in situ hybridization and other definitive tests should be used in addition to histopathology to confirm ND, so as to provide accurate and reliable advice to poultry farmers.