Marek's disease in local chicken strains of Ethiopia reared under confined management regime in central Ethiopia

The prevalence, clinical and pathological manifestations and extent of mortality due to Marek's disease (MD) was investigated from November 2003 to January 2004 among indigenous chickens of Ethiopia reared under confined management at the Debre Zeit Agricultural Research Center, central Ethiopia. Clinical signs, mortalities, gross and microscopic examinations as well as virological and serological test results were used for the study. Data from 503 local chickens (28 Jarso, 84 Konso, 88 Tepi, 151 Tilili and 148 Horro) were analyzed. The study indicated an overall significant difference between manifestation of clinical signs in acute (65.2%) and chronic forms (34.8). respectively (p < 0.01). There was also significant difference among ecotypes in manifestation and forms of MD (p < 0.01). The overall mortality was also very high (p < 0.01). Mortality assessment among age and chicken ecotypes revealed a significant difference (p < 0.01). MD fatality rate was very high in this study where 97.9% diseased birds died. Post mortem investigation revealed nodular tumorous lesions in. most visceral organs. Histopathological investigation revealed lymphocyte infiltration of visceral organs and nervous tissues. Serological prevalence study of MD using the Agar gel immuno-diffusion test (AGID) technique on 70 randomly sampled local chickens revealed an overall prevalence rate of 72.9%. MD antibody prevalence was not significant among chicken ecotypes. The result of the present study gives a hint for the possible reason behind the report that local chickens are unfit for confined management. MD was a serious health problem, and hence, from this study evidence is emerging to suggest the need for MD vaccination while rearing local chickens under confined management. Further detailed study on MD in local chickens and on the effectiveness of available MD vaccines in reducing the incidence of morbidity and mortality of local chickens under confined management is recommended.