Abstract   

    A study was conducted to assess the prevalence and various risk indicators of Marek's disease (MD) in commercial layer flocks. A total of.207 layer flocks were studied around Gojra, district Toba Tek Singh from July 1998 to June 1999. Data were collected through cross-sectional epidemiological methods regarding their demography, management practices, prophylactic procedures and concurrent diseases. Prevalence attack rate of Mb in this population was 20.77% (43/207). A mortality rate ranging from 5.40 to 11.60 per cent was recorded. The maximum prevalence was observed in birds of 13 to 30 weeks of age. Eleven out of 12 categorial variables had significant relationship with flock MD status. The most important risk factor of the disease was early exposure of Immunosuppressive diseases like Gumboro, chicken infectious anaemia and coccidiosis, etc. (P<0.01). Other factors were non restricted movement of visitors (P<0.01), poor and un-isolated broodjng of chickens (P<0.01), presence of farm animals and pet birds (P<0,01 )0 It was also observed that the disease prevalence was quite high on farms owned by laymen in comparison with those managed by educated persons (P<0.0 1).    

Key words: Marek's disease, Epidemiology, Prevalence, Layer.