IMMUNODEPRESSION TO RANIKHET DISEASE VACCINATION DUE TO INFECTIOUS BURSAL DISEASE VIRUS IN CHICKEN

Birds affected with Infectious Bursal Disease (IBD) become immunologically crippled, There are reports of immunosuppression to vaccination against Marek's Disease (Cho, 1970), spirochaetosis (Rao and Rao, 1981) and Ranikhet Disease (Faragher et al., 1972; Westury, 1978 and Rosales et al., 1989). The immuuosuppressive effect of IBDV is dependent on the age of the chicken and the interval between the infection and subsequent vaccination (Rao and Rao, loc. cit.). Infectious bursal disease affects chicken mostly from 2 to 6 weeks of age. It is a common practice to vaccinate birds against Ranikhet Disease (R2B strain) at 6-8 weeks of age. Though there are few reports of immunosuppression to R. D. vaccination due to IBD, detailed studies on the effect of IBDV in chickens of different ages, keeping the RD vaccination schedule undisturbed, are lacking and hence the present work was undertaken.