[Study of immunity in coccidiosis in chickens experimentally infected with Marek's disease].

The immunity was studied against coccidiosis in birds that had preliminary been infected with Marek's disease. Results showed that birds infected with Marek's disease are unable to build up stable immunity against an oocyst infection of Eimeria tenella. The rate of mortality due to Marek's disease in birds infected with the virus of Marek's disease and additionally infected with oocysts of E. tenella was higher as compared with that in birds that were infected only with the virus of Marek's disease.