Pathogenicity of Eimeria brunetti in Bacteria-Free and Conventional Chickens

In pathogenicity studies comparing bacteria-free and conventional chicks parasitized with Eimeria brunetti, mortality was 15/62 in bacteria-free birds as compared to 7/61 in chicks with conventional flora. Visual lesion scoring using a scale of 0 to 4, produced means of 2.6 in bacteria-free birds as compared to 2.4 in the conventional controls. There was no appreciable difference in weight gains, feed conversion or microscopic lesions between the two groups. Cecal lengths were shorter in bacteria-free chickens than in conventional controls. This difference was probably due to a previously unreported effect of the gnotobiotic environment. Gnotobiotic uninfected cecal lengths were similar to those of gnotobiotic infected birds. The prepatent period was 135 hr in both infected groups. Moderate coagulative necrosis of the lower small intestine, rectum and ceca was observed in bacteria-free birds as well as those with normal flora. This study establishes the fact that the presence of secondary microbial invaders is not essential for E. brunetti either to establish itself, or to induce pathological change.