High Pathogenicity and Strong Immunogenicity of a Chinese Isolate of Eimeria Magna Pérard, 1925.

Coccidia infection of rabbits with one or several species of parasites of the genus Eimeria causes coccidiosis, a disease leading to huge economic losses in the rabbit industry. Eimeria magna, one of the causal agents of rabbit coccidiosis, was characterized as mildly pathogenic and moderately immunogenic in previous studies. In this study, we identified a Chinese isolate of E. magna by testing its biological features (oocyst morphology and size, prepatent time) and sequencing its internal transcribed spacer 1 (ITS-1) DNA fragment. This isolate is highly pathogenic; infection of rabbits with only 1×102 oocysts caused a 55% reduction in weight gain in 14days. In addition, immunization with 1×102 oocysts prevented body weight loss against re-infection with 5×104 oocysts, indicating the high immunogenicity of this isolate. Our study described the distinctive phenotype of the Chinese isolate of E. magna and contributed to the research of geographic variation of rabbit coccidia.