Pathological changes and antigen localization in the small intestine of rabbits infected with Eimeria magna

Coccidiosis is a major disease caused by various Eimeria species in rabbits. The aim of the present study was to investigate the haematological and pathological changes in rabbits infected with E. magna. Moreover, the localisation of coccidial antigens was examined in the intestines of rabbits with two kinds of serum as primary antibodies. In the present study, forty-five 28-day-old weaned rabbits were randomly divided into three groups and reared in three separate places. Group A was infected with 20×103 sporulated oocysts of E. magna, group B was only used to produce anti-E. intestinalis serum by infecting them with 3×103 sporulated oocysts of E. intestinalis, and group C was designated as the control group. According to histopathological evaluation of group A, the epithelial cells of the jejunum and ileum were parasitised with a large number of oocysts and other stages of E. magna. The haematological results showed that red blood cell counts, haemoglobin counts, haematocrit levels and the percentage of lymphocytes were significantly decreased in group A compared with group C (P<0.01), but white blood cell counts and the percentage of neutrophils were significantly increased (P<0.01). The weight of group A began to decrease on the 5th day after infection, and this decrease continued until the 9th day. Immunohistochemistry staining revealed that two kinds of coccidial antigens were basically located at the same sites of the intestine when anti-E. intestinalis serum and anti-E. magna serum were used as primary antibodies. Most likely, E. magna and E. intestinalis antigens have some similar antigenic determinants; this finding provides a theoretical basis for screening for common antigens of these two coccidian species.