Research Of Biological Characteristics And Pathogenicity Of Crypsporidium Meleagridis And Eimeria Maxima In Chicken

Cryptosporidium meleagridis, a intestinal parasite which can infect human, is one of the three common Cryptosporidium species of human being. In recent years, research related to C. meleagridis increasing, however, the biological characteristics has been in the exploration .To further understand the biological characteristics of C. meleagridis, lay the foundation for molecular biology research, C. meleagridis infection model with chicken was established; same day chickens infected with different dases C. meleagridis oocysts and different days chicken infected with same doses C. meleagridis oocysts, compare and research the pathogenicity. The results show that chicken infected with low dose(1.0×10²·mL^-1,1.0×10³·mL^-1) C. meleagridis oocysts don't show obvious clinical symptoms; necropsy no lesions; optical microscope and scanning electron microscopy detection no patasites.The results showed that 5 days Chicken infected with 1.0×10⁶·mL ^-1 the prepatent period was 4 days, and the patent period lasted 12 days, and the peak period was in PID5 and PID8. Main clinical signs was apparent loss of appetite, spirit of the depressed, diarrhea, etc; small intestine wall thinned; tissue section and scanning electron microscopy observed C. meleagridis parasited in duodenum, jejunum and ileum. There was little oocysts observes in 15-day-old chicken feces. Oocysts and clinical signs was not observed in 25-day-old chickens.This study used single oocyst isolation technique, separated Eimeria maxima oocyst from E. maxima positive chicken and experimental infection. Oocysts were observed in 130 hours after chicken were infected, the patent period lasted 9～10 days. The oocysts were oval and oocyst wall was yellow with the protoplasm was cinnamomeous. The shortest sporulated time was 32 hours. There was polar granule and 4 sporocysts with 2 sporozoites in oocyst. The average oocyst size was 35.7μm×28.4μm (32.4～39.3μm×25.1～32.4μm), form exponent was 1.26 . E. maxima was determined according to the prepatent period, parasite lacation, sporulated time and morphology characteristic. infect in chicken small intestine, 120 5-day-old chickens were divided into 4 groups, and infected with C. meleagridis oocysts 1.0×10⁶ mL ^-1, E. maxima oocysts 5.0×10⁴·mL^-1, same dose with both oocysts and same dose distilled water, respectively. The results showed that the prepatent period of co-infection group chickens shedding both parasite oocysts was consistent with chickens infected with C. meleagridis or E. maxima. PID5～10 d was the peak period of co-infection chickens shedding C. meleagridis. PID7 was the most oocyst production (6.0×10⁴·g^-1). The most peak of C. meleagridis infected chickens was PID8 and the oocyst production was 6.5×10⁴个·g^-1). The only peak period of co-infection chickens was PID6～12, however, peak period of chicken infected with E. maxima was PID6～9 and PID12～14. The most peak of shedding E. maxima from chickens in co-infected group (PID 6) was sooner than in E. maxima infected group ( PID 7). Main clinical signs were be observed in infected chickens, especially in co-infected group. Endogenous stages morphology of E. maxima could be observed in intestines of E. maxima infected chickens. Oocysts were not detected in control group, no clinical signs.This study has learned more biological characteristics about C. meleagridis, established C. meleagridis infection model with chicken, analyzed the pathogenicity, obtained purified E. maxima oocysts, and explored the pathogenicity and intercomparison of the two pathogenic agent. This paper provides a theoretical basis for controlling zoonotic cryptosporidiosis and prevention and treatment of coccidiosis, with public health significance.