| Rabbit coccidian is a kind of parasitic protozoan of Eimeria. According to research, 17 species of Rabbit coccidian exist, found in the animal's intestinal epithelial cells. Among rabbit coccidian, Eimeria stiedai is the most virulent, which parasitizes in the bile duct epithelial cells of rabbits, causing serious liver coccidiosis. Historically, chemotherapy has served as the conventional method in treating rabbit coccidiosis. Recently though, scholars have sought new ways to control the disease due to increasing problems such as resistant strains and drug residue. In recent years, while the Yangling rabbit industry has undergone rapid growth, the prevalence of rabbit coccidiosis has caused huge economic losses. This research investigates the infection rate of coccidiosis in rabbits in the Yangling area, using the saturated saline flotation method. We will discuss the biological characteristic and pathogenicity of EsYL strain.1 The results from the experiments show the infection rate of coccidian to be 83.5%, though the infection rate in different month-age rabbits varies. The infection rate in 1~2 month old rabbits is 99.4%, higher than that of rabbits older than 2 months. The infection rate of 3~4 and 5~7 months age is 97.0% and 78.7 % respectively. The infection rate in 12~24 months age is 38.9 %. In addition, 11 species of Eimeria were detected in infected rabbits. The E.perforans, E.flsvescens, E.irrestidua, and E.stiedai were dominant species with infective rates of 24.0%, 17.0%, 14.0% and 12.8% , respectively .2 Use of the EsYL Sporulared Oocysts orally infected to rabbits, then isolated the EsYL pure strains by the Oocysts isolate precipitation method and the generation subculture proliferation. With the isolated EsYL pure strains orally infected to rabbits again, we observe its incubation period, the first spore soocysts time, morphological characteristic, and process of morphological changes. The results tell us that Es incubation period was 14~16 d, and the Ovulation peak time was 21 d. The Oocysts is oval, with a size of 38.1μm~25.8μm×33.6μm~17.0μm, and a shape index of 1.7μm. The sporocyst is oval with stiedai body and spore angium debris, and a size of 13.0μm×11.0μm. Under the 29℃culture conditions, the first spore time was 39 h, and has the same process of morphological change as Emieria coccidia.3 We used the EsYL strain Sporulared Oocysts by orally infected to 24 young rabbits. The test group divided into 4 group(A, B, C, D), with Group A serving as the non-infected control group and groups B, C, D as infected groups. Each infected group was orally infected with 2.0×103, 1.0×104 and 5.0×104 Sporulared Oocysts. When we study the pathogenicity index value including the OPG, mortality, weight gained, liver index, serum aminotransferase, liver lesion score, and liver lesions, the results show that, compared with the control, Group D shows obvious pathological change(P﹤0.01), while Groups C and B show no obvious change(P>0.05). The results tell us that E.stieada(iYL) strain can cause highly serious liver coccidiosis in young rabbits. The study will provide scientific basis for liver coccidiosis of rabbit.
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