| Coccidiosis was one of the most common diseases occurring in chicken industry. It has significant meaning to understand the epidemiology of Coccidiosis in chicken. Eimeria maxima has moderate pathogenic, and it was one specie of coccidium that exists widely. According to the research of the infection institution of broiler chicken in Jiaodong district, the result showed that the infection rate of coccidium was 64.6%, and the infection rate of Eimeria maxima was 31.7%. In about 5- week-old the infection rate of the Eimeria maxima reach the peak. The research showed that it was universal of the Coccidiosis in Jiaodong district, and it should be paid more attention. Factors causing Coccidiosis were the mode of breeding, the environment sanitation of the chicken house and the drug and vaccine of Coccidium and so on. The breeding mode of broiler was mostly in ground in Jiaodong, it may be the reason for high infection rate of the Coccidiosis. The infection rate of the Coccidiosis and E.maxima has no significant meaning, which indicated that the breeding was balance in Jiaodong. According to relationship between the age of broilers and the OPG of E.maxima, it indicated that in 5- week-old the infection rate get to the top.Using single oocyst sepreating techniques, commix of Coccidiosisfrom different area in Jiaodong district was separated and 6 E.maxima species were isolated and identified. This kind of Coccidium mainly located in the middle area of small intestine, the oocyst was circularly, with a rough, golden wall, six hundred occysts were determined, with the range of 21.5~36.5umX 18.5~30.5um,average31.39umx22.10urn, and the average shape index was 1.42. Sporocyst has Stader's splint, not found the relict of the sporocyst, six hundred occysts were determined, with the range of 12.5-20.5um X 6.5-9.Oum, average 16.5umX 7.5um, the shortest sporogony time was 30-32h, the latent period was 129h~134h , were named Yi, Y2, Qi, Q2, Wi and W2respectively. Three strains pure E.maxima oocyst was used to make the pathogenesis experiment in broilers, one hundred AA broilers were divided into 10 groups( one group was uninfected group while the others were infected groups ) , each broiler was inoculated with 5X 104, 1 X 105 and 2X 105 sporogonized oocyst. The result indicated that there was no significant pathogenesis difference among Yi, Qi and Wi . If ten thousands sporogonized oocyst was inoculated ,the body weight gain was descend 53% comparatively. If 100 thousand was inoculated, the body weight gain descend 57.5% comparatively. If 200 thousand was inoculated, the body weight gain descend 74.7% comparatively , the mortality rate were 10%. The pathogenesis of every kind of Coccidium was important to evaluate their economic loss.To knowing the drug resistance of Coccidiosis, six E.maxima was isolated from six chicken industry in Jiaodong district, each AA chicken was inoculated 0.2 million sporogonized oocyst. After that Diclazuril,Amprolium Hydrochloride, Pabulum Salinomycini and Maduramicin were used to evaluate the drug resistance. ACI, RLS,ROP and POAA were used as the index in the experiment, the drug resistance degree were divided into four grade (S, LR, MR and CR). The results showed that four E.maxima strains had no durg resistance to Diclazuril, two E.maxima strain had low-grade to Diclazuril, two E.maxima strain had no drug resistance to Amprolium Hydrochloride, four E.maxima strains has low-grade drug resistance to Amprolium Hydrochloride, two E.maxima strain has low-grade drug resistance to Pabulum Salinomycini, four E.maxima strains have moderate drug resistance to Pabulum Salinomycini, six E.maxima strains have all drug resistance to Maduramicin. The research offered directory to constitute the drug scheme , enlarge the periods of the drug and control of Coccidiosis. Diclazuril, Amprolium Hydrochloride can be used reasonable, Pabulum Salinomycini can be used carefully and Maduramicin must be stop used .Crossing-protection of different E.maxima was compared by three chicken industry in different area of Jiao dong district. Seven month old AA broilers were vaccinated Yi, Qi and Wl through inoculated 3000 oocysts in total immunized 9 groups. In 19 days old, chicken were immunized by 100 thousands each one in 9 immunized groups and 3 not immunized groups, comparative protection and comparative body weight gain rate were tested and synthesized , the result indicated the protection of Yi to Qi and Wl, the protection of Yi to Yi had significant meaning. The protection of Qi to Yi and Wl, between the protection ofQi to Qi had significant meaning. The protection of Wi to Qi and Yi between Wi to Wi has significant meaning. It showed there has significant meaning of Yi Qi and Wi crossing-protection. According to the analysis of variance, it showed that Yj, Qi and Wi have high immunogenic. Taking the E.maxima as cardinal coccidium strain could get the best protection effect.
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