| During recent years, research into our understanding of Cryptosporidium and cryptosporidiosis has become increasingly diversified yet reviews tended to concentrate the molecular tools to solve questions about the on epidemiology and the cell culture,but up to now no medicine could cure this zoonotic protozoiasis. In this research comparing the methods of purifing and excysting Cryptosporidium.spp intend to establish the model of culturing Cryptosporidium in chicken embryo to study its endogenous developmental history and evaluation the effects of antiprotozoal drug on cryptosporidiosis .1. In order to obtain Cryptosporidium andersoni oocysts from feces to culture in vitro, the present study was undertaken to sepetate and purify Cryptosporidium andersoni oocysts using different diluted Sherther's solution with distilled water and PBS, in which recovery rates and excystation rates were compared. Resultsshowed that recovery rate was 83.70% when oocysts were floated by 2:1Sherther's sucrose solution diluted with distilled water in three times, and the number of oocysts was 101.50% more than with which Sherther's sucrose solution (P<0.01). Recovery rate and excystation rate of purified oocysts was 47.52% and 87.87% using solution sucrose diluted with distilled water, respectively, and the excystation rate of purified oocysts was insignificantly different compared with Sherther's sucrose solution diluted with PBS in the same methods.There were no significantly different in statistics in above two methods (P>0.05). It is indicated that 2:1Sherther's sucrose solution diluted with distilled water is economic and effective to separate Cryptosporidium andersoni oocysts from feces and its recovery rate is higher than Sherther's sucrose solution. Sherther's solution sucrose diluted with distilled water as an alternative to PBS has no obvious effect on oocyst activity, which can be used in vitro cultivation.2. To obtain purified Cryptosporidium oocysts from faces for specal test purposes. Sheather's sucrose solution diluted with distilled water as an alternative to PBS was used to purify three different Cryptosporidium.spp and density of sucrose solutions were determined. Recovery rates of purified oocysts were caculated and activity of oocysts were evaluated with malachite green stain method and excystation rates of oocysts. Recovery rates of purified Cryptosporidium andersoni, C.baileyi and C.suis oocysts were 47.52%, 49.55% and 41.70%, respectively. The average recovery rates was 46.26%. The activity rates of purified oocysts were 97.88%, 96.67% and 95.14% with malachite green stain method, respectively. The average activity rates of purified oocysts was 96.56%. Excystation rates of purified oocysts were 87.87%, 80.03% and 81.67% after incubating in a water bath at 37℃for 1 h , respectively. The average excystation rates of purified oocysts was 83.19%. Distilled water as an alternative to PBS is economic and effective to purify Cryptosporidium oocysts from feces. Purified Cryptosporidium oocyst activity is beyond 80.00% , which can be used for particular laboratory purposes.3. For understand biological characters of different Cryptosporidium species ,the excystion rates of C.andersoni,C.baileyi,C.parvum and C.hominis oocysts were compared in PBS and 0.75% synthetic sodium taurocholate solution(TDC)and it was researched futher that the excystion rates of C.bailey oocysts treated with different excystation solutions.The results showed that the gastric species C. andersoni was sensitive to temperature ,the excystion rates was high in 37℃PBS,but had not significant different between in 37℃PBS and in 0.75% TDC solution(P>0.05). The excystion rates of intestinal species both C.parvum and C.hominis were lower in 37℃PBS than in 0.75% TDC solution(P<0.01). C.baileyi oocysts could excysted in PBS and 0.75% TDC solution at 37℃(P>0.05)respectively,but the excystion rates in PBS and 0.75% TDC solution at 40℃were higher than at 37℃,respectively,and significant different(P<0.05),but in 0.75%,2×0.75% and 3×0.75% TDC the excystion rates had no significant differen(tP>0.05). The conclusions were that excystion rates of Cryptosporidium multiplied in different hosts and organs were extremely significant different. The gastric species were respond to temperature alone, but temperature and excystation solution were required to elevate excystion rate for intestinal species and the results of excystion of C.baileyi oocysts were approach to intestinal species. These observations were a supplement to other Cryptosporidium taxonomy,which were useful to study biological character of Cryptosporidium and culture in vitro.4.To study the endogenous developmental history in chick embryo, C. baileyi oocyst from chicken were inoculated in chicken embryo allantoic cavity of 10-day-old to observed development process of C. baileyi in SEM and TEM. The results showed that the life circle of C. baileyi in chicken embryo was about 96h and the social phenomennon and synchronism of C. baileyi in CAM. The most of new mature oocysts were near blood vessel and the number of oocysts in CAL was most in 168h in which the recovery of oocyst were applicable. These research are further to know Cryptosporidium endogenous developmental history and evaluation the effects of antiprotozoal drug in chicken embryo.5. To explore the effect of oocyst multiplication and pathogenicity of Cryptosporidium baileyi from chicken in chick embryo and chicken by compound sulfamethoxydiazine, sulfadimidine, diclazuril and azithromycin, the anticryptosporidial activity of these potential drugs were observed in chick embryo and chicken infected artificially with C. baileyi oocyst from chicken.The develepment of chick embryo and C. baileyi were both evaluated ,and the quantity of oocyst in chick embryo were counted. In addition, main clinical symptoms of cough, sneezing, dyspnea, pattern of shedding oocysts, weight gains, morbidity and mortality in chicken infected with the oocysts were observed. The results showed that the number of oocysts in chick embryo treated with compound sulfamethoxydiazine, sulfadimidine, diclazuril and azithromycin in comparison to control is 15.05%, 88.71%, 77.42% and 68.82% respectively. Moreover, compound sulfamethoxydiazine can reduce morbidity (20%), mortality(13.13%) and clinical signs of respiratory tract disease observed in chickens orally inoculated 40×104oocysts of Cryptosporidium baileyi at 4 days of age (30 chickens/group). It was also found that the intensity of oocyst discharge from chickens in treated group with compound Sulfamethoxydiazine was lower than that in untreated group. Sulfamethoxydiazine may be recommended in the prevention of avian cryptosporidiosis, as the compound is administered continuously in an adapted dose.
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