| Genus Cryptosporidium is a parasitic protozoan pathogen that mainlycauses diarrhea in both immunocompetent and immunocompromisedpersons. In addition to diarrhea, infection is associated with abdominalcramps, fever, nausea, dehydration, and weight loss. Cryptosporidiuminfection can lead to premature death in people withimmunocompromised conditions, especially AIDS patients, because theillness is not self-limited, as it is in immunocompetent persons. Infectioncan be acquired from infected persons or animals and from food- andwaterborne routes of transmission.In recent years, severe economical losses caused by large outbreaksof cryptosporidiosis in the USA and Canda have been reported.Developed countries' governments have awared the importance ofmonitoring the contamination and the distribution of Cryptosporidium inwater and in environment. Especially in situations of the spreading ofHIV and the immuno-depressed status caused by ubiquitousenvironmental and occupational hazards make it possible for the infectionand the spread of cryptosporidium. For all the reasons above,cryptosporidiosis has attracted much attention from the scientist and society.In the past, the diagnosis and epidemiology study ofcryptosporidiosis depends on detecting cryptosporidium oocysts in fecalby microscope. Modified fast acid method is the most frequently usedmethod. However, it brings much more workload and poorcompliance in field surveys and has limitations because of thepoor sensitivity especially in low endemic regions. So, serologicalmethods attain people's interest and have been applied in the field.Although immunological diagnosis does not offer an alternative toparasitological diagnosis, especially in clinical situation, thespecific antibody may someway reflect the characteristics ofepidemic for the endemic area population.We selected 2 communities differing in social-economicalconditions, water cosumation and sanitation status. The demaologyinformation and the serum of the population were collected. Withthe CP23 antigen based indirect ELISA, we quantitated theCryptosporidium specific antibody level of the population. Theprevalence status of Cryptosporidium in this area is estimatedaccording to the sero-prevalence determined by the cut-off values.The main results are as follows:1. Purified protein CP23 has been successfully prepared, based onwhich, we constructed the indirect ELISA method to detect thecryptosporidium specific antibody in our lab.2. It is the first time to report the cryptosporidium specificsero-epidemiology study for the population in China ruralcommunities. The cryptosporidium infection sero-positive rate for thepopulation of Mache village in Zhejiang province and Jiahu village inJiangxi province are 32.16% (173/538) and 70.20% (688/980)respectively. The difference of sero-positive rate is significant for thepopulation in these two communities (P=0.000). 3. Generalized estimating models analysis for cryptosporidiuminfection sero-positive rate and the related variants shows thateducation level, family income and schistosome infection has noinfluence on cryptosporidium infection sero-positivity in thepopulation of the same community, however, gender and age arerelated to cryptosporidium infection sero-positivity. Thecryptosporidium infection sero-positive rate between genders isdifferent. In population of Mache villiage in Zhejiang province, thecryptosporidium infection sero-positive rate of male is higer thanfemale in 6-10 age group, the rate is close in 21-30 age group andfemale are higher than male in other age groups. The sero-positiverate of male is close in all the age groups and age-dependent tendenceis shown in female. It reaches the highest value (48.05%) in 41-50 agegroup. The cryptosporidium infection sero-positive rate in all the agegroups is higer in female than in male. The positive rate of maleshows the age-dependent tendence and reaches the highest valus in41～50 age group (73.86%). The positive rate in female is close in allthe age groups and shows no such tendence.4. The education level (P=0.0239) and family income (P=0.000)of Zhejiang population is higher than Jiangxi. The difference ofeconomy level usally leads to different sanitation conditions. Thedifference of education level may lead to different habits. Theinfection of cryptosporidium is usually related to sanitation conditionsand habits. So, these results suggest a relation between theeconomical and education level to the difference of the sero-positiverate between these two villages.5. The B cell epitopes were predicted by screening the secondarystructure on the basis of prediction results of Parker Hydrophilicity,Emini Accessibility, Karplus & Schulz Flexibility and Kolaskar &Tongaonkar Antigenicity followed by a verification using ABCpred program. The predicted B cell epitopes locate at the region of aminoacids 273～278,103～115,129～146,31～37 for SA35, while 77～89,127～136,156～174,200～209 for SA40. These results will servefor the further research of these two cryptosporidium proteins.
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