Research On The Biological Characters Of Cryptosporidium Baileyi

As for its worldwide distribution of Cryptosporidium, Cryptosporidiosis has become one kindof parasitic disease that has been found in human and animals,significantly influencing the public sanitaryissues. Cryptosporidium baileyi is the predominant species in birds, and it is also the commonCryptosporidium species in chicken farms in China, however, the pathogenicity dosage of C.baileyi isunclear. In our study, three dosage of Cryptosporidium baileyi from duck were used to inoculate2-day-old chickens used and the clinical manifestation, weight gain,oocysts shedding regulation, bursa ofFabricius index, and scanning electron microscope (SEM) of parasitic site were obtained. Results showedthat1.6×106C.baileyi oocysts could cause obvious respiratory disease. The weight gain of infectedchickens significantly decreased, and the atrophy of bursa of Fabricius was severe. The pathogenicity andthe regulation of oocysts shedding of C.baileyi was associated with the dosage of Cryptosporidiumoocysts, with the major pathological change being respiratory disease and bursa of Fabriciusinflammation.In order to study the methods of Cryptosporidium cultured in chicken embryos,9-day-old broilerchicken embryos are inoculated with C.andersoni、C.hominis and C.baileyi oocysts, in which thedevelopments of Cryptosporidium were observed. Results showed that C.andersoni and C.hominisoocysts were found in the chorioallantoic membrane, but other developments of parasite were notobserved in chicken embryos. However, All developments of C. baileyi were observed in chickenembryos. This suggested that C.baileyi could complete the whole life circle in chicken embryos, but notC.andersoni or C.hominis, which was an aid to study Cryptosporidium cultuted in chicken embryos.In order to do research on the biological characteristics of the different parasitic host and differentparts of Cryptosporidium. In this test we used C.andersoni, C.baileyi, C.parvum and C.hominis for thestudy,we made an comparative analysis of their excystation rates in PBS and TDC solution by waterbath,and furthermore comparated the excystation rate of Cryptosporidium baileyi in various alimentaryliguid and different tempratures.Result: Gastric parasites are sensitive to temperature, Cryptosporidiumandersoni has higher excystation rates in PBS when37℃and no significant difference in0.75%TDCsolution at the same temperature（P＞0.05）. The excystation rate of intestinal parasites such as C.parvumand C.hominis is higher in0.75%TDC solution than in PBS （P＜0.05）. C.baileyi can partly excystate inPBS when37℃,similar result we got in37℃TDC solution（P＞0.05）, but its excystation rate is muchhigher when40℃,and no significant difference in different concentration（P＞0.05）.Our test indicatesthat excystation rates of oocysts from different parasitic locations in the same alimentary liguid, especially in PBS are significantly different. Oocyst excystation rates of gastric parasites species are highat appropriate temperature, but that of intestinal parasites requires not only the right temperature, and hasa strong dependence on alimentary liguid.The condition of oocyst excystation rates of C.baileyi is closerto gastric parasites species, it is a complementary of conservative gene classification analysis such asCryptosporidium18SrRNA, and this can lead us to learn more about in vitro culture and biologicalcharacteristics of Cryptosporidium.In order to detect Cryptosporidium baileyi in chicken embryo, Real-time qPCR method wasestablished with primers designed according the C.baileyi and chicken18S rRNA gene from GenBank.This method was validated on chorioallantoic membrane and allantoic fluid samples including C.baileyiafter7d innoculation. The results showed that amplification of DNA from C.baileyi oocyst were detectedand cells of chorioallantoic membrane were not. Standard curves of Real-time qPCR was precise(R2=0.998). The sensitivity of the assay was10oocysts in PBS. In summary, a rapid and specificreal-time qPCR method for the detection of C.baileyi in chicken embryo samples has been developed,which could be served as a valuable tool for evaluating reproduction and assessing potential drug ofC.baileyi cultured in chicken embryo.