Study On Pathogenesis And Phrlogenetic Development Of Cryptosporidium

Cryptosporidium is a kind of parasitic protozoon which could cause diarrhoea of human and animal, and cryptosporidiosis caused by it is a kind of zoonotic protozoiasis. So there were important significance to study on pathogenesis and phylogenetic development of Cryptosporidium.Cryptosporidium infection rate were investigated in chickens ,ducks, pigs and dairy cattles ,and also in worker in dairy farms in Henan Province and Beijing suburban .The cryptosporidia infestation percentage of 23 groups of duck s were 69.57%(16/23), that of 113 individual fecal specimen were 17.7%(20/113) in 8 pig farms, that of 70 individual fecal specimen collected randomly according to 10% percentage were 40%(28/70) in 7 dairy farms , that of 184 individual fecal specimen collected from Yawei dairy farm in Zhengzhou Henan Province were 22.3% in another test. Oocyst concentrtion in feces from both pig and duck were lower than that of dairy , no oocysts in chicken feces were tested were found in Beijing ,but not in Henan Province. The 34 worker in Yawei Dairy Farm were negative..A strain of Cryptosporidium derived from quails was indentified as C.meleagridis in previous experiment.The pathogenicity of the Cryptosporidium strain to ostriches,chickens,ducks and mice were studied,these experimental animals were designed immunocopetent and immune supperession group respectively. There were only diarrhea in quail, chickens, mice, ducks which infected with C.meleagridis, but no clinical signs in ostriches.There were multiple peaks in those immune supperession experimental animals. The experiments were carried out on pathology of some organs in young chinckens and mice that infected with Cryptosporidium meleagridis from quails, We found that Cryptosporidium derived from quails mainly parasitized in duodenum of mice and ileum of chicken which challenged with it, the intestinal villis of these experimental animal became atrophied and desquamated.These results were reference to the studies on C.meleagridis.A large number of spherical organisms with different sizes were embeded in the microvilli of the trache-as and bursa of Fabricius(BF) were found by scanning electron microscope. There were two types of parasitophorous vacuole,one had a spherical residual body in it and another not.Cryptosporidia and epithelium cell were linked with the comblike structure in the bottom of parasitophorous vacuole(PV). Every endogenous developmental stage of C.baileyi was located in the PV that formed by the microvillous membrane which rose and wrapped up the parasite.Oocysts of Cryptosporidium baileyi isolated from ostrich were orally inoculated into ostrich to observe their development by scanning electron microscope and transmission electron microscope. Typeâ… trophozoite in the BF of ostrich nuleus of it is distinct, typeâ…¡typetrophozoite of cryptosporidia in BF of ostrich fooder organelle was distinct, rough endoplasmic reticulum is rich. PV membrane of typeâ… merozont was rough,there were seven merozoites in typeâ… merozont, there were three podgy bananalike merozoites in typeâ…¡merozont.Residual body is distinct,rough endoplasmic reticulum of typeâ…¡merozont was very rich in these results.We characterized the small-subunit rRNA gene of the isolates from poultry in Beijing suburban,Henan province,Ningxia Hui Autonoomous Region.Results of the phylogenetic analysis revealed the presence of one genetically distinct species , the C.baileyi.The phylogenetic tree constructed from these sequence is in agreement with our previous results based on the small-subunit rRNA 830bp sequence of Cryptosporidium parasites.