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1、Section 3 CryptosporidiosisCryptosporidium is a kind of opportunistic protozoan parasites that are parasitic on epithelial cells of human and animal digestive tract and respiratory tract and can cause severe watery diarrhea.Cryptosporidium can be widely transmitted through air,soil,food and water,an
2、d can infect a variety of vertebrates such as mammals,birds,amphibians,reptiles and humans,and can cause a series of animal digestive tract diseases.1.PathogenCommon Cryptosporidium include:C.andersoni,C.baileyi,C.canis,C.felis,C.hominis,C.meleagridis,C.parvum,C.muris,C.bovis,C.galli,C.suisProtozoa
3、Apicomplexa Coccidea Eucoccidiorida Cryptosporidiidae CryptosporidiumClassification：The oocyst(thick wall type)is oval or spherical,4.6-5.4 m 3.8-4.7 m,the average size is 5 m 4.5 m,and the length:width ratio is 1.19.MorphologyParasitic site:inside the cell membrane of intestinal mucosal epithelial
4、cells.2.Life cycleAfter the host swallows the fully sporulated oocysts,the oocysts are decapsulated in the upper small intestine to release sporozoites.The sporozoites pass through the mucus layer and adhere to the intestinal cells,form a parasitophorous vacuole inside the cell membrane of the intes
5、tinal cells.The sporozoites differentiate into trophozoites in the vacuole,and then continue to develop type I schizonts,each mature schizonts contain 6-8 merozoites.The released merozoites invade nearby intestinal cells and continue this asexual reproduction cycle.The merozoites can also form type
6、II merozoites when they invade and develop again,and the latter contain 4 merozoites when they mature.When type II merozoites invade intestinal cells,they develop into macrogametocyte and microgametocyte.Each microgametocyte can release 16 or more microgametes when they mature.The microgametes combi
7、ne with the macrogametes to form zygotes,which begin to enter the sexual reproduction stage and form oocysts.There are two types of oocysts.The thin wall types(about 20%)sporulate directly in the intestine and release sporozoites for self-infection.The thick wall type oocysts become sporulated with
8、the excretion of feces.It can infect new hosts.Cryptosporidium can parasitize in a variety of mammals,birds,amphibians,reptiles and fish.Cyptosporidiosis includes two types:animal-to-human transmission and human-to-animal transmission.There are also reports that human-to-human transmission is possib
9、le.3.EpidemiologyThe vast majority of outbreaks of Cyptosporidiosis are due to drinking water pollution.However,it should be pointed out that food contaminated with oocysts such as fresh vegetables and salads can also cause this disease.In the United States,there has been an outbreak of Cyptosporidi
10、osis caused by apple juice pollution.The 1993 Cyptosporidiosis outbreak in Milwaukee and Wisconsin in the United States caused 400,000 illnesses and more than 1.6 million infections.The epidemiology of Cryptosporidium in the population has distinct regional characteristics.The results of a survey re
11、port showed that the average infection rate of Cryptosporidium in Chinese 10-year-old children is 50%,while that in Brazil is almost 100%in 2-year-old children,and the infection rate in young American adults is 16.9%.People with low immunity,especially those with innate immune diseases,tumors,radiat
12、ion and drug chemotherapy due to diseases,HIV infection,once infected with Cryptosporidium,the consequences are often much more serious than normal people.1.Direct or indirect transmission from person to person;2.Transmission between animals3.Transmission from animals to people4.Transmission by drin
13、king water and recreational water5.Transmission by contaminated food6.Possible airborne transmission.Route of transmission:The most obvious symptom is diarrhea.Young animals,especially young ruminants,are more prone to Cyptosporidiosis.The outbreak of Cyptosporidiosis in animal populations is affect
14、ed by a variety of factors such as breeding density,breeding season,mixed stocking,forage and drinking water pollution,and the clinical manifestations are affected by other intestinal pathogen infections and it is difficult to accurately diagnose.4.Clinical symptomsDuring histopathological examinati
15、on,mild to moderate intestinal villous atrophy(shortened villi,fused into pieces,and flattened ends),crypt hyperplasia,focal necrosis,and inflammatory reaction of the intrinsic membrane are often seen.5.Diagnosis：When the patient has suspected symptoms of Cyptosporidiosis such as watery diarrhea and
16、 the clinical antibiotic treatment is invalid for several days,it should be suspected as a cryptosporidium infection.At this time,fecal samples should be taken for special staining examination of oocysts.In addition,the endoscope can directly observe the intestinal wall lesions,directly grasp the su
17、spicious lesion tissue to examine the pathological changes and pathogens.Modified acid-fast stain:After the oocyst smear is fixed and dried,it is stained with carbohydrate acid red staining solution(containing basic magenta and carbohydrate acid)at room temperature for 3-5 minutes,washed with water
18、to remove the staining solution,and then decolorized with 3%hydrochloric acid alcohol decolorizing solution.Malachite green solution is counterstained.http:/www.dpd.cdc.gov/dpdx/HTML/ImageLibrary/Cryptosporidiosis_il.htm Immunology diagnosis:Diagnosis of molecular biology:Single oocyst PCR.At presen
19、t,the commonly used laboratory PCR diagnosis methods are nested PCR and real-time quantitative PCR.Immunomagnetic bead separation technology greatly improves sample preparation capacity(high price).6.Prevention:Wash hands frequently;segregate children with diarrhea in infant care centers in time;do
20、not go to public recreational water facilities when infected with Cryptosporidium;try to avoid contact with animals,especially feces of young animals,animals;eat raw food as little as possible.Treatment:Normal patient:self-limiting infection.Take supportive therapy such as infusion;or use the drug Nitazoxanide.