 | This articleis missing information about effects ofCryptosporidium infection on groups of animals other than mammals. Please expand the article to include this information. Further details may exist on thetalk page.(August 2023) |
| Cryptosporidium | |
|---|---|
 | |
| Oocysts ofC. muris found in human feces | |
Scientific classification | |
| Domain: | Eukaryota |
| Clade: | Sar |
| Clade: | Alveolata |
| Phylum: | Apicomplexa |
| Class: | Conoidasida |
| Order: | Eucoccidiorida |
| Suborder: | Eimeriorina |
| Family: | Cryptosporidiidae |
| Genus: | Cryptosporidium Tyzzer, 1907 |
| Species | |
See§ Species | |
Cryptosporidium, sometimes calledcrypto, is anapicomplexan genus ofalveolates which areparasites that can cause a respiratory and gastrointestinal illness (cryptosporidiosis) that primarily involves waterydiarrhea (intestinal cryptosporidiosis), sometimes with a persistent cough (respiratory cryptosporidiosis).[1][2]
Treatment of gastrointestinal infection in humans involvesfluid rehydration, electrolyte replacement, and management of any pain. For cryptosporidiosis, supportive treatment and symptom management are the primary treatments for immunocompetent individuals.[3] Anti-diarrheal medication, such asLoperamide, may be effective in slowing the rate of diarrhea.Nitazoxanide is the only drug approved for the treatment ofcryptosporidiosis in immunocompetent persons.[4] Supplemental zinc may improve symptoms,[5] particularly in recurrent or persistent infections or in others at risk forzinc deficiency.Cryptosporidium oocysts are 4–6 μm in diameter and exhibit partialacid-fast staining. They must be differentiated from other partially acid-fast organisms includingCyclospora cayetanensis.
Cryptosporidium causescryptosporidiosis, an infection that may present as adiarrhea, sometimes with a persistent cough in immunocompetent hosts.[clarification needed][1] Otherapicomplexan pathogens of humans include themalaria parasitePlasmodium and thetoxoplasmosis parasiteToxoplasma. UnlikePlasmodium, which transmits via a mosquitodisease vector, andToxoplasma which needs a feline asdefinitive host,[6]Cryptosporidium does not use a vector, and is capable of completing its lifecycle within a single host. It results incyst stages that are excreted in feces or through inhalation of coughed onfomites and are capable of transmission to a new host.[1][7][8]
A number of species infect mammals. In humans, the main causes of disease areC. parvum andC. hominis (previouslyC. parvum genotype 1).C. canis,C. felis,C. meleagridis, andC. muris can also cause disease in humans.[7]
Cryptosporidiosis is typically an acute, short-term infection, but can recur through reinfection in immunocompetent hosts, or become severe or life-threatening in immunocompromised individuals. In humans, it remains in the lower intestine and may remain for up to five weeks.[7] The parasite is transmitted by environmentally hardycysts (oocysts) that, when ingested, remain in thesmall intestine and cause an infection of intestinalepithelial tissue.[7] Transmission by ingestion or inhalation of coughed-on fomites is a second, less likely route of infection.[1]
Thegenome ofC. parvum, sequenced in 2004, was found to be unusual amongsteukaryotes in that themitochondria seem not tocontain DNA.[9] A closely related species,C. hominis, has also had its genome sequenced.[10]
Cryptosporidium has three developmental stages:meronts,gamonts andoocysts.[11] They reproduce within the intestinalepithelial cells.[12]TheCryptosporidiumspore phase (oocyst) can survive for lengthy periods outside a host. It can also resist many commondisinfectants, includingchlorine-based disinfectants.[13]
Manytreatment plants that take raw water fromrivers,lakes, andreservoirs for publicdrinking water production use conventional filtration technologies. Direct filtration, which is typically used to treat water with lowparticulate levels, includes coagulation and filtration but not sedimentation. Other common filtration processes includingslow sand filters,diatomaceous earth filters, and membranes will remove 99% ofCryptosporidium.[14] Membranes and bag- and cartridge-filter products removeCryptosporidium specifically.
Cryptosporidium is highly resistant to chlorine disinfection;[15] but with high enough concentrations and contact time,Cryptosporidium inactivation will occur withchlorine dioxide andozone treatment. In general, the required levels of chlorine preclude the use of chlorine disinfection as a reliable method to controlCryptosporidium in drinking water. Ultraviolet light treatment at relatively low doses will inactivateCryptosporidium.[16][17]
One of the largest challenges in identifying outbreaks is the ability to verify the results in alaboratory. The oocytes may be seen by microscopic examination of a stool sample, but they may be confused with other objects or artifacts similar in appearance.[18] Most cryptosporidia are 3–6 μm in size, although some reports have described larger cells.[18]
Boiling is believed to be the safest option for water contaminated byCryptosporidium.[19][20][21]
Dealing with stabilized compost – composting material that has gone through the phases where micro-organisms are digesting the organic matter and the temperature inside the composting pile has reached temperature up to 50–70 °C – poses very little risk as these temperatures kill pathogens and make oocysts unviable.[24]
Like many fecal-oral pathogens, the disease can also be transmitted by contaminated food, poor hygiene or turning compost in a localcompost site. Testing of water, as well asepidemiological study, are necessary to determine the sources of specific infections.Cryptosporidium typically does not cause serious illness in healthy people. It may chronically sicken some children, as well as adults exposed andimmunocompromised.
Recent evidence indicates that respiratory cryptosporidiosis may occur commonly in immunocompetent children with cryptosporidial diarrhea and unexplained cough. Findings from animal models, human case reports, and a few epidemiological studies suggest that Cryptosporidium may be transmitted via respiratory secretions, in addition to the more recognized fecal-oral route. ... Upper respiratory cryptosporidiosis may cause inflammation of the nasal mucosa, sinuses, larynx, and trachea, accompanied by nasal discharge and voice change (54, 61, 62). Cryptosporidiosis of the lower respiratory tract typically results in productive cough, dyspnea, fever, and hypoxemia (63,–66). ... While fecal-oral transmission is indisputably the major route of infection, transmission via coughing and fomites is also possible in situations of close contact (20). ... Because they lacked gastrointestinal symptoms and oocyst excretion, the latter cases establish the possibility of primary respiratory infection with Cryptosporidium, which may have been acquired by inhalation of expectorated droplets or by contact with fomites. ... This finding suggests that respiratory cryptosporidiosis may occur commonly in immunocompetent individuals.
Infection may improve with nutritional supplementation, particularly with regimens including zinc or glutamine. ... Nitazoxanide significantly shortens the duration of diarrhea and can decrease the risk of mortality in malnourished children.[22] Trials have also demonstrated efficacy in adults.[26, 27] ... Symptomatic therapy includes replacement of fluids, provision of appropriate nutrition, and treatment with antimotility agents. ... Replacement of fluids and electrolytes is the critically important first step in the management of cryptosporidiosis, particularly in patients with large diarrheal losses. Fluids should include sodium, potassium, bicarbonate, and glucose.
