Cryptosporidium, sometimes called crypto,<!--Compare analogous clinical usage, such as "strep" for Streptococcus and "staph" for Staphylococcus--> is an apicomplexan genus of alveolates which are parasites that can cause a respiratory and gastrointestinal illness (cryptosporidiosis) that primarily involves watery diarrhea (intestinal cryptosporidiosis), sometimes with a persistent cough (respiratory cryptosporidiosis).
Treatment of gastrointestinal infection in humans involves fluid rehydration, electrolyte replacement, and management of any pain. For cryptosporidiosis, supportive treatment and symptom management are the primary treatments for immunocompetent individuals. Anti-diarrheal medication, such as Loperamide, may be effective in slowing the rate of diarrhea. Nitazoxanide is the only drug approved for the treatment of cryptosporidiosis in immunocompetent persons. Supplemental zinc may improve symptoms, particularly in recurrent or persistent infections or in others at risk for zinc deficiency. Cryptosporidium oocysts are 4–6 μm in diameter and exhibit partial acid-fast staining. They must be differentiated from other partially acid-fast organisms including Cyclospora cayetanensis.
General characteristics
Cryptosporidium causes cryptosporidiosis, an infection that may present as a diarrhea, sometimes with a persistent cough in immunocompetent hosts. Cryptosporidium does not use a vector, and is capable of completing its lifecycle within a single host. It results in cyst stages that are excreted in feces or through inhalation of coughed on fomites and are capable of transmission to a new host.
A number of species infect mammals. In humans, the main causes of disease are C. parvum and C. hominis (previously C. parvum genotype 1). C. canis, C. felis, C. meleagridis, and C. muris can also cause disease in humans. A closely related species, C. hominis, has also had its genome sequenced.
Life cycle
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Cryptosporidium has three developmental stages: meronts, gamonts and oocysts. They reproduce within the intestinal epithelial cells.
The Cryptosporidium spore phase (oocyst) can survive for lengthy periods outside a host. It can also resist many common disinfectants, including chlorine-based disinfectants.
Immune System Evasion
A Cryptosporidium infection in the intestine causes epithelial cells to activate multiple defense mechanisms. They secrete chemokines and cytokines to mobilize immune cells to the infection site. Membranes and bag- and cartridge-filter products remove Cryptosporidium specifically.
Cryptosporidium is highly resistant to chlorine disinfection; but with high enough concentrations and contact time, Cryptosporidium inactivation will occur with chlorine dioxide and ozone treatment. In general, the required levels of chlorine preclude the use of chlorine disinfection as a reliable method to control Cryptosporidium in drinking water. Ultraviolet light treatment at relatively low doses will inactivate Cryptosporidium.
One of the largest challenges in identifying outbreaks is the ability to verify the results in a laboratory. 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. Most cryptosporidia are 3–6 μm in size, although some reports have described larger cells.
Diagnosis
The most common approach in diagnosing cryptosporidiosis is detection of the Cryptosporidium oocysts, oocyst antigens, or oocyst DNA in stool samples. Due to the difficulty surrounding detection of these oocysts, there should be a minimum of three stool samples collected on three separate days to rule out the parasitic infection in patients with severe diarrhea.
- People, including swimmers, who swallow water from contaminated sources
- People handling infected cattle
- People exposed to human feces
- People who turn compost that has not gone through its phase where temperatures over 50 °C are reached
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.