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Cryptosporidium Antigen, Feces

Cryptosporidium is a parasite that causes cryptosporidiosis, a profuse, watery diarrhea. Cryptosporidium is the leading cause of outbreaks of diarrhea linked to water and the third leading cause of diarrhea associated with animal contact in the United States. The principal Cryptosporidium species that infect humans are C. parvum, which can be transmitted zoonotically or anthroponotically, and Cryptosporidium hominis (formerly known as C. parvum genotype I), which primarily is transmitted anthroponotically.

Cryptosporidium is an extremely chlorine-tolerant intracellular protozoan parasite. Oocysts can survive more than 7 days in properly treated water. Fecal-oral transmission of Cryptosporidium can occur via ingestion of contaminated recreational water, drinking water, food, or via contact with infected persons or animals, most notably preweaned calves. Oocysts are immediately infectious upon excretion, are excreted in much higher numbers than the human infectious dose which is 10 oocysts or less.

Groups at risk of infection include the immunocompromised, especially those with HIV infection, family members and sexual partners of infected patients, children and caretakers in day care centers, animal handlers and travelers. Symptoms of cryptosporidiosis may include diarrhea, abdominal pain, nausea and vomiting, fever, malaise, and respiratory problems lasting from several days to more than a month.

In immunocompetent persons, cryptosporidiosis can range from asymptomatic infection to diarrhea that typically lasts up to 3 weeks. Immunocompromised persons might experience chronic, severe diarrhea that can lead to malnutrition and substantial weight loss, potentially causing death.

A rapid antigen detection assay for use on stool specimens is available, and has 95% sensitivity and 98% specificity. This is an improvement over fluorescent stains and allows accuracy when a single specimen is tested. Cryptosporidium is also included in the FilmArray Gastrointestinal Panel that tests for 22 common pathogens.

Specimen requirement is 10 grams of randomly collected stool in a sterile container.


Gharpure R, Perez A, Miller AD, Wikswo ME, Silver R, Hlavsa MC. Cryptosporidiosis Outbreaks — United States, 2009–2017. MMWR Morb Mortal Wkly Rep 2019;68:568–572. DOI: icon

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