Atlas of foodborne infections
transmitted by contaminated food and water

Atlas of Patogens Contents Information sources Glossary Administration

Cryptosporidium parvum

CZ: kryptosporidie
EN: cryptosporidia

Fruits and Vegetables
Water and Beverages


Foodborne Disease:
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cryptosporidiosis - watery diarrhoea, stomach cramps, upset stomach and slight fever


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Cryptosporidium parvum, cause of the disease cryptosporidiosis, is a one-celled, microscopic obligate intracellular parasite (protozoa) and a significant cause of waterborne illness worldwide. It is found in the intestines of many herd animals including cows, sheep, goats, deer, and elk.

The infective stage of the organism, the oocyst is 3 μm in diameter or about half the size of a red blood cell. The sporocysts are resistant to most chemical disinfectants but are susceptible to drying and the ultraviolet portion of sunlight. Some strains appear to be adapted to certain hosts but cross-strain infectivity occurs and may or may not be associated with illness. The species or strain infecting the respiratory system is not currently distinguished from the form infecting the intestines. People get cryptosporidiosis by consuming food or water contaminated with C. parvum oocysts (infective stage of the parasite) - oocysts are the environmentally resistant stage of the organism and are shed in the faeces of a host (human or animal); by putting anything into your mouth that has touched the stool of a person or animal with cryptosporidiosis. Incidence is higher in child day care centres that serve food. Fertilizing salad vegetables with manure is another possible source of human infection. Large outbreaks are associated with contaminated water supplies.

Symptoms include watery diarrhoea, stomach cramps, upset stomach, and slight fever. Some cases may be without symptoms. Symptoms appear 2 to 10 days after ingestion of C. parvum oocysts. The illness usually goes away without medical intervention in 3 to 4 days, but in some outbreaks in day-care centres, diarrhoea has lasted 1 to 4 weeks. In people with AIDS and other individuals with weakened immune systems, cryptosporidiosis can be serious.


Cryptosporidium parvum
Source: Life cycle of genus Cryptosporidium
oocysts of genus Cryptosporidium
Source: size of oocysts 5 micrometers
oocysts of cryptosporidia
Source: Ziehl-Neelsen staining, pink oocysts

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