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A genus of protozoan parasites that cause gastrointestinal diseases of medical and veterinary importance. These protoctists are placed in the same phylum as the malaria parasites. However, they lack apicoplasts and have no second host, unlike Plasmodium (q.v.). Cryptosporidia have complex life cycles with motile and non-motile forms in both asexual and sexual stages. They spend most of their lives within the epithelial cells of the gut or in its lumen. The infective phase of Cryptosporidium is a cyst that contains several haploid sporozoites enclosed in a thick capsule. The cysts are about 3 μm in diameter, are easily spread via water, are resistant to most chemical disinfectants, and can be removed from drinking water only by filtration. C. parvum, the cause of cryptosporidosis in humans, has a genome size of 9 million base pairs distributed among 8 chromosomes. See Classification, Protoctista, Apicomplexa.

Subjects: Genetics and Genomics — Medicine and Health.

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