Cryptosporidium parvum is one of several species that cause cryptosporidiosis, a parasitic disease of the mammalian intestinal tract.
Often transmissions occur by the ingestion of contaminated public water supplies, making transmissions common in places such as water parks and public pools.
Primary symptoms of C. parvum infection are acute, watery, and nonbloody diarrhea. C. parvum infection is of particular concern in immunocompromised patients, where diarrhea can reach 10–15 l per day. Other symptoms may include anorexia, nausea/vomiting, and abdominal pain. Extra-intestinal sites include the lung, liver, and gall bladder, where it causes respiratory cryptosporidosis, hepatitis, and cholecystitis, respectively.
Infection is generally self-limiting in immunocompetent people. In immunocompromised patients, such as those with AIDS or those undergoing immunosuppressive therapy, infection may not be self-limiting.