Cryptosporidiosis

Cryptosporidium is an intestinal parasite infecting a variety of animals, e.g. humans, cattle, sheep, rodents, cats and dogs, but also birds, fish and reptiles.  Most human cases of cryptosporidiosis are due to two species; Cryptosporidium hominis, which mainly infects humans, and the zoonotic species Cryptosporidium parvum, which also infects domestic animals, in particular young calves and lambs. In addition, several other zoonotic species can infect humans, including Cryptosporidium meleagridis, Cryptosporidium cuniculus, Cryptosporidium ubiquitum, Cryptosporidium canis, Cryptosporidium felis, Cryptosporidium viatorum and Cryptosporidium sp. chipmunk genotype I.

In humans, the infection can be without any symptoms, however, healthy individuals often develop a diarrhoea that spontaneously resolves over a couple of weeks. By contrast, patients with impaired immune system may develop profuse, life-threatening, watery diarrhoea that is very difficult to treat with currently available drugs.

Transmission is fecal-oral by ingestion of infectious oocysts, by direct contact with infected persons or animals or through contaminated water and food. Cryptosporidium oocysts can survive for months in moist soil or water and survive harsh environmental conditions (e.g. heat, cold) for extended periods of time.

Outbreaks have been reported in hospitals, daycare centres, within households, among people eating the same food, among people pursuing recreational water activities (in lakes and swimming pools), and in municipalities with contaminated public water supplies. Water distribution systems are particularly vulnerable to contamination with Cryptosporidium, which can survive most disinfection procedures such as chlorination.