Cryptosporidiosis in HumansGeneral MicrobiologyCryptosporidiosis is a gastrointestinal disease caused by pathogens of the Cryptosporidium genus. In 1907, parasitologist Ernest Edward Tyzzer made observations on the genus and concluded that Cryptosporidium are intracellular protozoan parasites. The genus was named due to its absence of sporocytes within the oocytes, and of 16 species, C. parvum and C. hominis are the more important pathogens in humans (Tzipori 2008).
Because Cryptosporidium oocytes are resistant to commercial disinfectants and microbial drugs, several precautions are to be taken in water sources over the world. Cryptosporidiosis in immunocompetent people causes short-term diarrheal illness, while in immuno-deficient patients, such as those with AIDS, the disease causes cholera-like illness and often death (Current 1991).According to a case-control study, it was found that the largest reservoir of C. parvum is in animals, and the largest reservoir of C. hominis is humans. C. hominis is acquired through direct or indirect contact with other infected humans. Cryptosporidiosis caused by C.
hominis is highest in children ages 0-4 and can be transmitted through toilet contact even when symptoms are not present. Also, urban areas and areas with higher socioeconomic status individuals are at higher risk for C. hominis. This species is more prevalent in urban areas due to more person-to-person contact, day care centers, nursing homes and swimming pools. C. parvum is found in livestock and is transmitted directly or indirectly to humans. This species is usually transmitted through fecal contaminated drinking water and in rural areas where there is a higher probability of animal contact. (Lake 2007)Cryptosporidium exists in the environment as a 5-?µm-diameter oocyte containing four sporozoites (Clark 1999).
The life cycle of C. parvum can be divided into six developmental events: excystation, merogony, gametony, fertilization, oocyst wall formation, and sporogony (Current 1991). When ingested, the oocytes travel through the gut lumen to the small intestine. There, the oocytes rupture, releasing the sporozoites which then adhere to and invade the epithelial lining of the gastrointestinal tract