The protozoan Cryptosporidium parvum was first described in 1907 in asymmetric mice, and for decades now it has been known to be a pathogen of at least 40 mammals and varying numbers of reptiles and birds.
Although the first documented human case was not recorded until 1976, this disease has a worldwide prevalence of 1-4% among patients with diarrhea, and it appears to be increasing.
It is estimated to cause infections in from 7 to 38% of AIDS patients in some hospitals.
The prevalence of C. parvum is diarrheal stools is similar to that of Giardia lamblia.
In human disease is self limiting in immunocompetent individuals, but it is a serious infection in the immunocompromised, such as AIDS patients.
The protozoan is known to be present in at least some bodies of water and this exist the potential for food transmission.
The fecal-oral route of transmission is the most important, but indirect transmission by food and milk is known occur.
C. parvum is an obligate intracellular coccidian parasite that carries out its life cycle in one host. Following ingestion of the thick-walled oocystsm, they excyst in the small intestine and free sporozoites and penetrate the microvillous region of host enterocytes, where sexual reproduction leads to the development of zygotes.
They invade host cells by disrupting their own membrane as well as that of their host.
Host cell acting polymerization at the interface between the parasite and the host cell cytoplasm has been found to be necessary for infection.
The first demonstrated waterborne outbreak of cryptosporidiosis occurred in Braun Station, Texas, in 1984 following the consumption of artesian well water.
There were actually two outbreaks – one in May and the other in July, with 79 victims. A second outbreaks with 13,000 victims occurred in Carrolton, Georgia in 1987 and oocysts were found in the tools of 58 of 147 victims.
The clinical course of cryptosporidiosis in human depends on the immune state, with the most severe cases occurring in the immunocompromised.
In immunocompetent individuals, the organism primarily parasitizes the intestinal epithelium and causes diarrhea.
The disease is it self-limiting, with an incubation period of 6-14 days and symptoms typically last 9-23 days.
In the immunocompromised diarrhea is profuse and watery with as many as 71 stools per day and up to 171 per day reported.
Diarrhea is sometimes accompanied by mucus but rarely blood.
Cryptosporidiosis: History, definition, outbreak
