Cryptosporidium Parvum: Transmission and Infection
*If you ever use this, please e-mail me at antisoma@hotmail.com. I 'd just like to know.
Cryptosporidium parvum: Transmission and Infection
Cryptosporidium parvum is a protozoan intestinal parasite causing a short-term enteric illness in individuals with functioning immune systems, and can cause a potentially fatal infection in immunosuppressed individuals. Because of C. parvum 's resistance to many of the procedures used to process drinking water and food, and the parasite 's extremely high fecundity, the potential for a large scale outbreak is very high. In fact, C. parvum was responsible for an outbreak in Milwaukee in 1993 when an estimated 403,000 people became ill. This was the largest waterborne outbreak of disease in United States history. This paper will cover some aspects of C. parvum 's life cycle, human sickness caused by the parasite, routes of transmission, and practices of control.
There are six different species of Cryptosporidium, C. parvum being the only species which infects mammals (Gutierrez, 1990). Oocysts, which are ingested by the mammal host, each contain four sporozoites. Upon excystment in the small intestine, the sporozoites infect an intestinal epithelial cell by becoming attached to the base of the microvilli. The sexual stages follow, where zygotes and eventually oocysts are formed. But C. parvum also has an "auto-infecting" asexual stage in which thin walled oocysts are produced to cause infection farther along in the intestine (Donnelly & Stentiford,1997). Approximately 20% of the oocysts produced will have these thin walls, leaving 80% of the oocysts to be excreted out of the host and into the environment, where they will be infective immediately. Thirty oocysts are enough to cause infection, and one infected person can excrete over a billion oocysts in one day (Graczyk et al., 2000). Symptoms of Cryptosporidiosis in immunocompetent individuals include watery diarrhea (up to 3 liters a day), cramps, weight and
Cryptosporidium parvum: Transmission and Infection
Cryptosporidium parvum is a protozoan intestinal parasite causing a short-term enteric illness in individuals with functioning immune systems, and can cause a potentially fatal infection in immunosuppressed individuals. Because of C. parvum 's resistance to many of the procedures used to process drinking water and food, and the parasite 's extremely high fecundity, the potential for a large scale outbreak is very high. In fact, C. parvum was responsible for an outbreak in Milwaukee in 1993 when an estimated 403,000 people became ill. This was the largest waterborne outbreak of disease in United States history. This paper will cover some aspects of C. parvum 's life cycle, human sickness caused by the parasite, routes of transmission, and practices of control.
There are six different species of Cryptosporidium, C. parvum being the only species which infects mammals (Gutierrez, 1990). Oocysts, which are ingested by the mammal host, each contain four sporozoites. Upon excystment in the small intestine, the sporozoites infect an intestinal epithelial cell by becoming attached to the base of the microvilli. The sexual stages follow, where zygotes and eventually oocysts are formed. But C. parvum also has an "auto-infecting" asexual stage in which thin walled oocysts are produced to cause infection farther along in the intestine (Donnelly & Stentiford,1997). Approximately 20% of the oocysts produced will have these thin walls, leaving 80% of the oocysts to be excreted out of the host and into the environment, where they will be infective immediately. Thirty oocysts are enough to cause infection, and one infected person can excrete over a billion oocysts in one day (Graczyk et al., 2000). Symptoms of Cryptosporidiosis in immunocompetent individuals include watery diarrhea (up to 3 liters a day), cramps, weight and
References: Donnelly, J.K., Stentiford, E.I. (1997) "The Cryptosporidium Problem in Water Food Supplies" Lebensm.-Wiss.U.-Technol., 30, 111-120 Gutierrez, Yezid (1990) "Diagnostic Pathology of Parasitic Infections with Clinical Correlations" 94-107