Cryptosporidium Essay ⋆ Environment Essay Examples ⋆ EssayEmpire

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Cryptos p oridium is the genus of parasitic protozoans that cause cryptosporidiosis, a diarrheal disease of humans found worldwide and transmitted locally through contaminated drinking water. Outbreaks occur frequently in dairy farming regions because young cows readily transmit the disease via feces. The organism was discovered in 1907, but it is considered an emerging infectious disease because physicians first observed its role in human illness during the 1970s. Cases of diarrhea are now frequently attributed to this parasite, and the infection is endemic in many developing countries. Cryptosporidium may infect large portions of local populations and may be severe, persistent, or fatal among those with compromised immune systems such as AIDS patients. In the 1980s, increasing rates of cryptosporidiosis were associated with the spread of HIV. Even those with healthy immune systems experience acute symptoms, including abdominal cramps and frequent, watery diarrhea as well as fever and nausea for one to two weeks.

Cryptosporidium Carriers

A wide variety of livestock and vertebrate wildlife species carry Cryptosporidium, and their feces are the primary source of the parasite in water supplies. The oocyst stage of the Cryptosporidium life cycle is the agent of transmission; its hardy shell allows it to survive for long periods and under a variety of conditions outside the body of the host. The practice of permitting cattle near streams is most commonly blamed for the deposition of Cryptosporidium oocysts in water. Livestock exclusion, and particularly exclusion of young cows, from stream areas may help keep oocysts out of drinking water and therefore prevent outbreaks; however, oocysts may travel through groundwater or soil as well. Feral pigs and free-ranging deer also carry the parasite and shed oocysts in their feces, and so may be important contributors to contamination in areas where their populations are high. Cryptosporidium has been found even in protected watersheds far from human habitation and agricultural activities.

Cryptosporidium oocysts may persist even in treated water; they survive outside the body of host organisms and are resistant to chemical disinfection methods such as chlorination. Filtration is the only means of removing oocysts from water, but it is not absolutely reliable. Outbreaks have occurred where filtration systems were in compliance with federal water safety standards, and one study has suggested that up to 97 percent of surface waters in the United States contain Cryptosporidium.

Historical Outbreak

The most notable outbreak of cryptosporidiosis occurred in Milwaukee, Wisconsin, in April 1993. Public health investigators believe that spring runoff carried Cryptosporidium oocysts from nearby abattoirs and cattle grazing establishments into Milwaukee’s rivers and hence to Lake Michigan, the source of the drinking water supply. Over 400,000 individuals contracted the disease, and several patients with immune deficiencies continued to suffer symptoms over a year after the initial exposure. Though filtration plants were operating within legal standards, changes in turbidity should have alerted managers to the need for corrective measures. The outbreak cost the city several million dollars, strapped local health facilities, and left key public service agencies understaffed. Since the 1980s, the U.S. Congress has amended the Safe Drinking Water Act to mandate additional checks against Cryptosporidium contamination. Water treatment facilities must now test more frequently for water turbidity, but this is not a failsafe against outbreaks.

Bibliography:

Joan Aron and Jonathan Patz, , Ecosystem Change and Global Health (Johns Hopkins University Press, 2001);
George Dissmeyer, ed., Drinking Water from Forests and Grasslands: A Synthesis of the Scientific Literature (USDA, 2000);
Ronald Fayer, , Cryptosporidium and Cryptosporidiosis (CRC Press, 1997);
Dennis Juranek, “Cryptosporidiosis: Sources of Infection and Guidelines for Prevention,” Clinical Infectious Diseases (v.21, 1995).