Microorganism

Description

Clinical Syndrome

Cyclospora cayetanensis

Protozoa with oocysts 8-10 µm in diameter

Prolonged, self-limited diarrhea with average duration of 30 days

a SS RNA = single-strand RNA.

b DS DNA = double-strand DNA.

c PCR = polymerase chain reaction.

Giardia has also been detected in treated effluent and is much more resistant to disinfection with chlorine than bacteria.

Cryptosporidium was first described as a human pathogen in 1976. Cryptosporidiosis causes severe diarrhea; no pharmaceutical cure exists. Average infection rates in the United States, as measured by oocyst excretion in a population, have ranged from 0.6 to 20 percent (Fayer and Ungar, 1986). The disease can be particularly hazardous for people with compromised immune systems (Current and Garcia, 1991). Since 1985, seven reported waterborne outbreaks of cryptosporidiosis have occurred in the United States (Lisle and Rose, 1995). In 1993, Cryptosporidium was responsible for the largest waterborne disease outbreak ever recorded in the United States, causing approximately 400,000 illnesses in Milwaukee, Wisconsin. This outbreak was attributed to contamination of the surface water supply by either animal or human wastes (MacKenzie et al., 1995). All research to date suggests that the current standards for water chlorination are inadequate for inactivation of Cryptosporidium oocysts (Korick et al., 1990; Peeters et al., 1989). Cryptosporidium oocysts have been detected in municipal wastewater, but their concentrations and removal by wastewater treatment processes have not been fully evaluated (Madore et al., 1987; Rose et al., 1996; Villacorta-Martinez et al., 1992).

Diseases From Enteric Viruses

The enteric viruses are obligate human pathogens, which means they replicate only in the human host. Viruses are the smallest pathogenic agents. Their simple structure of a protein coat surrounding a core of



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