Detection of Giardia Cysts and Cryptosporidium Oocysts in Water Samples by PCR

THE enteric protozoa Giardia and Cryptosporidium are intestinal parasites that can cause gastroenteritis when they are ingested by humans. Giardia is the most common cause of parasitic infections in humans in the United States [1,2] and can cause lengthy bouts of diarrhea in infected individuals [3], Numerous waterborne outbreaks of giardiasis and cryptosporidiosis have been documented [4-7]. Low numbers of Giardia cysts and Cryptosporidiumoocysts are usually found in water supplies [2]. Cysts and oocysts are the infectious units of the microorganisms, and the development of approaches for the detection of these in water samples necessitates simple, efficient, and cost-effective methods. In addition, since an infection in humans can be initiated by as few as one to ten viable cysts [8], detection methods and viability assays need to be very sensitive. Currently, it is assumed that any Giardia and Cryptosporidium found in water is potentially infectious [9]. However, cysts or oocysts that are not viable do not pose a threat to human health. Therefore, it is important to be able to differentiate between viable and nonviable microorganisms.