The search for Cryptosporidium oocysts and Giardia cysts in source water used for purification

Abstract

Cryptosporidium and Giardia are intestinal parasites which cause a self limiting gastro-enteritis, in healthy people but severe and often fatal disease in immuno-compromised individuals. Both organisms are characterised by the ability to survive in an aquatic environment with Cryptosporidium having a high tolerance to most of the drinking water disinfectants. The absence of bacteria associated with feacal pollution does not necessarily indicate the absence of Cryptosporidium or Giardia. Being a common cause of waterborne disease, the requirement for detecting the presence of these organisms in environmental and treated water samples is growing. Although cysts and oocysts can be found in natural waters from any source, the risks of contamination are much greater in surface waters than in ground waters. A number of waterborne outbreaks of cryptosporidiosis, from potable and recreational water have been recorded. In many cases these outbreaks have occurred from water that complies to current microbiology standards.

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