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A HISTORICAL PERSPECTIVE OF DETECTION METHODS FOR GIARDIA CYSTS AND CRYPTOSPORIDIUM OOCYSTS IN WATER
Citation:
Schaefer, F W. A HISTORICAL PERSPECTIVE OF DETECTION METHODS FOR GIARDIA CYSTS AND CRYPTOSPORIDIUM OOCYSTS IN WATER. Presented at USGS Workshop "Building Capabilities for Monitoring & Assessment of Public Health Microbiology", Columbus, OH, March 13-14, 2000.
Impact/Purpose:
1) Refine new, practical methods for the detection of CCL-related and emerging waterborne human protozoa.
2) Perform field tests of devices or methods that have been developed under this task.
3) Evaluate these methods or devices in a variety of water matrices and parasite concentrations.
This work in this task supports CCL2 and 3 and is expected to be completed by 9/07.
Description:
In the mid-20th century Giardia was classified as a non-pathogenic commensal organism and Cryptosporidium was not recognized yet. However as early as 1946 a waterborne outbreak of giardiasis was suspected. From 1965 to 1979 it became clear that Giardia lamblia was indeed a human pathoge and was responsible for waterborne gastroenteritis. Unlike bacteria, there are no simple culture methods for enteric protozoan parasites, so detection and identification were limited to microscopic observations. Because the densities of cysts and oocysts in water often can be less than one per liter, volumes between 10 and 1,000 liters must be examined. The initial sampling approach of the Centers for Disease Control and Prevention was to use a sand filter on a flatbed truck, while that of the U.S.EPA was to use a fiber wound cartridge filter which became the standard. Buoyant density flotation protocols employing zinc sulfate, sucrose, Percoll, and Percoll-sucrose have been used to purify and further concentrate the cysts and oocysts. Percoll-sucrose eventually became the standard flotation medium.