Nonpoint Source Contaminants Research
Cryptosporidium spp. Oocyst and Giardia spp. Cyst in Wisconsin Waters

Background

Cryptosporidium spp., an enteric protozoan pathogen, seized national attention during the mid-1990's when Cryptosporidium parvum oocysts contaminated the City of Milwaukee's drinking water supply. The source of this contamination was never confirmed. Once ingested, this parasite multiplies in the gastrointestinal tract causing diarrhea and vomiting. In Milwaukee and surrounding communities, over 403,000 people became ill due to contaminated water.

Responding to the outbreak, the Wisconsin legislature directed the DNR to study Cryptosporidium contamination in state waters. Giardia, a similar organism and the most commonly reported enteric pathogen in Wisconsin, was also included since the test used to detect Cryptosporidium oocysts can also detect Giardia cysts.

A stratified sampling plan focused on the southeast, northeast and northwest regions of the state where all lake drinking-water supplies are located. Within each region, samples were collected from streams in agricultural, urban, and "pristine" watersheds; all lake drinking-water supply intakes; finished drinking water (if intakes tested positive); and from wastewater treatment plant final effluent. Well-water sampling in the northeast region was later added to the study.

Objectives

To assess Cryptosporidium and Giardia background levels in streams, lake drinking-water supplies, selected well-water supplies, and waste treatment plant effluent. To examine the relationships of regions, land use, seasons, weather, and water quality characteristics to Cryptosporidium and Giardia occurrence and concentrations.

Benifits

This study reveals the statewide severity of the problem and what actions might prevent future outbreaks.

For more information on this topic, please contact:
Steve Greb (608) 221-6362