Water Quality Tests Miss Significant Health Risk

Following the outbreaks, the Environmental Protective Agency (EPA) issued procedures for monitoring and protecting water supplies from C. parvum. A new Johns Hopkins School of Public Health study calls those procedures "deficient."

"The most significant deficiency of the current watershed protection program is that environmental factors contributing to water contamination are not clearly recognized," said Thaddeus K. Graczyk, PhD, research associate, Molecular Microbiology and Immunology, author of the study looking at watershed contamination by waterfowl feces.

The study, published in the September issue of Applied and Environmental Microbiology, used wild ducks to determine whether C. parvum picked up by wild waterfowl on land passed through their digestive systems and into water supplies. Finding that waterfowl do excrete C. parvum into water supplies, subsequent failures of water filtration facilities to detect the parasite poses a significant public health threat.

"Birds, particularly migratory waterfowl, residing in the watershed area should be considered a potential factor in the contamination of water," said Dr. Graczyk. "A flock of Canada geese visiting a protected water supply may help meet wildlife conservation goals, but they also have disease and epidemiological implications."

Water treatment facilities do test for C. parvum by an "immunofluoresence antibody assay" (IFA), but the researchers note that IFA, prone to render false positives by identifying noninfectious cryptosporidium, also may not be carried out at appropriate times, missing the infectious varieties. The study concluded that modification of watershed control activities may reduce contamination and decrease the potential for outbreaks of cryptosporidiosis.

Generally a self-limiting diarrheal illness, cryptosporidiosis can lead to death for immune compromised persons.