ISSUE 35: Are the incidence of the protozoan parasites, giardia and cryptosporidium, in streams and surface waters always linked to the presence of livestock ?
RESPONSE: Cryptosporidium made headlines in 1993 when it got into the Milwaukee water supply causing 100 deaths. The illness lasts only a few days in most people with healthy immune systems, but those with severely weakened immune systems can develop life-threatening infections. The source of the contamination of Milwaukee’s water supply, which is drawn from Lake Michigan, was never determined. This parasite can be spread in a variety of ways, but always through fecal matter. Cryptosporidium can infect and be shed by about 80 species of animals, including humans, cattle, sheep, goats, pigs, horses, dogs, cats, and various wildlife species, such as deer, elk, raccoons, opossums, feral pigs and rabbits. Surveys indicate that cryptosporidium is common in untreated surface water throughout North America. Although cattle are often suspected as sources of cryptosporidium, studies have not established a clear link between livestock and the presence of the parasite in lakes and streams. Survey
