Source: Ian Chadwick - THE ENTERPRISE-BULLETIN
Cryptosporidium is a tiny protozoan: a single-cell parasite that usually lives in the intestines of animals, wild and livestock. However, it can also infect humans and their pets.
It enters its hosts as oocysts: tiny, protective capsules, similar to eggs, but only a micron in diameter. Each oocyst contains one to four "sporozoites" that can develop into adults. The oocysts break open inside the host's intestines, allowing the parasite to grow and spread (through both sexual and asexual reproduction). During their spread, they irritate the surfaces of the small intestine, which causes diarrhea. Eventually the form more oocysts which are transmitted through feces into the water and to other hosts.
Cryptosporidium can also be passed from human-to-human, or human-to-pet orally; through contaminated lakes and swimming pools.
It doesn't take a lot of the creature to make a person sick. Studies done at the University of Texas showed 62 per cent of volunteers who drank infected water got sick ingesting as few as 30 oocysts. A British study suggests even a single oocyst can be infectious. In comparison, it takes about 10,000 cholera bacteria to cause cholera.
Only 39 per cent of those infected in the study developed symptoms. The researcher in charge of the tests suggested the protozoan was responsible for 10 per cent of all chronic diarrhea in the United States.
In most people, infection leads to an `explosive' attack of watery diarrhea within four to six days, and lasts five to 11 days. Most healthy people with normal immune systems don't suffer more than diarrhea and related symptoms: only people with immune deficiencies, elderly ill or very young infants face serious health risks.
Although first described in 1907, it wasn't until 1976 that the first case in a human was identified. In 1981, the first case in an AIDS patient was described. Most of the fatalities due to cryptosporidium have been in AIDS victims who suffer from compromised immune systems and are not able to recover from the parasite.
Outbreaks of the parasite have been relatively rare until the last decade, but may have been diagnosed as other illnesses or infections. Outbreaks have occurred in water systems ranging from simple chlorination to full filtration and ozonation.
Generally outbreaks have been blamed on agricultural sources: runoffs from feedlots or manure piles, or farmers spraying liquid manure on fields before spring runoff. In the U.S., tests found 77 per cent of all lakes and 75 per cent of all rivers sampled had cryptosporidium. Tests done on filtered and disinfected water systems in the United States showed cryptosporidium in 27 per cent of all samples.
In 1983, there was an outbreak in a New York City daycare. In 1984, it occurred in well water in Braun Station, Texas. In 1986 it struck 56 people in Albuquerque, New Mexico. There was a river water outbreak in Carrolton, Georgian (13,000 cases), in 1987 that affected several municipal water systems in the area. In 1988 it infected a swimming pool in Los Angeles. Waterborne outbreaks occurred again in 1992 (Medford and Talent, Oregon, 3,000-15,000 cases; a Pennsylvania campground, 551 cases; and Kitchener-Waterloo, 1,000 cases, where water is both filtered and ozonated); 1993 (Milwaukee, the largest to date, infecting over 400,000 people, killing 100 and sending 4,000 to hospital) and 1994 (Las Vegas: 110 sick and 19 dead; and rural Washington State).
In 1994, tests of 151 water supplies from three watersheds around Vancouver showed cryptosporidium in 26 samples. It was detected in rivers around Philadelphia in 1995. In many cases, cryptosporidium has been found in company with another microorganism, giardia, also known to cause gastrointestinal illness (also spread by animal feces in water, commonly called "beaver fever").
While cryptosporidium was not positively identified in any of the water samples taken from Collingwood, giardia was found in one sample. Giardia is, however, inactivated by chlorine, while cryptosporidium isn't. Cryptosporidium is 14 times more resistant to chlorine and 30 times more resistant to ozonation than giardia, although tests show the parasite can be killed by ozone treatment if given the appropriate exposure time.
Home filtration system can be effective, if the filter is one micron or less (absolute), and the manufacturer guarantees it will remove cryptosporidium oocysts. However, filters must be regularly maintained and/or replaced according to manufacturers' directions. There is always a danger improperly maintained filters will themselves become a breeding ground for bacteria.
Reverse osmosis and distillation systems will also work to purify drinking water.