The principle source of Cryptosporidium contamination is believed to be animals, both domestic and wild. Oocysts can survive chlorine treatment, which means that Cryptosporidium resists conventional disinfection methods. The water must be filtered in order to remove Cryptosporidium. Most community water systems in Minnesota use wells to get their water from under the ground. Twenty-six community water systems in Minnesota use surface water.
Surface water is open to the environment and more susceptible to contamination.
The water system must be operating at optimum levels at all times so that a breakdown does not occur at this critical point in the treatment process. One of the challenges in detecting and dealing with Cryptosporidium is that current testing methods have not proven to be reliable, even in closely controlled studies cosponsored by the U. S. Environmental Protection Agency and various academic experts. Even the best laboratories in the country have a problem with detecting Cryptosporidium and reproducing test results. The inconclusive results mean that a negative test doesn't guarantee that the water supply is free of Cryptosporidium nor does a positive test signal a public health emergency. As more reliable testing methods are developed, water supply systems will have more options for detecting potential problems and responding to them quickly.