The Centers for Disease Control recommended that Lake Powhatan be temporarily closed to prevent the spread of cryptosporidium (crypto), according to a Buncombe County Health Department notice on Friday, Aug. 28.

Three cases of Crypto have been reported to the Buncombe County Department of Health and a fourth case is suspected. Each affected person reported being in the lake in August.

The Forest Service is fully cooperating and has closed Lake Powhatan to swimming and fishing until at least September 12, 2010, the Health Department notice says. Other facilities at the lake will remain open.

Crypto is a parasite that may be found in recreational water. Recreational water includes water in swimming pools, hot tubs, Jacuzzis, fountains, lakes, rivers, springs, ponds, or streams. The parasite is introduced into the water by sewage or feces from humans or animals and can then be spread when the water is accidently swallowed. Cryptosporidiosis is a diarrheal disease caused by microscopic parasites of the genus Cryptosporidium. Both the disease and the parasite are commonly known as "crypto."

Symptoms usually include stomach pain, nausea, vomiting, diarrhea and fever, and often last as long as one to two weeks. If you suspect that you have crypto, contact your health care provider or Buncombe County Department of Health at 250-5109.

Crypto raises public health concerns because it is difficult to remove from public drinking water systems, and it can enter undetected into public drinking water because ordinary tests don't detect it, according to the Wisconsin Department of Natural Resources.

"Many species of Cryptosporidium exist that infect humans and a wide range of animals. The parasite is protected by an outer shell that allows it to survive outside the body for long periods of time and makes it very resistant to chlorine disinfection," according to a CDC report.

While this parasite can be transmitted in several different ways, water is a common method of transmission and Cryptosporidium is one of the most frequent causes of waterborne disease (drinking water and recreational water) among humans in the United States, the CDC report says.

"In April 1993 thousands of Milwaukee residents and visitors were stricken with a flu-like illness caused by a tiny yet potent protozoan called Cryptosporidium," according a Wisconsin Department of Natural Resources report. "The outbreak sickened 403,000 people and was linked to inadequate treatment of drinking water taken from Lake Michigan. No specific source of the cryptosporidium was ever identified but runoff from abnormally heavy spring rains most likely carried the crypto to the lake from a variety of sources."

Crypto is hard to detect, the Department of Natural Resources report notes. "Detecting Cryptosporidium in drinking water requires sampling a large volume of water because the organisms usually are widely distributed. The current standard method of detecting crypto is to pipe from 500 to 1,000 gallons of water through a filter with openings less than one micron in size to collect any fine particles and protozoans that are present."

Crypto is hard to remove from public drinking water, the report says. "Treating drinking water using normal doses of disinfectants such as chlorine does not kill Cryptosporidium oocysts. Researchers have found it takes 90 minutes to kill 90 percent of Cryptosporidium oocysts in a water sample treated with 80 milligrams of chlorine per liter of water. Normally, chlorine is applied at about one milligram per liter. Stronger disinfectants, such as ozone, do a better job of killing these protozoans in a shorter time."

"Another safeguard that took effect in June 1993 is new, more restrictive federal requirements for turbidity (cloudiness) in treated drinking water," according to the report. "Treatment plant operators must test more often for turbidity as well as meet a more stringent standard for turbidity. The impact of the standard will not totally prevent Cryptosporidium from becoming a problem in drinking water, but it will give officials faster notice of problems so other steps can be taken to protect public health from this troublesome protozoan."