The popular Lake Elmo Park Reserve swimming pond remains closed today after Washington County Parks staff Thursday began treating the popular swimming site for a parasite suspected of causing illnesses in two people who swam there recently.
County workers decided to “super chlorinate” the swimming pond as a precaution to eradicate a parasite that causes cryptosporidium.
“Park visitor safety is our main concern,” said John Elholm, parks directors.
Elholm said state Department of Health guidelines call for 25.5 hours of chlorine treatment to eradicate the cryptosporidium parasite. He added that officials expect to reopen the swimming pond this weekend.
“We’re confident it will be open Saturday morning,” he said.
Two people with laboratory confirmed cases of cryptosporidium have been reported to the MDH, according to Trisha Robinson, a state epidemiologist.
“Cryptosporidium is a diarrhea illness,” she said. “It is caused by a parasite. The tricky part with cryptosporidium is its incubation period can be as short as two days and as long as two weeks,” she said.
The two people with the confirmed cryptosporidium cases reported that they swam at the Lake Elmo park pond in two weeks prior to the onset of their illness, according to Yvonne Klinnert, county public information manager. Two other lab-confirmed cases of cryptosporidium were reported in people who said they swam at the Lake Elmo pond just outside the incubation period, she added.
Klinnert said it is possible the cases could be related. She added that none of the cases required hospitalization.
“It (cryptosporidium) can cause complications in some individuals. About 20 percent (of cases) require hospitalization,” Robinson said.
The parasite that causes cryptosporidium typically gets in recreational waters by someone already infected, Robinson said.
“The way it gets into most recreational bodies of water is when a person who is ill gets in the water,” she said. “They’re not typically infectious until they have symptoms.”
The other problem with cryptosporidium is that it is resistant to chlorine levels considered safe to swim in, according to Robinson.
“There are levels the chlorine is brought up to and left there,” she said. “It will take about one to two days.”
That is why the Lake Elmo park pond was closed for treatment, Klinnert said.
“The high levels of chlorine needed to kill any potential organisms will mean the pond will be closed for at least 24 hours,” Klinnert said. “The level of chlorine will dissipate naturally, and when it lowers, swimmers will be allowed back in the pond.”
Klinnert added that the county Department of Public Health and Environment staff will provide education and signs informing anyone who has diarrhea not to swim while suffering from the illness and for two weeks after symptoms end.