ST. PAUL -- The microscopic parasite suspected in the death of a 14-year-old Minnesota boy is rare - especially in colder climates - but that doesn’t mean swimmers should let their guards down, a state health official says.
“People should assume that there is a low level of risk in every lake,” said Trisha Robinson, supervisor of the waterborne diseases unit for the Department of Health.
Hunter Boutain of Alexandria died Thursday of a brain disease called primary amebic meningoencephalitis after swimming in Lake Minnewaska in western Minnesota’s Pope County.
The infection is commonly caused by Naegleria fowleri, which lives in bodies of warm freshwater and can attack a victim’s brain through the nose. If state and federal health officials can confirm the parasite caused the boy’s death, it would be the third such death recorded in Minnesota.
The first was that of 7-year-old Annie Bahneman, who died in August 2010 after swimming in Stillwater’s Lily Lake. Two years later, 9-year-old Jack Ariola Erenberg died of the same infection after swimming in the same lake.
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Health officials say only 35 cases of the infection were reported in the U.S. from 2005 to 2014, and Robinson said that although the parasite can strike anytime and anywhere, the danger is slim.
“Lots of people can go swimming in the same location and get water up their nose, too, and not be infected,” she added.
Robinson said it is not known why Naegleria fowleri and its related infection have surfaced in Minnesota in the past five years. Before 2010, no case had been detected north of Missouri.
“There’s no million-dollar answer for that,” she said. “But it’s certainly more likely to occur when water temperatures are higher.
“In both 2010 and 2012, we experienced incredibly warm temperatures for a large period of time, which would heat up the body of water.”
She added that the parasite can survive freezing, too, so it can persist from one year to the next.
Other factors, she said, could include better testing methodologies and more awareness from the public and doctors.
“I think that awareness in general has certainly increased over time,” she said. “It was always thought that this was something of Southern states only, so certainly our cases here demonstrate that that’s not the case.”
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Confirmation of a link to last week’s death could take weeks, she said.
Anderson answered several questions related to primary amebic meningoencephalitis, also known as PAM, and the Naegleria fowleri parasite. Her answers are lightly edited.
Q: Should Minnesotans be worried about contracting PAM?
A : I think it understandably does incite fear in individuals, but it’s really important for people to understand that infections are very rare. People are exposed to a number of different things that would be more likely to cause problems, and there are lot of different waterborne diseases you can get. But I certainly understand how scary this can be since it is almost always fatal.
Q: Can bodies of water be tested for the parasite?
A: There’s no rapid, reliable test for Naegleria in water, and even if you do not find it, it doesn’t mean that it’s not there. So testing is not a reliable way to go about any sort of prevention. If you think of water testing in general, it’s a snapshot in time from that sample that you pull. There certainly can be uneven distribution in a body of water in the location. And the number of amoeba can vary over time within the same lake or river.
Q: What is the process in confirming PAM?
A: There are a number of different tests, and we work in conjunction with our partners at the federal Centers for Disease Control and Prevention to do that. We do additional tests of clinical materials - samples that are taken from a body such as from cerebral spinal fluid. Confirmation testing has to do with the patient, not the water.
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Q: Has testing changed in recent years?
A: We do have additional tests that have not been available in the distant past, including a type of molecular test that looks for the amoeba in an individual who is suspected of having it.
Q: Are there times of the year when these infections most commonly occur?
A: The parasite thrives in warm water, so people would be more likely to be infected when water temperatures are high and where levels are low.
Q: Does stirring up the lake bottom increase risk?
A: The parasite can encyst in the lake sentiment, and that’s why it’s recommended that people avoid digging in or stirring up the sediment.
Q: Is it true that Naegleria fowleri could be found in tap water?
A: It has been associated with tap water, but again it’s important to note that the only way people can get exposed is by water going up their noses. You cannot be exposed by drinking water.
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Q: Does chlorine kill it?
A: Chlorine does kill it. So there is no risk in properly chlorinated and properly maintained swimming pools.
Q: Who is most susceptible to the infection?
A: It’s been more frequently identified in children and in males, but that most likely is due to those individuals taking part in activities that would be more likely to have water go up their noses. So they may be exposed to the parasite more frequently.
Q: What can people do to minimize the risk?
A: Keep your head above water when swimming or wear nose clips.
