October 1, 2007

Amoeba Infection That Killed Teen Noted

By Annette Wells



The death of an Arizona boy infected by an amoeba after swimming at Lake Havasu has caught the attention of officials responsible for Lake Mead, Lake Mohave and Nevada's hot springs.

They want to know if those bodies of water also harbor the microscopic killer Naegleria fowleri, which enters the body through the nostrils and eats away brain tissue. They also want to know how much of a risk the microbe might pose to the thousands of Jet Skiers and swimmers who recreate in those waters each year.

The parasite is rare and there is no treatment for its infection, which is similar to bacterial meningitis, health officials say.

Currently, no one is testing for the amoeba in Lake Mead or Lake Mohave.

"It would be like looking for a needle in a haystack," said Kent Turner, chief resource manager for the National Park Service' Lake Mead Nevada Recreational Area.

"We have never, in the past, particularly thought of Lake Mead as a likely place to harbor this amoeba, but it certainly is of interest to us that it was found at Lake Havasu," he said. "What we certainly intend to do is to discuss this with people who have dealt with it, just what conditions seem to increase the probability of contact with it. ... The issue for us is not to be too overly concerned, but also not to totally ignore our responsibility to investigate the possibility."

According to the federal Centers for Disease Control and Prevention, Naegleria fowleri is a free-living amoeba found worldwide predominantly in warm bodies of fresh water, such as the shallow portions of lakes and rivers, and in hot springs. It also exists in poorly maintained and inadequately chlorinated swimming pools, as well as soil. It feeds off algae and bacteria found in fresh water and swimming pools.

J.C. Davis, a spokesman for the Southern Nevada Water District, said the area's drinking water is not an issue with the amoeba.

"The critter likes warm temperatures," he said. "We have sophisticated water systems that not only keep the water cool but protect against contamination."

Between 1995 and 2003, there were 23 Naegleria fowleri infections documented in the United States.

This year, however, the CDC is reporting six cases - three in Florida and two in Texas, in addition to the case involving the Arizona boy.

The father of the Arizona boy, David Evans, told the Associated Press nobody knew his son, Aaron, was infected with the amoeba until after he died on Sept. 17. At first, the teen seemed to be suffering from nothing more than a headache.

"We didn't know," Evans said. "And here I am: I come home and I'm burying him."

After doing more tests, doctors said Aaron probably picked up the amoeba a week before, while swimming in the balmy shallows of Lake Havasu.

Aaron was brought to Sunrise Hospital and Medical Center in Las Vegas where he died.

According to the CDC, people are infected when water containing the amoeba goes up their nose. The parasite travels to the brain and destroys brain tissue.

The infection leads to primary amebic meningoencephalitis, a brain inflammation.

Symptoms start one to 14 days after it's contracted, with victims complaining of neck stiffness, headache, fever and nausea. As the disease progresses, infected persons will appear confused and may experience seizures and hallucinations.

"The brain is one area of the body that even with a small change can have major effects on your entire body," said Brian Labus, a Southern Nevada Health District epidemiologist. "It is a very complicated system and anything affecting its tissue or fluid can lead to death."

The health district has received a few reports over the past 10 years about possible Naegleria fowleri infections. It is unknown if they contracted the infection in Nevada or elsewhere, Labus said.

"It's a rare enough thing that we do investigate it, but it's not something you'll find on an annual report," he said. "It falls into that category of other diseases."

Turner said he knew of at least one Naegleria fowleri case in the 1980s in which the individual might have contracted it at a Lake Mead hot spring.

"These infections occur almost every year, and many lakes and hots springs in the United States are contaminated, so this is a difficult disease to prevent versus reduce risk," said Michael Beach, a specialist within the CDC's Division of Parasitic Diseases, in an e-mail Friday. "Because the amoeba is heat-loving, hot springs present a risk. These are traditionally soaking-type uses, which is a reduced risk since putting your head under the water is necessary for exposure to occur."

Turner said signs are posted at Lake Mead's hot springs, directing visitors not to submerge their heads.

Benefiting Lake Mead and Lake Mohave though is their depth and cooler waters.

Lake Havasu averages a depth of about 35 feet, while Lake Mead averages about 400 to 500 feet. Lake Mohave exceeds 100 feet, Turner said.

"There's a difference in the water mixture as well," he said. "The open water is mixed by wind, which tends to cool it. The better mixed the water, the less probability that this (amoeba) could develop."

Turner said water flowing into Lake Havasu comes from shallow channels of the Colorado River. In the summer months, there is "significant" opportunity for that water to be warmer than what exists in Lake Mohave and Lake Mead.

Beach said the federal agency hasn't sent out any health alerts to states regarding the amoeba.

Every year, prior to Memorial Day weekend, the CDC does sponsor recreational water illness prevention week to educate people about water safety and illnesses but this has no specific focus on Naegleria fowleri, he said.

"This is a tragic disease but we also need to consider that hundreds of millions of visits to recreational water venues occur each year so the risk of infection is quite low," Beach said. "The only way to prevent such infections is to stop swimming, which is not likely to be the choice of most swimmers."

The Associated Press contributed to this report.

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