Brain-eating amoeba: Where are infections most common, and who is at risk?

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Most cases of N. fowleri infection in the U.S. are contracted in contaminated recreational waters. (CDC)

(NEXSTAR) – Two children have died this week after becoming infected with Naegleria fowleri, a microscopic organism more commonly known as a “brain-eating amoeba.” The parasite, primarily found in warm freshwater and soil, can cause a devastating and fatal infection in nearly all cases.

Infection of N. fowleri usually occurs after the organism enters the nasal cavity and crosses the epithelial lining into the brain, where it begins destroying the tissue of the frontal lobe, explains Dr. Dennis Kyle, a professor of infectious diseases and cellular biology at the University of Georgia and the scholar chair of antiparasitic drug discovery with the Georgia Research Alliance.

This brain infection, known as primary amebic meningoencephalitis (PAM), can lead to symptoms including fever, headaches, stiff neck, seizures and hallucinations, among others. These symptoms usually start within five to nine days of exposure. Death usually occurs within another five days, according to the CDC.

Unfortunately, most cases of N. fowleri infection are observed in children. But it’s likely for no other reason than that they’re more prone to be active in the water, Kyle explains.

“It’s very commonly found in nature, in soil or warm freshwater around the world… Or in places where the water is warm for other reasons, like a thermal hot spring, or pool water that isn’t chlorinated properly,” Kyle says.

“This time of year is when we typically hear about these cases,” he adds. “When people are out doing summer activities in the water, or on the lakes.”

The CDC currently classifies N. fowleri infections as rare, with only 34 reported cases in the U.S. between 2010 and 2019. Of those, the vast majority (30) were infected during recreational water activities, while others were infected using contaminated tap water for nasal irrigation, or, in one case, on a “backyard slip-n-slide.”

But despite the relatively low case numbers, Kyle says researchers — and especially the families of those who died of a brain-eating amoeba infection — generally dislike the term “rare.”

“This is something that is in every warm water lake around the South, so it’s there,” says Kyle, who adds that science doesn’t quite know why more people aren’t getting infected. He further notes that anybody of warm freshwater can harbor the amoebae, citing two cases of N. fowleri in Minnesota in 2010 and 2012. One of the cases from this week was contracted in Northern California, too.

“The warming climate, you would think, could potentially have an effect on the infections,” he adds. “Warmer water means more people get infected.”

N. fowleri infection might not even be that “rare,” either, as doctors believe it’s underreported or misdiagnosed in many parts of the world. In Pakistan, for instance, Kyle says there were no reported cases for many years until a doctor returning from studies in the U.K. was able to diagnose “dozens” of cases that, if not for increased awareness, would have been misdiagnosed.

“Sometimes it’s thought to be viral or bacterial meningitis,” Kyle explains. “It’s not until physicians are working through it before they realize. In many of the cases, the diagnosis came back very late. Sometimes post-mortally.”

Kyle also believes that early diagnosis may make a difference in the outcome of the infections, citing a Florida doctor who was able to identify the early stages of infection in a young boy and place him into a medically induced coma to prevent brain swelling during treatment.

Even still, chances of survival are slim with current treatments. Kyle, also the director of the University of Georgia’s renowned Center for Tropical and Emerging Global Diseases, knows of only four documented cases of survival in the U.S., and “maybe” seven globally.

Current treatments usually include a combination of drugs, usually involving antifungals and antibiotics including amphotericin b, miltefosine, fluconazole and azithromycin. But “none work very well by themselves,” according to Kyle, whose well-documented work with drug discovery includes studies and screenings of treatments in the hopes of finding something that could kill the amoeba faster.

“I think we need better drugs than we have, to really make a difference,” he says.

In the absence of such treatments, taking proper precautions is the best defense against N. fowleri infection. The CDC suggests limiting the amount of water going up the nose. Kyle adds that it’s best to avoid bodies of warm freshwater (which produce surface temperature readings of 75 degrees F and up, for extended periods of time), and especially avoid jumping or diving into such waters. He also recommends using nose plugs, keeping your head above the surface, and properly cleaning and chlorinating wading pools, swimming pools and spas.  

Kyle is also a big proponent of amoeba awareness, as it’s not something people often think about on hot summer days.

“If we had more awareness, better support, more people working on this — then we could possibly come up with better diagnostics and better treatments in a reasonable amount of time, and avoid these devastating things that are happening.”

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