Tiny but deadly: a look at Naegleria fowleri
In 2013, 12-year-old Kali Hardig went to a water park in Little Rock, Arkansas, with her family. It was supposed to be a fun summer outing, but 30 hours later, Hardig was rushed to the hospital with a high fever and severe bouts of vomiting.
Hardig had contracted Naegleri fowleri, otherwise known as the brain-eating amoeba. The infection is very rare — only about 130 cases have been reported in the United States since 1962 — but it is almost always a death sentence. The amoeba causes primary amebic meningoencephalitis, or PAM, which ravages the central nervous system. Because of the rarity of N. fowleri infection, and because the symptoms of PAM mimics the symptoms of bacterial meningitis, it’s difficult to diagnose until after death.
The infection has an onset of between one to nine days after exposure to N. fowleri, and afflicted people often die within one to 18 days, according to the CDC. Of the 143 people ever diagnosed with PAM since it was first reported in 1962, only four people have survived.
N. fowleri is a naturally occurring microbe that thrives in warm freshwater, making ponds, lakes and rivers a veritable breeding ground. The amoeba infects humans when a swimmer gets water into his or her nose. The amoeba travels along the olfactory nerve, which regulates the sense of smell, and up into the brain.
N. fowleri normally feeds on bacteria at the bottom of the lakes and rivers the amoeba inhabits, explained CDC researcher Jennifer Cope in an interview with LiveScience.com. Once it reaches the brain, it begins eating away at brain cells.
Despite how long the science world has been aware of N. fowleri and the severe effects of the rare affliction, not much is known about the amoeba.
Because of this, it’s very difficult to find a scientist who would classify as an expert on the topic. Charles Gunnels, assistant professor of biology at Florida Gulf Coast University, is honest about not knowing much about the amoeba past what he has read in articles and scholarly texts.
There are several dozen species of Naegleria, but only N. fowleri has a lethal effect on humans. Whether this species only affects humans isn’t known for sure.
“We don’t know if other organisms, like raccoons or some wading birds, like ducks, have to deal with this parasite,” Gunnels said. “More often than not, parasites tend to attack a single species. It’s not even clear that we’re the intentional target of the amoeba.”
Gunnels explained that there is a theory that a vast majority of people are made immune to the effects of the amoeba through prior exposure. The antibody creates a memory of the exposure and how it managed to fight off the infection, and when the person is exposed again, the antibody uses that memory to attack the disease and destroy it.
According to Gunnels, in becoming exposed to and subsequently fighting off the infection, a person who develops antibodies against the infection might never know they came in contact with N. fowleri and possibly never will.
In other words, a person who comes in contact with N. fowleri won’t even become ill.
Researchers also don’t completely know why the amoeba has the effect is does only when water containing N. fowleri enters the body through the nose. The infection cannot be contracted by ingesting water containing the amoeba, nor can it be contracted by getting that water into open wounds.
Treatment of the infection is very much in its experimental stages even today, due primarily to the rarity of the infection. In the case of Kali Hardig, doctors used anti-fungal drugs to help beat down the effects of PAM, which helped prior survivors of the disease. They also tried a drug called miltefosine, which is normally used for breast cancer treatment but previously displayed antiamoebic properties.
The use of those drugs appeared to help Hardig, though the benefits aren’t uniform; doctors used miltefosine on a boy with PAM back in 2010 and it proved ineffective as the boy eventually died from the infection. At the time of Hardig’s treatment, miltefosine hadn’t even been FDA-approved and was considered an “investigational new drug.”
According to the CDC, N. fowleri has been detected in fresh samples of cerebrospinal fluid collected from infected patients after their deaths. This begs the question: can the collection of CSF aid in a quick diagnosis of PAM?
“Oh, sure, but let’s think about what that means,” Charles Gunnels said. “That means actually getting a spinal tap, and that’s not something most people would be interested in doing until they’ve gotten rid of all other possible explanations for their illness. Most doctors probably wouldn’t be interested in that stage of medical diagnosis.”
Gunnels argues that going straight to a spinal tap without additional evidence can be considered drastic.
“What [doctors] are going to be doing is looking for maybe chemical signals, maybe changes in brain activity, maybe neurological signals — just signals that our bodies give, or the amoeba give, that allow us to see the presence of [the infection],” Gunnels said. “That all takes a lot of time and, unfortunately, a lot of examples before we really figure it out.”
Kali Hardig spent seven weeks in the hospital. Within a week of her release, the teen was going back to school.
Her survival story is not one that many, if any, survivors of PAM can tell. Another boy Hardig’s age contracted the disease and survived, but with permanent brain damage.
Despite Hardig’s positive outcome, reports on the brain-eating amoeba have incited panic in many, especially tourists to the southern United States.
Gunnels agrees that the panic is justified. “You’ve got something unique, strange, a single-celled amoeba that kind of looks like the one we all looked at in high school biology and this amoeba, this itty-bitty thing, can get into our brains and kill us? Oh my god, it’s terrifying,” he said.
However, Gunnels urges people, both locals and tourists, not to avoid nature in order to keep from contracting the infection. Instead, Gunnels says, take appropriate precautions: “Use a nose plug to keep the water from going up your nose, or just play around up to your waist. But definitely make sure you go out and have fun.”
