News | August 22, 2011

Brain-Eating Amoebas: Separating Fear From Fact

By Kevin Westerling, Editor

The three deaths this summer due to Naegleria fowleri, the so-called “brain-eating amoeba,” are both tragic and scary, due largely to the age of the victims and the seemingly benign circumstances surrounding their infection. Most recently, on August 13, a 16-year-old girl died after swimming in a river. Prior to that, a man in his 20s was stricken after he simply rinsed his nose with tap water. The first victim, a boy just nine years old, died a week after attending a fishing day camp.

The invading organism responsible for these deaths thrives in warm water, and thus most commonly strikes between July and September. According to WebMD, Naegleria fowleri can be found in lakes, ponds, rivers, untreated swimming pools, untreated well water and municipal water, and in thermally polluted water, such as power plant runoff. The amoebas are deadly when they invade through the nose, proceeding to feast on the host’s brain for lack of other food. Symptoms may resemble those of meningitis, including headache, fever, stiff neck, vomiting, and loss of appetite, with death typically occurring about a week after symptom onset. An article posted by CNN reports that N. fowleri infection of the brain, known as primary amoebic meningoencephalitis (PAM), is more than 95% lethal, adding that nearly two-thirds of the victims are under the age of 13.

Alarming as these details are, it should also be noted that PAM is not at all common, with just 35 reported cases in the U.S. since 2001, according to Jonathan Yoder of the Centers for Disease Control And Prevention, cited by WebMD. Furthermore, studies suggest that many people have antibodies to fight off the amoebas, and therefore may have contracted and fought off the infection. Yoder explains, however, that it’s difficult to draw a clear conclusion from these findings. “We have asked ourselves, ‘Is this a rare infection that is always fatal, or a more common one that is only sometimes fatal?’ We don’t know the answer.”

What we do know is that N. fowleri cannot survive in salt water or properly treated municipal water, and that it will not cause brain infection when ingested. PAM only results when the amoeba finds its way into the nose, typically through recreational activities in warm freshwater — a likely explanation for the relative youth of its victims. And while these cases are always fear-inducing, it is helpful to remember that they remain an extreme rarity.

N. fowleri itself does seem to be proliferating, however. Most often seen in the Southern and Southwestern states, a recent case was recorded in Minnesota. Though it’s no time to panic, this is certainly a situation to monitor for the long-term sake of water quality and safety.