Health Editor’s Note: The last thing you want to think about when taking a refreshing dip to cool off, is that you can be exposing yourself to an ameba that can harm you by eating your brain. This is not a science fiction scenario, but a real-life possibility if you swim in warm, fresh water. The tough part with dealing with the ameba Naegleria fowleri, first discovered in 1965, is that it is difficult to diagnose with only a few centers having the ability to identify this critter. It is very rare to get this disease and over half of all cases in the US have been in Texas and Florida.
The ameba Naegleria fowleri usually feeds on bacteria but when it accidentally finds itself in a human body, will settle for brain tissue. The ameba enters the nose and moves along the ofactory (used for smelling) nerve into the ofactory center in the front of the brain. Symptoms as not very specific but may be fever, stiff neck, head ache, vomiting, seizures, altered mental state, hallucinations, drooping eyelids, inability to taste, and coma. By the way, all of these symptoms can be from having meningitis, which is often the diagnoses given. Between zero to eight cases are seen every year, with other cases not being accurately diagnosed due to the many vague symptoms that can be associated with other diseases. Evidence may only be found on autopsy and this has occurred in more than one person who was diagnosed with meningitis.
Where can the ameba Naegleria fowleri be found? It may exist in mud puddles, warm lakes, ponds or rock pits, warm and slow-flowing, low water level rivers, untreated well or municipal water, hot springs or other geothermal water sources, run-off from power plants, aquariums, and even in soil, including house hold dust. It is not found in bodies of saltwater or in properly treated pools and spas.
Activities that force water into the nose, such as diving, water skiing can lead to this infection. People who have dunked their heads into hot springs or cleaned nostrils with neti pots (using untreated tap water) have also been infected.
If infected, symptoms may occur between two to 15 days. Death usually follows in three to seven days with only a very few surviving the infection. Death usually occurs three to seven days after symptoms appear. Only a very few have survived this infection and treatments are limited.
How can you avoid this ameba? Under no circumstances put your head under warm, fresh water, either naturally occurring or in a spa or pool. If you can stand to do this, wear a nose clip when entering fresh water. Do NOT dunk your head under warm bodies of water. This brings to mind scenes from the movie, Jaws, but now the predator is a happenstance ameba, who has found itself in your nose and will make a living there. Now we can fear a head dunk in warm, fresh water. What is this world coming too?………Carol
—Here’s how the CDC does its detective work in suspected cases of infection with the brain-eating ameba Naegleria fowleri.
By Kristin Bundy Published: September 22, 2017
Reviewed by Ware Kuschner, MD, Chief, Pulmonary Section, US Department of Veterans Affairs Palo Alto Health Care System, Palo Alto, California
While millions of Americans safely swim in freshwater lakes and rivers every summer, there are an extraordinarily small number of people who become infected with free-living, “brain-eating” amebas; 37 cases were reported in the US between 2006-2015.1 These single-cell organisms, known as Naegleria fowleri, thrive in warm freshwater.1 In rare instances, the ameba enters the brain via contaminated water through the nose, causing a serious and often fatal illness known as primary amebic meningoencephalitis (PAM).1
Fortunately, PAM occurs very infrequently. But because it is so uncommon, there are only a few centers around the world that are equipped to confirm infection. One such center is the US Centers for Disease Control and Prevention (CDC) Waterborne Disease Prevention Branch (WDPB).2
In rare instances, Naegleria fowleri, a brain-eating ameba that thrives in warm freshwater, can cause a serious and often fatal illness known as primary amebic meningoencephalitis.
Naegleria enters the brain through the nose via contaminated lake or river water.
CDC Waterborne Disease Prevention Branch runs an emergency operations center where physicians can connect with experts in the field regarding potential infections.
The WDPB includes a small group of experts who provide guidance to physicians on the signs and symptoms of PAM. “CDC doesn’t see or treat patients, but we do provide clinical consultations because the infections are so rare,” said Jennifer Cope, MD, medical epidemiologist at WDPB. “Because it can be an urgent issue, physicians can contact us through the emergency operations center, where operators answer calls 24/7 and can connect physicians with someone on call.”
Dr. Cope said that the WDPB typically engages in about 70 to 80 consultations per year—most of which aren’t actual cases of PAM, but rather inquiries from physicians who are concerned about an infection or who have questions about testing or treatment.
The CDC is one of only a few groups that can confirm these infections through laboratory testing, according to Dr. Cope. A standard hospital can look at cerebral spinal fluid under a microscope but cannot confirm PAM without specific laboratory tests that are found at the CDC. In the past, diagnoses often only occurred after autopsy, when the amebas appeared on brain biopsy stains. However, in recent years, the CDC developed a polymerase chain reaction (PCR) test that detects amebas in cerebral spinal fluid obtained by lumbar puncture while patients are still in the hospital. Once a diagnosis is made, the CDC can advise physicians on appropriate treatment.
The coordination of diagnosis and treatment from the CDC occurs through the state and local health departments, noted Dr. Cope. Members of the WDPB don’t actually provide patient care. Instead, their role is to track infections around the country and conduct epidemiological investigations to determine where and how patients may have come into contact with the amebas.2 The WDPB also analyzes possible risk factors for infection, ways to sample and detect the organisms, and potential ways to control them.2
The biggest question still remains—what causes just a few individuals to be singled out for infection each year? “The risk of PAM for the many millions of people who go swimming in lakes every summer is small—the most cases we’ve ever reported in a year was eight,” said Dr. Cope. “Even with some potential underdiagnosis, it’s clearly a rare infection. We wish we better understood the mechanisms that could explain why that one person gets infected, and everyone else is fine.”
Until more is known, the CDC suggests some common sense prevention tactics for summer swimmers, including holding their nose or using nose clips, keeping their heads out of freshwater while swimming, skipping freshwater-related activities when it is especially hot outside, and refraining from digging up sediment while in shallow, warm freshwater areas.3 None of these measures have been tested, noted Dr. Cope, so the CDC can’t say that they will work 100%. But she does suggest, “The more you can keep water from going up your nose, the better.”
- Centers for Disease Control and Prevention. General Information. Frequently asked questions. What is Naegleria? April 12, 2016
- Centers for Disease Control and Prevention. Division of Foodborne, Waterborne, and Environmental Diseases (DFWED). Waterborne Disease Prevention Branch. May 24, 2016
- Centers for Disease Control and Prevention. Naegleria fowleri —primary amebic meningoencephalitis (PAM)—amebic encephalitis. Swimming. March 20, 2014.