Could Your Pet Have a Brain-Eating Amoeba?

Patrick Mahaney, VMD, CVA, CVJ
Updated: July 31, 2015
Published: September 24, 2013
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When visiting my family in Massachusetts in the summertime, I spend as much time as possible swimming or water skiing in the freshwater lake I’ve been going to since I was a child. Fortunately, the lake is fed by underwater springs, is quite deep, and has never been known to harbor any pathogens that could cause severe illness in humans or animals.

Some of the more shallow waters in areas of the country that are prone to drought and extreme heat are not guaranteed to be as safe, as evidenced by the recent reports of a child falling severely ill from a water-borne parasitic infection.

In mid August, 2013, USA Today reported the tragic story of seventh grader Zachary Reyna, who became afflicted by a life-threatening illness after engaging in what seemed to be normal summertime activity. (Fla. boy fighting 'brain-eating' amoeba) Zachary was knee boarding in a freshwater channel a short distance from his home in LaBelle, FL he was infected with a water born parasite, Naegleria fowleri.


What is Naegleria fowleri?

Naegleria fowleri is a water-borne organism that enters the body through openings, primarily the nose, and then migrates into soft tissues, including the brain. Once Naegleria fowleri establishes itself in the brain, it causes an often-fatal condition called Primary Amebic Meningoencephalitis (PAM).

Naegleria fowleri is commonly referred to as a "brain-eating amoeba." An amoeba is a single celled organism capable of living outside of a host in the appropriate environmental circumstances, such as warm, fresh water.

brain eating parasite, water parasite, brain infection, Naegleria fowleri


Is Infection with Naegleria fowleri Common?

According to the Centers for Disease Control and Prevention (CDC):

In very rare instances, Naegleria infections may also occur when contaminated water from other sources (such as inadequately chlorinated swimming pool water or heated and contaminated tap water) enters the nose. You cannot get infected from drinking water contaminated with Naegleria.

The CDC reports that from 2003 to 2012, there have been 31 Naegleria fowleri infections in the U.S. Contaminated recreational water was the source for 28 people and the remaining three became infected after undergoing nasal irrigation using contaminated tap water. To me, there seems to be some concern about the infectious potential of drinking water, as some people may not be using appropriate water filtration devices or other treatments before they consume water out of the tap for routine hydration.

Since 1962, 128 people in the U.S. have been infected by Naegleria fowleri; only one has survived, according to the CDC. The lone survivor was Kali Hardig, a twelve-year-old girl from Benton, AK who contracted Naegleria fowleri from a water park approximately two weeks before Zachary Reyna contracted the parasite.

Since the story broke, Zachary has passed away from complications related to his infection. Two other boys also swam in the same water where Zachary got sick, but the boys have not fallen ill.

Diane Holm, a Florida Department of Health spokeswoman, stated that "In Florida, the months of July, August, and September are the warmest, so any standing fresh water is going to be warm and have the potential to host Naegleria fowleri."


Could Your Pet Be Infected with Naegleria fowleri?

According to, “Not all mammals are affected by Naegleria fowleri; dogs can play in the same water that infects humans with no implications themselves.”

As this didn’t quite settle with me, I cross-referenced the topic on the Veterinary Information Network (VIN) and found that hosts that are susceptible to Naegleria fowleri are humans and mice (when done experimentally). There was a case study showing one dog infected by Naegleri fowleri. See: Amebiasis in a dogs with gastric ulcers and adenocarcinoma. How exactly the dog was exposed to the disease could not be determined.


How Can Infection with Naegleria fowleri be Prevented?

As treatment of this organism does not yield a high likelihood of resolution (i.e., the mortality rate is exceedingly high), it’s best to focus on prevention.

The CDC gives the following tips on Naegleria fowleri prevention:

  1. Hold your nose shut, use nose clips, or keep your head above water when taking part in water-related activities in bodies of warm freshwater.
  2. Avoid putting your head under water in hot springs and other untreated thermal waters.
  3. Avoid water-related activities in warm freshwater during periods of high water temperature and low water levels.
  4. Avoid digging in, or stirring up, sediment while taking part in water-related activities in shallow, warm freshwater areas.


Even more rarely, infections have been reported when people submerge their heads, cleanse during religious practices, or irrigate their sinuses (nose) using heated and contaminated tap water.

If you are making a solution for irrigating, flushing, or rinsing your sinuses (for example, by using a neti pot, sinus rinse bottle, or other irrigation device), use water that has been:

1. previously boiled for 1 minute (at elevations above 6,500 feet, boil for 3 minutes) and left to cool;

2. filtered, using a filter with an absolute pore size of 1 micron or smaller;

3. purchased with a label specifying that it contains distilled or sterile water.

Rinse the irrigation device after each use with water that has been previously boiled, filtered, distilled, or sterilized, and leave the device open to air dry completely.

Although the apparent incidences of dogs (or cats) becoming infected with Naegleria fowleri is low, I still would advocate employing the same safety precautions for pets to prevent them from becoming infected with a potentially incurable disease.

Dr. Patrick Mahaney


Steele, K.E. Amoebiasis in a dog with gastric ulcers and adenocarcinoma. J. of Vet. Diagnostic Investigation 9(1): 91-93. 1977. 

Images: Tom Klimmeck and CDC images / Thinkstock

Last reviewed on July 31, 2015