Hidden danger lurks in some Florida lakes and ponds

TAMPA - Like many girls her age, Liza Hollingsworth loved animals, art, music and sports. At age 10, the young honor student from Mount Pleasant, S.C. had an exciting life ahead of her.

But on June 14, just three days after complaining of a headache, Liza Hollingsworth was dead. Her killer was a tiny single-celled organism with a morbid attraction to the human brain.

Primary amoebic meningoencephalitis (PAM) is a very rare, but almost always fatal disease caused by a free-living amoeba commonly found in warm water lakes and ponds in the Southern United States. The amoeba, Naegleria fowleri, enters the human body through the nose or sometimes the ear. Within days, the victim suffers severe headaches, nausea, slips into a coma and then dies.

The illness is difficult to diagnose and even more difficult to treat. Another frightening aspect of the amoeba is its prevalence in freshwater ponds and lakes throughout Florida, including the Tampa Bay area.

Health department officials in area counties say testing for the amoeba’s presence is cost-prohibitive, but also unnecessary since it probably exists in nearly every closed, untreated body of freshwater.

The only way to ensure protection is to avoid swimming in waters that have the amoeba.

“Basically the organism likes to stay in the surface mud layer in a spot where there isn’t a lot of changeover in the water,” environmental specialist Charles Vogt said. “Swimming lakes that have a huge changeover and keep the water moving and diluted greatly reduces the possibility of an infection.”

Vogt said that does not mean it won’t occur, but people can prevent themselves from becoming infected.

“It really shows up when it’s hot, so steer clear of swimming in these places when it’s really hot,” he said.

Bob Washam, director of the environmental division of the Martin County Health Department, said Martin has no lakes permitted for bathing. There is a permitted swimming area at Jonathan Dickinson State Park that being part of the Loxahatchee River is brackish water.

However residents may still unwisely choose to swim in private retention ponds or canals.

“There has never been a case of N. fowleri in Martin County, but there was one in Orange County last year,” he said. “Here the main danger in freshwater lakes is alligators.”

Washam said “it’s probably in a lot” of the freshwater ponds and lakes in the county and he would recommend parents not let their children dive or swim in them.

“I hate to hear about it happening to child,” he said. “It’s always fast and fatal.”

N. fowleri infects its host when water enters the nose. The amoeba then migrates along the olfactory nerve into the brain. Once there, it multiplies and actually feeds on brain cells killing them quickly, and affecting the entire central nervous system.

Symptoms include loss of smell followed by severe headaches, vomiting and fever until rapid onset of coma and then death.

The scientific community uses the word “rare” to describe the incidence of infection by this tiny pathogenic organism, but super rare is probably the more appropriate term. Although first identified in 1965 in Australia, U.S. cases have been attributed as early as 1937. Since then, 125 cases have been reported.

Unfortunately, because of the nature of its attack, N. fowleri is almost always fatal. Of the 125 cases reported, 124 resulted in death.

In 2007, six cases of PAM in the United States were reported to the Centers for Disease Control, including three from Florida. All six patients died. In 2009, the one U.S. death reported was from Florida.

The problem with treatment of the disease is its diagnosis. Symptoms of PAM are similar to viral meningitis or bacterial meningitis, also serious illnesses, but with much better success rates for treatment. PAM requires visual inspection of the spinocerebral fluid to determine presence of the amoebae.

What to know about Naegleria infections

Caused by a freshwater amoeba, most active July-September

Infects people primarily through the nose

Infections are extremely rare, but almost always fatal

Initial symptoms start one to 14 days after infection

Seek immediate help if fever, headaches, stiff neck or vomiting develop

In the United States, there were 121 cases documented between 1937-2007 with just one survivor

Between 1998 and 2007, there were 33 U.S. deaths primarily in Southern states, including Florida

There were four deaths in Florida in 2007

During a similar 10-year period, in comparison, there were 36,000 drowning deaths in the United States.

Source: Centers for Disease Control and Prevention