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Deaths Linked To Freshwater Amoeba

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By Neil Johnson and Josh Poltilove of The Tampa Tribune

Published: September 8, 2007

ORLANDO - A third Central Florida death this summer is linked to a freshwater amoeba, the Florida Department of Health has confirmed.

Results from the Centers for Disease Control confirmed findings from the Orange County Medical Examiner indicating an amoeba-related infection of the brain or spinal cord led to deaths. A statement from the state health department did not identify the victim or say where specifically the infection occurred.

Naegleria fowleri amoeba is microscopic and most commonly found in top few inches of sediment in the bottom of lakes and ponds with mud floors, according to the health department. Infection is rare but more likely during summer months.

Earlier this week, a state environmental epidemiologist said the health department only was aware of 13 Florida deaths caused by the amoeba in the past 30 years.

Doctors know the amoeba enters the body through the nose and travels to the brain, where it causes an infection and swelling called amoebic encephalitis. It is nearly always fatal, though it can be treated with antibiotics if caught quickly enough.

It strikes quickly once symptoms appear – headache, fever, nausea and vomiting, followed by lethargy, stiff neck and confusion. Death can occur seven to 10 days after symptoms show up.

Stirring up the sediment suspends the amoeba in the water, so it can reach the nasal passages. Florida's shallow lakes are perfect for exposure to the amoeba because they warm quickly and it's easy to stir up the bottom.

But scientists do not know how many of the creatures need to be in the water to present a danger or whether there is a safe concentration. They also do not know how many amoebas an individual has to inhale to become infected.

Though mostly young people have died from the amoeba, doctors don't know whether age is a factor or whether younger people simply tend to be more active swimmers and do things to stir up the water, said the environmental epidemiologist, Carina Blackmore.

"We don't know why these few people were affected and not the thousands of others who swim in freshwater," she said this week.

Health officials say to avoid swimming in stagnant lakes, ponds or retention areas. The amoeba does not occur in well-maintained swimming pools.

Flowing rivers tend to be cooler than shallow lakes or ponds and may not harbor as many of the amoeba, though scientists are not certain, Blackmore said.

Doctors suspect cooling water during the fall and winter contains fewer of the amoebae because fewer infections occur during cool months. That may be because not as many people swim and no one knows how cool the water must be to be safe.

"We don't know the magic temperature when they go into an inactive winter form," Blackmore said. "We can say we see human cases in the late summertime, and those have had exposure to shallow, warm lakes and swimming activity."

Here are some precautions to take to avoid the amoeba, according to the Department of Health:

* Wear nose clips or hold your nose when swimming, jumping or diving in any fresh water. Closed nostrils reduce your risk of infection by amoeba, a rare but life threatening condition.

* Don't swim in warm standing water, such as ponds, lakes, storm water retention areas or in areas posted "No Swimming."

* Avoiding areas with obvious algal blooms; contact with blooms may cause skin rash, burning eyes and a runny nose.

Reporter Josh Poltilove can be reached at 863-259-7691 or at jpoltilove@tampatrib.com.

Reporter Neil Johnson can be reached at (813) 259-7731 or njohnson@tampatrib.com.

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