Developments in Brief : Killer Amoeba Attacks the Brains of Swimmers

A killer amoeba that lurks in freshwater lakes and unchlorinated swimming pools, attacking swimmers’ brains, has claimed the lives of at least 138 people worldwide over the last two decades, researchers said.

The microscopic organism, which prefers bodies of water that reach surface temperatures of at least 95 degrees, first came to light 22 years ago in Australia. Since then, it has claimed 55 lives in the United States, said Dr. Julio Martinez, a neuropathologist at Presbyterian-University Hospital in Pittsburgh.

Most people are naturally immune to the amoebas, called naegleria fowleri, he said. But if the single-cell organisms attack the brain, death is almost certain.

The organisms are found in swimming pools and natural bodies of freshwater around the world, Martinez said. They can enter a swimmer’s body through his nose and cause a disease called amoebic meningoencephalitis, which destroys the brain.

Once the amoebas reach the brain, they multiply rapidly. “Within a matter of hours, there are millions,” Martinez said. Within three or four days, “the brain becomes very swollen and victims go into a coma and die.”

He said only one person has survived the disease--a 9-year-old girl in San Francisco who contracted the amoeba in a swimming pool. Three or four days later, she developed the typical symptoms of the disease--headaches, nausea, vomiting and a high fever. She was successfully treated with antibiotics, Martinez said.

To ward off the amoebas, swimmers should wear nose plugs, and pool operators should be sure to chlorinate the water properly, he said.