Oct 08, 2007

Brain-Eating Amoeba Found in 12 Tucson Water Wells

Brain-eating amoebas have taken up residence in Tucson's water supply as recent tests have shown their presence in 12 wells.

While the discovery of the killer amoeba, known as Naegleria fowleri, is surprising to at least one UA researcher, the microscopic bug's presence in the Old Pueblo's water supply doesn't pose any health risks.

Tucson Water chlorinates its well water before distribution, killing the amoeba before the water hits taps. But the amoeba's presence in our underground water source—probably as a result of biodegradable oil used in pumps—is a surprise. The amoeba is usually found in surface water such as rivers and lakes.

"The organism is everywhere," said Charles Gerba, a microbiology professor with the University of Arizona's Department of Soil, Water and Environmental Science. "It feeds on bacteria."

Naegleria fowleri made headlines recently when it killed a 14-year-old boy who had gone swimming in Lake Havasu last month.

Essentially, the amoebas enter the body through the nose and travel to the brain, where they feed until the person dies. The only way to get infected is to snort water. A person can drink water that has Naegleria fowleri and never be infected.

While the amoeba sounds like something out of a horror film, people come into contact with it all the time, although infection is rare. It lives in soil and is often present in warm bodies of water, particularly hot springs and lakes. Pools, if not chlorinated properly, can become homes to the microbes.

While Tucson Water chlorinates its groundwater before distribution, Gerba said he was concerned about private wells that aren't necessarily chlorinated. There were roughly 250 private wells in the greater Tucson area in 2004, state records show.

So, researchers also sampled 20 private wells, but they found no presence of Naegleria.

The discrepancy has led Gerba to think Naegleria fowleri is showing up in the Tucson Water wells because of biodegradable oil that's used as a lubricant for pumps. Pumping capacity in private wells is much smaller, and, as such, the pumps don't rely on engines, he said.

Essentially the amoebas are entering the Tucson Water wells to feed on the bacteria.

"I think it's just the circumstance of they switched to biodegradable oils for lubrication," he said. "It may have always been there, but people are more aware of Naegleria now."

Naegleria was discovered in the 1960s and the federal Centers for Disease Control and Prevention have tracked only several hundred cases worldwide. Between 1995 and 2004, 23 people in the United States were infected by Naegleria fowleri, the CDC says.

Because the microscopic organism thrives in warm water, Gerba said he expects to see the trend of more and more cases continue as the Earth's climate becomes warmer.

"I think we are going to see more problems with more microbes in water with the warming trend," he said. "It seems to be a trend, and I think it will continue."