Mosquito fish could be enlisted to help fight West Nile virus

ST. LOUIS -- Health officials may turn to a tiny fish to help fight the spread of the West Nile virus.

The mosquito fish, no bigger than the pinkie on your hand, thrives in backwaters, streams and ditches. It can eat as many as 500 mosquito larvae per day. The fish is native to much of Southern Illinois and eastern Missouri and is widely sold by fish hatcheries.

"They will not do the whole thing by any stretch of the imagination," Mark Ritter, who oversees mosquito control for the city health department, told the St. Louis Post-Dispatch. "But they can make an impact."

Ritter and other health officials note there are many sites where mosquitoes lay their eggs where the fish couldn't be used, such as the tiny pools of water found in old tires, birdbaths and stopped-up gutters.

But in small ponds or small ornamental pools, the mosquito fish could be extremely effective, they said.

Controlling mosquitoes is taking on a greater sense of urgency now that the mosquito-spread West Nile virus has killed 52 people in Illinois and five in Missouri this year. Illinois had more deaths than any other state.

The northern house mosquito, one of the primary carriers, typically lays its eggs in stagnant water, such as swamps or small ponds where mosquito fish can thrive.

Many people who are bitten by an infected mosquito don't develop any symptoms of the disease. People over 50 are at the greatest risk. Symptoms include a headache, high fever and neck stiffness.

Many fish hatcheries sell the mosquito fish as a way of controlling mosquitoes and as food for larger fish. One mosquito control district in California is so enthusiastic about the fish's ability to fight mosquitoes that it distributes the fish free to pond owners in the district.

Ritter said he had been told by some state officials that the mosquito fish should not be introduced into any new areas in the state. However, Ken Drenon, the Missouri Department of Conservation's ombudsman, said there were no rules barring the mosquito fish from being released into privately owned ponds in the state.

Larry Cruse, regional fisheries administrator for the Illinois Department of Natural Resources, said mosquito fish should be used in conjunction with other methods, such as spraying, to reduce the mosquito population.

"What we've got to do to battle this is a variety of measures, natural and chemical," Cruse said.