Anti-mosquito effort aimed at thwarting virus

Philip Green drives a pickup truck through the shallow River des Peres in the St. Louis area Monday as three other city workers sit in the back and lob gray, golf ball-sized pellets into the water.

They're throwing larvacide, a product that's not harmful to humans or wildlife, but will keep mosquitoes from growing into adults. It's part of the city's effort to keep the mosquito population down, and help fight the West Nile virus.

Most people who get infected with the West Nile virus do not become ill. Some develop flu-like symptoms. In rare cases, the disease can be fatal with severe encephalitis, a swelling of the brain.

In 2002, 168 human cases were reported in Missouri with seven deaths. Last year, the overall numbers of cases went down to 64, but the state saw eight fatalities, said Dr. Howard Pue, the state public health veterinarian.

Pue and other health officials said there's no way to know for certain how hard Missouri will be hit by West Nile this year. He said cases of West Nile typically drop off after the first year or two in an area, but it shouldn't disappear completely.

"It's not going to go away," Pue said.

While there were no human cases of West Nile in Cape Girardeau County last year, the Cape Girardeau Public Health Center will continue with its state-supported West Nile program, said Jane Wernsman, the center's assistant director.

Mark Ritter, environmental health manager for St. Louis, said larvaciding is just one effort to curb the city's mosquito population. He said the larvacide has an insect growth regulator that time-releases into the water over 150 days and keeps the pests from becoming adults. They absorb juvenile hormones that prevent them from developing into grown, biting mosquitoes.

The city monitors and treats hundreds of locations for mosquitoes, Ritter said. It also uses aerosol spraying to kill adults.

Fog in Cape Girardeau

Larvacides are also used in areas of standing water around the city of Cape Girardeau, said Steve Cook, the city's environmental services coordinator.

In addition to the larvacide, Cape Girardeau will use a pesticide mixture of malathion and mineral oil in fog form.

"We would be fogging if it wasn't for the cool weather. It needs to warm up a little," Cook said.

He said fogging will be done two times a week at first and may increase to three times a week if conditions worsen.

Cutting down on the number of mosquitoes means they're less likely to bite birds infected with the virus in large numbers. Infected mosquitoes can pass the virus to humans -- and some animals, like horses. There's no evidence that people can directly get the virus from birds, other animals, or spread it from person to person, except for infected pregnant women who can pass it along to an unborn child.

About 13 miles of the River des Peres get close attention every year because the river is shallow, with still pools and brushy banks, conditions mosquitoes like. It's also close to homes.

"If you're a mosquito, this is a great place. If you're a mosquito, this is pretty close to heaven," Ritter said.

While there is no way to determine exactly when West Nile season starts, people should start protecting themselves as soon as they notice the presence of mosquitoes," said Karen Hunter, environmental health specialist for Dunklin County.

Mosquitoes "are happier in warmer, humid weather, which Southeast Missouri is known for," Hunter said.

Staff writer Kathryn Alfisi contributed to this report.