July 23 2004

Pesticide use against West Nile virus needs more study

By Alexandre Da Silva
Scripps Howard Foundation Wire

WASHINGTON – More studies are needed on the health-risks linked with pesticides used against mosquitoes carrying West Nile virus and on their effectiveness, a panel of experts said Friday.

Many state and local governments have been fighting West Nile virus, which is incurable and can be fatal, by spraying a variety of pesticides to kill the mosquitoes that transmit the virus to humans.

“Where the data is coming in, we are just not seeing an increase number of West Nile fatalities in non-spraying communities,” said Jay Feldman, executive director of Beyond Pesticides, a non-profit organization advocating pesticide safety.

Feldman and other scientists held a briefing sponsored by the National Academies, which studies major issues and advises the government.

He said pesticides should be a last resort and that preventive measures should be used to hamper the spread of a virus that infected nearly 10,000 people in the United States last year, killing 262. He said exposure to pesticide could cause cancer and other illnesses.

Though he agreed pesticide might be harmful, David Gaines, a public health entomologist with the Virginia Department of Health, said pesticide is the only effective way to kill adult mosquitoes already infected with the virus.

West Nile virus is transmitted to humans by infected mosquitoes, blood transfusions, transplants and from mother-to-child during pregnancy. The virus originated in the West Nile District of Uganda in 1937 and has since spread to Europe and North America.

Mosquitoes get the virus from feeding on infected birds. Some 2 million infected birds have died in the United States since the first case of the virus was reported in the United States in 1999, said Cyrus Lesser, chief of Maryland’s Department of Agriculture Mosquito Control Section.

No cases have yet been found in Hawaii, Alaska or Oregon. The Centers for Disease Control and Prevention estimated that for every 150 people infected with the virus, about 20 percent will show symptoms – which include fever, headache, body ache, rashes and vomiting – and one will become seriously ill.

Because mosquitoes reproduce in shallow, still water, Feldman said people should empty flowerpots, dig ponds deeper and poke holes in old tires and other containers around their homes.

“You get all your junk, you dry it and you drain it,” said Feldman, who also pushed for more government-sponsored community meetings and public education.

Feldman quoted a U.S. General Accounting Office report that said the public is poorly educated on domestic pesticide use. He noted that pesticides also kill other species and make people drowsy and nauseated, symptoms mirroring those of the West Nile virus.

“We need to begin looking at alternative methods … to avoid exposure to what we don’t know much about,” Feldman said, as he showed a picture of a truck blowing pesticide at a group of children in the street.

Lesser said cases in which communities overdid on pesticide are isolated and happen because they are new to the system. He added that pesticides could be useful for communities with more elderly people, who may have challenges cleaning breeding areas around their homes and are more susceptible to the disease.

But Lesser said using pesticides require “a lot of permits” and can cost as much as $600 per treated acre depending on how it is sprayed. Pesticides also need repeated application, especially after it rains, he said.

Gaines, who defended using pesticides, said it’s hard to decide when and at what levels pesticide should be used based on current studies.

“We are learning more and more,” said Lesser.

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