West Nile virus worries specialists

Thousands of mosquito-control specialists will swarm Savannah, Ga., next week to swap tips and get a head start on how to combat the bloodsuckers that will re-emerge this spring.

The event will be the 70th annual meeting of the American Mosquito Control Association. Starting Monday, industry leaders, public health officials and scientists will discuss ways to control the spread of the pest and the life-threatening diseases some mosquitoes cause, such as the West Nile virus and malaria.

West Nile virus will be a top concern, given that the number of human cases in the United States more than doubled — from 4,156 to 9,136 — between 2002 and 2003, according to the federal Centers for Disease Control and Prevention.

Asked about the outlook for West Nile virus in 2004, CDC spokesman Tom Skinner said, “It’s too early to tell. But we fully expect West Nile virus to continue its westward movement.” At this point, he said, Oregon and Washington are the only two states that have not reported any human cases.

As for eradication of the pest, Jeff Heusel, assistant director of the Chatham County Department of Mosquito Control in Georgia, said, “No. That’s not even a remote possibility.”

But he said there is a “lot of sharing of (mosquito-control) ideas and technologies,” both nationally and internationally.

As evidence of the sharing that goes on, Mr. Heusel cites a mixing plant in his county that formulates a frequently used pesticide. “The concept came from Charleston [South Carolina], and we automated the process more,” he said.

Mr. Heusel said Florida provided his county with an innovation known as “high-pressure” helicopter spraying for adult mosquitoes, which is more efficient than traditional spraying techniques.

Mosquitoes are prolific. Females lay between 100 and 300 eggs at a time, depending on the species. And some females may lay as many as 1,000 eggs during an average 30-day adult lifetime.

Only female mosquitoes bite. They sip blood from victims to nourish eggs within their body. Some mosquitoes sip as much as one and a half times their own weight in blood.

Mr. Heusel stressed that only some mosquitoes carry diseases. In Chatham County, which includes Savannah, “We have 38 species of mosquitoes. But there are only 11 or 12 here that I would call pests that pose health-related risks.”

But even the common house mosquito, which belongs to the genus Cutex, can transmit certain kinds of parasitic worms and can carry encephalitis viruses. Encephalitis is a condition marked by swelling of the brain.