Mosquito Research Project: You Can’t Swat City Hall

After reassuring local officials that the project makes more sense than it appears, a regional mosquito control district is going ahead with plans to release up to 30,000 of the insects in a Los Angeles suburb--then try to trap them again.

Officials of the Southeast Mosquito Abatement District say the mosquitoes, dusted with a florescent powder that glows under ultraviolet light, will be turned loose early next month in a residential neighborhood in Norwalk and a nearby park in Downey. About three dozen traps will then be set around the area to recapture the mosquitoes as part of a research project to learn more about their habits in urban and suburban environments.

The release, the second of its kind in California, is part of an ongoing UC Berkeley project prompted by this decade’s outbreaks of viral encephalitis, which is carried by mosquitoes, in the Los Angeles Basin.

The Norwalk City Council on Tuesday approved of the mosquito release, calling it a worthwhile scientific endeavor despite the objections of one council member that the proposal sounded irrational and perhaps even dangerous.

“I think it’s wrong that we should be the guinea pig for the universe,” complained Councilwoman Grace Napolitano.

Questioning the wisdom of adding to the city’s mosquito population, Napolitano, who represents Norwalk on the mosquito abatement board, warned that the research bugs might attack people allergic to their bites or even spread the encephalitis virus.

When the council was told that the experiment will cost the city nothing, she interjected, “Just bites.”

But Jack Hazelrigg, an entomologist who serves as the district’s assistant manager, reassured doubters that mosquitoes prefer bird and animal flesh.

Although he said he cannot guarantee that his winged research subjects will be harmless, Hazelrigg said, “The risk of dying is much greater stepping out the front door than from contracting encephalitis from these mosquitoes. . . . I think the benefits of what we’re doing far outweigh the risks.”

Officials of the mosquito abatement district--which covers southeast Los Angeles County and the San Fernando and San Gabriel valleys--said that by working with the Berkeley team they gain a better understanding of where and how far mosquitoes travel in urban areas.

Scientists Surprised

Because viral encephalitis had been considered a rural disease before the Southern California outbreaks of the 1980s, research centered on mosquitoes in rural areas, said Richard P. Meyer of Berkeley’s School of Public Health. The urban cases surprised scientists, who still don’t know why the virus, which can cause inflammation of the brain and spinal cord and is potentially fatal, suddenly appeared in the basin, he said.

They also don’t know much about how mosquitoes behave in an urban-suburban environment, characterized by drainage ditches, swimming pools and landscaping generally not found in rural areas. Researchers would like to know whether the mosquitoes are breeding extensively in back yards, or primarily in river channels and the like. The answers will influence control efforts, Hazelrigg said.

In the first mosquito release in the urban-suburban study, between 30,000 and 40,000 of the insects were released in the Orange County community of Rossmoor last month. There were no problems or citizen complaints, according to James P. Webb, an ecologist with the Orange County Vector Control District, and researchers later trapped between 5% and 10% of the insects, an unusually high recapture rate.

For the Norwalk-Downey area experiment, officials will collect 20,000 to 30,000 immature mosquitoes from around the county, then rear them to adulthood before their release, tentatively scheduled for Sept. 7 and 8, Hazelrigg said.

As mosquito populations go, the number is a sprinkling, said Hazelrigg, noting that hundreds of thousands of the insects can hatch in a single evening in an unmaintained back yard swimming pool.

Researchers began studying a three-square block area in the northwestern corner of Norwalk after a local resident contracted encephalitis, in 1986, monitoring the area since then to determine the number and kinds of mosquitoes that frequent the neighborhood.

Napolitano is not the only person to question the logic of releasing thousands of blood-thirsty insects in a housing tract. The issue was debated by the research team, according to Meyers, who is a member of the group. But he said the potential threat is diminished this year because of the dry weather and the fact that the encephalitis virus has not been detected in the mosquito population this season.

“We don’t expect it to present any immediate public health risk,” he said.

After their release in Norwalk and in Wilderness Park in Downey, which borders the San Gabriel River, the mosquitoes will be collected in traps baited with carbon dioxide, to simulate a blood host, and fermented water, which simulates a stagnant pool.

Joining the council majority in endorsing the release, Norwalk Councilman Mike Mendez asked only that the release dates be publicized. He joked that he himself will be out of town when the mosquitoes are released, commenting, “I’ll be gone, so that’s fine.”