In the News

March 21, 2006
Central Valley Business Times, Stockton

Central Valley Researcher Builds a Better Mosquito Trap An Offer Mosquitoes Can't Refuse Walter Leal with ovitrap. (Photo by Kathy Keatley Garvey) Walter Leal is a hunter. His quarry is powerful enough to kill a horse or even a human. Yet it’s so small, you can kill it with your hand. It’s the mosquito – specifically those carrying the West Nile virus. Mr. Leal, an entomology professor at the University of California, Davis, draws gravid mosquitoes – females ready to deposit their eggs – to his chemically scented oviposition traps set in Sacramento, Fresno, Shasta and Los Angeles counties. Culex mosquitoes, the principal carriers of West Nile virus, buzz excitedly around his traps, drawn by the tantalizing smell, the whirring movement of battery-operated fans, and the water-filled tray. "The smell is offensive to us, but the mosquitoes like it," says Mr. Leal, who has been perfecting the "stinky" chemical compound mixture for the past four years as part of a federally funded grant. Once sucked into the traps, the mosquitoes can be tested for the presence of West Nile virus, which last year killed 18 people in California and infected some 900 others throughout the state. Health officials found the killer virus in all of California's 58 counties last year. Mr. Leal's ovitraps work much better than the host-seeking standard traps, says medical entomologist Anthony Cornel, director of the Mosquito Research and Control Laboratory at the UC Kearney Research and Extension Center in Parlier. During the height of the West Nile epidemic last year in Fresno County, as many as 18 percent of the mosquitoes collected in Mr. Leal's ovitraps tested positive for the virus, says Mr.Cornel, who also serves as associate director of the UC Davis Center for Vectorborne Diseases. To the outsider, the ovitrap resembles a metal tool box nestled in a water-filled tray. Generally, female mosquitoes consume a blood meal and later – after the blood is digested and nutrients converted to egg yolk -- look for a place to "oviposit" or lay their eggs. The ovitraps, to be placed in Sacramento, Los Angeles, Fresno and Redding beginning in late May or early June, are like sentinel chickens in that entomologists can alert the public to an outbreak of West Nile virus. Last year 1,053 sentinel chickens from 31 California counties tested positive for West Nile/St. Louis encephalitis antibodies, indicating they were infected with the mosquito-borne disease. The ovitraps are also somewhat like the canaries in coal mines that alert the miners of the presence of dangerous underground gases. Sacramento County, which tallied 175 cases of West Nile virus infections last year, proved to be the nation's hot spot for the virus, according to the Centers for Disease Control and Prevention. The ovitraps also serve another purpose: they indicate the size of mosquito populations. "Last year when the mosquito abatement district was night-spraying pesticides in Sacramento County, we saw a decrease in mosquito populations and more dead ones -- the mosquitoes were dead or dying in our traps," Mr. Leal says. "So we could tell right away that the spraying was working well." News ~ News Tips ~ Related News Contact: Kathy Keatley Garvey Communications UC Mosquito Research Program Department of Entomology 396 Briggs Hall University of California, Davis Davis, CA 95616 Phone: (530) 754-6894 E-mail: kegarvey@ucdavis.edu