COUNTYWIDE : Virus Find Prompts Alert on Mosquitoes

County officials on Monday urged residents to wear long-sleeved shirts at dusk and guard against mosquitoes because some birds on which the insects feed are infected with St. Louis encephalitis.

So far this year, no Orange County resident has contracted the potentially fatal brain inflammation from a mosquito bite, nor have any mosquitoes trapped here been infected with encephalitis.

Still, health officials became concerned last month after the county Vector Control District discovered encephalitis virus in an unusually high number of birds--16 of 167 sparrows and house finches tested. Nearly all the birds were from Central Park in Huntington Beach.

The 9.6% infection rate is more than double that usually found in Orange County, said Vector Control District Manager Gilbert Challet, who recommended that all county residents, not just those in Huntington Beach, take precautions against mosquitoes.

Added Dr. George Gellert, the county’s deputy health officer: “What we have here is obviously a reservoir for infection.”

Still, Gellert cautioned, “it’s nothing for the public to be alarmed about. But reasonable measures need to be taken to reduce a very small personal risk to a nonexistent risk.”

He recommends wearing mosquito repellent, especially at dusk when mosquitoes are most active, and eliminating potential breeding areas by emptying basins around potted plants and ensuring that pools are well-chlorinated. He also suggests making sure homes are adequately screened.

In addition to trapping hundreds of mosquitoes and testing the blood of wild birds, Challet and his staff are monitoring three flocks of chickens to see if encephalitis will surface. So far, only the wild birds have tested positive.

Usually, at this time of year, when the nighttime temperatures drop to the low 60s or 50s, mosquitoes die off, Challet said. But with warm weather and water to breed in, the mosquitoes will continue to thrive.

Encephalitis, an inflammation of the brain, can be caused by viral or bacterial infection or sometimes a systemic response to vaccination or illness. In many adults, symptoms could be mild, with headache, fever and malaise much like the flu. But, particularly for young children or the elderly, the disease can lead to hospitalization and death.

Through this June, eight county residents had contracted encephalitis, and none of the cases were caused by mosquitoes, Barbara Peck, a county health official, said.

In addition to the discovery of encephalitis in Orange County birds, two strains of the virus have been found in mosquitoes in Pomona, Malibu and Torrance, the Los Angeles County Department of Health Services announced Monday.