NEW THREAT FEARED FROM MOSQUITOES OFFICIALS ISSUE HEALTH WARNING.

Byline: Robert Monroe Staff Writer

Mosquito season is back with a new buzz this year: Public health officials are concerned that the deadly West Nile encephalitis might strike here.

Although the mosquito-borne West Nile strain hasn't appeared in California yet, the unknowns of the virus are enough to put county health officials on alert. It killed seven people in New York last year.

``This is a new experience,'' said Luann Munns, spokeswoman for the Greater Los Angeles Vector Control District. ``We all have our ears open and are very aware of the possibility. If you don't look for it, something can come up and bite you.''

This week, the county issued its annual public health warning advising residents to eliminate stagnant pools of water, which could serve as breeding grounds for mosquitoes.

In California, the more common form of mosquito-borne disease is the St. Louis encephalitis virus, which causes inflammation of the brain and spinal cord. From 1984 to 1997, there were 26 reported human cases of the disease, including one fatality.

Nonetheless, county health officials said the West Nile strain could spread on the wings of infected birds. On the East Coast, the disease has been carried by crows, among 18 other bird species, bitten by carrier mosquitoes. For reasons not yet understood, crows carry especially high levels of the virus in their blood before dying from the infection.

County public health entomologist Gail Van Gordon noted that crows are not confined to the East Coast and that a gradual spread of the virus is possible. The disease spreads to humans when they are infected by mosquitoes that bite birds with the virus.

``We are watching for it,'' she said. ``Migrating birds could bring it from the East to the West.''

Because there is no cure for the virus, county officials are advising residents to drain standing pools of water. Health officials also want to prevent any flare-ups of the St. Louis strain.

``It continues to be important. We want to avoid any cases of St. Louis encephalitis because of its seriousness,'' county Public Health Officer Jonathan Fielding said.

County officials credit the lack of recent mosquito-borne diseases to their vigilance in monitoring everything from stagnant, greening pools of water where mosquitoes breed to chickens that could carry the virus in their blood after being bitten.

Because of Southern California's mild climate, crews from the vector control district check swimming pools year-round instead of waiting for mosquito season, which lasts through October.

They monitor 470 problem pools that could serve as spawning grounds for larvae of the most common Southern California mosquito, Culex quinquefasciatus, and the rarer kind more likely to carry encephalitis, Culex tarsalis.

The district builds the list using complaints from neighbors, requests for help and aerial surveillance in which vector control officers fly over the Valley looking for green pools. Tools for eradication include a growth-retarding chemical, thin sheets of oil sprayed over pools to suffocate the larvae and even schools of larvae-eating minnows.

``California state as a whole is a lot more proactive than New York,'' Munns said. ``Now we can never afford to be complacent.''

< MOSQUITO TIPS

Because mosquitoes breed in the warmer months, May through October is considered mosquito season. Here are a few tips on how to avoid their bites.

--Eliminate water sources. Mosquitoes need standing water to breed. Remove it from buckets, tires, planters and other outdoor containers.

--Maintain ponds, fountains and pools. Use the proper chemical treatments to keep water from turning green and stagnant. Fish that feed on mosquito larvae are available from local mosquito vector control districts.

--Experience the great outdoors - in the middle of the day. Mosquitoes are most active from dusk into the evening. If hiking, mountain biking or camping, especially near natural water sources, limit your exposure. Use insect repellent and wear long pants and long-sleeve shirts.

Source: Los Angeles County Department of Health Services 

CAPTION(S):

3 photos, box

Photo:

(1) A small scoop of rainwater from an untended swimming pool in Northridge contains some of the thousands of mosquitoes in various stages of development in the pool.

(2) Vector control specialist Rande Gallant examines some mosquitofish, used by the Greater Los Angeles Vector Control District - and available to the public - to control mosquitoes by eating their larvae.

(3) Ronnie Helo of the Vector Control District adds pellets to inhibit mosquito growth in the water that has accumulated in a Northridge swimming pool.

Evan Yee/Staff Photographer

Box: MOSQUITO TIPS (See text)