The Mosquito War : Extra-Rainy Winter Could Yield Big Crop of Disease-Carrying Insects; Abatement Experts Are on Alert

This enemy lurks in neglected swimming pools across Los Angeles County, in back yard hot tubs, birdbaths, goldfish ponds, in clandestine crannies such as the water that collects inside abandoned tires.

The enemy is the mosquito, and its ranks swell mightily when heavy rains leave countless puddles of brackish water--exactly the setting where mosquito larvae thrive. So as the rainiest Southern California winter in years draws to a close, experts are girding themselves for a Normandy-style invasion.

“Where there’s smoke, there’s fire. And where there’s water, there’s mosquitoes,” warned Robert Saviskas, the top mosquito control official in western Los Angeles County. Saviskas reports that local mosquito counts are three times higher than normal for early March.

The mosquito wars ahead could be big, brutal, bloody. The pesky, fast-breeding insect not only bites human flesh, but some species can carry diseases such as potentially fatal encephalitis.

The opposition is mustering early, armed with weapons such as larvae-eating fish, killer bacteria and sentinel chickens.

This week, in a preemptive strike, three veteran mosquito warriors already were crisscrossing southwestern Los Angeles County in hopes of quashing the dreaded mosquito explosion. At one point, they scrambled through thick brush to inspect a potential enemy stronghold--a pond-sized puddle behind Mira Costa High School in Manhattan Beach.

Mark Brooks, a mosquito control field supervisor, grimly surveyed the scene: a curving expanse of murky water, thick vegetation, floating leaves beneath the eucalyptus trees. This bucolic setting soon could become home to hundreds of thousands of mosquitoes, Brooks warned.

“This is an ideal spot for mosquito breeding. Left unchecked, it’d be a real problem for us,” he said.

So Brooks and two colleagues went to work. Earlier that morning, they had paid a visit to an ornamental garden on the grounds of the U.S. Department of Veterans Affairs West Los Angeles Medical Center. There, in a picturesque series of six pools, the district is raising Gambusia affinis , commonly known as “mosquito fish.”

The innocuous-looking brown-gray fish resemble the common guppy and grow a mere three inches or less. But their ravenous appetite for mosquito larvae has made them a favored weapon in the arsenal of the district, which stocks thousands of them in reservoirs, drainage channels and other South Bay bodies of water.

Brooks’ team scooped about 1,000 tiny fish out of the ponds with nets, lowered them into a tank aboard a pickup truck and headed southeast to Manhattan Beach. There, one technician placed about 30 of the fish in the pool of stagnant water, where they will breed and feed on mosquito larvae.

Next the team moved to a marshy area in nearby Redondo Beach. Using long spoon-like tools, they scooped up water and studied it in search of larvae.

“See this little wriggler here?” Brooks said, pointing to a Lilliputian-sized larvae.

To stave off more larvae in the marsh, workers sprayed small amounts of a bacteria, known as “Bti,” that kills mosquito larvae. Although the sprayings often stir concern among onlookers, district workers say the spray is environmentally safe.

The mosquito season traditionally runs from May to October. But recent rains have sparked early control efforts throughout Los Angeles County, which is served by five mosquito-abatement districts and two other control agencies.

“They’re all planning way far in advance,” said Gail Van Gordon, public health entomologist with the county Department of Health Services.

Most of the South Bay west of the Harbor Freeway is served by the Los Angeles County West District, while the area east of the freeway is covered by the Southeast Mosquito Abatement District, which is not reporting a significant increase in mosquitoes so far this year.

But the western district has seen two signs of heightened activity: more adult mosquitoes caught in monitoring traps, and stepped-up complaints from mosquito-bitten residents.

“This is the worst year on record,” said Saviskas, executive director of the west district--which has been keeping records only since 1983. “By the time May comes, we’re going to have an awful lot of problems.”

Control officials worry that considerable mosquito breeding may occur around private homes--in clogged rain gutters, fish ponds and even in the water collecting inside flowerpots and boats.

They are encouraging area residents to contact the control district offices for information about how to discourage mosquito breeding. For instance, residents can get free mosquito fish for their ponds and unused swimming pools.

Of the 21 mosquito species that live in Southern California, only a handful are known disease-carriers. But the fact that a few species can carry encephalitis is enough to worry health officials. Encephalitis symptoms range from flu-like conditions to swelling of brain tissue and death.

The mosquito-borne disease that is of most concern to local health officials is St. Louis encephalitis. Mosquitoes can pick up the germs that cause the disease when they bite infected birds. They can then pass it on to humans. The county’s last major outbreak of St. Louis encephalitis occurred in 1984. Sixteen people, one of whom died, were diagnosed with the disease.

To help monitor the spread of encephalitis-carrying mosquitoes, control workers maintain and test so-called “sentinel flocks” of chickens. This week, five white Leghorn chickens arrived to take up residence in a coop near the Mobil Oil Corp. refinery in Torrance.

Two entomologists tested the chickens to ensure that they were free of disease. They gently bound the chickens’ feet and held them while making a tiny pinprick in the chicken’s comb and squeezing a small amount of blood onto a piece of litmus paper.

The chickens will be retested every two weeks, and their blood sent to a public health laboratory at UC Berkeley to assure they have not contracted the virus.

Control experts are not letting their guard down, especially after rainy winters such as this one. They will continue prowling the South Bay in search of mosquito-breeding sumps, swamps and bird baths.

Perusing a vacant Redondo Beach lot, Brooks pointed to a discarded car tire. “Tires like that that’ll hold water? They love it, they love it.”

Fighting Mosquitoes

The rains that soaked the South Bay this winter have left puddles and damp areas where mosquitoes can lay eggs. Experts are urging residents to take these steps to ensure that back yards do not become breeding grounds:

* Empty and remove unneeded containers such as cans, barrels, buckets and old tires that can collect rain and sprinkler water. Store other containers upside down.

* Place larvae-eating fish in ornamental ponds and animal water troughs.

* Use swimming pool filter and skim daily to remove eggs and larvae. Keep pool covers tightly sealed and free of rainwater.

* Clear rain gutters and fix leaky water equipment.

* Cover small boats or store them upside down. Don’t let bilge water accumulate.

More information is available from the Los Angeles County West Mosquito Abatement District, (310) 915-7370, or the Southeast Mosquito Abatement District, (310) 927-6526. Both districts offer home consulting visits and supplies of larvae-eating fish, free of charge.

Source: Los Angeles County West Mosquito Abatement District.