Mosquito War : Region’s Insect Counts Are 3 Times Higher Than Normal, Officials Warn


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 and bloody. The pesky, fast-breeding insect not only bites human flesh, but some species can also carry such diseases as potentially fatal encephalitis.


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

In preemptive strikes early this month, three veteran mosquito warriors already were crisscrossing western 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 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-size larvae.

To stave off more larvae in the marsh, workers sprayed small amounts of a bacterium, 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.


The Los Angeles County West District, which includes most of the Westside and South Bay, 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 also say that considerable mosquito breeding may occur around private homes--in clogged rain gutters, fishponds and even in the water collecting inside flowerpots and boats.

They are encouraging residents to contact the control district offices for information about how to discourage mosquito breeding. For instance, the mosquito fish gathered at the VA center ponds have now been deposited in a large tank at the district’s Culver City headquarters and are available free to residents for placement in back-yard ponds and unused swimming pools.

Of the 21 mosquito species that live in Southern California, only a few 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 found to have the disease.

To help monitor the spread of encephalitis-carrying mosquitoes, control workers maintain and test so-called “sentinel flocks” of chickens. One such flock was delivered this month to a testing site at the La Brea Tar Pits, where the St. Louis encephalitis virus has been detected in sentinel chickens in each of the past two years.

The chickens’ blood is tested beforehand to ensure that they are free of disease. They then are retested every two weeks, and their blood is sent to a public health laboratory at UC Berkeley to see if they have contracted the virus.



In addition to the Tar Pits, district mosquito fighters are paying special attention this year to two other spots on the Westside.

The Ballona Wetlands are a traditional breeding ground. “It produces millions and millions of mosquitoes because of the way it retains water,” Saviskas said.

And the district has carefully monitored western Malibu, where virus-carrying mosquitoes were found in 1991.

In all three areas, workers are using mosquito fish and larvae-killing bacteria to quell mosquito-breeding.