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Latest Buzz on Mosquitoes : Officials Warn of Population Explosion of ‘Billions’ of the Pesky Pests

Times Staff Writer

Brace yourself for mosquitoes. The pesky pests are back.

Aided by warm weather that made them feel sexier and wet weather that created liquid nurseries for their young, mosquitoes are breeding like crazy all over Los Angeles County.

“Oh gosh, there are just billions of them,” said Dr. Frank W. Pelsue Jr., general manager and medical entomologist of Los Angeles County’s Southeast Mosquito Abatement District.

“It warmed up in January. The mosquito population started to explode then. It is starting out like 1984. Our . . . trap counts are higher this year than last year by about 50%.”

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Pelsue has been making the rounds of city councils in his sprawling mosquito control district, seeking the assistance of municipal officials in cleaning up the old tires, trash cans, flower pots, rain barrels, barbecues, swimming pools, anything else that can harbor mosquito larvae.

A single bird bath can be home to thousands of mosquito wrigglers, Pelsue said.

“It is important that we get the message out,” he told Carson officials recently.

“We have been receiving a flood of phone calls about mosquitoes,” responded Carson Mayor Sylvia Muise.

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‘Makings of a Very Good Year’

The increase in mosquitoes has been noticed in other parts of the Los Angeles Basin.

“It has all the makings of a very good year,” said Norman Hauret, who oversees mosquito control for the western mosquito district.

“We have ordered additional vehicles. We have increased our budget to hire more people.”

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To Hauret, the homes, the swimming pools and the Southern California life style add to the mosquito problem.

“You have acres and acres of homes and they all have backyards. Some have swimming pools that aren’t maintained,” he said. “We all contribute to the problem because we water our lawns and we wash our cars and kids play in the water. Our way of life is a contributing factor to it.”

Weather conditions this year also have favored mosquitoes, experts say.

From December through March, when the high temperatures in Los Angeles are normally in the high 60s, this season they have been in in the mid to low 70s. The lows similarly have been three to seven degrees above normal. And in April and May, when the highs are usually in the low 70s, this year they have been in the mid to high 70s.

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In warm weather, mosquitoes hatch, grow to maturity and mate within a week; in colder weather the cycle can take as long as 30 days.

Rainfall has also been higher this year. Fourteen inches of rain fell in Los Angeles through the end of May, about 3 1/2 inches above normal.

Although the annoying itch of mosquito bites provokes most calls for eradication help, Pelsue, Hauret and other mosquito fighters are more worried about the viruses--St. Louis encephalitis, Western equine encephalitis and malaria--that mosquitoes can transmit.

No Illnesses So Far

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So far this year there have no cases of encephalitis, and no malaria cases have been linked to mosquito bites in Los Angeles County, Pelsue said.

In 1984, the county reported 16 cases of St. Louis encephalitis, a viral disease that attacks the covering of the brain. In 1985, when cold dry weather kept the mosquito population in check, one case was reported.

The object of all the official attention is an insect that will fly a mile toward the lights of human habitation, head toward a warm object giving off the moisture and carbon dioxide of exhaled breath, and finally land on an individual who somehow smells right.

“Some people are attractive to mosquitoes and some are not,” Pelsue said.

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Once she has landed--only female mosquitoes drink blood--the mosquito seeks a tiny capillary vein, using heat sensitive organs on her antennae and nose to locate the warmth of blood near the surface of the skin. Its two mandibles make a tiny slit in the skin and in goes the hollow tube that sucks the blood.

How Virus Is Transmitted

“As it is doing (this), it is secreting salivary juices to prevent coagulation and make the blood flow better. This causes the local reaction. If the mosquito happens to be infected with a virus, this comes in the salivary juices,” Pelsue said.

Unlike South Florida, where mosquitoes are so bad and their habitat so extensive that aerial spraying to kill adult mosquitoes is the only practical method, Southern California mosquito fighters attack larvae in their pools.

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Mosquito abatement officials are offering free mosquito-eating fish--a top-feeding minnow about 2 1/2 inches long with the scientific name of gambusia affinis-- to stock fish ponds and bird baths.

“If you can’t put fish in, you should drain it,” Pelsue said. “If it’s something you can’t drain, you should call us and we will treat it with light oil. It suffocates the mosquito larvae; it creates a film on the water and prevents them from breathing.” The La Brea tar pit pools were treated Monday.

Officials also spray a growth inhibitor that prevents mosquitoes from maturing.

“People should check their own backyard to see if there are any wigglers, and, if they have any mosquitoes, to call us,” Hauret said.

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