Biting Times : Infestation: Big upswing in number of mosquitoes proves to be downside of heavy winter rainfall.

It might be biting news, but San Diego has an early mosquito population boom on its hands--and necks and ankles--this spring, thanks to heavy rains and warmer weather.

Meanwhile, entomologists are keeping a close eye on some types of the insects, which can carry encephalitis, malaria and other diseases.

The mosquitoes have been breeding away with the warm and humid conditions they like best, said Marilyn Corodemas, manager of the vector surveillance and control division of the county’s Department of Health Services.

Stagnant bodies of water that collect throughout the county in pools, bird baths and other household receptacles--as well as puddles and ponds formed by heavy rains--have given the bloodsucking bug population a real shot in the arm.

“Anywhere that you have water, you will have mosquito breeding and since we have had all this rain, even most areas that are usually drier, like golf courses, are showing an increase in the number complaints and bites,” Corodemas said.

Mosquito larvae samples from area wetlands, rivers ponds and other bodies of water show that the numbers of the insects have increased by the millions, Corodemas said. Mosquito eggs are laid every seven days and hatch when the weather is ideal for the bugs, Corodemas said.

Authorities are keeping a close watch on the twice-a-month dip samples because some have produced eggs of the Culex mosquito, known to carry encephalitis, and Anopheline type mosquitoes, known to carry malaria, Corodemas said.

“We have a (year-round) surveillance program where we collect adult female mosquitoes and identify them to species because some of them are capable of transmitting virus,” said Moise Mizrahi, chief of vector surveillance and control division for the Department of Health Services.

The surveillance program includes shipping samples of the bugs to the state board of health and monitoring residents for signs of infections in regions where dangerous eggs were found, officials said.

In addition, the department keeps three flocks of fowl at mosquito breeding grounds in north, central and south San Diego because birds are able to host the encephalitis virus, Mizrahi said. By periodically checking the birds’ blood, inspectors are able to determine the prevalence of encephalitis-bearing mosquitoes in the area.

To keep down the numbers of all the stinging insects, vector control personnel have planted mosquito-eating minnows in selected areas and flooded some bodies of water with larvae-suffocating mineral oil and mosquito-targeting bacteria.

St. Louis encephalitis, also known as sleeping sickness, can cause headaches and flu-like symptoms and, in extreme cases, coma and death.

The last reported case of exposure to encephalitis in San Diego County was in 1984, said Dr. Michele Ginsberg, chief of AIDS and community epidemiology for the Board of Health.

Malaria is a disease caused by a parasite transmitted via mosquito bite. It is characterized by periodic attacks of chills and fever.

The last case of locally acquired malaria occurred in Oceanside in 1990, she said.

“The potential exists for malaria transmission and encephalitis, especially when there is a wet year,” Ginsberg said. “We have very good vector control, but the key to avoid cases is to recognize cases promptly so that control measures can be implemented.”

So far, it is mostly the relatively harmless Aedes mosquito that has inundated the region. The quarter-inch-long bugs do not spread disease, but have an irritating bite, Corodemas said.

Last year, from July to December, the department reported receiving 367 complaints about mosquito bites.

Although bug bite figures have not yet been tabulated, officials expect the number of complaints to increase as temperatures rise.

The mosquito season peaks from May to October, but some of the bugs lay eggs all year, said Mizrahi.

The eggs hatch when the weather and water temperature is warm or cold enough to suit them. San Diego County has more than 20 types of mosquitoes, he said; California has more than 50.

To help stunt the mosquito population growth, homeowners should invert containers in outdoor areas that might hold water, and keep pools, ornamental ponds and bird baths clean, Corodemas said.

In addition, the department is offering free minnows to those who need to control insects in their area and is urging those with mosquito problems to call 694-2888.

“The whole intent of the program is prevention,” Mizrahi said. “If we find sources of the insects and eliminate them, then we can target them before they become adults.”

Mosquito Season Arrives Recent rains left behind puddles where mosquitoes can breed. Within the span of a week, thousands of new ones can emerge from sources of standing water as small as a bucket. The pests breed year-round, but spring rains lead to peak activity in summer. 1) Eggs Laid (Days 1 and 2): The female mosquito lays 100 to 400 eggs, which hatch into larvae. Local species can lay up to 1,000 eggs in a lifetime. 2) Larvae Grow (Days 3 and 4): Larvae breathe through tubes while remaining below the water’s surface. Long, hairy “mouth brushes” help them sweep up and eat tiny plants and animals. 3) Metamorphosis (Days 5 and 6): A grown larva changes into a pupa, in which skin covers a rapidly changing adult. A mature adult emerges after about two days. 4) Adult Emerges (Day 7): The adult rests until strong enough to fly. Females live up to three weeks in summer and maybe for months in winter, in order to lay eggs in the spring. Males live 10 to 20 days.

How a Mosquito Bites Only female mosquitoes “bite,” a misnomer since they actually pierce the skin. Blood provides protein for the female’s eggs, which she cannot get by sipping plant nectar. Skin pierced: Mosquito pushes several needle-like “stylets” through the skin of an animal or person and into a blood vessel. Saliva flows into the bite to prevent clotting. Saliva of some mosquito species will cause an itchy welt. Blood drawn: Mosquito sips up to 1 1/2 times her weight in blood. Abdomen swells with blood. She leaves behind a droplet from intentines to reduce her weight before flying away. Researched by: DANNY SULLIVAN / Los Angeles Times