Rain Spells Deluge for Mosquito Swat Team : Health: County Vector Control District says water pools around homes are biggest breeding worry.

Under the right conditions, mosquitoes are rather prolific. In the next few seconds, virtually every female mosquito could deposit as many as 400 eggs each in any puddle throughout the county. And today, the conditions don’t get much better.

With record-breaking rainfall in March, the Orange County Vector Control District is gearing up for a boom in the county’s mosquito population, triggered by the recent renewal of parched water sources, both natural and urban.

“Once you have free-standing water, mosquito treatment needs to start,” said Fred Beams, the district’s assistant manager. “Female mosquitoes will search out that water, which doesn’t have to be stagnant, just quiet and still.”

That kind of water can be found in any marsh, flood-control channel, riverbed or street gutter, all of which the county’s control agents routinely monitor. But after a rain, Beams said, new breeding pools pop up wherever water is allowed to collect, potentially making homeowners the unwitting breeders of the pesky insects.

“Our biggest problems right now are back-yard sources, such as a wheelbarrow, ornamental fish ponds or a swimming pool,” Beams said. “A swimming pool not taken care of is actually a back-yard swamp. A typical pool like that can be a breeding area for 150,000 mosquitoes in a week to 10 days.”

Mosquito experts say that even in the dead of winter, this process occurs. The only seasonal difference is that mosquitoes mature faster in the summer, said Mir Mulla, a UC Riverside entomologist whose specialty is mosquitoes.

“We definitely have a lot of mosquitoes breeding right now. The temperature at the present time is just right for reproduction for a number of species,” Mulla said.

In Orange County alone, 21 different mosquito species thrive, the most common called the southern house mosquito, found throughout the southern United States, Mexico and the tropics, Mulla said. One thing all types of mosquitoes have in common is that the female does the biting.

“The female mosquito lives on plant nectars, just as the males do,” Beams said. “But the blood urge comes for reproduction.”

That makes the female the culprit in transmitting disease. Its bite carries the potential for spreading such diseases as encephalitis and malaria. Studies to date, however, show that the HIV virus, which causes AIDS, is not mosquito-borne.

The most common disease is St. Louis encephalitis, often called sleeping sickness, which causes an inflammation of the brain lining. It can be lethal. Last fall, Beams said, an epidemic hit Florida, killing about 30 people out of almost 200 reported cases.

“This is our biggest fear with mosquitoes,” Beams said.

To combat the pests, Vector Control District officials have switched from hazardous chemicals to biological methods that kill mosquitoes, such as small fish and even bacteria. But on the home front, Beams said, the Vector Control District simply encourages people to dump or drain places where water collects.

Those who do not want to dump excess water in these drought-sensitive times should call the district for help, Beams said. The district will be glad to do the same thing it does in ponds and lakes all over the county--stock them with mosquito fish, a natural predator of the insect.

“We suspect a lot of people will be saving water, which is fine, but give us a call and we’ll deliver the fish,” Beams said. “They’ll live very well in most areas.”

A free pamphlet about how to combat mosquitoes is available from the Orange County Vector Control District by calling (714) 971-2421.

BACK-YARD BREEDERS

A month of rain has left many Orange County back yards as breeding havens for mosquitoes.

SPAWNING GROUNDS: Mosquitoes breed in one of 10 back yards. Rain gathers in wheelbarrows, buckets and open containers, turning them into mosquito-breeding areas. Water collecting in one wheelbarrow can spawn up to 15,000 mosquitoes a week.

CONTROL AT HOME: Residents should dump water from containers, covering them or turning them upside down; cover swimming pools or clean with a filter and skimmer every day (chlorine will not kill mosquito larvae); repair screens and avoid outdoor work at dusk or dawn when mosquitoes are most active.

MOSQUITO FISH: The 2-inch fish, used in ornamental pools or fountains, require no care and eat mosquito larvae as they emerge from their eggs. These fish are available free from the Orange County Vector Control District.

DISEASES: Encephalitis, an inflammation of the lining of the brain, is the most common danger from mosquito bites in the Western United States. There have been no cases in Orange County since 1984, when six cases were reported. Mosquitoes can transmit diseases, but studies show that they are not carriers of the HIV virus that causes AIDS.

WEEKLONG BIRTH CYCLE

Mosquitoes breed year-around. In a week to 10 days, mosquitoes grow from eggs into adults. A female mosquito can bear up to 3,000 young in her lifetime.

Source: Orange County Vector Control District

Written by DANNY SULLIVAN / Los Angeles Times