Swimming pools pose West Nile threat

Thousands of abandoned swimming pools, another casualty of the real estate market meltdown, have become breeding grounds for mosquitoes that can carry the West Nile virus, Orange County vector control officials said Tuesday.

Murky, stagnant water acts as a perfect petri dish for mosquito breeding, say officials who note that as debt-ridden homeowners walk away from their mortgages, paying the pool guy is not high on their to-do list.

What has alarmed officials is a report of 13 birds found dead with the virus in Orange County in the first nine days of May. There were no reports of humans with the virus.

“Thirteen birds in such a short time frame is reminiscent of 2004 conditions,” said Robert Cummings, Orange County Vector Control science director.

During that critical year, four people died in the county and 28 died statewide after becoming infected with the virus.

The virus is transmitted to people and other animals by infected mosquitoes. A mosquito acquires the infection by feeding on a bird with the virus in its blood. The virus lives in the mosquito and is transmitted to a new host when it bites a person or other animal.

Other areas have not reported a similar abundance of dead birds with the virus.

“Luckily, we have not had those types of numbers, but we’re trying to get the message out to the public to be aware,” said Truc Dever, a spokeswoman for the Greater Los Angeles County Vector Control.

A crow with the disease was recently found in Santa Clarita.

“One of the problems we’re having is with all the foreclosures, we have many abandoned swimming pools and also neglected or uncollected trash,” Dever said.

Vector officials could not explain why the birds were reported dying in Orange County and not in other areas.

The number of Orange County homes going into foreclosure jumped 167% from the first quarter of 2007 to the same period this year. That represents a dramatic increase from 2,644 homes to 7,082 -- though not all homes had pools.

But more swimming pools are built in Southern California than the rest of the state, which has about 1.5 million pools, said the California Spa and Pool Industry Education Council.

In Orange County, the dead birds -- nine crows, two house finches, a hermit thrush and a black-headed grosbeak -- were found in a wide-ranging area that included San Clemente, Anaheim, Brea and Huntington Beach.

Six birds were collected in Garden Grove, said Michael Hearst, a spokesman for the vector control district.

Hearst said that doesn’t mean Garden Grove is a problem area; it could just mean that more Garden Grove residents contacted the district after seeing a dead bird.

Dr. Hildy Meyers, Orange County medical director of epidemiology, warned that as temperatures rise, the county could start to see cases of people contracting the disease.

“We expected West Nile virus to pop up and potentially cause human illness because it’s spread by mosquitoes and they’re more common and breed faster in the warm summer time,” she said.

Residents should take precautions and use insect repellent, wear long-sleeved clothing, check window screens and, if necessary, avoid outdoor activities from dusk to dawn.

“People need to be aware of West Nile virus,” Meyers said. “Some of the symptoms include fever, headache, body ache, a rash, and nausea and vomiting.”

About one in 150 people can develop a severe illness, she said.

The state’s worst year was in 2004 when 830 human cases were reported.

The virus also infected 540 horses, resulting in 230 deaths. A vaccine is available for horses.

Vector control districts don’t have enough field inspectors to cover Southern California, especially now because of the rising number of vacant homes, officials said.

Mosquito larvae can develop in a week in as little as a quarter-inch of water.

“West Nile is endemic, meaning it’s here to stay depending on weather conditions and mosquito abundance,” Dever said. “Even with no rain and even a drought, you still have people watering their lawns.”

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david.reyes@latimes.com

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West Nile virus cases (Orange County Edition)

Thirteen dead birds with West Nile virus were reported in Orange County from May 1 to May 9, making a total of 14 for the year to date.

Number of dead birds testing positive for West Nile virus

As of Tuesday

Orange County: 14

Greater Los Angeles County: 1

California*: 14

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Location of birds in Los Angeles & Orange counties

Anaheim: 3

Brea: 1

Fountain Valley: 1

Fullerton: 1

Garden Grove: 6

Huntington Beach: 1

San Clemente: 1

Santa Clarita: 1

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Virus transmission cycle

1. Non-infected mosquito bites infected bird and contracts the virus (an infected mosquito can also bite and infect birds).

2. Infected mosquito bites human or horse and transmits virus. People and animals, being “dead-end” hosts, do not transmit the virus via casual contact.

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Mosquito life cycle

1. Female lays eggs on still water.

2. Larva develops.

3. Pupa develops, emerges as adult.

Goes from egg to adult in 1-2 weeks

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*As of May 14-figures exclude Orange County’s latest bird counts

Sources: Greater L..A. County and Orange County vector control districts, California Department of Health Services, U.S. Centers for Disease Control and Prevention

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Los Angeles Times