EMPTY HOMES POSE RISK TO HEALTH POOLS: MOSQUITO LARVAE THRIVE ON ABANDONED PROPERTIES.
Requests to fight West Nile virus doubled last month as a spike in home foreclosures led to thousands of abandoned swimming pools and tougher economic times pushed pool maintenance to the bottom of homeowner priority lists.
And what's the county's key weapon on the front lines against the mosquito-borne disease?
A tiny silvery fish, known as Gambusia affinis, which has a Pac-Man-like appetite for mosquito larvae that thrive in stagnant water.
In May, the Greater Los Angeles County Vector Control District received 288 requests for service, up from 145 in May 2007. The agency is using the silvery mosquitofish on a record number of homes amid skyrocketing foreclosures, including an increase of more than 200 percent in the San Fernando Valley since spring of 2007.
The need for more fish comes as West Nile virus -- passed on to humans, horses and birds by mosquito bites -- has made its appearance earlier than its usual summertime entrance.
"All of the evidence is pointing to a very active West Nile season," said Truc Dever, spokeswoman for the vector-control agency.
Crow case in Valley
While health experts can't predict the problem's intensity this season, state figures back up the local numbers.
As of Wednesday, 18 California counties have reported cases of West Niles virus this year -- including in a crow found in Woodland Hills last month -- up from just nine during the same period last year, said Vicki Kramer, chief of the California Department of Public Health's Vector-Borne Disease Section.
While no human cases have been reported so far, known bird deaths from West Nile have quadrupled from 25 to 100. And state officials attribute the increase at least in part to foreclosures, saying they have identified abandoned pools through aerial photography.
The virus is transmitted to humans by mosquitoes that feed on crows and other birds infected with the disease. Most mosquitoes do not carry the virus, and most people bitten by mosquitoes don't become infected with West Nile.
Though the disease cannot be passed on from human to human, the American Red Cross has seen an increase in the presence of the virus among potential blood donors. There were 29 potential donors statewide who tested positive for the virus last year, up from 14 in 2006.
Increasingly, vector-control agents called out to homes bring along mosquitofish, knowing they're probably going to need them.
Fish prove invaluable
Many trips are to foreclosed homes or homes of financially strapped residents who can keep their front yards manicured to give the appearance of economic stability, but have surrendered their swimming pools to algae and slime.
"These fish have proven their weight in gold," said Ron Helo, a senior vector-control agent who makes house calls.
Recently, he released 20 mosquitofish into the opaque, green waters of a blue-tiled, courtyard pool at an abandoned Aetna Street home in Woodland Hills.
Mosquitofish are considered an invasive species to California, first brought to the state in 1922 to control mosquitoes. It is against the law for them to be released into habitats where native animals and plants flourish.
But because a female mosquitofish can gulp thousands of mosquito larvae, vector agents prefer them to larvicide. They are either caught in controlled pools or purchased from private vendors.
Aetna Street resident Karo Karapetyan called the Los Angeles County Department of Health about the abandoned pool in the neighborhood because of the abundance of mosquitoes and the bites he got. The department contacted the vector-control agency.
"I had a big bite on my arm that was this big," Karapetyan said, raising his left forearm to show the scars of a silver-dollar-size bite.
Because the home was abandoned, Helo had access to the pool. But vector-control officials are facing the challenge of determining when they can and cannot enter the backyard of a foreclosed, bank-owned home. Foreclosures have hit an estimated 4,000 L.A. County homes with backyard pools.
Dever said her agency is working with health officials, real estate agents and banks to legally enter the backyards.
"The health and safety code gives us a certified authority if there is a public health risk, but if it's an occupied home, the residents have a right of privacy," Dever said.
To make sure residents know their pool might be a health risk, vector- control agents have been working on Saturdays, when owners or renters are likely to be home.
"If the gate is wide open and we know the home is vacant, if we can tell the pool is breeding mosquitoes," Dever said, "we will go in there."
Vector-control agent Ron Helo releases mosquitofish into the pool at a Valley home, vacant after mortgage foreclosure. West Nile disease is carried by mosquitoes that lay eggs in stagnant water.
Tina Burch/Staff Photographer
West Nile predator
SOURCE: Discover Life
Gregg Miller/Staff Artist