State Takes Aim Before It Sprays for West Nile

The truck heads out at 2:20 a.m., creeping through slumbering cul-de-sacs and releasing a colorless pesticide fog.

“[This] is a last resort. I don’t like to do it. But we don’t have a choice; we’re in an epidemic,” said Min-Lee Cheng, manager of the West Valley Vector Control District in Chino.

As West Nile virus spreads across California, government officials say spraying pesticides is the most powerful tool they have to wipe out mosquitoes carrying the disease.

But the state, no stranger to pesticide controversy, is taking a significantly different approach from other regions of the country that have grappled with the sometimes deadly but fairly rare new disease.

In the Northeast, the Midwest and the South, officials resorted to mass aerial sprayings to combat West Nile virus. When the disease began killing people in the United States -- in New York City in 1999 -- then-Mayor Rudolph Giuliani ordered wide-scale daytime spraying of city streets. That and similar spraying in New England triggered lawsuits by pesticide crews, fishermen who said catches had been wiped out, and others.

By contrast, California, where the disease arrived last year, has relied so far on ground-level spraying around targeted river beds, flood channels and handpicked neighborhoods in Los Angeles and San Bernardino counties with high counts of infected mosquitoes. The approach has drawn praise from some experts, but criticism from others who say the limited spraying is less effective, and the pesticides being used here may pose health risks.

In recent weeks, workers for the region’s vector control districts have used larvicides to target juvenile mosquitoes in sewage ponds, manure pits and other spots they’re likely to be found. They have focused spraying efforts to kill adult mosquitoes on Machado Lake in Harbor City, the Rio Hondo and San Gabriel river corridors, and small sections of Fontana, Colton and Chino.

“They’re not trying to do a Sherwin-Williams and paint the world” with insecticides, said William Reisen, a UC Davis research entomologist. “They’re using ounces per acre.”

The West Valley district covers 200 square miles in five cities, which amounts to 128,000 acres, but it is targeting 250 acres in Chino. Crews think stubbornly high counts of infected mosquitoes there may be from industrial cattle yards or a weed-choked flood control channel. Before spraying, district workers sent notices to more than 600 affected homeowners and followed up with door-to-door visits.

“We spray in the middle of the night because the mosquitoes are out, but the humans aren’t, unless they’re closing down the neighborhood bars,” said Cheng.

In Chino on a recent morning, the trucks halted on three occasions -- once when a jogger loped by in the murky darkness at 3 a.m., and twice when lone cars drove by. The rest of the time, the sprayer released a steady mist of Pyrenone 25-5.

The chemical cloud drifted among bushes, houses and the ground, visible only when caught by the yellow blinking light atop the truck or under humming street lights. When a trickle of commuter traffic began to appear on the streets at 4:30 a.m., the operation ended.

Limited ground-level spraying does allow some adult mosquitoes to escape. “The problem is getting them in the backyard, because the house acts as a barrier,” Reisen said.

But limited spraying is more acceptable to the public, he said. “Do I want vector control districts to stop all the traffic over LAX

Ramiro Salazar, a mosquito-control worker with the West Valley district, agrees. Sitting with his finger near the trigger of a truck-mounted Pro-Mist pesticide fogger, he said: “People in California don’t like chemicals sprayed on them.”

Vermin-control districts were set up at the turn of the 20th century in Los Angeles and San Francisco to eliminate insects in swamps that were being developed into housing. When mosquitoes infected with St. Louis encephalitis began killing people in the 1930s, the districts expanded across much of the state.

But spraying became highly controversial in the 1980s and 1990s, when California officials ordered the pesticide malathion sprayed from helicopters and airplanes onto residential neighborhoods to combat the Mediterranean fruit fly. The sticky insecticide coated cars and houses and brought about more than 6,600 claims of poisonings of people and pets. The spraying prompted wide-scale protests and lawsuits.

At that time, state officials said the spraying was needed to protect California’s multibillion-dollar agriculture industry. West Nile, though deadly in a small number of cases, has yet to generate a similar level of concern.

According to the state’s latest figures, the number of West Nile infections in California has risen rapidly, nearly doubling from 53 cases reported as of July 29 to 103 cases by Aug. 5. Federal and state public health officials have warned that based on the experience of other states, August and September, active mosquito-breeding times, could be the worst months.

Two Californians have died of the disease this year: a Fullerton man in June and a Grand Terrace man in July. An elderly Long Beach man has been hospitalized with virus complications, health officials said Thursday. The same day, Orange County confirmed its second case.

Most people infected with West Nile virus do not experience symptoms. About 20% may develop headaches, fever and body aches within two weeks of infection. The elderly and those with compromised immune systems are most susceptible. Nationwide, in the five years since the disease appeared in the United States, about 600 people have died and 15,000 human cases have been reported in 46 states. By contrast, influenza, a long-established illness, kills about 20,000 people annually in the United States.

Scientists differ on how to weigh the risks of the disease against the risks of pesticide spraying.

“People have to understand that the stuff they’re spraying has its own risks,” said Sheldon Krimsky, a Tufts University professor who, along with scientists from Harvard and Boston universities, has reviewed pesticide use for health officials in Massachusetts.

He says pesticides create dangers to the public for little benefit. In his research, “we could find no scientific data that the broadcast spraying of these in urban areas decreases the incidence of West Nile virus,” he said.

Krimsky said his review found that ingredients in pesticides used in California had caused liver and endocrine-system damage in laboratory animals and had not been adequately studied in humans.

But other experts say that spraying pesticides to kill adult mosquitoes does reduce the spread of West Nile virus and that the chemicals being used are safe and effective if used properly.

“There’s a long track record of successful use of adulticides in reducing mosquito populations,” although they can be tricky to use in urban areas, said Roger Nasci, a research entomologist with the federal Centers for Disease Control and Prevention. Adulticides are poisons that target adult mosquitoes.

A CDC report on pesticides used to control mosquito populations in nine states from 1999 to 2002 found 133 reported cases of acute illness in humans. The report concluded that although the risk of illness was low, spraying should be a last resort.

California officials are steering clear of malathion this time, instead using pesticides called pyrethroids and pyrethrins, nerve toxins designed to kill insects and then dissipate quickly.

The nine-page label on the pyrethrin being used in Chino warns that the pesticide can be harmful to people and pets if swallowed or inhaled, and may cause nausea, vomiting and diarrhea. Large quantities can result in nervous system effects such as dizziness, tremors and loss of coordination. The product is toxic to fish, and also to shrimp and crabs.

David Parsons, a spokesman for the U.S. Environmental Protection Agency, which regulates pesticides, said that no pesticide is considered 100% safe, but that he was unaware of problems caused by pyrethroids.

“Our advice on pesticides is, really try to minimize the use of pesticides whenever possible,” he said. “We think they’re all effective if used according to the label.”

John Wargo, a professor of risk analysis and environmental policy at Yale University who studies the effect of pesticides on humans, said “focused spraying can work.... It sounds like they’re being quite judicious and careful,” he said, referring to California’s efforts.

All agree that the best solution would be for people to alter their behavior and avoid contact with mosquitoes -- such as not being outside from dusk to dawn, when mosquitoes are most active, and wearing long-sleeved shirts and long pants. That can be a problem on stuffy summer evenings.

“I think the spraying is necessary,” said Robert Real, field supervisor for the West Valley Vector Control District, who has been working overnight shifts on the spraying. Trying to persuade people to change their behavior to avoid mosquitoes is unlikely to work, he said. “You explain it to them, but people aren’t about to start wearing long-sleeve shirts in 90-degree weather.”