Once bitten

Spraying insecticides over heavily populated urban areas may not be the ideal way to control the West Nile Virus, but it sure gets people’s attention.

Readers by now should be well-acquainted with the daily drama surrounding the Sacramento-Yolo Mosquito and Vector Control District’s decision to perform “adulticide” on local mosquito populations, in a last-ditch attempt to control a dramatic spike in human cases of the virus.

Soon, people throughout Sacramento found themselves wondering if it was OK to walk their dogs during the spraying or to comfort a squalling child with a stroll around the block. They were told not to worry about the potential health effects of pyrethrin and PBO (a potential carcinogen) because the amounts of the chemicals being applied were so tiny and diluted. But, for those who worried anyway, there was the advice to close up windows, turn off air conditioners and wait it out until morning in their sealed hot boxes—for planes that might or might not come depending on the vagaries of the Delta breeze.

For vector-control czar David Brown, one lesson of the August mosquito wars is this: “Maybe we should have gone out there in big bold letters saying, ‘WE WILL SPRAY.’”

In its defense, the mosquito district and public-health officials said this was no arbitrary decision—that the plan had been in the works for two years. But many Sacramentans didn’t know that, didn’t know that aerial spraying was even an option and didn’t know much of anything about the chemicals that were being used.

Anxiety and a fierce debate were natural and inevitable—and could have occurred before the planes were cleared for takeoff.

“The district should have been more aggressive about letting the public know that this was in our plan,” said Dave Tamayo, who serves on the vector-control board.

Spraying opponents point out that many cities haven’t sprayed to kill adult mosquitoes in years, relying instead on aggressive “larviciding” programs. “Once you start spraying for adults, it means you’ve already lost the war,” said Don Mooney, an environmental attorney who sued unsuccessfully to stop the spraying program.

Jason Lamers, the spokesman for the Public Health Department of Fort Worth, Texas, said that city stopped spraying insecticide back in 1991, before West Nile hit Texas.

“We don’t do it because it doesn’t work,” Lamers explained, adding that public-health officials there also are concerned about asthma and allergies that could be triggered by airborne pesticides. The city has had between one and three human cases of West Nile Virus each summer since 2003, and no deaths.

In Cheyenne, Wyo., Bob Lee is director of environmental management for Laramie County. Lee said his county has been West Nile-free and has avoided having to spray for adult mosquitoes through an aggressive program of killing mosquito larvae before they hatch. The larvicide is actually a mixture of naturally occurring bacteria considered completely safe to humans and wildlife. (The local district also uses the bacteria to kill mosquito larvae.)

“We basically just bust our asses,” Lee said. “Nobody has to be warned, you don’t have to drag all the toys inside, and I’m not pissing anybody off.”

And yet, Cheyenne and Fort Worth haven’t faced a bona fide West Nile outbreak on the scale of Sacramento’s—whether through hard work or just luck and geography. Lamers, when asked what would happen if there were suddenly 20 or more human cases in his city, conceded, “Yeah, that’s a tough one.”

In Sacramento County in late July, there were two reported human cases of West Nile Virus. Six cases were reported by July 29, less than a week before the district decided to take to the air. The number of cases had mushroomed to 21 by August 5 and continued to climb even as the spraying went ahead. Tamayo said that the decision to suppress adult mosquito populations had to be made quickly despite concerns about the chemicals. “You know, I consider myself an anti-pesticide activist. I don’t think we have perfect information [about the chemicals]. But I don’t think we had time to perfect that information either.”

On the other hand, said Tamayo, “There’s very solid evidence that people will get sick and die [from West Nile Virus]. It’s not a scare tactic; it’s a fact.”

There were more than 83 cases in the county by last Tuesday. But all of the reported cases of West Nile Virus probably were contracted in June, long before the aerial spraying began.

It may be weeks before there is enough information to discern whether the spraying program actually worked. “If those numbers don’t go down, that’s when we’ll get very concerned,” said Brown. And that could mean more spraying. Brown added that the best offense is for residents to look around their own property and rid it of standing water that might breed the insects—and to call the district if they need assistance. “If we don’t get help from the public, we may have to do it again.”