W. Nile prevention a dilemma
Should communities spray?

By Marcos Mocine-McQueen 
Denver Post Staff Writer
Monday, July 05, 2004 

In the battle against the West Nile virus, the choice seems simple enough: To spray or not to spray? 

But health concerns about insecticides and debate over the effectiveness of spraying complicate matters in ways befitting a Shakespearean story line.

With Colorado leading the nation in West Nile cases and deaths, cities and counties are taking more preventive action, including aggressive spraying of pesticides.

Last year, 2,947 Coloradans were infected with West Nile; of those, 63 died. As of July 1, eight cases have been confirmed this year.

Many health officials say the West Nile threat demands widespread spraying to control mosquito populations and, ultimately, the disease itself. Other scientists counter that spraying poses its own health risks and may not control mosquito numbers.

The lack of consensus leaves community leaders befuddled.

"There really is nothing definitive that says spraying is safe and effective," said Frank Bruno, Boulder's city manager.

Health officials, however, do know that when a community sprays, humans get exposed.

Last year, the American Association of Poison Control Centers recorded more than 12,000 exposures to pyrethroid, the primary pesticide used for mosquitoes. Of those, 2,260 required hospital treatment, though there were no fatalities.

In Colorado, 74 people have registered with the state as pesticide-sensitive.

So how does a community balance the exposure risks between pesticides and the disease? There is no good answer, Bruno said.

"On one hand if we chose not to spray, the city would be accused of being insensitive to human life and suffering," he said. "On the other hand if we did spray, the city would be accused of being insensitive to human life and suffering."

Boulder officials have decided to spray only as a last resort. For now, the city will continue to promote ways for residents to protect themselves.

Many city and county officials have turned to John Pape, an epidemiologist with the Colorado Department of Public Health and Environment, for help in sorting out the spraying dilemma. Pape agrees that pesticide spraying presents a risk, but he says the threat posed by West Nile is far greater.

"(Pesticides) have a place - they are tools in our tool box," Pape said. "In most cases they are the last ones we should pull out. Still, it's a very important tool, and there are numbers showing that."

He points to Fort Collins, where mosquito spraying was started late last season. Sprayed areas had a faster drop in adult mosquito population than areas that weren't sprayed, Pape said.

But those numbers don't necessarily match those used by David Pimentel, a Cornell entomologist who is skeptical of spraying's effectiveness.

Though he lamented the lack of science in the field, Pimentel studied a handful of spraying operations across the country and found the results disappointing.

In an article in the Encyclopedia of Pest Management, Pimentel concluded that spraying "for control of mosquitoes and West Nile virus is relatively ineffective (and) costly, and has been associated with environmental and public health risks."

West Nile victims, however, have seen their own health risks.

Nancy Foster believes she was bitten last August.

It was just an itch.

Then came fatigue and a fever, followed by debilitating leg pains, paralysis and, finally, total blackout.

"Then the next weeks are gone," Foster said. "I don't remember them."

She was suffering from encephalitis, a swelling of the brain. It is one of the worst incarnations of West Nile. The brain presses against the skull, and tissue is damaged or killed.

Though Foster has been home for months, she still suffers the effects of the illness, making it hard to do things as simple as driving to the store.

"I can't feel whether my foot is on the pedal," Foster said. "I actually have to look down and see it. I can't drive at night, because I can't see down there."

Her short-term memory is so bad that if she doesn't place her keys by the front door as soon as she walks in, she will have to spend hours searching for them. She loses thoughts in midsentence.

"I don't know if I'll ever recover," Foster said. "The doctors say I might, I might not."

Like public health officials, Foster urges people to use DEET, an insect repellent. Cities and counties should do everything possible to prevent West Nile's spread, she added.

"I think they should spray," Foster said. "We need to do anything we can so other people don't have to go through this. I never thought a little mosquito could do this."

In contrast, Mary Louise Chavers has suffered not from West Nile but from pesticide exposure.

She, too, says officials should do everything in their power to stop West Nile - except for spraying. Chavers recently told the Boulder City Council about her pesticide-related symptoms - severe headaches, tremors, inability to focus, difficulty talking and lethargy.

Those conditions are similar to West Nile symptoms.

Often, Chavers doesn't know an area has been sprayed until her nose picks up the "acrid" smell, and then it's too late.

"It's like living in a sniper zone," Chavers said. "I really don't feel comfortable walking through neighborhoods during the summer anymore."

The state Department of Agriculture has certified her as "pesticide-sensitive," and she posts no-spraying signs at her home.

"But the pesticides move on the winds with the ease of birds," she said.

Health officials who support spraying acknowledge that it poses serious risks. Improper pesticide use can kill off bees or affect fish as well, Pape noted.

And in Colorado, where sensitivity to the environment is high, public officials cannot dismiss such facts in the name of public health, Bruno said.

Like Boulder, many cities have taken a measured approach, emphasizing public education that includes urging citizens to wear long sleeves and use DEET when out after dusk.

Some cities, including Boulder, also have launched larvicide programs, which aim to kill the mosquito larvae.

Meanwhile, community leaders look for more answers.

"Our staff looked for definitive work that would tell us that spraying is absolutely safe for people or the environment, and we didn't find any," said Bruno, Boulder's city manager. "We found that it's just not out there."