The Morning News Says Spraying Saved Dallas from West Nile, but That's Not the Whole Story

Dallas County recently discovered its sixth person to test positive for the West Nile virus this year, in a season that's seen one death. It's a much less troubling situation than last year, when there were 400 human infections and 20 deaths.

The Dallas Morning News has an easy explanation for the lower numbers this year: spraying.

"Top officials in the Dallas County health department Tuesday commended local mosquito-spraying efforts for staving off a potentially larger outbreak of the West Nile virus this year," a recent News report begins. "This year went very well," Zach Thompson, the county health director, tells the paper.

Hey, but what about that whole campaign that a bunch of locals have been organizing these past few months, pressuring the county and the city to rely less on adult insecticide sprays and more on non-toxic larvicides?

Schutze reported recently that it seemed like the county might actually be taking these environmentalists' crazy ideas seriously, a major improvement for Dallas. "We are going to consider as part of our 2014 strategy looking at the larviciding scenario that they have mentioned," Zach Thompson, the county health director, told Schutze at the time.

Yet this most recent News report presents this summer as a success story thanks mainly to all that spraying. There's a brief mention of the county handing out free Mosquito Dunks -- tablets with larvicides that people can put in water -- but there's otherwise no talk at all larvicides or of the concerns that local beekeepers and others have raised about insecticides killing more than just mosquitoes.

The News story was based on a presentation at a county meeting given by Thompson, the county health director. When I challenged him on some on the spray-happy points he apparently made in the presentation, he said it was "disingenuous" of me to ask him about quotes he gave another newspaper, and suggested that his actual West Nile presentation was more nuanced than the DMN story lets on.

"They did larviciding, they looked at breeding, possible breeding locations for the mosquitoes, and when they could not be identified, we did do some targeted ground spraying to reduce the abundance" of mosquitoes, he said. Yet he won't provide his actual presentation. (First he said it would be online by the end of last week, then by Friday night. When I called him again this morning he said he was at a press conference and hung up on me.)

Also not mentioned in the News report is that West Nile Virus is down across the country. In fact, Denton city officials tell Unfair Park that they also had a successful year, with only one case of human West Nile Virus and no deaths. And Denton didn't have to spray any insecticides to get those good numbers.

"I think active use and identification of mosquito habitats and larvicides is probably the most effective way to go. ... Certainly there is a time that spray is useful but I think if you do some of these other things prior, you can reduce the necessity of any sort of spraying," says Dr. James Kennedy, a professor at UNT who specializes in the ecology and biology of mosquitoes. He's also the guy who has been testing mosquitoes for Denton, and he hasn't found any positive pools of the virus this summer. While the city of Denton did spray during last year's bad outbreak, for this year, "we don't spray, we haven't seen the spread of West Nile either," Kennedy says.

Meanwhile, the alternate universe in the DMN and perhaps the county's actual report presents adult insecticides as the best prevention method: "The county launched a more aggressive attack against the insects, urging cities to send out truck sprayers whenever they detected an abundance of Culex mosquitoes," the paper writes. "That preemptive step was believed to have reduced infection rates when the virus eventually appeared."

But a truly pre-emptive approach would stop the the virus from ever having to "eventually appear" in the first place. To stop the virus before it starts, experts say nontoxic larvicides are the way to go, because the larvicides target the mosquitoes when when they're cute little immobile larvae.

"It's actually very difficult to control mosquitoes at the adult stage," says Kenneth Banks, Denton's Director of Environmental Services and Sustainability. (He declined to comment on Dallas' approach, saying every city is different.)

Dr. Jerome Goddard, an entomologist at Mississippi State University, agrees that spraying insecticides can be a "worthwhile tool" but adds that "if you're asking do I think that pesticides have made the cases go down this year, I'd say no ... if somebody were to say, 'Well we started spraying more this year, that's why it's down,' well that's just not true."

Observational data indicates that West Nile Virus only gets bad about once every four years. There are several theories as to why, a popular one being that the birds that survived a bad year developed resistance the next year.

"It's what we would call like a flock immunity. The birds are getting naturally immunized against the disease once there's an outbreak here," says Kristy Bradley, the epidemiologist at Oklahoma's state health department. She's also diplomatic about the importance of using adulticides in the right situations, but understands concerns raised by others about the toxicity of the spray.

"These are chemicals that aren't specifically targeting and killing mosquitoes, they are targeting beneficial insects as well," she says.

The main Dallas group pushing for a larvicide-first approach here, Citizens for Safer Mosquito Control, also supports spraying -- they just want officials to spray larvicides instead of adulticides. They say that they respect the attention they've received so far from local officials and are now waiting for an actual commitment.

"The city told us they would like time to meet with the county in order to fully digest and review all the information before meeting with us again," Citizens for Safer Mosquito Control's Jenny Land tells Unfair Park in an email.

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Amy Martyn
Contact: Amy Martyn