CDC: Aerial spraying worked in Dallas County, but threat remains

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by MATT GOODMAN

wfaa.com

Posted on August 30, 2012 at 5:15 PM

Updated Friday, Aug 31 at 4:43 PM

 DALLAS – Dallas County’s aerial spraying campaign against mosquitoes carrying West Nile was successful, cutting the primary species that carries and spreads the virus by as much as 93 percent. 

On Thursday afternoon, County Judge Clay Jenkins and Dallas Mayor Mike Rawlings joined Dr. Janet McCallister, an entomologist with the Centers for Disease Control, to discuss initial results that, for the first time, show whether the county’s decision to spray from above was effective.

The most striking statistic came from eastern Dallas County, where the population of Culex mosquitoes –– which, McCallister said, is the primary breed that spreads West Nile –– was sliced by 93 percent. 

However encouraging, Jenkins and Rawlings were both quick to remind the public that the threat is hardly over. 

“We will see more human cases, both because of the lag in reporting time, and also because of the simple fact that we cannot kill every carrier mosquito,” Jenkins said. “West Nile virus is here to stay, it’s endemic.” 

It was tough to gauge a measurable amount in more centralized and northern areas in the county that have seen more deaths and human cases of West Nile, McCallister said. 

When the county was sprayed, it was split into separate zones. The first two, both in the northern chunk of the county, got theirs over a course of five nights because of inclement weather. 

The eastern portion that made up Zone 3 was over and done with in two nights, making it easier for the CDC to analyze the impact of the spraying. Thus, McCallister couldn’t give the same type of specifics for the entire county. 

She did say that those areas saw a decline in the mosquitos, the question is how large of one. 

“With our preliminary look at the data, the populations in those areas were decreased,” she said. “We’re just looking to refine that analysis.” 

And the CDC has months of analysis ahead of it. McCallister said the final report likely won’t be completed until early 2013. But she’s been asked to announce the findings as they are discovered. 

“We have a real-time epidemic that exists today and we want to provide … as much real-time information that the CDC can provide,” Jenkins said. 

He and Rawlings both touted the four D’s of personal responsibility –– Rawlings prefaced his mentioning of them with, “You probably don’t want to hear it again, but I’m going to tell you again” –– that remind residents to dress in long-sleeved, light-colored clothes, drain standing water, stay inside during dawn and dusk and use mosquito repellant containing the pesticide DEET. 

“Let me be very clear, I agree with the judge. This is not over and we must continue our vigilance,” Rawlings said. “We are continuing our awareness campaign.” 

Rawlings and Jenkins both said they would not advise another round of aerial spraying inside the city. But they expect to continue to see human cases until the first hard freeze of the winter. 

The spraying cost at least $3 million –– Jenkins wasn’t sure whether that included paying state workers for their service in the county –– although that will be covered by the state of Texas and partially reimbursed by the federal government. 

“We know that aerial spraying in other places of the country have saved lives,” McCallister said. “We fully expect that’s what’s occurred here in Dallas County, as well.” 

Email mgoodman@wfaa.com

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