Although Dallas County is sending trucks through neighborhoods in an effort to spray mosquitoes that might be carrying West Nile virus, Central Texas officials say they prefer a more measured approach.
The virus has killed six people in Dallas County, one in Houston and one in Travis County this year. Central Texas officials are focusing their efforts on mosquito breeding areas and public education.
"Spraying is the least effective method," said Joe Staudt, a supervisor in the rodent and vector program of the Austin/Travis County Health and Human Services Department. "It's the method we use of last resort."
Staudt said insecticide â€" released as a fine mist â€" doesn't hang around the environment for long and won't kill mosquitoes unless they come in contact with it. The mist will only kill adult insects, not their larvae. What's more, mosquitoes can build up resistance to the chemical that they then pass down through generations.
Wetter weather has brought mosquitoes out en masse in parts of Texas. North Texas seems to be the epicenter, with hundreds sickened. In Dallas County, it takes only one infected insect for officials to send out trucks that fog neighborhoods with insecticide.
"We're using an integrated approach," said Zachary Thompson, director of Dallas County Health and Human Services. "When we're in the middle of an outbreak of a Third World disease in a 21st century country, we're going to do everything we can to stop it."
In Travis County, one person over the age of 50 â€" a risk factor for West Nile â€" died last month of the disease. Travis health officials said Friday that there were seven other cases.
Spraying is sometimes done in unincorporated portions of Travis County. In Williamson County, where the Williamson County and Cities Health District is investigating two cases of the more serious form of the ailment, West Nile neuroinvasive disease, officials said spraying isn't done at all.
Mosquitoes breed around creeks and standing water. Staudt said his department uses a larvicide, a brick of extended-release chemicals aimed at killing larvae before they can grow wings and begin feeding off humans.
The Austin/Travis County health department decides where to spray and where to lay bricks based on information gathered through traps for mosquitoes, which are tested for West Nile. Staudt said 18 ZIP codes in Travis County have seen West Nile-infected mosquitoes.
Residents are advised to take precautions against possible infection. They include eliminating standing water where mosquitoes can breed; staying indoors at dusk and dawn when mosquitoes are most active; spraying with DEET-containing insect repellent; keeping swimming pools treated and circulating; and removing debris from ditches and low areas.
Health department spokeswoman Carole Barasch said there hasn't been pressure to use more of the insecticide.
"There would have to be a rapid onset percentage-wise of illness," she said. "It would have to be a very large percentage."
Contact Benjamin Wermund at 246-1150. Twitter: @BenjaminEW
Additional material from staff writer Mary Ann Roser and The Dallas Morning News
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