The practice of 'fogging'
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The fog of war against mosquitoes
April 4, 2016Updated: April 4, 2016 11:03pm
A Bexar County crew sprays for mosquitoes in the Canyon Crossing neighborhood on the far West Side.
Bexar County’s opening salvo in this year’s war on mosquitoes came from a small cannon spraying a thin mist of insecticide over a far West Side subdivision Monday night.
With 1,300 miles of county-maintained roads to safeguard, the 2016 mosquito eradication effort had to start somewhere, and it just happened to be the Canyon Crossing subdivision near U.S. 90 West and Loop 1604.
As residents walked and jogged at dusk through the densely packed neighborhood, a Bexar County public works truck slowly ambled down its streets releasing the insecticide Vector Flex 20:20, which is formulated to kill mosquitoes while being safe for use in populated areas, including parks and playgrounds.
Over the next several months of warm weather, the county roads will get at least three passes from the fogging trucks, which require calm winds to operate, county officials said.
Starting several weeks ahead of its usual spraying schedule because of concerns about the Zika virus, the fogging campaign is one of several tactics the county is using to kill mosquitoes that might bear diseases. The fog kills only airborne mosquitoes, so the county and other entities are targeting the insects in their breeding areas, especially standing water.
County public works crews will be placing larvicides in wet areas and installing mosquito traps so insects can be tested for diseases. The county also is launching a community awareness campaign to encourage use of insect spray, long-sleeved clothing and other anti-Zika protective measures.
While the education effort is aimed countywide, the fogging is only done along county-maintained roads — not on private property — and only in unincorporated areas of the county. Consequently, the spraying addresses the mosquito problem mainly on the suburban fringes of the county.
Metropolitan Health District public relations manager Carol Schliesinger said Metro Health doesn’t spray in city neighborhoods except as a last resort. Rather, it focuses on killing mosquitoes in moist breeding areas. Fogging hasn’t been conducted in San Antonio since 2012 during a deadly West Nile virus outbreak, she said.
Fogging isn’t very effective against the Aedes aegypti mosquito, which is blamed for spreading Zika, Schliesinger said.
“It’s a container breeder that’s active during the day. That’s part of the reason we don’t do fogging,” she said.
Officials at the U.S. Centers for Disease Control and Prevention also doubt the effectiveness of fogging in the Zika fight.
On Monday, a CDC official said the culpable mosquito stays in and around homes, making fogging an inefficient option. CDC Director Dr. Thomas Frieden told Fox News that community health agencies should target Aedes aegypti mosquitoes indoors and outdoors, attacking larvae as well as adult insects. But that’s what Bexar County officials said their comprehensive program does.
Last week, Metro Health said no new cases of Zika have been confirmed here since Feb. 10, leaving the number at three. They’re among 28 confirmed cases statewide and among 300 nationally, officials said.
The confirmed U.S. cases all are linked to travel abroad to Zika outbreak areas, but the menace is getting nearer, officials said.
At a Zika summit in Atlanta last week, health officials said the Zika epidemic that has spread from Brazil through Latin America and the Caribbean is a growing threat in the United States.
The Aedes aegypti mosquito was thought to be mainly in the U.S. South, but last week the CDC reported that the mosquito has surfaced in parts of the Midwest and Northeast. Across the nation, health agencies are stepping up anti-mosquito efforts and trying to be more proactive about it than during the West Nile virus response, health officials said.
The nonfatal Zika virus, with mild, flu-like symptoms, is believed to pose major risks for pregnant women. Zika may be linked to fetal deaths and birth defects.