Monday, August 1, 2016

Doing Battle with the Zika Mosquito

There's some good news on Zika.

Thanks to the foresight of the Collier Mosquito Control District, much of Southwest Florida is ready and able to fight the mosquito that carries the Zika virus. And not just Zika. CMCD has the capability  to detect and control other emerging threats from mosquitos -- like Dengue, Chikungunya and even a reemergence of Yellow Fever.

Here are some of CMCD's tools:

  • Special monitoring traps for Aedes aegypti, the Zika mosquito.
  • Analytical capabilities, including viral RNA testing.
  • Effective insecticides for both adult mosquitos and larvae.
  • Unique spraying devices on helicopters that create tiny-droplet aerosols, minimizing the amount of insecticide needed for effective treatment.
  • A first-of-a-kind ground-level blower to distribute larvicide granules over infected areas.
Dr. Mark Clifton, a CMCD Research Entomologist and national expert on Aedes aegypti, explains that all mosquitos are not the same. Most encountered in Southwest Florida are so-called "wild mosquitos" -- carriers of West Nile virus, St. Louis encephalitis, Eastern Equine encephalitis. When the number of mosquitos exceeds statutory limits in traps scattered about the area, the infected section is patterned-sprayed by fixed-wing aircraft. (CMCD has three such planes.)

Aedes aegypti, on the other hand, is generally not found over wide areas. It's an "urban pest." It's found tucked around homes and businesses. Treatment of Aedes aegypti is tight and surgical -- spray from low-flying helicopters and even from the ground.

Here's how CMCD would go after mosquitos carrying the Zika virus. If a person was diagnosed with the virus, special traps would be placed in the vicinity of that person's home or business. Aedes aegypti caught in those traps would be tested for Zika. If infected mosquitos were found, people would be notified, and the area would be sprayed with an adult-kill insecticide and, optionally, with a larvicide. Then the area would be monitored to ensure the treatment was effective.

The challenge is finding the infected mosquitos. (At this writing, none have been found in the Miami area where the first locally contracted Zika cases were reported.) In Southwest Florida and elsewhere, Zika-infected mosquitos must be found before eradication can begin.

What about transmission of the virus? Clifton explains that Aedes aegypti mosquitos travel less than 100 meters. So Zika will be spread, not by infected mosquitos, but by infected people traveling and being bitten by mosquitos in other parts of the state. Those mosquitos, in turn, can multiply, bite other people and continue the cycle.

CMCD points out the best defense is not to be bitten in the first place. There are a number of sensible precautions.
  • Eliminate sources for Aedes aegypti -- standing water in places like waste tires, cans, birdbaths, buckets, gutters, flowerpots and saucers. Swab out bromeliad cups. Seal septic tanks.
  • When outdoors, especially at dawn and dusk, wear long trousers and long-sleeved shirts.
  • Apply an EPA-approved mosquito repellent, e.g., one containing DEET.
If infected mosquitos are found, do we have the chemicals to knock them out without harming people? Yes. Sprayed from aircraft, available insecticides typically have a kill rate of 80-90%; that's considered effective control. The chemicals are oldies, workhorses approved long ago by the EPA. Naled and Malathion are organophosphates, effective against adult mosquitos. Methoprene is an unsaturated fatty acid ester, used to treat larvae.

The problem, Clifton says, is not with the existing products, which do fine. The problem is there are few, if any, back-ups available in the event Aedes aegypti develops resistance to the current insecticides. But that's a concern for the future.

For now we're in good shape. Dave Farmer, a CMCD commissioner, says, "Between our state-of-the-art DNA testing capabilities and our professional staff, we are well prepared to fight Zika. Mosquito control has never been more important."

CMCD has a new smart phone app that provides information about mosquitos, including spraying schedules. The app can be downloaded for free. See www.CMCD.org for details. 

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