Mosquitoes carrying West Nile Virus near Casper airport to be sprayed - Casper, WY Oil City News
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Mosquitoes carrying West Nile Virus near Casper airport to be sprayed


CASPER, Wyo. — Natrona County Weed & Pest is preparing to use an aircraft to spray mosquitoes in an area west of the Casper-Natrona County International Airport beginning on Saturday, Aug. 17.

That is after they detected “a pretty hot sample” of mosquitoes carrying West Nile Virus in that area on Aug. 9, according the NC Weed & Pest mosquito supervisor John Leman.

This map shows a spray boundary, showing areas which will not be impacted by the aerial sprays. (Courtesy of Natrona County Weed & Pest via Facebook)

Leman said that it is specifically the Culex tarsalis mosquito species which is of most concern.

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“It is the most competent vector for spreading the virus,” he said.

Mosquitoes can transmit the virus to birds, particularly corvids. Leman mentioned that crows, magpies, bluejays, robins and sparrows are frequent reservoirs for the virus.

While the virus can eventually kill birds, Leman said they can live with West Nile. The concern is that other mosquitoes may feed upon these birds and then bite humans, transmitting the virus.

Leman said there have already been a few cases of West Nile Virus in humans this year and so NC Weed and Pest is taking steps to try to limit the spread of the virus.

“Mid-July through the end of August is the peak time for West Nile,” he added.

Weed and Pest uses surveillance traps throughout the county. Leman says that these are moved around, with about 10 hung on a nightly basis.

They are able to monitor mosquito populations and species from these traps and are also able to use a “Ramp” tester to check them for West Nile Virus.

Leman says that a 50 mosquito sample size is used during such testing and that their test of the area west of the airport “detected a pretty hot sample.”

Because that area is fairly large, Weed and Pest will bring in an aircraft to spray and treat the mosquitoes biologically.

They’ll use a Permethrin-based spray solution, applying less than an ounce per acre.

“The product being applied will be ‘Duet HD’, which is a synthetic pyrethroid,” Weed & Pest said on Facebook. “The application rate will be .94 oz/acre, which should not pose any health issues to livestock, domestic animals or humans.”

The sprays will take place in the later evening and should be complete by about 10 pm, Leman says.

“The products break down pretty quickly,” he added, noting that there isn’t much concern that the sprays will have a big impact on other insect species such as bees.

Weed & Pest also sprays areas around the county, particularly along the river, using their fog trucks.

Those fogging activities also take place in the evenings.

Weed & Pest sometimes provides updates on their Facebook page about areas where fogging activities will occur.

People are also able to comment on that page to point out areas where they think fogging activities may be needed. Weed & Pest makes note of these suggestions and may organize fogging activities based on this public feedback.

Standing water is of particular concern as a breeding ground for mosquitoes. Leman suggested that if people have things like buckets, pools or birdbaths with standing water around their homes, they should consider draining those.

He also said people may want to wear protective clothing, particularly in the mornings and evenings when mosquitoes are most active.

Applying a repellent with at least 20% DEET is an effective way to prevent bites from happening, Leman added.

Leman said that Weed & Pest will continue to monitor mosquito populations and test them for West Nile Virus.