Aug 3, 2017 - By Katie Roenigk and Daniel Bendtsen, Staff WritersResidents are advised to practice the "Five Ds" of mosquito-bite prevention.
West Nile virus has been detected this week in a pool of mosquitoes in rural Riverton.
"There is activity in the area," Fremont County Weed and Pest assistant supervisor Nancy Pieropan said Wednesday. "(Now) people can behave like there's West Nile in the system - because there is."
The infected bugs were caught Monday in a trap on North Smith Road, but Pieropan said the location isn't as relevant as the test result.
"A mosquito will fly a couple miles," she said. "If (West Nile) is in the system, it's in the system."
City employees concur with her characterization of the situation: Even though Riverton doesn't spray for mosquitoes in the North Smith area, Pieropan said municipal employees plan to ramp up their bug abatement program as a result of this week's positive test.
"(They are) going to start treating more in town because of that," she said. "They're going to double spray."
Riverton Mayor Lars Baker - who was Weed and Pest supervisor before he retired in 2013 - said the precaution could prevent transmission to humans, but he isn't optimistic.
"We generally detect (West Nile) in the mosquito population at the same time we detect it in the human population," he said.
To avoid mosquito bites, officials recommend residents follow the "Five Ds:" Avoid spending time outside at dawn and dusk; dress in shoes, socks, long pants and a long-sleeved shirt outdoors and ensure clothing is light-colored and made of tightly woven material; drain standing water from area properties; and use insect repellant containing DEET.
Just because West Nile didn't show up on Pieropan's testing strips until this week, Baker noted, doesn't mean the virus hasn't been around in Fremont County.
"It just means we can't find it," he said.
In an effort to better monitor the mosquito population, Riverton's weed and pest program operator Jared Blury has been moving one of the city's bug traps among several different locations this year.
The mobile trap started the season on Sunset Drive, but Pieropan said there wasn't a lot of mosquito activity in that area, so the contraption was moved to a spot near Adams Avenue.
This week it was relocated again, this time closer to the Wind River, and now Pieropan said it's by Aspen Park Elementary School.
The diversity of sample sites helps the city ensure its mosquito control methods are effective, Pieropan said.
"We try to have a science-based program instead of, 'We're just going to spray like crazy and hope for the best,'" she said. "He's just wanting to sample different areas to see ... how successful the program is, or where he needs to focus more."
West Nile is especially concerning this year, Baker said, since more than half of mosquitoes now found are culex tarsalis, the species that carries the disease.
For example, last week a trap on Davis Lane in west Riverton contained 22 culex out of a total of 40 mosquitoes.
The week before that, 46 out of 78 bugs in that trap were West Nile carriers.
Similarly, a trap on Carbine Lane in Lander held 184 mosquitoes Tuesday, of which 97 were culex.
Almost all of the mosquitoes trapped this week on Ohio Avenue in Hudson were culex: Out of 98 mosquitoes in the container, Pieropan's data showed 83 were West Nile carriers.
On July 25 the same trap held 141 mosquitoes, including 125 culex.
Ironically, Baker said the concentration of mosquitoes in general has been low this year.
He attributed the situation to heavy flooding this spring that likely washed the mosquito population downstream to Boysen Reservoir.
"Those who go to Boysen for recreation know how bad it is out there," he said.
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