Mosquito count dwindles; summer program ending

Sep 7, 2017 By Katie Roenigk, Staff Writer

A trap left out on Davis Lane in Riverton had no mosquitoes in it when it was collected Wednesday.

Numbers were low this week elsewhere in the county, too, prompting Fremont County Weed and Pest assistant supervisor Nancy Pieropan to put an end to her mosquito program for the summer.

"Unless there is a noticeable increase in mosquito numbers or complaints this will be the last week trapping and testing is done in Fremont County in 2017," she said in an email Wednesday.

In an interview Thursday with The Ranger, she said the mosquito season is "pretty much winding down," attributing the decrease in the bugs to the lack of moisture in the area and the onset of cool evenings.

The lower temperatures also tend to keep people indoors in the evening, she noted, decreasing bite risk.

West Nile

Despite the lower number of mosquitoes in traps, Pieropan said there is still a chance for the culex tarsalis variety to transmit West Nile virus.

"I'm not going to say people won't be bit," Pieropan said. "There are still mosquitoes around, (and) it's still possible for mosquitoes to be hatching."

Daytime temperatures will be in the 80s for the next week, and Pieropan said those conditions are "certainly warm enough" for mosquitoes.

"(They'll) be around until there's a good, cold frost," Pieropan said.

As of Wednesday, there was no evidence of disease transmission in Fremont County in 2017, but Pieropan said someone bit by a carrier in August may only start to feel symptoms of West Nile this month.

"If there was a human case now I wouldn't be that surprised," Pieropan said.

The Centers for Disease Control and Prevention says most infected people will not get sick, but about 20 percent have a fever and experience flu-like symptoms.

Fewer than 1 percent of people with West Nile virus develop serious, sometimes fatal, neurologic illness.


The only culex tarsalis mosquito Pieropan caught this week tested negative for West Nile virus. It was found on North Smith Road in a pool of 73 mosquitoes.

Last week, the same trap held 105 of the bugs, including three culex. Riverton's other trap, near the Adams Avenue ditch, contained only two mosquitoes Wednesday, neither of which were culex tarsalis. Last week that container held 57 mosquitoes and one culex.

A trap in Arapahoe held 41 mosquitoes and no culex Wednesday, down from 171 mosquitoes and one culex last week.

In Hudson the trap on Ohio Avenue contained two mosquitoes this week and no culex, down from 12 mosquitoes and nine culex last week.

South of Hudson on Snavely Lane there were 98 mosquitoes and no culex Wednesday, down from 290 mosquitoes and two culex last week.

Finally, the five traps set in Lander held a total of 20 mosquitoes and no culex Wednesday, down from 71 mosquitoes and 12 culex Aug. 29.

The decrease in Lander comes despite the fact that municipal employees have stopped spraying for mosquitoes.

"They're like, 'It's done,'" Pieropan said, calling the decision "totally understandable." Riverton has cut back on spraying, she said, mainly because one of the city's foggers is out of commission. As of Wednesday, however, Riverton's remaining truck has continued to spray.

the town with mosquito repellent.

Pieropan congratulated cities throughout Fremont County for successful mitigation efforts this summer.

"I think people should be grateful," she said. "These mosquito control programs make a difference - you can see that from the numbers in rural areas compared to the numbers in urban areas. ... Their hard work greatly reduced the number of mosquitoes in Fremont County communities and helped prevent the transmission of West Nile virus."

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