Mosquito spraying to occur in south Fort Collins to combat high West Nile virus risk

Samantha Ye

city map
Pesticide spraying will begin at dusk and end by 2 a.m. on Sunday, August 26 and Wednesday, August 29, weather permitting, according to the City. The fogging will cover the red highlighted areas (Image courtesy of the City of Fort Collins).

With the risk of contracting West Nile at its highest of the season so far, the City of Fort Collins will spray pesticides in south Fort Collins twice next week, according to a news release.

Spraying will begin at dusk and end by 2 a.m. on Aug. 26 and Aug. 29, weather permitting, according to the release. The fogging area covers Horsetooth Road to Harmony Road and extends to Trilby Road between Shields Street and Lemay Avenue.


Residents can track the spraying progress on the vehicle tracking website.

Vector Disease Control International, the City’s contractor, will be using a permethrin-based product applied in a fine mist. Permethrin is a common insecticide for such public health projects, according to the National Pesticide Information Center.

To minimize pesticide exposure, residents are recommended to stay indoors, bring pets inside and keep doors and windows closed for 30 to 60 minutes after spraying. Residents can also cover organic gardens, ponds and water features with a cloth sheet or tarp to further minimize pesticide exposure, according to the release. 

The decision to spray came from the area’s high West Nile vector index of over 0.8, said Amanda King, City communications and public involvement director. 

The vector index indicates the concentration of infected mosquitoes in an area, King said. Once the index hits or exceeds 0.75, a spraying operation is triggered for the specific treatment zone.

There are 53 mosquito traps across the City, King said, which give weekly trapping results.The traps help observe the Culex mosquito populations, which are the principal carriers of West Nile, according to the Baylor College of Medicine.

Katie O’Donnell, Larimer County Department of Health and Environment public information officer, said it is normal to see a steady increase of the vector index throughout the summer, making now the highest of the season.

The first case of human West Nile fever in Fort Collins this year was confirmed on Aug. 9, according to a previous press release. 

At least four significant cases of West Nile have been confirmed in Fort Collins, though there is usually a delay in reporting, O’Donnell said. The time between someone getting bitten to them showing severe enough symptoms to go to the doctor to then getting results from an official blood test usually delays confirmation for about a month.

About 20 percent of people infected with West Nile develop a fever and other symptoms including headache, body aches, joint pains, vomiting, diarrhea or rash, according to the Center for Disease Control and Prevention. Severe or fatal symptoms are rare.


Still, it is highly recommended for everyone to take precautions, especially wearing bug spray, O’Donnell said.

“It’s such a simple thing to do,” O’Donnell said. “I know people don’t like to put it on but if you can’t get bit by a mosquito, you can’t contract West Nile, so it’s really easy to protect yourself.”

The City recommends following the Four D’s:

  1. Drain: Homeowners and renters should drain any standing water, such as bird baths, clogged gutters where mosquitoes can breed
  2. Dress: Wear lightweight, long-sleeved shirts and long pants while outdoors. Spray clothing with insect repellent since mosquitoes may bite through clothing.
  3. Defend: Apply an approved insect repellent sparingly to exposed skin. The Environmental Protection Agency provides guidelines for choosing a suitable repellant.
  4. Dawn/Dusk: Limit time spent outdoors at dusk through dawn, peak Culex mosquito feeding times.

Collegian reporter Samantha Ye can be reached at or on Twitter @samxye4.