Mosquitoes trapped in Garfield County show West Nile presence

July 17, 2013

Mosquitoes trapped in Garfield County show West Nile presence Vegetation Management Division addresses mosquito populations with treatment applications GARFIELD COUNTY, CO – The Colorado Department of Public Health and Environment (CDPHE) has determined that some of the mosquitoes trapped in three locations in Garfield County showing the presence of Culex have tested positive as being carriers for West Nile Virus. Colorado Mosquito Control sent five mosquito pool samples to CDPHE to analyze the collected samples for West Nile Virus. Three of the five July 9-10, 2013 pool submittals tested positive, stemming from mosquitoes collected in Willow Creek in Battlement Mesa, Parachute Cottonwood Park and Mile Pond Road, just southeast of Rifle.

Traps are located at 11 locations throughout the county. Garfield County Vegetation Management contracts Colorado Mosquito Control, Inc to check the traps once a week. The traps provide information on adult mosquitoes and help guide control efforts. Colorado Mosquito Control submits weekly updates to the county regarding the traps, which are available from the home page of the county website, and are posted online at The charts in the update reflect the quantity of mosquitoes trapped in a single night in a specific location, and also break down the trap count by individual species.

The species of mosquito of concern is Culex tarsalis. Culex is indicated in red in the update’s pie charts. Culex numbers that approach 50 or greater in a trap, in a single night are a concern. This usually leads to a limited, truck-mounted fogging of the affected area for adult mosquitoes by Colorado Mosquito Control. When Culex counts are in that range, residents should safeguard themselves to minimize their exposure to mosquitoes. Culex is most active at dawn and dusk.

Culex (the carrier of West Nile), was high last week in the following spots in Garfield County:

Location Culex
Willow Creek in Battlement Mesa 112
Parachute Cottonwood Park 107
Rifle Rest Area 95
Mile Pond Rd 66
Silt Roundabout area 48
Coal Ridge High School 55


The season’s first human case of West Nile virus was reported on July 3, 2013 in Delta County, prompting Garfield County Public Health Department staff to increase awareness and prevention efforts. The department is encouraging residents to drain standing water, dress in long sleeves and pants at dusk and dawn when mosquitoes are most active, and use an effective insect repellent.

“We live in an area where Culex mosquitoes – the ones that carry the West Nile virus, are present. But that doesn’t mean we need to refrain from doing the outdoor activities we enjoy; it just means we need to take a few simple precautions,” said Yvonne Long, director of Garfield County Public Health. “When it comes to discouraging mosquito bites, DEET is the gold standard by which all other repellents are judged.” When compared to other active ingredients, DEET-based products provided the most complete protection for the longest amount of time. However, there are a variety of other options to choose from.

“We know that DEET is effective and safe when used properly,” said Long. “However, we also know that people are interested in alternatives, and may not know which of these are effective against bites.”

For people looking for alternative active ingredients, including those derived from plants, there are resources available to help make the appropriate selection. The Environmental Protection Agency (EPA) website “Search for a Repellent that is Right for You,”, lists EPA registered repellents and the amount of time each is effective.

“Be sure to choose a repellent with a protection time that fits your activity, perspiration level, your environment, and how attractive you are to insects. It is also very important to re-apply repellent according to label instructions,” says Long.

For more information on West Nile virus prevention, contact the Garfield County Health Department at 970-625-5200, or For information regarding the county’s mosquito control program, please contact Steve Anthony, Garfield County vegetation manager, at 970-945-1377, ext. 4305.