Mosquitoes with West Nile Virus found in Mesa County |

Mosquitoes with West Nile Virus found in Mesa County

Sharon Sullivan
Juvenile mosquitos are collected in this jar where later adult mosquitoes will emerge from the water and fly up through the inverted funnel and into a holding chamber . From there they are easily collected for identification or experimentation.
Grand Valley Mosquito Control District |

The lovely wet monsoon season gracing the Grand Valley also unfortunately provides plenty of breeding grounds for mosquitoes — in puddles, kiddie pools, and in buckets and on top of tarps where water has settled.

Since June, many mosquitoes throughout Mesa County have tested positive for West Nile Virus. While most people do not develop symptoms, the virus can cause fever, headache, body aches and fatigue, as well as more serious problems such as meningitis and encephalitis, according to the Mesa County Health Department.

Currently, “thousands of backyards are full of mosquitoes,” said Zane McCallister, general manager of the Grand River Mosquito Control District. “I recommend to homeowners they dump water sources.”

After all the rains recently, the mosquito control district is finding stagnant water and mosquitoes everywhere. Backyard pools that are treated with chlorine are not a problem, he said.

So far, no human cases in Mesa County have been detected, McCallister said.

The district has collected mosquitoes from 78 different locations for state laboratory testing. Of 18 mosquito samples gathered last week, nine tested positive for West Nile Virus.

“We divided the pools into different regions and found the virus about everywhere,” McCallister said. “There are pretty big numbers right now.”

“The number of Culex mosquitoes that transmit the disease are quite a bit higher than average,” said health department epidemiologist Thomas Orr.

The health department recommends preventing mosquito bites by using insect repellent and wearing long sleeves and pants. Residents may also want to stay indoors at dawn and dusk when mosquitoes are most active, the health department advised. And, people are strongly urged to dump any standing water on their property.

Monday through Friday, the Mosquito Control District treats stagnant water sources with a biological larvicide that kills mosquitoes.

It’s “like a Godsend from the pesticide world,” McCallister said, because “it’s effective, but it doesn’t affect other creatures.”

For more information, contact the Grand River Mosquito Control District at 970-257-0191 or

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