The mosquitoes are biting,  but West Nile not in Mesa County ... yet

The bad news is mosquitoes are coming out in full force in the Grand Valley right now.

The good news is those mosquitoes aren’t the kind that carry West Nile virus, said Steve DeFeyter, environmental health director at the Mesa County Health Department.

“Overall, our mosquito numbers are climbing,” DeFeyter said. “We’ve seen a lot of the floodwater variety mosquitoes. We call them nuisance mosquitoes.”

Indeed, a run of wet weather this spring has the annoying, biting, blood-sucking pests hatching around the valley. However, the Culex mosquito has not yet been detected with any regularity in the county’s sampling efforts. Culex mosquitoes generally don’t hatch until mid- to late-July and this year appears to be following that trend, DeFeyter said.

Mosquitoes lay eggs in wet or low-lying areas, usually when rivers and waterways are low. Mosquitoes hatch when those water levels rise again.

Keeping your yard free of standing water can reduce the amount of mosquitoes nearby.

DeFeyter suggests emptying anything containing standing water, such as bird baths, horse troughs or doggie bowls, every seven days. A koi pond or water feature can be breeding grounds for mosquitoes.

“There are agents you can use if you can’t get rid of water feature,” DeFeyter said of larvicide products available for purchase.

The Grand River Mosquito Control District controls mosquito larvae within its boundaries, which includes most of the Grand Valley. However, the district does not extend from 20 Road to 30 Road and down to the Colorado River, a swath of the valley with the highest population of people.

The Health Department is responsible for testing and reigning in mosquito larvae in those areas, and will trap and test mosquitoes for the virus around the valley.

DeFeyter said it’s too soon to know whether the summer season will bring an influx of West Nile virus. West Nile is spread by mosquitoes and can kill birds and horses.

Few human deaths have been reported in Colorado, and those deaths were mainly in the elderly population or in those with already weakened immune systems.

One person died in Colorado last year of West Nile Virus, and total of 71 cases were reported.

There were technically no cases of West Nile in Mesa County last year.  In 2007, Mesa County had 34 cases and one death from West Nile virus. The county had similar numbers in 2006, with two deaths and 38 cases.

“It takes a while for (mosquitoes) to get rolling because they have not hatched yet,” DeFeyter said. “There’s no question that we seeing a lot of nuisance mosquitoes. Right now were seeing a dozen Culex mosquitoes to 480 Aedes Vexans (common mosquitoes.) If you can keep the population low enough you can probably forestall the outbreak.”


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