While Routt County Environmental Health Director Michael Zopf was investigating a sewage complaint at an old septic tank Monday, he came across a mess of mosquito larvae.
"There were several hundred mosquito larvae wriggling around," Zopf said.
Those larvae show that despite bouts of cool, rainy weather, Routt County residents are still susceptible to bites from mosquitoes carrying West Nile virus, Zopf said. This summer, a bird and a horse were found infected by the virus in Routt County.
"Yes, (infections) are on the decline and yes, mosquito larvae are on the decline," Zopf said. "But people should still be vigilant, I believe."
Zopf said that he expects mosquito season to be over by Oct. 1, or when weather in the area shifts to winter's cool, rainy and snowy conditions.
Until then, officials recommend that people take precautions such as wearing insect repellent containing DEET whenever they're outdoors and limiting outdoor activity at dawn and dusk when the mosquitoes carrying the virus feed.
It is also recommended that people drain standing water on their property and check that window screens are in good condition.
This summer, one bird and one horse tested positive for West Nile virus in Routt County, out of the 16 birds and two horses tested.
The virus-positive bird was a raven found dead on Village Drive near Mount Werner at the end of August.
The horse, which was found to have the virus Aug. 14, was from Toponas, but Zopf said it is likely that the horse contracted the virus while on the Front Range.
The horse spent most of the summer on the Eastern Plains and the Front Range. One week after it was brought to Toponas, it began to show neurological signs of West Nile, Zopf said.
"I think it's entirely possible that this horse was infected in an area other than Routt County," he said.
The horse survived the virus, Zopf said.
Last summer, no reports of infections were reported in Routt County, but there were some cases reported in nearby areas, including one horse in Moffat County that tested positive.
As of Monday in Colorado, 1,817 human infections had been reported this summer, including 38 deaths.
In Mesa County, there have been five infections and two deaths, and in Rio Blanco County there have been three infections this summer.
State officials expect the virus to be more prevalent on the Western Slope next summer.
Routt County will set up a surveillance survey early in the year to give people information about the numbers and types of mosquitoes prevalent in the area, which could help people be more aware and better prepared, Zopf said.
"I hope we don't see anywhere near the increases they saw in (eastern Colorado)," Zopf said. Last year, the state saw 13 cases; this year, the number is fast approaching 2,000.
"With everybody being vigilant and people taking care of the standing water around their homes, that's going to go a long way toward them protecting themselves from disease."
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