Hot weather along the Front Range is giving mosquitoes a boost as summer approaches, and drought could push them closer to humans.
So far, however, Colorado hasn’t seen an unusual number of cases of West Nile virus, the main disease carried by mosquitoes in this part of the country. Mosquito surveillance is just starting, which makes it difficult to know whether the bugs have been able to take advantage of favorable conditions.
Colorado had a relatively mild winter, which likely allowed more mosquitoes to survive, said Jim Fredericks, senior vice president for public affairs at the National Pest Management Association.
When temperatures reach the high 80s, mosquitoes also mature faster, allowing the population to compound as more reach the age to lay eggs, he said.
“You can squeeze in more generations during a so-called mosquito season,” he said.
Mosquitoes need standing water to lay their eggs, so the state’s drought conditions would seem to work against them, Fredericks said. At the same time, they’re quite resourceful and will rely more on water pooling in manmade items if they don’t have a suitable pond available, he said.
“We end up having water sources around structures” when people water their gardens or cool off with a hose, he said.
While all mosquitoes may be annoying, the ones Coloradans need to worry about are from the Culex group of species, which transmit West Nile virus, said Greg Ebel, a professor of microbiology, immunology and pathology at Colorado State University’s Center for Vector-Borne Infectious Disease.
The previous two West Nile seasons were relatively severe, but right now, the limited data isn’t pointing to a repeat of that, Ebel said.
Jefferson County reported one case in early June, involving a person who was hospitalized, but survived. Last year, the state health department reported 286 cases, with half involving neurological complications. (The actual rate of complications is likely much lower, because most people don’t get tested for West Nile.)
Mosquito surveillance around Fort Collins started a week ago, and that first round didn’t pick up enough West Nile-infected Culex specimens to raise concerns, Ebel said. One week of data isn’t enough to draw conclusions, though, and local conditions can lead to different mosquito populations, he said.
“The warm winter might be concerning, but we don’t really know that yet,” he said. “It’s been a pretty dry spring.”
The Denver Department of Public Health and Environment said it will start trapping and testing mosquitoes for West Nile next week, as well as monitoring 70 water sites and applying chemicals if needed.
Public mosquito control, such as spraying water with substances that kill larvae, is highly effective in reducing populations and the odds of disease, Ebel said.
Individuals also can protect themselves by draining any standing water around their homes, avoiding outdoor activity between dusk and dawn, keeping window screens repaired and using an with the U.S. Environmental Protection Agency, such as DEET.
