LONGMONT — Worth Parker, an employee with Colorado Mosquito Control, would have preferred nicer weather as he searched for and destroyed mosquito larvae Wednesday.
Parker and fellow CMC employee Matt Hendrix stomped through 15 boggy sites in the rain hunting for the insects, which can carry West Nile virus.
“We really haven’t gotten much done because it’s been raining,” Parker said, dipping a sampling cup into standing water along Lykins Gulch in west Longmont. “When it rains, it disturbs the surface and drives (the larvae) down to the bottom.”
Just as Parker got ready to move to the next site, Hendrix found a green, centimeter-long larva. The pair returned to their truck, gathered their larvicide and began spreading granules of the poison around the ditch.
They won’t know whether the species of mosquito in the ditch was Culex tarsalis, the breed most likely to spread West Nile virus, until the larva is examined in a CMC lab.
West Nile is carried by birds and transmitted to humans by mosquitoes that bite the birds, then people.
CMC, which is contracted to control mosquitoes in Boulder County, will monitor and treat areas where mosquitoes live throughout the summer, but crews like to start early and kill the larvae because it’s more effective than spraying to kill adult mosquitoes, Hendrix said.
Marshall Lipps, who supervises mosquito treatment at roughly 1,600 sites in Boulder County and 309 in Longmont, said a slight boost in West Nile virus infection rates may be in store because of a
“We may see a little spike in the numbers early on,” Lipps said. “But that doesn’t mean the entire season is going to be bad.”
This summer, the number of West Nile cases is expected to be similar to last summer’s and nowhere near the “major epidemic” of 2003, Lipps said.
The number of Colorado residents infected with West Nile virus exploded in 2003, with state health officials tallying 2,947 cases, including 63 deaths. That compares with 14 cases statewide in 2002, according to the Colorado Department of Public Health and Environment.
At one point in 2003, Larimer County officials counted 546 cases with nine deaths and declared a health emergency.
In 2004, the virus was less prevalent, with 291 cases and four deaths statewide.
Weld County leaders are betting that West Nile cases in 2005 will decline. In 2003, 402 people tested positive for the disease in Weld County. Six people died.
Last year, eight people tested positive for West Nile in Weld County.
Weld County commissioners late last year reallocated the $400,000 they spent on mosquito control in years past to the Weld County Sheriff’s Office to put more deputies on the street.
As a result, CMC will only monitor — and not spray — mosquitoes in unincorporated Weld County this spring and summer.
Weld County leaders said that in Eastern states where West Nile has taken hold, the number of cases drops off after the first few years.
“(West Nile) is on its downward trend,” Weld County Commissioner Mike Geile said. “If in fact that’s not true, we have the monitoring.”
The number of Weld County larva-monitoring sites has dropped from about 3,400 in 2004 to about 1,000 this year. Most of those are in and around several Weld County municipalities — including Platteville, Dacono, Frederick, Mead and Erie — that are still contracting with CMC for mosquito control.
Late last month, tests confirmed that a nestling great horned owl found near the intersection of Weld County roads 13 and 26 was positive for West Nile.
CMC and Boulder County health workers believe West Nile is here to stay and the number of cases will fluctuate with the type of spring and summer weather the state has.
“Historically, West Nile virus is a roller-coaster disease,” said Tony Stilwell, CMC operations manager for northeastern Colorado. “It goes up and down depending on the weather. It’s a very temperature-sensitive disease.”
In fact, he said, Tuesday night was the first time an adult mosquito was caught this season. It will be sent to the state laboratory to test for West Nile.
CMC began setting traps in Boulder County last week. The county will spend $326,395 for treatment in unincorporated areas this year and $13,975 on monitoring, county spokesman Jim Burrus said.
In addition to testing mosquitoes, throughout the spring and summer the county also will monitor blood donors for West Nile and test birds for the disease, according to Joe Malinowski, consumer protection coordinator for Boulder County Public Health.
Brad Turner can be reached at 720-494-5420, or by e-mail at email@example.com.
Jenn Ooton can be reached at 303-684-5295, or by e-mail at firstname.lastname@example.org.