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West Nile tested county

Donna Gray

In the summer of 2003, Colorado experienced its worst epidemic of West Nile virus, with 3,000 cases and 63 deaths. Garfield County watched as the infectious disease made its way west. Last year, the majority of cases were on the Front Range – in Boulder, Arapahoe, Denver, Douglas, Larimer, El Paso and Weld counties.It was simply a matter of time until the virus, which began its inexorable march on the East Coast, arrived on the Western Slope.But thanks to a well-coordinated effort of local government and the county public health service – and a little luck – Garfield County averted what could have been a deadly year for West Nile virus.Public education and an aggressive mosquito control program helped keep the numbers of West Nile cases to five in Garfield County this summer. All cases were relatively mild. The county experienced none of the more severe manifestation of West Nile, such as meningitis, infection of the spinal fluid or the sometimes fatal encephalitis – inflammation of the brain. And no one in Garfield County died from the disease.It was a different story, however, in neighboring Mesa and Delta counties where the majority of cases in the state occurred in 2004. As of Oct. 4, 271 human cases were reported in Colorado, with three deaths. Of those, 233 cases were listed as mild fever, 22 as meningitis, 17 as encephalitis, and three deaths. Mesa County had 127 cases, with 10 cases of meningitis, 10 encephalitis and three deaths. Delta County had the second-highest number, with 22 cases and no deaths.Proactive stanceIn the early spring, Garfield County and the seven municipalities within the county, hired Colorado Mosquito Control Inc. of Brighton to mount a comprehensive mosquito eradication and public education program.Together with the Garfield County Public Health Service, county government got the word out about the potential epidemic.”I did over 40 PowerPoint (presentations) to 1,200 people,” said Garfield County public health nurse Mary Meisner. “I went to senior centers, nursing homes, and community groups over a period of 12 months starting last fall.”With volunteers from county and municipal government, Meisner set up tables at the summer festivals such as Strawberry Days, where people picked up information about the disease and how to prevent it.Virus information went out in Silt’s utility bills and people went door to door passing out literature in New Castle.”I think the success was due to everyone working together to get the word out,” Meisner said.Mosquito controlColorado Mosquito Control Inc. began its eradication and education program in April, covering an area of 100 square miles.Areas where mosquito larvae were hatching were identified and mapped and larvacide was applied. Traps were set out to determine hot spots of mosquito infestation around the county and adult mosquitos were treated with insecticide.The numbers of trapped mosquitos spiked in July and August. However, the numbers of culex mosquitos, which carry the disease, reached their highest levels in mid-September, with all species dropping off dramatically after Sept. 17.Colorado Mosquito Control also responded to calls from citizens about mosquito control and worked with the public health department to educate the public.Colorado Mosquito Control’s approach was to hit mosquitos at an early stage of development. To do so, it deployed technicians to locate and map places where mosquitos had laid their eggs and were hatching into larva.In addition to treating them with larvacide, Colorado Mosquito Control also went after adult mosquitos, spraying areas with high populations. Fogging with insecticide was a last resort, but it applied the chemical it used in very small amounts that were not harmful to humans or animals and broke down readily in the environment.”Each mosquito season seems to bring a unique set of circumstances created by the complex interactions of temperature, precipitation, irrigation and mosquito Biology,” Colorado Mosquito Control wrote in its final report to Garfield County. “This summer was a perfect summer to implement an IPM (integrated pest management) program in Garfield County. Because of the lower precipitation levels on the western slope, most naturally occurring water pools remained dry or manageable.”In June and July, Colorado Mosquito Control began its larvacide program, targeting areas where the highest numbers of insects were trapped, including the Highway 82 corridor between Glenwood Springs and Carbondale, Parachute, Rifle and Silt Mesa.Toward the end of August and the first week in September, the county reported its first cases of human West Nile virus and the first reports of mosquitos carrying the disease in both Parachute and Rifle. Specifically, the mosquitos positive for West Nile were trapped in the baseball fields and rodeo grounds in Parachute and in the Lyons Pond next to Interstate 70 in Rifle.By Sept. 24, all larvaciding, trapping and spraying concluded after traps showed steadily declining numbers of mosquitos.”Overall the 2004 season was a success,” the report said. “Although human cases still occurred, the goal of the first year was to lay the groundwork for an Integrated Program. Sites were mapped, and a large amount of adult surveillance was completed. This gives Garfield County hard data to better form their cooperative mosquito program in the future.”During the 2004 summer season, West Nile showed up in much of the nation. According to the Centers for Disease Control and Prevention, of the 1,191 confirmed cases of West Nile virus nationwide, 1,129 were reported in Nebraska, South Dakota, Texas, Wyoming, California, Arizona and Utah. The largest number of cases in one state, 235, was in Colorado, primarily from the Western Slope. Six people died across the country, three of them in Mesa County.2005 WNV seasonCMC said it usually takes two to three seasons to locate and map the majority of mosquito larva sites in an area. It estimates it’s mapped 65 percent of the sites in Garfield County. Larva control will improve as more sites are located.Areas of particular emphasis for next year are the rodeo-baseball fields in Parachute, Lyons Pond in Rifle, both sides of the Colorado River south of Interstate 70 in Silt, and the Roaring Fork River corridor along Highway 82 to the county line.They are areas of high mosquito population and also had high concentration of culex mosquitos this summer.Judging by recent behavior, West Nile virus is not likely to go away anytime soon. “It’s an emerging infectious disease,” Meisner said. People will have to remain vigilant next year. They need to remember the “three D’s”: , dress in long pants and long sleeves and drain all standing water; culex mosquitos are active from dusk to dawn.”It’s an emerging infectious disease,” Meisner said. People will have to remain vigilant next year. They need to remember the “three D’s”: , dress in long pants and long sleeves and drain all standing water; culex mosquitos are active from dusk to dawn.


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