West Nile virus new primary mosquito-borne illness in metro
Minnesota has seen a rise in Lyme disease cases since 2000 and Washington County is among several counties seeing a majority of cases, a Metropolitan Mosquito Control District official told the Board of Commissioners Tuesday.
MMCD Executive Director Jim Stark said more Lyme disease, human anaplasmosis and babesiosis cases are being reported in the state because of growing deer tick populations due to more insects and the disease-causing bacteria surviving milder winters.
“We’re seeing the range of the deer tick population spread,” he said. “There’s a fairly high tick load in Washington County.”
An MMCD pamphlet lists Washington County among several areas in the state reporting a majority of Lyme disease cases. The other areas are the extreme eastern parts of Wabasha, Winona and Houston counties in southeastern Minnesota and Chisago, Kanabec, Mille Lacs, Crow Wing, Pine, Aitkin, southern Carleton and extreme southwestern St. Louis counties.
Stark said the highest deer tick populations in the metro area are in Washington, Anoka and extreme northern Ramsey counties.
“With our warmer winters, the ticks do a little better, and the bacterium does a little better,” he said.
MMCD figures show there were 1,201 Lyme disease cases in Minnesota in 2011, with 88 cases in Washington County. There were 782 HGA cases in the state in 2011, with 23 in the county.
“Tick-borne diseases are more prevalent,” he said.
Although the MMCD uses several methods to control the mosquito population, Stark said the agency has few methods to control deer and wood ticks.
“We really can’t kill ticks. They’re hard-bodied insects,” he said.
Instead, Stark said tick-fighting efforts focus on educating people about protecting themselves from ticks and recognizing Lyme disease symptoms. Prevention methods include staying out of underbrush; wearing light-colored clothes so the small deer ticks are visible; use insect repellent; do a complete body check after being in the woods, shower and towel dry vigorously; save activities like brush cutting for August when all stages of deer ticks are at their lowest numbers, and carefully check children and pets.
Stark said ticks have four life stages — eggs, larva, nymph and adult — and a 2- to 3-year life cycle during which they must feed on blood before molting to their next life stage. Ticks must remain attached to a host for 24 hours to transmit Lyme disease and both nymphs and adult ticks can transmit the disease.
Early Lyme disease symptoms include a “bulls-eye” rash, headache, fever, chills, fatigue and muscle and joint pain. Early treatment with antibiotics is effective in preventing damage from Lyme disease. Persons should see their doctor if they suspect they are infected.
Mosquito control is the MMCD’s main task over the agency’s 2,900-square-mile region covering the seven metro-area counties and including 70,000 wetland areas.
“It’s one of the largest and most well-funded districts in the nation,” he said, adding that the agency has a $17.7 million budget this year.
Mosquito control efforts focus on controlling the spread of West Nile virus from birds to humans via mosquitoes, Stark said.
“West Nile virus is the primary mosquito-borne virus in the Twin Cities,” he said.
There were 70 West Nile virus cases reported in the state last year, with 15 of those cases in the metro area, Stark said. Washington County had one West Nile virus case.
Stark said the MMCD uses several methods to control mosquitoes. During the insect’s larval stage, the agency uses mosquito-specific bacterium and growth hormone treatments, he said. The agency uses truck-mounted sprayers and a barrier spray to control adult mosquitoes.
Stark admits that controlling mosquitoes depends on temperature and rainfall.
“There’s never a normal year in Minnesota with weather and trying to control mosquitoes,” he said. If you have dry years, you’ve still got those wetlands and those are where those disease mosquitoes are laying their eggs. Everything we do is predicated on rainfall.”