Deer ticks, Lyme disease on rise in Minnesota

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The number of Minnesota residents contracting Lyme disease hit a record high level in 2004 and the areas where people are most likely to get the tick-borne illness appeared to expand north and westward, state health officials said today.

A total of 1,023 Lyme disease cases were reported in Minnesota in 2004, according to Minnesota Department of Health (MDH) records, surpassing the previous high number of 867 cases in 2002. Also, a substantial number of Lyme disease cases in 2004 occurred in several counties that have had few reported cases in past years. The new areas are the eastern two-thirds of Becker County, southern Beltrami County, southern Clearwater, all of Hubbard, southern Itasca and eastern Todd County.

“Clearly, the threat of Lyme disease is increasing in Minnesota ,” said Dr. Harry Hull, state epidemiologist with MDH. “People need to recognize when they are at risk and take steps necessary to protect themselves.”

Deer ticks (also called black-legged ticks) carry the bacteria that cause Lyme disease, an illness that can cause debilitating arthritis as well as serious heart and nervous system problems.

“We’re approaching the peak time of year for Lyme disease, when the risk of being exposed to the illness is greatest,” said David Neitzel, an MDH epidemiologist specializing in diseases carried by ticks and mosquitoes. “Eighty percent of Minnesotans who develop Lyme disease are exposed to infected ticks between mid-May and mid-July.”

About 70 percent of the people who get Lyme disease in Minnesota are exposed to it in wooded, brushy areas in 24 central, east-central and southeastern Minnesota counties where deer ticks are commonly found. Most of the other cases involve Minnesota residents who were exposed in western Wisconsin.

Areas in Minnesota where you’re most likely to find deer ticks include Aitkin, Anoka, Becker, Beltrami, Carlton, Cass, Chisago, Clearwater, Crow Wing, Hubbard, Houston, Isanti, Itasca, Kanabec, Mille Lacs, Morrison, Pine, Ramsey, St. Louis, Sherburne, Todd, Wabasha, Washington and Winona counties. Much of the Twin Cities area lies outside this “high-risk” zone.

Although deer ticks are typically active from April through October, the weeks between mid-May and mid-July represent the period of greatest activity for the nymph stage of Ixodes scapularis. The ticks are most likely to spread disease during the nymph stage, when they are very small and can feed without being detected.

Deer ticks are smaller and darker in color than the common wood ticks that people may also encounter this time of year. They also lack the wood tick’s characteristic white markings, and the back end of the female deer tick is reddish in appearance.

To protect yourself from tick bites, health officials suggest that you:

* Know when you’re in tick habitat – brushy, wooded areas – and that you will need to take precautions. Unless you spend time in woods, simply being in a high-risk county won’t place you at risk.
* Use a good tick repellent, such as products containing permethrin (which can be used on clothing) or DEET, and follow the manufacturer’s directions.
* Wear clothes that will help to shield you from ticks. Long-sleeved shirts and long pants are best. Tuck your pants into the top of your socks or boots, to create a “tick barrier.”
* Check frequently for ticks, and remove them promptly. Ticks actually have to bite you – and remain attached for one to two days – to transmit Lyme disease.
* Remove ticks slowly and gently, using a pair of tweezers. Avoid folk remedies like Vaseline, nail polish remover or burning matches – they are not a safe or effective way to remove ticks.

If you do develop signs or symptoms of a tick-related illness, you should see a physician right away, Neitzel emphasized. One early sign of Lyme disease is a characteristic “bulls-eye” rash, consisting of a reddened area, sometimes with a clear area in the middle, at the original site of the tick bite. The rash may expand in size to cover a very large area (usually greater than two inches), or even appear in several places on other parts of the body.

Not everyone develops the rash, however, so it’s also important to be alert for symptoms of Lyme disease – fever, headache, chills, and pain in the muscles or joints – if you’ve spent time in “tick country” during the past month.

Deer ticks can also transmit two other serious illnesses – human anaplasmosis (HA), formerly called human granulocytic ehrlichiosis (HGE), and babesiosis. The symptoms of HA and babesiosis do not include a rash, but they are otherwise similar to the symptoms of Lyme disease. Symptoms of HA can include a sudden onset of fever of 102 degrees or more, chills, shaking, severe headache and muscle aches. Babesiosis is characterized by high fever, muscle aches, fatigue and loss of appetite. Some people can be infected with more than one disease by the same tick bite. For example, 20 of the 149 HA cases in 2002 also had evidence of Lyme disease.

Minnesota recorded 473 cases of Lyme disease in 2003, compared with 867 cases in 2002. Reports of the illness have been on the increase in recent years. Only 283 cases were reported to MDH as recently as 1999.

During 2004, both human anaplasmosis and babesiosis also increased substantially. There were 139 cases, up from 78 cases of HA in 2003 (the record was 149 in 2002). Babesiosis cases reached a new high of nine cases in 2004 (there was one in 2003 and seven in 2002).

More information about Lyme disease and other tick-borne diseases is available on the MDH Web site or by calling MDH at (612) 676-5414.


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