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Tick-borne diseases on the rise; health agencies urge precautions

The number of Minnesotans who became ill from tick-borne diseases jumped to record levels in 2010, including a dramatic increase in human anaplasmosis, state health officials report. As this year's tick season arrived, they urged Minnesotans to increase their efforts to protect themselves from ticks.

Minnesota's three most common tick-borne diseases are all carried by the blacklegged tick, often called the "deer tick." During 2010, cases of these diseases reported to the Minnesota Department of Health (MDH) totaled as follows:

Human anaplasmosis: 720 (more than double the 300-plus cases in recent years).

Babesiosis: 56, up from 31 in 2009.

Lyme disease: 1,293, up 21 percent from 2009 and slightly above the 2007 level of 1,239.

"We're seeing a continuing and troubling trend of marked increases in cases of tick-borne diseases in Minnesota," said Dave Neitzel, MDH epidemiologist specializing in tick-borne diseases. "We are particularly concerned about anaplasmosis, with case numbers now rivaling Lyme disease in some areas of the state." In Aitkin, Beltrami, Carlton, Cass, Crow Wing, and Hubbard counties, where tick-borne diseases are common, reported human anaplasmosis cases exceeded Lyme disease cases in 2010.

Cases of other serious but less common diseases carried by ticks in Minnesota have also increased in number. "We're concerned about new cases of tick-borne diseases that hadn't been detected in Minnesota before 2008," Neitzel said. These newer diseases include Powassan virus disease and a new form of ehrlichiosis, both of which appear to be carried by the blacklegged tick. A different form of ehrlichiosis, as well as Rocky Mountain spotted fever and tularemia, are also occasionally reported in Minnesota residents.

Tick-borne illnesses can range from mild to severe. Complications can include swelling of the brain, organ failure, and death. About 30 percent of the 2010 anaplasmosis patients were hospitalized, and one patient died. Nearly half of the babesiosis cases were hospitalized and one patient died. "With Minnesota's more common tick-borne diseases reaching epidemic levels in some areas, it is crucial that Minnesotans protect themselves from tick bites to prevent serious tick-borne illness," advised Dr. Ruth Lynfield, Minnesota State Epidemiologist.

The risk of tick-borne diseases in Minnesota is greatest from late spring through mid-summer, when ticks are most active. During autumn, blacklegged ticks are active again.

The best way to prevent tick bites is to avoid tick habitat during those seasons:

Wooded or brushy areas for the blacklegged tick.

Grassy or wooded areas for the American dog tick ("wood tick"), which carries Rocky Mountain spotted fever.

If you can't avoid tick habitat, use repellent to reduce the risk of disease:

DEET-based repellents (up to 30 percent DEET), which can be applied to clothing or skin for temporary protection.

Permethrin-based repellents, which are used to pre-treat fabric and can protect against tick bites for at least two weeks.

People who live on heavily wooded property, whether permanent homes or cabins, often encounter ticks on a daily basis. Since daily repellent use can be more challenging for these people, they should consider the following landscape management techniques:

To make your yard less attractive to ticks:

Keep lawns mowed short.

Remove leaves and brush.

Create a landscape barrier of wood chips or rocks between mowed lawns and woods.

To reduce tick numbers at your yard-woods interface:

Apply pesticide treatments in the spring or early summer along the edges of wooded yards and trails; follow pesticide label instructions carefully.

Details on personal protection and landscape management to reduce tick-borne disease risk are available at

Early detection of tick-borne illness is important to prevent severe complications, so seek medical care if you develop an illness suggestive of a tick-borne disease after spending time in tick habitat. Signs and symptoms of the various tick-borne diseases can include, but are not limited to, rash, fever, headache, fatigue, muscle aches, joint pain or swelling, and facial droop.

These symptoms can also be involved in other diseases, so it is important for a patient's medical provider to consider tick-borne and non-tick-borne causes. Except for Powassan disease, which is caused by a virus, all of Minnesota's tick-borne diseases are treatable with antibiotics.

More information about Minnesota's tick-borne diseases, including signs, symptoms, and prevention, is available on the MDH website ( or by calling MDH at (651) 201-5414.