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Deer ticks are expanding their range in the
Upper Midwest and southern Canada, new ticks are moving into the
area and existing ticks are picking up new diseases, increasing the
threat of illness to hikers tramping through the region's woods.


      Minnesota health officials last week reported the state's first
death from Rocky Mountain spotted fever, as well as the state's
second-ever case of brain inflammation from the Powassan virus --
similar to West Nile, but spread by ticks instead of mosquitoes. 


      Officials are also watching to see if the lone star tick, which
can spread a Lyme-like disease, establishes itself permanently. The
tick until recently wasn't often found north of southern Iowa, but
about a dozen have been identified in Minnesota this year. So far,
no infections have been reported.

      Scientists aren't sure why tick populations are expanding, but
many suspect one factor could be that subtle changes in the climate
are tipping the ticks' complicated ecosystems toward expansion. 

The
Minnesota Health Department has applied for a grant to study how
climate change is affecting the state's tick population, and
Wisconsin is seeking funding for its own study.

      "We think about climate change all the time," said David
Neitzel, a Minnesota department expert in insect-borne diseases.
With climate change, he said, "There is going to be a change in
all the diseases we work on."

      Deer ticks are a well-known threat to infect humans with their
bite. Lyme disease, the best known infection spread by ticks, can
result in fever, headache, fatigue and rash, and if left untreated
can linger and spread damage to joints, the heart and the nervous
system.

      Rocky Mountain spotted fever is spread by the American dog tick,
also called the wood tick. While the tick is common in Minnesota,
the bacteria is considered very rare here.


 Nationally, most cases
are in the southeastern U.S. The symptoms include fever, vomiting,
severe headache and a distinctive spotted rash.

      While none of the Upper Midwest states do a comprehensive tick
census, they track the spread of ticks by following up on confirmed
disease cases, doing some of their own sampling and identifying
ticks sent in by the public.

      In Minnesota, deer ticks have expanded to the northwest from the
traditional high-risk areas of eastern and central Minnesota.
Neitzel said he's seen it personally on his property in Becker
County.

      "I've been stomping around up there since the early 1970s, but
in just the last few years we're seeing black-legged ticks up
there," he said. Deer ticks are also known as black-legged ticks.

      Canadian health officials report a growing deer tick population
just north of Minnesota's northern border, where there were none in
the early 1990s. 


In Wisconsin, the ticks are marching from the
northwest to the southeast. And in Iowa, the deer ticks are moving
from the northeast toward the southeast and the center of the
state.


      "We're watching it, and certainly we're concerned," said Dr.
Patty Quinlisk, Iowa state epidemiologist.

      The number of Lyme disease cases has been climbing in each state
since 1993, according to figures from the Centers for Disease
Control and Prevention. The number of cases more than doubled from
2000 to 2007 in all three states, reaching 1,814 cases in
Wisconsin, 1,238 cases in Minnesota and 123 cases in Iowa.

      In Canada, government health researcher Nicholas Ogden found
that in the early 1990s there was only one area infested by the
ticks. Now, there are tick populations all along the northern
border of Minnesota and the northeastern United States.

      "Recent studies have suggested that the risk of exposure to
Lyme disease is emerging in Canada because the range (of the
black-legged tick) is expanding, a process that is predicted to
accelerate with climate change," he wrote in a June 2009 article
of the Canadian Medical Association Journal.

      Melissa Kemperman, an expert in tick-borne diseases with the
Minnesota Department of Health, said a changing climate can affect
many variables for the ticks. "It's not just the heat and
humidity," she said.

      For example, if birds and mammals move into new territory their
ticks could hitch a ride. If that new habitat has plenty of food
and shelter -- and doesn't get too cold in the winter - the ticks
could get established year-round, she said.


      Also, humans can change tick habitat. To cite just one example,
Neitzel said, when timber companies cut down an older section of a
forest the new growth is better for ticks. There are more
ground-level shrubs to live in and more mice and deer on which to
feed.

      Public health officials say the changes mean anyone who goes
into the woods needs to be extra vigilant. It also means that more
doctors need to be on the lookout for tick-borne diseases in their
patients.

Gallery

Child's death from spotted fever is state's first

Health

Chris Williams

Author

Deer ticks are expanding their range in the
Upper Midwest, increasing the threat of Lyme disease to hikers and others tramping through the region's woods.

Risk of tick disease rising in Upper Midwest

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