Ticks expand territory, pick up diseases

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MINNEAPOLIS (AP) — 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 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.

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