A New Tick Arrives in Northern Michigan

This is a story about ticks and Lyme disease. It’s also a story about mice and birds and how climate may be changing the ecology of diseases.

Leslie_Littlefield
Dr. Leslie Littlefield

According to our state’s Department of Health and Human Services, Lyme’s is the most commonly reported vector-borne human disease in Michigan. In fact, 55 cases have been reported already this spring, 6 in northern Michigan. But Lyme’s may be more prevalent in our pets.

Traverse City veterinarian, Dr. Leslie Littlefield says that dogs are sentinel species for humans because they’re likely the first to catch Lyme’s disease.

“Yes, dogs do get Lyme disease. They’re again a sentinel for Lyme disease because it’s caught and we see it in dogs before people. Dogs get more ticks on them; they’re down in the grasses and so it’s a very common problem.”

“We keep track of ticks here and we’re pulling them off more frequently. The time of the year that we see ticks is becoming longer too. They don’t like the cold cold winters we use to have. And, other than the last two years, we haven’t had a cold winter like that in 15 years – since I was in college.”

If our region had fewer ticks and no Lyme disease just a decade ago, what happened? One answer appears to be the movement of animals.

Dr. Philip Myers
Dr. Philip Myers

Dr. Philip Myers, a zoologist and ecologist studies the movement of small mammal populations in northern Michigan. He says the data is compelling.

Lyme disease is associated with white-footed mouse. Though deer mice carry it too. It is mostly closely linked, for whatever reason, to the white-footed mouse.

Noting that the deer mouse is a northern species, Myers says, “white footed mice probably weren’t in northern Michigan at all until the early 1900’s. I looked at both species. The question was, is southern species replacing the northern species.”

“I now have 27 years of data.” Myers’ research shows that the early end to winters result in a boom in white footed mice. “If winter ends early, the white footed mice have a huge advantage. Their numbers just take off.”

Myers points out that the explosive growth in the white footed mouse populations and their movement north reflects a similar movement by many rodent species. The research clearly shows the northward migration of at least 8 species of rodents.

“It’s more than a coincidence that they’re all moving northward.  population is not just in Norther Lower Michigan,” Myers said.

Bill_Scharf_cardinal
Dr. William Scharf

New bird and tick species appear to be frequenting northern Michigan too! Just last summer, Traverse City-based avian parasitologist, Dr. William Scharf reported the first occurrence of a southern species of tick in our region.

“I discovered a tick called exodius brunius which has been found in southern states for a long time. Last year I found one of them on a bird in Northern Michigan at Chippewa Run near Empire, a Leelanau Conservancy preserve. I learned this had also been found down near Kalamazoo. It’s a southern tick found in Louisiana, Georgia, and places like that. And now we have it in Michigan.”

Scharf says that occurrence of ticks on birds used to be fairly rare.  I’ve been doing this since 1968. From 1968 until now it was uncommon to see ticks on birds, and now it’s extremely common, and I’ve seen as many as 100 ticks on one bird’s ear. That’s the place where they tend to congregate is in ears of birds.”

“We think the climate is changing enough so that it’s becoming favorable for the ticks. The ticks are able to hitch a ride on the birds and stay on the birds longer,” Scharf says. “The fact is the birds act as carriers for the ticks and spread them around.”Dog

 Apparently, climate change is driving big changes in the animal populations in Northern Michigan as well as the insects that act as vectors for human disease. According to Dr. Leslie Littlefield, the challenge to our health and the health of our pets needs to be faced head on.

Ticks present an emerging threat, Littlefield says. “It’s not going to get better, there’s no way. It’s only going to get worse. So we’re going to have to learn to live with this.”

[Note:  We thank Dr. Philip Myers for the use of many of his photographs in producing the video. And thanks to David Poinsett for his assistance on the video camera.]

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