Part Two: On the Move

By Sean Corcoran
August 14, 2012


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Female adult lone star tick (Amblyomma americanum).
Photo by: James Gathany, Center for Disease Control and Prevention

The ticks are out in Wellfleet this year. At the Sven Bed and Breakfast, innkeeper Alexandra Grabbe says that collectively, her and her husband have been bitten five times.

"I've seen them on laundry that I've washed because we line dry the sheets," she said. "Just the other day, in a room where a child had been sleeping, I found a tick on his sheet and immediately contacted his parents and said, 'You need to keep an eye out in case he was bitten.' They're like indestructible. They're horrible."

The inn is set back in the woods next to Old King's Highway, a scenic, unpaved road that dates back to the Colonial days. It's just a few miles to the seashore. But sometimes guests are so horrified by the presence of ticks that they flee.

Grabbe describes one family who found two ticks in a cottage.

"And they were just hiding when I was cleaning," she said. "Maybe on a piece of the bed or something. They're so small, you can't really see them. And these guests from England had a small child, a toddler. And they were terrified. And they actually left three days early because of the ticks."

Grabbe says she sees more ticks this year than last, and she attributes that to the weather. But ecologists now know that that the abundance of small mammals such as mice, shrews and chipmunks are what really determine whether young, disease-infected ticks prosper or die.

But for ticks, blood meals appear to be catch-as-catch-can, and they'll just as readily latch onto a passing ground bird as a mouse. In fact, when it comes to long-distance travel, the birds are the ticks' most reliable form of transportation.

Brenda Boleyn, retired biology professor and the chairperson of the Cape and Islands Lyme Disease Task Force.
Sean Corcoran/WCAI

NANTUCKET

Ornithologist Vern Laux points to the skies above the Linda Loring Nature Foundation on Nantucket at a pair of bomb-diving osprey. Nantucket is directly along one of the world's most significant migratory pathways for birds. It also has a significant tick problem.

"Apparently birds are in fact one of the ways these move around," he said.

Laux has scientific colleagues who have studied the correlation between tick movements and bird migrations.

"The ticks, they hang on to the birds heads," he said. "Well, if these ospreys are going to South America for the winter, the To-hees, the yellow warbler we saw just crossing a little while ago, most of these birds also are going to central or south america for the winter. And if there's ticks on their heads, they'll travel along with them."

Research shows that birds can carry ticks great distances during migrations, usually on the birds' heads, which are difficult to groom. After taking blood for a few days, the ticks falls off the birds and into their new home. In fact, that's the working theory regarding how a new species of tick came to arrive on Cape Cod from the Southern and Western United States -- the Lone Star tick.

"The first Lone Star Tick on the Cape was actually found here in Truro," said Brenda Boleyn, a retired biology professor and chairman of the Cape and Islands Lyme Disease Task Force. "And we learned about this tick because the camper realized there was something interesting and took it to a ranger."

There's disagreement about just what diseases the Lone Star can transmit. But since it first was identified on Cape Cod about six years ago, reports have become more frequent.

"The following year," she said, "a Lone Star tick was found by a student in Wellfleet on the bayside where no people were. Presumably that tick had been delivered by a bird. And after that a few ticks were found in Sandwich, and I had a dog picking them up in Truro."

Ticks have different techniques for finding hosts, and the Lone Star is the ultimate tick predator. It sees its prey and hunts it down. The local black-legged ticks, commonly called deer ticks, are more opportunistic. They wait on grasses and along the forest floors for different mammals to come along. Adult black-legged ticks rarely are found on mice. Research shows they climb higher up from the forest floor than young nymphs and larva, perhaps seeking larger prey such as deer, raccoons, dogs -- or horses.

Black-legged ticks -- the ones that carry Lyme Disease -- can sense carbon dioxide changes. So when a horse comes heavy-breathing down the path, the tick raises its front pair of barbed arms like it's signaling a touchdown, and it waits for the horse to brush against it.  

Megan Amsler is regularly picking ticks off her horses in Falmouth. One of her older horses, Nezeer, recently came down with Lyme Disease, as have other local horses she knows about.

"I had the vet come out," Amsler said, "and she did a test, and oh yeah, she said, this poor guy, his skin is crawling. And that's what feels like to him -- his skin is crawling."

Twenty-three hundred miles away from Cape Cod, at the Western College of Veterinary Medicine in Saskatchewan, Canada, Associate Professor Katharina Lohmann says she is trying to get ahead of the arrival of tick-borne diseases there.

Lohmman recently began a study collecting horse blood samples from diagnostic labs across Ontario, Manitoba and Saskatchewan to test them for the tick-borne diseases Anaplasmosis and Lyme.

"We got interested in this, or I got interested in this, based on a case," she said. "Basically, in the fall of 2010, I received a phone call from a veterinarian who was looking at a horse who was just kind of lethargic, and it looked a little bit jaundice. So she sent in some blood and they informed her from the lab that this horse had anaplasmosis. And so she called me about that because she wanted some information and was very surprised about that finding, as was I."

Lohmman says she knows of the one horse and a few local dogs in the region who've been infected, which is a surprise because Anaplasmosis has never been seen in this part of the world before.

"In Canada, to my knowledge," she said, "at this point there's very few areas where we have established tick populations of these specific ticks, which are called black-legged ticks that carry the diseases that we're interested in specifically. And there shouldn't be any populations in Saskatchewan that we know of. "

Just because a tick travels to a far-flung area of the world on the head of a bird, doesn't mean it'll find itself in a habitat suitable for its needs. But Lowman says there are scientific papers predicting how tick habitats are expanding North and West because of Climate Change.

"So that's the other reason why we're looking at this now," she said, "to sort of get a baseline with the idea that maybe if over time this changes, at least we have some information of where things are now."

The tick problem can't be attributed solely to migrating birds. If you blame the birds you have to blame the mice and then you have to blame the sugar maples and the oak trees that feed the mice. There's a lot of blame to go around. Ticks are free of Lyme disease when they hatch, and it takes an entire ecosystem of plants and animals to determine the tick's survival, and whether or not it will become infected with disease.  



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