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Low tick counts continue to mystify county researchers

December 3, 2018

ORLEANS, Mass. (AP) — Before hunters bring down a deer by bow or gun, ticks typically have already made a meal from the living creature.

An individual carcass could be host to dozens of crawling male and engorged female ticks, especially deer ticks — so many that hunters say they have to be careful handling their kills.

But in a twist that has biologists puzzled, tick experts from Barnstable and Plymouth counties who spent Monday at weigh stations collecting ticks from deer carcasses for a research project found little sign of the parasitic arthropods.

Of the two deer that Barnstable County entomologist Larry Dapsis searched at the weigh station at Goose Hummock in Orleans, one yielded 20 ticks — and the other deer, just one.

“Something happened to the tick population we can’t explain,” Dapsis said.

The findings were even more surprising at Reedy’s Archery in Middleboro, where Blake Dinius, entomologist with the Plymouth County Extension Service, found that only 11 of approximately 40 deer carcasses brought to the weigh station there were worth sampling.

“The rest were almost devoid of ticks,” Dinius said.

Hunters and a state wildlife biologist told him the tick-free deer situation was “atypical, something they don’t see that often,” Dinius said.

Dinius and Dapsis are collecting ticks for research by Stephen Rich, a microbiologist who runs the TickReport at the University of Massachusetts Amherst.

“It does appear that tick densities are relatively low this year,” Rich said.

Tick-free deer have been found at each of the 12 sites where he and his partners, including Dapsis and Dinius, have conducted sampling, Rich said in an email.

But people shouldn’t let down their guard when it comes to tick protection, said Rich, who said the tick sampling is partly being used for surveillance and to detect the “inevitable arrival” of the Asian longhorned tick.

“I would admonish people not to interpret the current trend as indicative of the future or a sign of relaxed risk,” Rich said. “It only takes one bite.”

Elise Costa, who helps run the weigh station at the Powderhorn Outfitters in Hyannis, said “some of the deer we’re seeing are absolutely bloated with ticks.”

Costa said she hunts in the woods between Orleans and Hyannis and “I always come out with ticks on me” — ticks that are destined to die since she wears clothing treated with the insecticide permethrin.

There seemed to be some geographical patterns emerging, with tick-laden deer coming from Middleboro and tick-free deer coming from places like Carver, Dinius said.

The results were perplexing because Carver is usually considered to have a large population of ticks, Dinius said.

Dinius also hunted for ticks Saturday with Rich’s team in Norwell, which has one of Plymouth County’s highest rates of Lyme disease.

“We didn’t find anything in the course of three hours,” Dinius said.

In the same locations in May and June, 100 ticks were collected in half an hour, Dinius said.

“Something happened from May/June to November for there to be no ticks,” Dinius said. “I’ve heard a lot of guesses on the topic,” he said.

Some researchers think the dry hot spell earlier in the summer killed off moisture loving ticks, while others wonder whether the more recent wet weather led to some kind of fungal development that killed the arthropods, said Dinius, who will be back out Saturday sampling more deer carcasses for ticks.

“Everyone is happy” at the idea tick numbers may be going down, Dinius said. “But I’m looking for them.”

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Online: https://bit.ly/2ANb2kz

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Information from: Cape Cod (Mass.) Times, http://www.capecodtimes.com

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