Study Aims to Better Understand How Ticks Transmit Diseases

Dec 7, 2018

Credit https://uwm.edu/field-station/deer-ticks-revisited/

Researchers at UMass Amherst are conducting a multi-year, multi-site study on tick biology and behavior. This year, Barnstable County joined  the study, providing samples from deer that hunters brought to check-in stations on the Upper and Outer Cape. 

County entomologist Larry Dapsis took deer blood and tick samples to send out to the Western Mass lab. WCAI's Kathryn Eident talked with him about what he learned in the process, and about what researchers are hoping to do with the data.

Eident: You've been seeing some deer with fewer ticks on them than you might have expected, but then again some deer coming in from certain areas seem to be just crawling with ticks. What does that say to you when you see that disparity?

Dapsis: Well, it it's my first year doing this, so my expectation was that we were going to get all our samples in the first day because I expected all the deer to be loaded with ticks. And that just wasn't the case. Hunters remarked to me that this year they're seeing fewer ticks on themselves versus the previous year or so. So, it suggests that the tick numbers might be down, but the fact that you see some deer that are loaded with these things just verifies one of the things we know: Ticks aren't uniformly distributed. They appear in patches. But, they're seeing similar things in Plymouth County, and Central Mass, and in the western part of the state that's also participating in this study.

Eident: Do you think that weather this summer and fall had anything to do with maybe slightly lower numbers of ticks around? We had a hot dry summer and a rather wet fall. Do you think that plays any role?

Dapsis: I believe it could. We had the hot dry weather when the nymphs were active. They're certainly subject to desiccation, so it could have had a material impact on them. The fall wet rainy weather--we know that there is a parasitic fungus that exists in the soil and it could have created conditions to have that fungus more active than it usually is. And, it could be a combination of two. And, it also could be a function of the structure of the animal host community.

So, did we have fewer mice in certain areas? Fewer chipmunks? So, there is probably three or four different things that we could point to. So, we're never going to sort it out. These are the things that happen it's a very dynamic ecosystem.

So, does it suggest that because we're seeing fewer ticks this year that that sets the stage for future events? Not remotely. This next year could be a rebound year for the tick population for a variety of reasons. So, we've seen historically tick populations go up and down but they they never go away.

Eident: Righ,t they are here to stay. And then just back to the deer check-in stations how many deer have you checked so far and how many do you think you will check?

Dapsis: I'm done sampling. We were targeting a total of 20 for each location. I've got 16. So Steve Rich at UMass thinks that that's sufficient.

We took blood samples. It seems to be pretty well-known that bacteria that causes Lyme disease does not survive in the blood of deer. So this will allow us to really get numbers that, OK, do you not find this pathogen in deer blood? And if you don't ,what are the factors in deer blood that prevent them to build up this bacteria and harbor it. And then it's an open question for the other pathogens that these deer ticks can transmit.

The engorged female ticks that we removed, they're going to replenish the colony out at UMass Amherst. So, what they'll do is allow those female ticks to lay their eggs, and then they'll rear themm under controlled conditions. And, by and large, tick larvae are known to be disease-free. There's some evidence though, that the pathogen that causes relapsing fever can be passed from mother to offspring. So again, this will give us numbers to kind of verify. So, it's a good overall comprehensive study.

Eident: Larry Dapsis, county entomologist, thanks so much for talking with us. And we'll be checking in with you soon.

Dapsis: Thanks again Kathryn.

*This transcript was lightly edited for grammar and clarity.