Science Shortfall: Why Don’t We Know How Best To Fight Ticks And Lyme Disease?

Part of our Losing to Lyme series

Beneath the midsummer Martha’s Vineyard sun, the gentle wind breathes waves of motion into a flag-sized swath of white fabric laid out on a large rock. Suddenly, an eye-catching bit of motion: a black, eight-legged speck on the move. Tick scientist Sam Telford pounces. He snatches it with his tweezers and tucks it into a small plastic vial with a satisfying pop.

There, the deer tick, endemic carrier of Lyme disease and other infections, lands in a comfy habitat of green leaves Telford has prepared for it. “I need these ticks to stay alive,” he says.

Martha's Vineyard tick project coordinator Dick Johnson, who was working with Sam Telford of Tufts, snatches a tick with his tweezers. (David Scales for WBUR)

Martha’s Vineyard tick project coordinator Dick Johnson, who was working with Sam Telford of Tufts, snatches a tick with his tweezers. (David Scales for WBUR)

Telford will gather dozens of them in the course of a Chilmark morning, as part of research that has brought him tick-hunting to Martha’s Vineyard so many times that he’s lost count. For 30 years, Telford, a professor and epidemiologist at Tufts University’s Cummings School of Veterinary Medicine, has been working to understand ticks and the diseases they spread to humans.

These years have brought some progress: We have widely accepted practices for personal tick-bite protection, from repellents to body checks. But the biggest and most important question remains unanswered: How do we stop the spread of Lyme?

“What have we done for Lyme disease?” Telford asks. “The incidence keeps increasing and increasing, the distribution keeps increasing and increasing.”

Good Science Is Hard To Do

Take, for example, deer control. One of Telford’s first projects, back in the 1980s, looked at what happened to tick numbers when the deer population on Great Island in south Cape Cod was reduced.

The $20,000-per-year study showed that cutting the number of deer worked to cut the number of ticks, which depend on sucking deer blood during their life cycle. But it lacked definitive proof that the drop in ticks also brought a drop in Lyme disease, because the modest funding did not cover a study big enough to draw a clear conclusion.

Deer studies like Telford’s illustrate a central problem with Lyme and tick-borne disease prevention: We don’t know the most effective recipe to reduce tick populations and prevent Lyme because the studies that would definitively answer questions like that have not been done. Should your town follow Telford’s advice and cull deer populations? Spray public spaces? Trim back trails? Do all of the above?

The problem is complex, too complex for a simple answer.

“For a very long time, people have been looking for that silver bullet or the magic answer to make Lyme disease go away,” says Catherine Brown, the state’s public health veterinarian. “We’ve known for a while now that’s just not going to happen.”

Put another way, trying to fight Lyme is like “trying to solve a multivariate equation with 18 variables and only knowing two of them,” says Henry Lind, the co-chair of the Barnstable County Lyme/Tick-Borne Diseases Task Force.

Ideally, when scientists do a study, they control all important factors, then change just one or two and observe the impact. But in an environment as complex as what surrounds tick-borne diseases, many factors affect the ecosystem.

We know deer, white-footed mouse and chipmunk populations are important in the tick life cycle. We know if they have a lot of food one year, they have more babies. We know ticks like warm, humid areas like leafy underbrush, and thrive in warm, wet summers but their numbers dwindle in drought.

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