What if one way to reduce people’s risk of tick-borne disease began not with the tick, but with the deer it depends on?
Michigan State University researchers are building on years of wildlife disease research to explore how free-ranging white-tailed deer could safely receive an oral treatment capable of killing ticks or reducing their ability to reproduce, potentially disrupting a critical part of the tick life cycle.
The concept is somewhat like the flea-and-tick medications people give their dogs and cats. But safely and effectively delivering an oral treatment
to wild deer across landscapes shared by wildlife and people is far more complicated.
It’s a challenge MSU researchers Jean Tsao and Henry “Rique” Campa III have already spent years working to solve.
“Our goal is to find ways to protect people from tick-borne disease while also sustaining healthy wildlife and the ecosystems we all depend on,” said Tsao, a professor in the Department of Fisheries and Wildlife in the College of Agriculture and Natural Resources with an appointment in MSU’s College of Veterinary Medicine. “This work gives us an opportunity to explore how we can reduce tick populations by targeting a wildlife host that is critical to the tick life cycle.”
Why deer matter
Blacklegged ticks, which can transmit the bacterium that causes Lyme disease and several other diseases, depend on different wildlife hosts throughout their life cycle. Juvenile ticks often feed on small mammals such as mice, while adult blacklegged ticks commonly feed on white-tailed deer.
Deer do not give blacklegged ticks the bacterium that causes Lyme disease, but they play an important role in sustaining tick populations. After feeding on deer, adult female ticks drop off and can lay hundreds and even thousands of eggs.
Interrupting that process could help reduce future generations of ticks.
“One possibility is an oral treatment that would work like the flea-and-tick medications people give their dogs and cats,” Tsao said. “The idea is to determine whether treating deer can block enough ticks from reproducing and thereby significantly reduce the tick population.”
For MSU, the idea builds on earlier research that will complement the goals of newly announced federal funding.
Campa and collaborators from MSU and state and federal agencies previously developed and evaluated methods for orally delivering a vaccine against bovine tuberculosis to wild white-tailed deer in Michigan’s northeastern Lower Peninsula.
More recently, Tsao, Campa, post-doctoral scientist Matthew Buchholz and their collaborators have been applying that expertise to another challenge: developing a reliable way to deliver medication to deer in suburban landscapes, where people may encounter blacklegged ticks close to home.
The researchers have tested specially designed food-based delivery units that deer will eat, then used biomarkers to determine whether deer consumed them while they also monitored deer with trail cameras. The work examines not only whether treatment can reach deer, but how it could be distributed without creating unintended risks for deer or other wildlife.
“We’re not starting from scratch,” Campa said. “We’ve already worked with partners across Michigan to develop and test a system for delivering an oral bovine tuberculosis vaccine to wild white-tailed deer. Now, we can build on those relationships and that experience to ask whether a similar approach could eventually be used to reduce ticks and the diseases they spread.”
Building the next phase
New federal funding announced by the U.S. Department of Health and Human Services will allow the MSU team to plan the next phase of the research.
MSU is a partner in the Midwest Center of Excellence for Vector-Borne Disease, which is headquartered at the University of Wisconsin–Madison, and will conduct the center’s deer-targeted research under a new federal initiative studying wildlife-based approaches to tick control.
The immediate goal is not to begin distributing tick medication to deer. Instead, the funding will support development of a feasibility study to determine what would be required to safely test the approach in Michigan.
That includes identifying ecological and regulatory questions, understanding public awareness and attitudes, determining what additional partnerships are needed and developing a research plan that could eventually be tested under real-world conditions.
“To conduct this kind of research responsibly requires much more than developing a treatment,” Campa said. “Wildlife managers, public health experts, regulatory agencies, researchers and the communities where the work could take place all have important roles. That collaboration has been critical to our previous work with deer, and it will be just as important here.”
The researchers hope the resulting framework could eventually help other scientists and wildlife managers adapt similar approaches elsewhere.
A broader approach to vector-borne disease
The deer research is part of nearly a decade of MSU involvement with the Midwest Center of Excellence for Vector-Borne Disease, which brings together researchers and public health partners to develop and evaluate ways to prevent diseases transmitted by ticks and mosquitoes.
At MSU, that work also includes University Distinguished Professor Edward Walker of the Department of Entomology, who has studied insecticide-treated resting boxes designed to reduce populations of mosquitoes that can transmit eastern equine encephalitis, or EEE.
MSU researchers also work with state and local public health agencies, help train health departments in vector surveillance, support mosquito-control programs and provide research opportunities for students and early-career scientists.
Together, the work reflects a One Health approach that recognizes the connections among human, animal and environmental health.
More than half a million Americans are diagnosed with tick-borne diseases each year, according to the U.S. Department of Health and Human Services, and ticks continue to expand into new geographic areas.
Personal precautions such as using repellents, wearing protective clothing and checking for ticks remain important. But researchers also are looking for ways to reduce the number of ticks people encounter in the first place.
“If we can find a safe, practical way to target ticks through the wildlife hosts they depend on, we may be able to intervene much earlier in the cycle,” Tsao said. “The long-term goal is straightforward: fewer ticks, fewer opportunities for people and pets to encounter them and less risk of tick-borne disease.”
