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PHOTO: White-footed mice have been found to be a major contributor to the spread of Lyme Disease through ticks a study in the Midcoast found.
PORTLAND — Tracking the types of ticks that plague Maine helps scientists predict which tick-borne pathogens might become a problem. New research shows that blacklegged ticks have been increasing in abundance in a Midcoast forest over the past 30 years — and bringing more Lyme disease with it.
Blacklegged ticks infected with a certain bacteria are the primary vector for Lyme disease, a bacterial infection that can cause joint, heart and nervous system damage.
Researchers from the University of Maine and the Maine Medical Center Research Institute’s Lyme & Vector-Borne Disease Laboratory collected and tested ticks from small mammals in the Holt Research Forest in Arrowsic over the course of three decades. Jack Witham, a recently retired associate scientist with UMaine’s Center for Research on Sustainable Forests, collected more than 3,000 ticks from more than 10,000 animals for the study.
When tick surveillance began in 1989, researchers found only vole ticks, squirrel ticks and dog ticks feeding on mice, voles, squirrels, chipmunks and shrews. The first blacklegged tick was found on a red squirrel in 1996 and the first detection of the Lyme bacteria in 2001. By 2007, the blacklegged tick population was established, with all life stages of a breeding population present: eggs, larvae, nymphs and adults.
Researchers are concerned that this pattern will repeat for additional vector tick species that are expanding north toward Maine.
“This study reinforces other studies that illustrate patterns of emergence and establishment of ticks and tick-borne pathogens. It also reminds us that public health is tied to how we manage our natural environment,” said Susan Elias, first author and staff scientist at the Maine Medical Center Research Institute’s Vector-borne Disease Lab, who conducted the research as part of her Ph.D. work at UMaine.
The researchers suggested that the emergence of blacklegged ticks in the Holt Research Forest could be linked in part to climate change and an increase in the local population of white-tailed deer, the primary blood meal host for adult ticks (though deer are not reservoirs for the bacteria that causes Lyme disease).
Meanwhile, one small mammal in the study rose above the rest when it came to carrying blacklegged ticks. White-footed mice represented the majority of all the study’s captures, hosting 94% of all the blacklegged ticks found; 15% of all white-footed mice had blacklegged ticks on them.
What’s more, the population of white-tailed deer and white-footed mice overlap in Maine. White-footed mouse populations, too, have been found to be expanding northward.
“Continued surveillance at the Holt Research Forest would be helpful, especially since we anticipate the emergence of the lone star tick in Maine,” Elias said.
The study was published in the Journal of Medical Entomology in December.
