A penny illustrates the size of the deer tick. Photo by Graham Hickling, University of Tennessee.
Potentially debilitating Lyme disease doesn’t afflict people everywhere that the ticks harboring it are found. At least not yet. A five-university consortium led by a Michigan State University researcher wants to find out why.
“These ticks are on the move. As ticks expand into new areas, more people will likely become infected,” said MSU fisheries and wildlife assistant professor Jean Tsao, who will lead the four-year, $2.5 million study.
“We have a really intriguing scientific puzzle to solve – many factors change as we move from north to south, and we need to be smart with our study design to unravel these,” she said. “Our study also has practical goals – we aim to provide the health community and the public in the various states with some reassurance, or warning, about what their future will hold for spread of Lyme disease. Understanding the reasons why Lyme disease is such a problem in some areas will help us manage the disease better, and lower the risk to human health.”
In 30 years, the tiny blacklegged tick has cut a huge swath through 10 northern states by carrying a bacterial infection now annually afflicting more than 20,000 North Americans. Curiously, the same parasite commonly known as the deer tick also is found in southern states, where Lyme disease is comparatively rare.
“Researchers do not know how climate, vertebrate biodiversity, tick genetics or other factors affect the maintenance of the pathogen and its relative abundance in an area,” Tsao said. “So as the ticks spread, will tick populations in new areas be infected like northern populations or mainly clean of infection like southern populations?”
The disease has a range of symptoms including rash, fatigue, joint aches and shooting pain, and now is widespread in Minnesota and Wisconsin and along the northeastern seaboard. And although ticks also are found in the forests of the Upper Peninsula and eastern Lake Michigan shoreline, the disease has yet to make serious inroads in Michigan beyond Menominee County in the southwestern U.P.
That might not be the case for long, Tsao said, as infected ticks ride deer, mice, birds and other hosts into new areas. Her colleague Edward Walker’s lab discovered recently established populations of Lyme disease ticks in southwestern Michigan in the early 2000s, she noted, and during the last six years MSU doctoral student Sarah Hamer has tracked the invasion up the shore of Lake Michigan.
Tsao and colleagues are looking into potential new explanations for the uneven incidence of Lyme disease. The researchers plan to study how various ecological factors affect the Lyme disease cycle by simultaneously applying standardized survey methods at 12 sites spanning Massachusetts to Georgia and Minnesota to Mississippi.
Participating with MSU in the National Science Foundation-funded study are researchers from the University of Montreal, the University of Rhode Island, Hofstra University, the University of Tennessee and Georgia Southern University.