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Tick invasion spreads across America: Can Lyme disease be far behind?

More than 20,000 North Americans are afflicted each year by Lyme disease, a bacterial infection that is carried by the blacklegged tick (also known as the deer tick). But although the ticks are spreading across the continent, Lyme disease is not a problem everywhere they are found. Scientists are hoping that if they can find out why,...

More than 20,000 North Americans are afflicted each year by Lyme disease, a bacterial infection that is carried by the blacklegged tick (also known as the deer tick).

But although the ticks are spreading across the continent, Lyme disease is not a problem everywhere they are found. Scientists are hoping that if they can find out why, they might be able to unravel the secrets of Lyme disease that would help people avoid infection.


A penny illustrates the size of the deer tick.

Photo by Graham Hickling, University of Tennessee.

“These ticks are on the move. As ticks expand into new areas, more people will likely become infected,” said Michigan State University fisheries and wildlife assistant professor Jean Tsao, who will lead the four-year study. (Tsao is in the picture below, courtesy MSU.)


“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, according to MSU. “Curiously, the same parasite commonly known as the deer tick also is found in southern states, where Lyme disease is comparatively rare,” the university said in a statement about Tsao’s project.

“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?”


Lyme disease risk map courtesy CDC

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, MSU added.

“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 Upper Peninsula.”

That might not be the case for long, Tsao said, as infected ticks ride deer, mice, birds and other hosts into new areas.


This image shows the stages and relative sizes of tick species encountered in North America. Only the blacklegged (deer) ticks are known to transmit Lyme disease.

Illustration courtesy CDC

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.


Lyme disease patients who are diagnosed early, and receive proper antibiotic treatment, usually recover rapidly and completely. A key component of early diagnosis is recognition of the characteristic Lyme disease rash called erythema migrans. This rash often manifests itself in a “bull’s-eye” appearance, and is observed in about 80 percent of Lyme disease patients.

Photo and caption courtesy CDC

Tsao and colleagues are looking into potential new explanations for the uneven incidence of Lyme disease, MSU said. “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.


Instructions on how to remove a tick courtesy New York State Department of Health

Get more information about Lyme disease:

Learn About Lyme Disease (Centers for Disease Control and Prevention)

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Author Photo David Max Braun
More than forty years in U.S., UK, and South African media gives David Max Braun global perspective and experience across multiple storytelling platforms. His coverage of science, nature, politics, and technology has been published/broadcast by the BBC, CNN, NPR, AP, UPI, National Geographic, TechWeb, De Telegraaf, Travel World, and Argus South African Newspapers. He has published two books and won several journalism awards. In his 22-year career at National Geographic he was VP and editor in chief of National Geographic Digital Media, and the founding editor of the National Geographic Society blog, hosting a global discussion on issues resonating with the Society's mission and initiatives. He also directed the Society side of the Fulbright-National Geographic Digital Storytelling Fellowship, awarded to Americans seeking the opportunity to spend nine months abroad, engaging local communities and sharing stories from the field with a global audience. A regular expert on National Geographic Expeditions, David also lectures on storytelling for impact. He has 120,000 followers on social media: Facebook  Twitter  LinkedIn