The discovery was made in a residential backyard in Maine where researchers were collecting rabbit ticks and testing them for pathogens, according to a statement from the university.
The new bacteria, Rickettsia sp. ME2023, can cause spotted fever rickettsioses in humans, including Rocky Mountain spotted fever, which has a death rate of 20 to 30 percent if not treated promptly with the antibiotic doxycycline, the statement said.
When the ticks from Maine tested positive for a bacteria like the one that causes Rocky Mountain spotted fever, Guang Xu, a research professor of microbiology at UMass Amherst, conducted DNA testing that identified a distinct new strain, “unlike any other known strain,” but similar to one that caused severe cases of fever in California a few years ago, the statement said.
“We now know there is something different, something novel, than what was previously known,” Stephen Rich, a microbiologist at UMass Amherst, said in the statement.
Advertisement
Although rabbit ticks can be found throughout North and South America, they are uncommon in New England. Deer ticks, which are carriers of Lyme Disease, and dog ticks are the ones that most commonly bite people, researchers said.
“So, it was a mystery,” Xu said. “Why are there some cases of Rocky Mountain spotted fever in New England? This finding may solve part of the puzzle. Maybe the rabbit ticks are the vector.”
Advertisement
The discovery was made by scientists working on Project ITCH, an acronym for Is Tick Control Helping, which surveys residential properties across New England, to develop best practices for local trick control.
Researchers next plan to work with rabbit hunters in Massachusetts to collect more ticks and further their understanding of the potential impact on public health, Rich said.
Collaborating researchers at the University of Maine sent UMass Amherst more rabbit ticks to test.
The test results showed that out of 296 ticks collected from 38 towns in nine counties in Maine, 6.1 percent tested positive for the new Rickettsia genotype, according to the statement.
“This wasn’t a needle in a haystack,” said Rich, executive director of the New England Center of Excellence in Vector-borne Diseases at UMass Amherst. “It looks like lots of the rabbit ticks there have this pathogen.”
Though rabbit ticks don’t often feed on people, researchers are eager to figure out the risk and possibility of “spill over” into ticks that bite both rabbits and people.
“For example, a deer tick could feed on a rabbit and pick up this infection from the rabbit tick and potentially infect a person with that,” Rich said.
But some experts on tick-borne diseases and disorders caution that the rabbit tick research is still in the early stages.
While the findings are “interesting,” it is “premature to say that it has any public health significance,” said Sam Telford III, professor and director of the department of infectious disease and global health at Tufts University.
Epidemiological studies are needed to make that determination, Telford said in an email.
“There are many infectious agents that are maintained by ticks, but relatively few of them have been demonstrated to cause human disease,” Telford said. “This demonstration rests on actual case reports of human disease.”
Advertisement
Professor Thomas Mather, who heads the Tick Encounter Resource Center at the University of Rhode Island, said that since rabbit ticks rarely bite humans they probably don’t “represent much of a direct risk for humans.”
Out of more than 85,000 photos of ticks submitted to the University of Rhode Island’s tick survey, only two or three were this type of rabbit tick, Mather said.
“People rarely encounter them,” he said.
“But, it definitely could help the new strain circulate more widely in nature with an increasing risk for spillover” from ticks that do bite humans, Mather added.
Spotted-fever infections, typically spread by dog ticks, have climbed in the past two decades in the United States from 495 cases in 2002 to a peak of 6,248 in 2017, according to information from the Centers for Disease Control and Prevention.
More than half of the cases between 2018 and 2022 were from Alabama, Arkansas, Missouri, North Carolina, and Tennessee, according to the CDC.
Tonya Alanez can be reached at tonya.alanez@globe.com. Follow her @talanez.
