Babesiosis is an emerging tickborne disease increasing rapidly in the northeastern U.S., with cases also appearing in the Southeast and Florida. The number of people infected with babesiosis in the U.S. rose by 25% from 2011 to 2019, according to a recent Centers for Disease Control and Prevention report.
The disease is caused by Babesia parasites, which can enter the bloodstream of humans and other mammals through the bite of the blacklegged tick, Ixodes scapularis, a species that lives throughout the East, including Florida.
The rise in babesiosis cases is likely due to an increase in ticks and their hosts and the encroachment of residential areas into tick habitats, said veterinary parasitologist Jeff Gruntmeir, a postdoctoral fellow at the University of Florida College of Veterinary Medicine and an associate of the UF Emerging Pathogens Institute.
As part of Gruntmeir’s work with the CDC’s Southeastern Center of Excellence in Vector-Borne Diseases, he analyzes ticks for disease-causing agents, a critical step in the fight to identify, track and treat emerging public health threats. While much of his research focuses on more common tickborne diseases in the South, such as ehrlichiosis and rickettsia, Gruntmeir said babesiosis is also in his sights.
“There are human cases here in Florida and scattered across the Southeast, but there’s very little actual surveillance for Babesia species in ticks,” Gruntmeir said. “There are probably many babesiosis cases that we don’t know about. Surveillance of our ticks can help us uncover unknown risks that are circulating in our environment.”
Gruntmeir is also a member of the Dinglasan Laboratory, led by Rhoel Dinglasan, Ph.D., M.P.H. Dinglasan is a professor in the department of infectious disease and immunology in the UF College of Veterinary Medicine, directs the Southeastern Center of Excellence in Vector-Borne Disease, and is a member of the UF EPI.
Surveillance involves collecting ticks in their natural habitat and sampling their DNA to determine which pathogens they carry. These samples are stored so they can be re-examined in the future.
Babesiosis on the move
In the Northeast, the blacklegged tick primarily feeds on white-footed mice, which serve as the reservoir for Babesia parasites. These mice also harbor the organism that causes Lyme disease, another pathogen transmitted by blacklegged ticks. Neither Lyme-causing bacteria nor the strain of Babesia parasite that commonly causes disease in humans have been found in Florida ticks or wildlife. Florida cotton rats, however, carry a similar Babesia strain, Gruntmeir said.
Florida’s human cases of babesiosis are likely due to the movement of people and animals from areas where the disease is more common, though local transmission cannot be ruled out, Gruntmeir said. The Florida Department of Health reported 51 cases of babesiosis in Florida from 2019-2021.
Scientists have identified more than 100 species of Babesia parasites, several of which can cause disease in humans. There are likely other species of disease-causing Babesia parasites that haven’t yet been identified, Gruntmeir said. Most discoveries of new tickborne pathogens have occurred in the last 20 years due to improved detection methods.
While babesiosis cases tend to be concentrated in the upper Midwest and the Northeast, particularly New England, the disease is moving southward along the Appalachian Mountain range, Gruntmeir said.
Managing risk for people and pets
Most people who are infected with Babesia parasites do not have symptoms. For those who do, common symptoms of babesiosis include fever, chills, sweats, headache, body aches, loss of appetite, nausea and fatigue. Babesia parasites infect red blood cells, potentially leading to anemia, jaundice and dark urine. The disease can be fatal, particularly among people with compromised immune systems or those who lack a spleen. Babesia can also be transmitted via a contaminated blood transfusion and from an infected mother to her baby during pregnancy or delivery. Treatment is available for those who need it.
Humans aren’t the only ones vulnerable to babesiosis. Other species of Babesia parasites can infect dogs, cats, cattle and horses. Ticks can also gain entry to homes via pets, detach and then bite people.
“The best thing that owners can do for their pets and livestock is protect against biting arthropods such as fleas, ticks and mosquitoes,” Gruntmeir said. “The more quickly a blood-feeding insect or arthropod is killed, the less likely it is to transmit infection. Those first 24 hours are really critical.”
Why tickborne diseases may be on the rise
Several factors could be contributing to the increase in babesiosis and other tickborne diseases, Gruntmeir said. As residential developments expand into areas that were previously fields and forests, they encroach on habitat for ticks and their hosts, increasing the risk of tick bites. Remnants of this habitat around water and other drainage areas near neighborhoods can be ideal environments for tick hosts, such as deer, raccoons, squirrels, opossums, rodents, coyotes and bobcats.
“Particularly in Florida, those are areas where ticks can flourish amongst us and then be deposited throughout our environment,” Gruntmeir said. “Ticks can reside in places we don’t even think about, such as piles of sticks or overgrown yards and flowerbeds around our house.”
Climate change is also extending the season for ticks, which become more active as temperatures increase.
Training the next generation of disease researchers
In addition to studying parasites, Gruntmeir also works with the center of excellence led by Dinglasan to train the next generation of tickborne disease researchers. The center offers online tick training modules to researchers and students, as well as Tick University, which is an intensive course that teaches students, public health officials and vector control professionals how to identify ticks, collect them in the field and screen them for pathogens. Course participants then deploy what they’ve learned at universities and state departments of health across the Southeast.
“As we gain more DNA samples and manpower, we’re constantly increasing the amount and breadth of research we’re doing to address tickborne diseases,” Gruntmeir said. “We’re also starting to touch on how to apply tick control methods in the Southeast, using the baseline data that we have through our surveillance and pathogen screening efforts.”
Tick bite prevention tips
The CDC offers guidance on how to prevent tick bites.
Written by: Natalie van Hoose