Tick-borne ‘American malaria’ cases rising at startling rate

HERSHEY, Pa. — Babesiosis, a potentially life-threatening tick-borne illness often dubbed “American malaria,” has been spreading at an alarming rate across the United States. Researchers from Penn State reveal that cases of this parasitic disease have surged by an average of 9% each year from 2015 to 2022.

This dramatic increase, likely fueled by climate change, is reshaping our understanding of tick-borne illnesses and their impact on public health. Even more jarring, the research published in the journal Open Forum Infectious Diseases uncovered that four out of every 10 babesiosis patients are unknowingly battling multiple tick-borne infections simultaneously.

Babesiosis is caused by microscopic parasites that infect red blood cells, transmitted primarily through the bite of infected black-legged ticks. Some refer to it as “American malaria” due to its similarity in symptoms and transmission. Cases can range from asymptomatic to life-threatening, particularly in older adults and those with weakened immune systems.

The recent rise is attributed in part to climate change, which is expanding the habitat of ticks and their animal hosts.

“Changing factors like temperature, humidity, rainfall and length of season have influenced the population and distribution of vectors like ticks as well as the population of animals that serve as reservoir hosts, like deer,” says lead author Paddy Ssentongo, an infectious disease fellow at the Penn State Health Milton S. Hershey Medical Center, in a statement.

Researchers analyzed data from 3,521 babesiosis patients using the TriNetX database, which contains clinical information from over 250 million individuals. They discovered that 42% of babesiosis patients were also infected with at least one other tick-borne disease, a rate higher than previously reported. The most common coinfection was Lyme disease, affecting 41% of babesiosis patients, followed by ehrlichiosis (3.7%) and anaplasmosis (0.3%).

Contrary to expectations, the study found that patients with coinfections did not experience more severe outcomes compared to those with babesiosis alone. In fact, the mortality risk was actually higher in the babesiosis-only group.

“Having both babesiosis and Lyme disease seemed not to be associated with worse mortality,” Ssentongo notes. “It’s speculated that the concurrent presence of other tick-borne infections in the blood could alter the immune response by possibly ‘boosting’ it to effectively fight infections.”

“These findings suggest that clinicians should have a heightened vigilance of co-infection of other tick-borne illness among patients admitted with babesiosis,” he adds.

This surprising finding may be related to differences in treatment approaches. The study revealed that patients with coinfections were more likely to receive doxycycline, an antibiotic commonly used to treat Lyme disease and other tick-borne bacterial infections. While not typically used for babesiosis alone, the researchers speculate that doxycycline might have some beneficial effects against the babesia parasites.

“For patients with babesiosis, we add on doxycycline as we’re investigating whether or not the patient has Lyme disease or other tick-borne diseases, and we’ve seen better outcomes at our medical center with this approach,” Ssentongo explains.

This observation raises intriguing questions about potential new treatment strategies for babesiosis.

The study also highlights the seasonal nature of babesiosis, with cases peaking during the summer months. Geographically, the majority of cases were reported in Northeastern states, consistent with the known endemic regions for the disease.

“If you live in areas where babesiosis is endemic, mostly states in the Northeast and the Midwest, take precautions, especially during the summer months. Practice tick-bite prevention practices,” Ssentongo suggests. “Wear long-sleeved shirts and pants and light-colored clothes. Use tick repellant and check for ticks after spending time outdoors.”

While the study provides some reassurance about the severity of coinfections, it also highlights the complex nature of tick-borne diseases and the need for continued research. As climate change continues to alter tick habitats and potentially increase human exposure to these pathogens, understanding the dynamics of diseases like babesiosis becomes increasingly crucial for public health.