What is babesiosis? The potentially deadly disease is on the rise

You’ve heard of Lyme disease — now, infectious disease experts are warning of another serious tick-borne illness that’s on the rise: babesiosis.

“If you live in areas where babesiosis is endemic, mostly states in the Northeast and the Midwest, take precautions, especially during the summer months,” said lead study author Paddy Ssentongo, an infectious disease fellow at Penn State Health Milton S. Hershey Medical Center.

Ssentongo’s team found that rates of babesiosis, a potentially life-threatening disease sometimes referred to as “American malaria,” increased an average of 9% a year in the US between 2015 and 2022. Plus, four in 10 patients were found to be co-infected with Lyme disease or another tick-borne illness.

Ssentongo blames the babesiosis uptick on changes in the length of seasons, temperature, humidity and rainfall influencing the tick population.

His findings were published Tuesday in the journal Open Forum Infectious Diseases.

Here’s everything you need to know about babesiosis.

What is babesiosis?

Babesiosis is a disease caused by the Babesia parasite. It is primarily transmitted through the bite of a black-legged tick, also known as a deer tick. Like with malaria, the parasite infects red blood cells.

Transmission can also occur via blood transfusions, transplants and from mother to child.

The Penn State research team identified 3,521 people infected with babesiosis between October 2015 and December 2022. Most of the cases occurred in the summer in Northeastern states.

Forty-two percent of the babesiosis patients had at least one other tick-borne disease — a higher rate than in prior research.

Among those patients, 41% were co-infected with the bacterium responsible for Lyme disease while 3.7% showed signs of ehrlichiosis and 0.3% with anaplasmosis.

Babesiosis deaths are rare — in 2019, the US death rate was 0.57%. Five people died that year in New York, two in Massachusetts and one in Maryland.

Ssentongo said he was surprised that the risk of death was higher among the babesiosis-only group than the co-infection group.

“Having both babesiosis and Lyme disease seemed not to be associated with worse mortality,” he said. “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.”

Babesiosis symptoms

Some babesiosis patients may not have symptoms, according to the Centers for Disease Control and Prevention.

Others might develop flu-like symptoms a week after infection or several weeks later. Symptoms include:

• Fever
• Chills
• Sweats
• Headache
• Body aches
• Loss of appetite
• Nausea
• Fatigue

The disease can be deadly for older adults and those with a weakened immune system, liver or kidney disease and/or without a spleen.

Babesiosis treatment

A blood test can confirm the presence of the Babesia parasite.

The antibiotics azithromycin and atovaquone typically treat the illness. In severe cases, a process that exchanges abnormal red blood cells for healthy ones may be used.

“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 said, adding that more research into this method is needed.

How you can prevent babesiosis

“Practice tick-bite prevention practices. Wear long-sleeved shirts and pants and light-colored clothes,” Ssentongo advised. “Use tick repellant and check for ticks after spending time outdoors.”