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Ticks carry more than Lyme disease.
Here’s what you need to know about babesiosis and Powassan

A deer tick on a blade of grass.
You’ve heard of Lyme disease. Did you know that deer ticks like the one pictured here also carry malarial-like babesiosis and potentially deadly Powassan virus? Getty Images

Beware, the tiny deer ticks emerging with warmer spring weather carry a lot more than Lyme disease.

They also transmit a malarial-like potentially serious disease called babesiosis that has seen significant spread across the Northeast and Midwest, according to the U.S. Centers for Disease Control and Prevention.

For example, cases of babesiosis increased by 1,602% in Vermont and 1,422% in Maine from 2011 to 2019.

And that’s not all. Deer ticks increasingly carry the Powassan virus, which the CDC says resulted in 267 hospitalizations and 36 deaths from 2004 to 2022. In fact, it’s deadly in 10% of people with a severe form of the illness.

Headshot of Constantin Takacs.
“Deer ticks are coming out of the leaf litter. And they’re hungry,” says Constantin Takacs, an assistant professor of biology at Northeastern. Photo by Matthew Modoono/Northeastern University

With deer ticks emerging in their nymphal, nearly invisible stage — think the size of a poppy seed — a Northeastern University tick scientist says it’s more important than ever for people to understand all of the diseases carried by the arthropods and how to prevent them.

What is babesiosis

“The weather is warming. Deer ticks are coming out of the leaf litter. And they’re hungry” for a blood meal, says Constantin Takacs, an assistant professor of biology at Northeastern.

Many people are familiar with Lyme disease, which is transmitted by the bite of a deer tick carrying a type of bacteria called Borrelia burgdorferi and can cause a rash, flu-like symptoms and muscle aches and pains among other symptoms.

Fewer know about babesiosis, which a CDC study says has increased significantly throughout New England, with smaller increases observed in New Jersey and New York. Cases also surge in the Upper Midwest during the warm summer months.

Like Lyme, babesiosis is transmitted by the bite of the black-legged deer tick.

But unlike Lyme, babesiosis disease is caused by a parasite, Babesia microti, that infects red blood cells, says Takacs, whose lab at Northeastern studies Borrelia burgdorferi.

“It’s distantly related to the malaria parasite,” Takacs says.

Not everybody who contracts babesiosis has symptoms, but those that do occur include fevers, muscle aches and joint pain, headaches, chills and sweats

People who are elderly or have a weak immune system or do not have a spleen are most at risk of developing severe, possibly fatal, cases involving kidney failure, low platelet counts and acute respiratory distress syndrome, the CDC says.

While Lyme disease is treated with the antibiotic doxycycline, babesiosis treatment includes a combination of antimicrobial medications such as azithromycin and atovaquone.

What is Powassan?

Powassan virus, as its name says, is a virus, Takacs says.

A member of the flavivirus family, it is closely related to the mosquito-borne illnesses dengue, Zika virus, yellow fever and West Nile virus, Takacs says.

The CDC says cases are on the rise, but the numbers are small — 44 cases in 2023 — compared to Lyme disease, which is estimated to infect tens of thousands of people every year. Powassan cases were reported in 11 states, including the six New England states, New York, Pennsylvania, Maryland, Minnesota and Wisconsin.

Initial symptoms of Powassan can emerge one week to one month after a tick bite and include fever, headache, vomiting and weakness but more severe cases can lead to encephalitis and meningitis, the CDC says.

The federal health agency says about half of people who survive severe cases of Powassan have long-term health issues, including headaches and memory problems.

There is no cure. Treatment consists of rest and fluids, including IV fluids in more severe cases.

How can ticks carry so many types of pathogens?

Bacteria, parasites, viruses — how is it possible for one small tick to carry so many different pathogens?

“The main reason is because they feed on blood. It’s very easy for them to pick up anything that is blood borne” from a host animal, Takacs says.

“Then, if those microbes are able to survive in the tick until the next feeding, suddenly you have a transmission.”

Like mosquitoes, ticks pierce the surface of the skin to draw blood, he says.  

“All animals have evolved to protect their exterior. But we have less protection when the pathogen has gotten into the blood. Spreading through the blood is more efficient than spreading through solid tissue.”

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Preventing tick-borne diseases

The CDC says to be aware if you are traveling to areas where tick-borne diseases are endemic and wear long-sleeved shirts and long pants when possible.

The federal health agency has instructions on how to spray clothing with products containing 0.5% permethrin, an insecticide, and how to do a tick check.

Since ticks hang out in brushy, grassy and wooded areas, the CDC recommends sticking to the center of trails and showering soon after being outdoors.

If you fall sick, talk to your health care provider about ordering the appropriate tests to determine if it’s a tick-borne disease. 

There are blood tests for Lyme, babesiosis and Powassan, but health care professionals often order treatment based on their clinical judgment since it can take a while for results to show.