Tick with babesiosis crawling on person's skin

What is babesiosis?

Medically reviewed on May 24, 2023 by Jillian Foglesong Stabile, MD, FAAFP. To give you technically accurate, evidence-based information, content published on the Everlywell blog is reviewed by credentialed professionals with expertise in medical and bioscience fields.

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Tick bites can lead to numerous health problems and tickborne illnesses, such as Lyme disease, Southern tick-associated rash illness (STARI), Rocky Mountain spotted fever (RMSF), and tularemia. [1]

However, a tick bite can also cause what’s called babesiosis, which occurs when a tick infected by microscopic parasites bites a human, thus transferring the babesia parasite into the bloodstream. Consequently, the parasites infect red blood cells, which can lead to flu-like symptoms and hemolytic anemia, or the destruction of red blood cells. [2]

All that said, we’re exploring the ins-and-outs of a human babesiosis diagnosis and what you can do to prevent the disease.

Understanding babesiosis

What is babesiosis? It all starts with Babesia microti, an extremely small blood-borne parasite that’s transmitted by deer ticks. [3] The babesia parasite is primarily found in animals, like white-footed mice, but humans can contract them, too. [2]

In fact, these parasites can infect just about anybody. The CDC reports that the median age of patients infected with babesiosis is 62 years. However, babesiosis has been found in patients as young as one year and as old as 103. [6]

Of those patients, 44% were hospitalized for at least a day. [6]

That said, babesiosis can be particularly severe and potentially life-threatening in [2]:

  • Elderly folks
  • Individuals without a spleen
  • People with a weakened immune system as a result of immunocompromising conditions
  • Those with liver or kidney disease

There are many ways in which babesiosis is spread. Young ticks—called nymphs—are the primary carriers of Babesia microti. They thrive in the warmer months and often take shelter in the brush of grassy lands or wooded areas in the Northeast and upper Midwest regions of the United States. [5]

Similar to how Lyme disease is spread, when you traverse through these types of areas, a deer tick may attach itself to you, burying its head deep into your skin to feed on your blood. That’s because they’re innately parasitic, just like Babesia microti.

These ticks are usually the size of a poppy seed. And while a tick bite is typically painless, it can infect the host with bacteria, viruses, and protozoans like Babesia microti.4 Tick bites may also cause [4]:

  • Swelling
  • Itchiness
  • Skin rashes

Like Lyme disease symptoms, tick bites with Babesia microti present can cause more severe symptoms, such as [2]:

  • Fever
  • Chills
  • Headaches
  • Body aches
  • Loss of appetite
  • Nausea
  • Fatigue

Symptoms will typically begin to show within a week of obtaining a tick bite. [2] However, some people infected with Babesia microti will show no symptoms. [5]

Babesiosis may also spread via blood transfusion or from a mother to her baby during pregnancy or delivery. [6]

Fortunately, the disease is both treatable and preventable. [5]

How to diagnose babesiosis

Those showing symptoms of babesiosis can visit their healthcare provider to address their concerns. Typically, a healthcare provider will examine a blood sample under a microscope to identify whether Babesia microti are present. [2]

Some medical facilities may share your blood sample with the CDC or health department to confirm the diagnosis. However, it’s not required to share your results with the CDC or a health department unless you live in a state that requires reporting. These states include:

  • Connecticut
  • Massachusetts
  • Minnesota
  • New Hampshire
  • New Jersey
  • New York
  • Rhode Island
  • Vermont
  • Wisconsin

That said, if you’re diagnosed with babesiosis, there’s a high chance that you may have contracted other tick-borne illnesses, such as Lyme disease or anaplasmosis, so your healthcare provider may test for those conditions as well. [2]

How to treat babesiosis

Once diagnosed, your healthcare provider can prescribe a combination of medications to remove the parasites from your body if they believe you’re at risk for severe symptoms. Your treatment plan may include antiprotozoals, antibiotics and antimalarial drugs, such as [7]:

  • Atovaquone
  • Azithromycin
  • Clindamycin
  • Quinine

Following treatment, symptoms will typically decrease after two days, and the parasites will be eradicated within two weeks. In some cases, babesiosis may resolve on its own if you have a strong immune system. [7]

If your babesiosis diagnosis has led to hemolytic anemia, your healthcare provider may choose to further manage the disease with a blood transfusion to replenish your red blood cell supply. Those with kidney disease may also need to undergo dialysis. [7]

How to prevent babesiosis

Babesiosis is largely preventable, even if you live in a hot zone. During spring and summer, make sure to only trek on cleared trails and avoid areas that may be infested with deer ticks, such as:

  • Moist, shaded areas
  • Tall grass
  • Bushes
  • Leaf litter

And stay away from small mammals, if possible. Deer and rodents are primary carriers of the Babesia microti parasite. You can also [7]:

  • Wear long sleeves and long pants
  • Use insect or tick repellent
  • Check yourself for ticks, and remove any ticks you find immediately by using tweezers to grasp the tick and pull upwards

Tick off possible diagnoses with Everlywell

Babesiosis occurs when microscopic parasites enter your bloodstream as a result of a tick bite. While some people are asymptomatic, others may experience flu-like symptoms and hemolytic anemia, which can be life-threatening to those who are immunocompromised.

Another tick-borne infection is Lyme disease. Everlywell offers an at-home Lyme Disease Test that checks for antibodies associated with Lyme disease bacteria.

With Everlywell, your blood sample is reviewed by a Clinical Laboratory Improvement Amendments (CLIA)-certified lab and board-certified physicians so that you can receive accurate, actionable data as soon as possible. Take control of your health and ensure your overall wellness with Everlywell.

Who's at risk of Lyme disease?

Lyme Disease Symptoms – What Are the Signs of Lyme Disease?

What Are the Long-Term Effects of Lyme Disease?


  1. Symptoms of tickborne illness. CDC. https://www.cdc.gov/ticks/symptoms.html. Published August 5, 2021. Accessed April 6, 2023.
  2. Babesiosis FAQs. CDC. https://www.cdc.gov/parasites/babesiosis/gen_info/faqs.html. Published May 19, 2020. Accessed April 6, 2023.
  3. Babesiosis. New York State Department of Health. https://www.health.ny.gov/diseases/communicable/babesiosis/fact_sheet.htm. Published July 2017. Accessed, April 6, 2023.
  4. Tick bites. Cleveland Clinic. https://my.clevelandclinic.org/health/articles/7234-tick-bites. Published February 27, 2022. Accessed April 6, 2023.
  5. Parasites - Babesiosis. CDC. https://www.cdc.gov/parasites/babesiosis/index.html. Published March 31, 2020. Accessed April 6, 2023.
  6. Data & Statistics. CDC. https://www.cdc.gov/parasites/babesiosis/data-statistics.html. Published October 9, 2014. Accessed April 6, 2023.
  7. Babesiosis. Cleveland Clinic. https://my.clevelandclinic.org/health/diseases/24809-babesiosis. Published March 7, 2023. Accessed April 6, 2023.
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