Babesiosis is unusual among tick-borne illnesses in the Southeast because it is not caused by bacteria. It is a parasitic infection that targets red blood cells, much like malaria. Cases were once concentrated in the Northeast and Upper Midwest, but the CDC now reports confirmed cases across Florida, Alabama, Georgia, South Carolina, North Carolina, and Virginia. Most healthy adults recover well with treatment. The disease becomes more serious in patients who are older, immunocompromised, or have had their spleen removed.
What Babesiosis Is
Babesiosis is caused by parasites in the Babesia family, most commonly Babesia microti in the United States. The parasite enters the bloodstream through the bite of an infected blacklegged tick (Ixodes scapularis), the same tick that transmits Lyme disease and anaplasmosis. Once inside the body, Babesia invades red blood cells and reproduces inside them, eventually causing the cells to burst.
Less commonly, babesiosis can also be transmitted through blood transfusion, which is why it is now one of the few tick-borne pathogens routinely screened for in the U.S. blood supply.
Symptoms
Symptoms usually begin 1 to 4 weeks after a tick bite, though they can take longer to appear. Mild cases may pass for a bad flu. Common symptoms include:
- Fever, often with shaking chills and drenching sweats
- Severe fatigue
- Headache and muscle aches
- Loss of appetite, nausea
- Dark urine (a sign of red blood cell breakdown)
Severe cases can involve hemolytic anemia, jaundice, low blood pressure, kidney failure, and respiratory distress. Babesiosis is especially dangerous in:
- People without a spleen (asplenic patients)
- Patients on immunosuppressive medications
- Adults over 50
- People with chronic liver, kidney, or heart disease
How Babesiosis Is Diagnosed
The diagnostic approach depends on how acute the illness looks and what other tests are being ordered:
| Test | What it shows | Strength |
|---|---|---|
| Blood smear (Giemsa stain) | Babesia “ring forms” or Maltese cross patterns inside red blood cells | Fast, specific, available at most labs |
| PCR (blood) | Detects parasite DNA | High sensitivity, useful in early or low-parasite cases |
| IFA antibody test | Identifies past or recent exposure | Helpful when smear and PCR are negative |
| CBC + chemistry | Hemolytic anemia, low platelets, elevated bilirubin and liver enzymes | Supports the picture |
Because the blacklegged tick frequently carries multiple pathogens, your provider may also test for Lyme disease and anaplasmosis at the same time. Our Lyme disease workup routinely covers these co-infections.
Treatment
Mild to moderate babesiosis is treated with:
- Atovaquone plus azithromycin for 7 to 10 days
Severe cases are treated with:
- Clindamycin plus quinine, often given IV in the hospital
- Possible red blood cell exchange transfusion if parasite levels are very high
Symptom improvement is usually within a few days of starting treatment, but full recovery from fatigue can take weeks. Asplenic and immunocompromised patients may need longer courses and closer follow-up.
Why Co-Infections Matter
Roughly 10 to 40 percent of blacklegged ticks in some regions carry both Babesia and Borrelia burgdorferi (the Lyme bacterium). Patients infected with both tend to have more severe and longer-lasting symptoms. If you have been diagnosed with Lyme disease and your symptoms feel worse than expected (especially with shaking chills, drenching sweats, or unexplained anemia), ask your provider about testing for babesiosis. Our internal medicine team regularly evaluates patients for combined infections.
Prevention
The same precautions that reduce risk for Lyme disease and anaplasmosis apply here:
- Cover exposed skin in wooded or grassy areas
- Apply EPA-registered tick repellent and treat clothing with permethrin
- Check yourself, kids, and pets for ticks after outdoor activity
- Shower within 2 hours of coming inside
- Remove attached ticks quickly with fine-tipped tweezers
- Be especially cautious if you are immunocompromised or have no spleen
Frequently Asked Questions
How long after a tick bite does babesiosis show up?
Most cases appear 1 to 4 weeks after exposure, but the parasite can stay quiet for longer in some patients.
Is babesiosis fatal?
It can be in high-risk patients, particularly those without a spleen or with serious underlying illness. In healthy adults, mortality is very low when the disease is treated promptly.
Can babesiosis be transmitted person to person?
Not through casual contact. The only documented routes are tick bite, blood transfusion, and, rarely, mother-to-baby transmission.
How is babesiosis different from Lyme disease?
They are caused by completely different organisms (parasite vs bacterium) and require different treatments. They can be transmitted by the same tick at the same time, which is why co-infection is common.
Where can I get tested?
Contact our office to schedule an evaluation. We see patients in person in Northeast Florida and provide telemedicine across Florida, Alabama, Georgia, South Carolina, North Carolina, and Virginia.
This article is informational and not a substitute for medical advice. Babesiosis can be serious in high-risk patients; seek prompt care if you suspect it.