Babesiosis
A tick-borne parasite infection of the red blood cells
Quick Facts
- Type: Tick-borne parasitic infection
- Spread by: Blacklegged (deer) ticks
- Key signs: Fever, chills, fatigue, sweats, anemia
- Higher risk: Older adults, no spleen, weak immunity
Overview
Babesiosis is an infection caused by microscopic parasites of the Babesia family that infect and destroy red blood cells. People usually become infected through the bite of an infected blacklegged (deer) tick, the same tick that spreads Lyme disease and anaplasmosis. Because the parasite attacks red blood cells in a way similar to malaria, the illness can resemble malaria, even though the two are caused by different organisms.
Many healthy people with babesiosis have only mild symptoms or none at all. However, the infection can be serious or even life-threatening in older adults, people without a functioning spleen, and those with weakened immune systems. It occurs mainly in the northeastern and upper midwestern United States, especially during warm months when ticks are active.
Symptoms
Symptoms usually appear from one to several weeks after a tick bite and can range from very mild to severe:
- Fever and chills
- Sweats, often drenching
- Fatigue and weakness
- Headache and body aches
- Loss of appetite and nausea
- In some cases, anemia from the breakdown of red blood cells, which can cause pale skin, dark urine, and yellowing of the skin or eyes (jaundice)
Serious cases can lead to very low red blood cell counts, low blood pressure, breathing difficulty, and organ problems. People without a spleen or with weak immune systems are most at risk for severe disease and should seek care promptly.
Causes
Babesiosis is caused by Babesia parasites. The main ways people become infected are:
- Tick bite: The most common route is the bite of an infected blacklegged tick. The tick usually needs to be attached for a period of time to transmit the parasite.
- Blood transfusion: Babesiosis can be transmitted through transfused blood from an infected donor, since the parasite lives in red blood cells.
- From mother to baby: Rarely, the infection can pass from a pregnant person to the baby.
It is not spread from person to person through everyday contact.
Risk Factors
- Spending time in wooded, brushy, or grassy areas where ticks live
- Living in or visiting regions where infected ticks are common
- Being over age 50 or having other health conditions
- Not having a spleen or having a poorly functioning spleen
- A weakened immune system from illness or medication
- Receiving a blood transfusion (a rare route of infection)
Diagnosis
Diagnosis is based on symptoms, possible tick exposure, and laboratory testing:
- Blood smear: Examining blood under a microscope can reveal the parasites inside red blood cells.
- Specialized blood tests: Tests that detect the parasite's genetic material or antibodies confirm the diagnosis.
- Supporting blood tests: Blood counts may show anemia and other changes from red blood cell breakdown.
Because the same ticks can carry other infections, a doctor may also test for Lyme disease and anaplasmosis when babesiosis is suspected.
Treatment
Treatment depends on how severe the illness is and the person's overall health:
- Antimicrobial medications: A combination of antiparasitic and antibiotic medicines is used to clear the parasite. The choice and length of treatment depend on severity.
- No treatment for symptom-free cases: Healthy people without symptoms may not need treatment, but this decision is made by a doctor.
- Hospital care: Severe cases may require hospitalization, and in life-threatening illness an exchange transfusion may be used to rapidly reduce the number of infected red blood cells.
- Supportive care: Fluids and treatment of anemia and other complications as needed.
People with weakened immune systems may need longer courses of treatment to fully clear the infection.
Prevention
Preventing tick bites is the key to avoiding babesiosis:
- Use EPA-registered insect repellent and treat clothing with permethrin
- Wear long sleeves and pants in tick habitats and tuck pants into socks
- Stay on cleared trails and avoid tall grass and brush
- Check yourself, children, and pets for ticks after being outdoors
- Remove attached ticks promptly with fine-tipped tweezers
- Shower soon after coming indoors
When to See a Doctor
See a doctor if you develop fever, chills, fatigue, or drenching sweats after possible tick exposure, even without a remembered bite. Seek prompt or emergency care if you have:
- High fever with severe weakness
- Dark urine, pale skin, or yellowing of the skin or eyes
- Shortness of breath, dizziness, or fainting
- Any serious symptoms if you lack a spleen or have a weakened immune system
People at higher risk for severe disease should be evaluated quickly, since babesiosis can progress rapidly in these groups.
Frequently Asked Questions
How do people get babesiosis?
Most people get it from the bite of an infected blacklegged (deer) tick. It can also rarely spread through a blood transfusion or from a pregnant person to the baby, but it is not passed by everyday person-to-person contact.
Is babesiosis like malaria?
It is similar in that both involve parasites that invade and destroy red blood cells and can cause fever and anemia. However, they are caused by different organisms and are spread differently, with babesiosis transmitted by ticks rather than mosquitoes.
Who is at risk for severe babesiosis?
Older adults, people without a working spleen, and those with weakened immune systems are most at risk for serious illness. These groups should seek medical care promptly if they develop symptoms after possible tick exposure.
How is babesiosis treated?
It is treated with a combination of antiparasitic and antibiotic medications. Mild cases in healthy people may need little treatment, while severe cases can require hospitalization and, rarely, an exchange transfusion.
Can babesiosis be prevented?
Yes, largely by preventing tick bites. Use insect repellent, wear protective clothing in tick areas, check for ticks after being outdoors, and remove attached ticks promptly with fine-tipped tweezers.
References
- Centers for Disease Control and Prevention (CDC). Babesiosis.
- MedlinePlus, U.S. National Library of Medicine. Babesiosis.
- National Institute of Allergy and Infectious Diseases (NIAID). Tickborne diseases.
- Mayo Clinic. Tick-borne diseases.