PRIMARILY CAUSED BY the protozoan parasite Babesia microti in the US, babesiosis is an infection that destroys red blood cells (RBCs).1 In the US, it is endemic to the Northeast and upper Midwest and typically transmitted by the deer tick, Ixodes scapularis.1-5 However, the transmitting species of babesiosis can vary globally. This bloodborne infection can also be transmitted by an infected donor via blood transfusion and, rarely, through organ transplantation or maternal-fetal transmission.6,7 This article discusses the clinical presentation, diagnosis, and transmission of babesiosis and offers prevention strategies for individuals spending time in deer tick habitats.
Signs and symptoms
After a tick bite, the incubation period for babesiosis ranges between 1 and 4 weeks. Transmissions via transfusion typically incubate over a period of 3 to 7 weeks, but this may range from 1 week to 6 months.1 For immunocompetent patients, the infection can last months to years and may remain undiagnosed.8
Most immunocompetent patients are asymptomatic or experience only mild, nonspecific signs and symptoms such as fever, malaise, chills, myalgia, and fatigue. Some patients experience nausea, emesis, night sweats, headache, dry cough, weight loss, anemia, and hematuria.2,9-11 Although most asymptomatic patients do not require treatment, symptomatic patients usually require antimicrobial treatment for 7 to 10 days with combination atovaquone and azithromycin or clindamycin and quinine.2
Babesiosis can be a severe and life-threatening infection for older adults and immunocompromised patients, such as those being treated for cancer or HIV infection and those who are asplenic.12 Patients may experience relapses for more than a year.8 Signs and symptoms may include fever and hemolytic anemia, leading to multiorgan failure, severe pancytopenia, disseminated intravascular coagulation, or splenic rupture.2,7,10,11 However, acute respiratory distress syndrome is the most common complication of the infection.1
In addition to antimicrobial medications, patients with severe babesiosis may require antipyretics, vasopressors, blood transfusions, exchange transfusions, mechanical ventilation, or dialysis to treat complications.2
Diagnosis and transmission
Babesiosis is diagnosed based on clinical presentation and patient history, such as a recent tick bite, blood transfusion, or trip to an endemic area.1,5Babesia can be detected inside RBCs via blood smear in the first 2 weeks of infection.10,11 Antibody testing can confirm the diagnosis.5 The polymerase chain reaction assay, immunofluorescence antibody test, and fluorescent in situ hybridization assay can each detect antibodies related to the infection.2,13,14
It may be necessary to run several tests, and negative results should not be used to rule out treatment.3 Currently available testing detects only two Babesia species, but there are over 100 species of Babesia throughout the world.3,14,15 The differential diagnosis may help to rule out similar, comorbid infections, such as Lyme disease, toxoplasmosis, and anaplasmosis.5
Although donors may be asked about existing infections during prescreening, blood blanks do not typically test donated blood for Babesia due to the unreliable testing.3,7 Blood products from asymptomatic donors may result in transmission and potentially fatal clinical illness in transfusion recipients.7 Approximately 11% of transfusion-related deaths are due to microbial infection, with up to 38% of these resulting from Babesia.3,13
There is no vaccine or prophylaxis for babesiosis. Infection is best prevented by avoiding contact with deer ticks, especially by those at increased risk such as immunocompromised individuals. Deer ticks are mainly found in wooded, brushy, or grassy areas in the northern, eastern, and midwestern US.
Simple protective steps may be taken to reduce the risk of exposure in tick-infested areas. Keep lawns mowed to avoid tick infestations. When hiking, walk toward the center of cleared trails and minimize contact with leaves, brush, and overgrown grass where ticks are likely to be found. Precautions during outdoor activities in known tick habitats, such as wearing a long-sleeved shirt and long pants with the legs tucked into socks, may keep ticks off of the skin. Light-colored clothing can make it easier to see and remove ticks before they are exposed to skin.16
Insect repellents may further reduce the risk of exposure. Follow the instructions on the product label, including details on how and where to apply it, how often to reapply it, and how to use it safely on children. Permethrin products may kill ticks that come into contact with treated clothing or footwear, but it should not be applied directly to the skin.16,17
After time spent outdoors, conduct a full-body exam and promptly remove any ticks that are found. Remember to check children and pets. Remove any ticks found on clothing before going indoors, and remove those attached to the skin as soon as possible.2 (See Proper tick removal and disposal.)
Remind patients about the risks of tick exposure and assess them for previous bites. With the exception of transfusions, organ transplants, or maternal-fetal transmissions, babesiosis is not transmitted person-to-person.6,7,18 In the cases of infection, teach patients and families to complete any prescribed antibiotic regimens as directed and educate them about potential risks and adverse reactions.2
Proper tick removal and disposal19
- As soon as possible, remove the tick using a pair of clean, fine-tipped tweezers.
- Grasp the tick as close to the skin's surface as possible and pull upward with steady, even pressure. Do not twist or make a jerking movement, as this can cause the mouthparts to break off and remain in the skin. These may also be removed with tweezers, but if you are unable to do so, leave it alone and let the skin heal.
- After removal, clean the bite area thoroughly with isopropyl alcohol and perform hand hygiene.
- Dispose of a live tick by putting it in alcohol, placing it in a sealed bag or container, wrapping it tightly in tape, or flushing it down the toilet. Never crush it with your fingers.
- Avoid folklore remedies such as using nail polish, petroleum jelly, or heat to make the tick detach from the skin. The goal is to remove the tick as quickly as possible rather than waiting for it to detach.
1. Krause PJ, Vannier EG. Babesiosis: clinical manifestations and diagnosis. UpToDate. 2019. www.uptodate.com
2. Centers for Disease Control and Prevention. Parasites—babesiosis. 2019. www.cdc.gov/parasites/babesiosis/index.html
3. Lymedisease.org. Lyme disease co-infection: babesiosis. 2018. www.lymedisease.org/lyme-basics/co-infections/Babesia
5. National Organization for Rare Disorders. Rare disease database: babesiosis. 2019. https://rarediseases.org/rare-diseases/babesiosis
6. Smith RP Jr, Elias SP, Borelli TJ, et al. Human babesiosis, Maine, USA, 1995-2011. Emerg Infect Dis
8. Parija SC, Kp D, Venugopal H, et al. Diagnosis and management of human babesiosis. Trop Parasitol
9. Peniche-Lara G, Balmaceda L, Perez-Osorio C, Munoz-Zanzi C. Human babesiosis, Yucatán state, Mexico, 2015. Emerg Infect Dis
10. Akel T, Mobarakai N. Hematologic manifestations of babesiosis. Ann Clin Microbiol Antimicrob
11. Leland DK. Touched by Lyme: a close look at six Lyme-related infections. Lymedisease.org. 2017. www.lymedisease.org/touchedbylyme-wayne-anderson
12. Columbia University Irving Medical Center: Lyme and Tick-Borne Diseases Research Center. Babesiosis. 2020. www.columbia-lyme.org/babesiosis
13. Marcum L. Lyme sci: Babesia
and the blood supply. Lymedisease.org. 2017. www.lymedisease.org/lyme-sci-Babesia-and-the-blood-supply
14. Scott JD. First record of locally acquired human babesiosis in Canada caused by Babesia duncani
: a case report. SAGE Open Med Case Rep
15. Healthline. Everything you should know about Babesia
. 2019. www.healthline.com/health/babesia
16. Centers for Disease Control and Prevention. Ticks: preventing tick bites. 2019. www.cdc.gov/ticks/avoid/on_people.html
17. Centers for Disease Control and Prevention. Parasites—babesiosis: prevention & control. 2019. www.cdc.gov/parasites/babesiosis/prevent.html
18. Centers for Disease Control and Prevention. Type and duration of precautions recommended for selected infections and conditions. 2018.
19. Centers for Disease Control and Prevention. Lyme disease. Tick removal and testing. 2019. www.cdc.gov/lyme/removal