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PubMed This is a summary of 17 peer-reviewed journal articles Updated
Infectious Disease

High-Risk Populations and Complications

At a Glance

Babesiosis can be severe and prolonged in high-risk groups like the elderly, immunocompromised, or those without a spleen. These patients typically require at least 6 weeks of targeted medication and close monitoring for serious complications like ARDS, spleen damage, and relapsing infection.

For most healthy people, Babesiosis is a temporary illness that clears up with standard treatment. However, for certain “high-risk” groups, the infection can behave differently, lasting much longer and requiring a more intensive medical approach [1][2]. If you fall into one of these categories, understanding why your body needs extra support is the first step in managing your recovery.

Why Some Populations are at Higher Risk

Three main groups are particularly vulnerable to severe or persistent Babesiosis:

  • Those Without a Spleen (Asplenia): The spleen is your body’s “filter.” Its job is to catch and remove damaged or infected red blood cells [3]. Without a spleen, the parasite can multiply much faster because there is no mechanical filter to remove the infected cells [4][5].
  • The Immunocompromised: This includes people with cancer (especially B-cell lymphoma), those who have received organ transplants, or anyone taking medications that suppress the immune system, such as Rituximab [6][1]. These patients may struggle to create the antibodies needed to kill the parasite.
  • The Elderly: People over the age of 50 often experience “immunosenescence,” a natural weakening of the immune response that makes it harder for the body to control the parasite [1][7].

Specialized Treatment Guidelines

Because the risk of the infection returning (relapsing) is high in these groups, the treatment “rule book” changes [6].

  • Duration: Instead of the standard 7-10 days, high-risk patients often need treatment for at least 6 weeks [6][8].
  • The “Two-Week Rule”: Doctors typically continue the medication for at least 2 weeks after the parasite is no longer visible on your blood smears [6][9].
  • Salvage Therapy: If the standard drugs (Atovaquone and Azithromycin) aren’t working, doctors may use “salvage” regimens. This might include Atovaquone-proguanil or a newer medication called Tafenoquine [9][6].

Potential Serious Complications

Vulnerable patients must be monitored closely for several rare but serious complications. If you experience new or worsening symptoms, it is important to communicate them to your doctor immediately.

  1. ARDS (Acute Respiratory Distress Syndrome): This is a rare but severe lung condition. Interestingly, it can sometimes be triggered after you start treatment because your body mounts a strong inflammatory response to the dying parasites [10][11]. Warning Sign: Sudden, severe shortness of breath or an inability to catch your breath. If this occurs, seek emergency medical care immediately.
  2. Splenic Complications: In patients who still have a spleen, the organ can become overtaxed. This can lead to a splenic infarction (tissue death) or, in very rare cases, a spontaneous rupture [12][13]. Warning Sign: Severe, sudden abdominal or side pain.
  3. HLH (Hemophagocytic Lymphohistiocytosis): An “immune storm” where the body’s defense system begins to attack its own healthy cells [14][15].
  4. Relapsing Disease: The infection may seem to go away only to return weeks or months later. This is common in patients on B-cell depleting therapies [6][16].

If you are in a high-risk group, your medical team will likely involve an infectious disease specialist and potentially a hematologist to monitor your blood counts and ensure the parasite is completely eradicated [2][17].

Common questions in this guide

Why is babesiosis more dangerous if I do not have a spleen?
The spleen acts as your body's filter to catch and remove infected red blood cells. Without it, the babesia parasite can multiply much faster because the mechanical filter used to clear it is missing.
How long is babesiosis treatment for high-risk patients?
Instead of the standard 7 to 10 days, high-risk patients typically need treatment for at least 6 weeks. Doctors usually continue the medication for at least two weeks after the parasites are no longer visible on your blood smears.
What are the warning signs of splenic complications with babesiosis?
A major warning sign of spleen complications, such as tissue death or rupture, is severe and sudden abdominal or side pain. If you experience this symptom, you should seek emergency medical care immediately.
Why might I experience breathing problems after starting babesiosis treatment?
Acute Respiratory Distress Syndrome (ARDS) is a severe lung condition that can sometimes trigger after starting treatment. This happens because your body mounts a strong inflammatory response to the dying parasites, leading to sudden, severe shortness of breath.
Can babesiosis come back after treatment?
Yes, relapsing disease is a significant risk for highly vulnerable patients, particularly those on immune-suppressing therapies like Rituximab. The infection may seem to resolve but return weeks or months later, requiring prolonged monitoring.

Questions to Ask Your Doctor

Curated prompts to bring to your next appointment.

  1. 1.Since I have a weakened immune system (or am missing my spleen), how long will my treatment continue, and when will we perform follow-up blood smears?
  2. 2.What specific signs of splenic complications or respiratory issues should I or my caregivers be watching for?
  3. 3.If my first-line treatment fails, are you prepared to use salvage therapies like Tafenoquine or Atovaquone-proguanil?
  4. 4.Should I be tested for G6PD deficiency before we consider certain alternative medications?
  5. 5.How often will we monitor my blood counts to check for secondary complications like HLH or autoimmune responses?

Questions For You

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References

References (17)
  1. 1

    Trust the Process: Prolonged Babesia Parasitemia in an Elderly Man with Asplenia from the American Midwest.

    Ivancich M, Lutwick L, Shweta FNU

    The American journal of case reports 2022; (23()):e936326 doi:10.12659/AJCR.936326.

    PMID: 35844076
  2. 2

    Management strategies for human babesiosis.

    Smith RP, Hunfeld KP, Krause PJ

    Expert review of anti-infective therapy 2020; (18(7)):625-636 doi:10.1080/14787210.2020.1752193.

    PMID: 32268823
  3. 3

    Severe babesiosis with associated splenic infarcts and asplenia.

    Sporn ZA, Fenves AZ, Sykes DB, Al-Samkari H

    Proceedings (Baylor University. Medical Center) 2021; (34(5)):597-599 doi:10.1080/08998280.2021.1930632.

    PMID: 34456483
  4. 4

    Possible Transfusion-Transmitted Babesia divergens-like/MO-1 Infection in an Arkansas Patient.

    Burgess MJ, Rosenbaum ER, Pritt BS, et al.

    Clinical infectious diseases : an official publication of the Infectious Diseases Society of America 2017; (64(11)):1622-1625 doi:10.1093/cid/cix216.

    PMID: 28329282
  5. 5

    A case of severe babesiosis treated successfully with exchange transfusion.

    Tanyel E, Guler N, Hokelek M, et al.

    International journal of infectious diseases : IJID : official publication of the International Society for Infectious Diseases 2015; (38()):83-5.

    PMID: 26232090
  6. 6

    Atovaquone-Proguanil: A Promising Therapy for Persistent Relapsing Babesiosis.

    Shahid M, Wechsler B, Parameswaran V, Diaz MA

    Case reports in infectious diseases 2024; (2024()):7168928 doi:10.1155/2024/7168928.

    PMID: 38774593
  7. 7

    Autoimmune hemolytic anemia associated with babesiosis.

    Narurkar R, Mamorska-Dyga A, Nelson JC, Liu D

    Biomarker research 2017; (5()):14 doi:10.1186/s40364-017-0095-6.

    PMID: 28405337
  8. 8

    Clofazimine, a Promising Drug for the Treatment of Babesia microti Infection in Severely Immunocompromised Hosts.

    Tuvshintulga B, Vannier E, Tayebwa DS, et al.

    The Journal of infectious diseases 2020; (222(6)):1027-1036 doi:10.1093/infdis/jiaa195.

    PMID: 32310272
  9. 9

    Tafenoquine for Relapsing Babesiosis: A Case Series.

    Krause PJ, Rogers R, Shah MK, et al.

    Clinical infectious diseases : an official publication of the Infectious Diseases Society of America 2024; (79(1)):130-137 doi:10.1093/cid/ciae238.

    PMID: 38814096
  10. 10

    A Case Report and Literature Review of Babesiosis-Induced Acute Respiratory Distress Syndrome.

    Yune PS, Islam I, Dicpinigaitis PV, et al.

    Case reports in infectious diseases 2022; (2022()):4318731 doi:10.1155/2022/4318731.

    PMID: 36411784
  11. 11

    Severe Babesiosis With Multifactorial Hemolysis and Pulmonary Complications in an Asplenic Patient at a Tertiary Cancer Center.

    Ayana G, Carlson S, Keraga BK, et al.

    Cureus 2025; (17(10)):e94343 doi:10.7759/cureus.94343.

    PMID: 41220440
  12. 12

    Splenic infarction in babesiosis: A rare presentation.

    Gupta A, Patel P, Manvar K, et al.

    Clinical case reports 2019; (7(8)):1591-1595 doi:10.1002/ccr3.2301.

    PMID: 31428398
  13. 13

    A Rare Presentation of Babesia-Associated Splenic Infarction in an Immunocompetent Young Male With Mild Parasitemia.

    Anthony JA, Nikolic D, Pepe R, Fraimow H

    Case reports in medicine 2026; (2026()):5210024 doi:10.1155/carm/5210024.

    PMID: 41488487
  14. 14

    Babesia microti infection and hemophagocytic lymphohistiocytosis in an immunocompetent patient.

    Go SA, Phuoc VH, Eichenberg SE, et al.

    International journal of infectious diseases : IJID : official publication of the International Society for Infectious Diseases 2017; (65()):72-74 doi:10.1016/j.ijid.2017.09.026.

    PMID: 28993284
  15. 15

    Babesiosis-Induced Hemophagocytic Lymphohistiocytosis Following Spontaneous Splenic Rupture in a Florida Resident: A Case Report.

    Jacob A, Nacer SA, Shah N

    Cureus 2025; (17(5)):e83360 doi:10.7759/cureus.83360.

    PMID: 40452714
  16. 16

    Persistence of babesiosis for >2 years in a patient on rituximab for rheumatoid arthritis.

    Raffalli J, Wormser GP

    Diagnostic microbiology and infectious disease 2016; (85(2)):231-2.

    PMID: 27036977
  17. 17

    A Case of Babesiosis in a Pregnant Patient Treated with Red Blood Cell Exchange Transfusion.

    Abittan B, Nizam A, Oey M, et al.

    Case reports in obstetrics and gynecology 2019; (2019()):9869323 doi:10.1155/2019/9869323.

    PMID: 31275683

This page is for informational purposes only and does not replace professional medical advice. If you are in a high-risk group and experience warning signs like severe shortness of breath or abdominal pain, seek emergency medical care immediately.

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