IDSA Releases New Guidelines on Diagnosis and Management of Babesiosis

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The Infectious Disease Society of American (IDSA) published a new guideline on the diagnosis and management of babesiosis.

The Infectious Disease Society of American (IDSA) published a new guideline on the diagnosis and management of babesiosis, a disease caused by intraerythrocytic protozoa that are transmitted by hard-bodied ticks. The guideline was published in a recent edition of Clinical Infectious Diseases.

Guideline Development: Methodology

In the development of this guideline, an IDSA expert panel convened to develop relevant clinical questions for the diagnosis and management of babesiosis. The panel conducted a literature review to identify answers to this set of clinical questions. Ultimately, the evidence found to support the answers to this question were summarized into the guideline document.

Diagnosis of Babesiosis

Early diagnosis of babesiosis in symptomatic patients accelerates the initiation of appropriate antimicrobial treatment. 

In the guideline, the IDSA recommends the use of a peripheral blood smear or polymerase chain reaction (PCR) test over antibody testing. The expert guideline panel commented that the diagnosis of babesiosis should rely on epidemiological risk factors and clinical evidence, all of which should be confirmed by blood smear or PCR.

A blood smear examination or PCR test should also be used to confirm a babesiosis diagnosis prior to treatment in patients with a positive Babesia antibody test. The panel noted that a single positive antibody test does not provide enough information to confirm or establish a babesiosis diagnosis as Babesia antibodies can often stay in the blood for at least 1 year after apparent infection clearance with or without therapy.

The guideline committee wrote that future research should look to develop antibody and/or antigen assays “capable of distinguishing acute from past infection,” as this could improve clinical utility.

Treatment Regimens for Babesiosis

In terms of treatment, the IDSA guideline panel recommends a combination approach.

  • Preferred treatment: atovaquone plus azithromycin
  • Alternative treatment: clindamycin plus quinine

Clindamycin and quinine dual approach can be used in some cases, particularly in immunocompromised patients who have a relapse while on the recommended treatment regimen. Treatment duration should be 7 to 10 days in immunocompetent patients, but this period is usually extended for immunocompromised patients.

Exchange transfusion using red blood cells is recommended for selected patients with severe babesiosis, but this was a weak recommendation in the guideline based on low-quality evidence. Exchange transfusion can quickly reduce parasitemia in some patients through the replacement of parasitized erythrocytes with nonparasitized erythrocytes.

The IDSA expert panel suggest that eligible patients for exchange transfusion should be those with high-grade parasitemia or at least 1 of the following:

  • Severe hemolytic anemia and/or
  • Severe pulmonary compromise
  • Severe renal compromise
  • Severe hepatic compromise

Additionally, the guideline panel recommends an expert consultation with a hematologist or transfusion services physician in addition to an infectious disease specialist when considering exchange transfusion. The expert committee adds that the potential benefits of exchange therapy, particularly in cases of life-threatening babesiosis, likely outweigh any adverse effects. Some potential adverse effects associated with this approach include:

  • Transfusion reactions
  • Worsening of thrombocytopenia
  • Complications associated with venous access devices

There is currently a lack of prospective studies that validate criteria for initiating exchange transfusion in these patients.

Monitoring Immunocompetent and Immunocompromised Patients

The guideline committee recommends monitoring Babesia parasitemia during treatment of acute illness in immunocompetent patients. This should be accomplished with the use of peripheral blood smears, but the guideline recommends against testing for parasitemia following the resolution of symptoms.

In immunocompromised patients, the guideline also recommends the use of blood smears for monitoring Babesia parasitemia even after these patients become asymptomatic. Monitoring should continue until the blood smears are negative. If blood smears become negative but symptoms continue, clinicians may consider the use of PCR testing. This recommendation for immunocompromised patients was a weak recommendation based on moderate-quality evidence.

The guideline committee wrote that there is currently no standardization in how to monitor highly immunocompromised patients. Close clinical and laboratory follow up is essential for these patients and the use of PCR could be used to help determine when antimicrobial treatment should be discontinued in some cases.

Due to the paucity of the literature, the IDSA expert panel noted that more research is needed on babesiosis, including research “to determine the frequency, efficacy, and cost-effectiveness of blood smear, PCR, and other laboratory testing (such as antigen detection) for monitoring immunocompromised hosts during and following antimicrobial therapy.”

Disclosure: Several study authors declared affiliations with the pharmaceutical industry. Please see the original reference for a full list of authors’ disclosures.


Krause PJ, Auwaerter PG, Bannuru RR, et al. Clinical practice guidelines by the Infectious Diseases Society of America (IDSA): 2020 guideline on diagnosis and management of babesiosis. Clin Infect Dis. Published online November 30, 2020. doi:10.1093/cid/ciaa1216