Antibiotic regimens for treatment of Babesia microti disease

IV: intravenously.
* Patients with mild to moderate disease are usually immunocompetent, have parasitemia <4%, and do not require hospital admission.
¶ The usual duration of therapy is 7 to 10 days. An extended course of therapy is needed when parasitemia and symptoms persist (refer to UpToDate text).^[1-4]
Δ Immunocompromised patients with mild to moderate B. microti infection may be treated on an outpatient basis with close monitoring. Antimicrobial therapy consists of oral azithromycin (500 to 1000 mg orally per day) plus oral atovaquone (750 mg orally twice daily).
◊ Atovaquone should be administered with a fatty meal.
§ Clindamycin plus quinine should be used if parasitemia and symptoms fail to abate with use of the preferred regimen (atovaquone plus azithromycin) or for patients unable to take the preferred regimen.
¥ The quinine doses listed are for the sulfate salt (which is the only quinine formulation available in the United States); 650 mg quinine sulfate is approximately equivalent to 542 mg quinine base and 8 mg/kg quinine sulfate is approximately equivalent to 6 mg/kg quinine base. In the United States, quinine sulfate is available as a 324 mg capsule; 2 capsules (648 mg quinine sulfate) is acceptable for adult dosing. Other countries may have different dosage forms and strengths.
‡ Severe babesiosis often occurs in older and/or immunocompromised patients and is associated with parasitemia ≥4% (although it can occur with parasitemia <4%). Exchange transfusion may be considered for patients with high-grade parasitemia (>10%) and/or any one or more of the following: severe hemolytic anemia and/or severe pulmonary, renal, or hepatic compromise. Consultation with a transfusion services physician or hematologist, as well as an infectious diseases specialist, is strongly advised.
† Azithromycin dose 1000 mg orally (given in combination with other antibiotics) has been used successfully for treatment of B. microti infection in immunocompromised patients. An initial one-time dose of azithromycin 1000 mg IV has been used for treatment of severe babesiosis but with very limited experience. While this IV dose has been shown to be safe, there are no published reports of the use of this dose for severe babesiosis. If azithromycin 1000 mg IV is used for initial treatment, subsequent IV doses should be reduced to 500 mg daily.
** There have been no studies of pediatric IV azithromycin dosing for babesiosis.
¶¶ For patients with severe disease, the total duration of therapy (eg, initial management plus step-down therapy) is typically 7 to 10 days. For immunocompromised patients, a higher dose of azithromycin (500 to 1000 mg orally daily) may be administered.
ΔΔ Highly immunocompromised patients are at risk of relapse despite receiving standard therapy and include those who have received or are receiving rituximab (eg, for B cell lymphoma or an autoimmune disorder), are receiving other immunosuppressive regimens (eg, for solid organ or stem cell transplantation or malignancy), have malignancy and are asplenic, or have HIV infection with low CD4 T cell counts (AIDS).