TREATMENT Babesiosis ASYMPTOMATIC B. MICROTI INFECTION
People who experience asymptomatic B. microti infection often are not diagnosed and treated. Current guidelines recommend antibiotic therapy for asymptomatic carriers only if parasitemia persists for >3 months. Laboratory-based tests are being developed for the purpose of screening the blood supply and will result in the identification of a greater number of asymptomatic B. microti carriers, raising the question of whether they should be treated. MILD TO MODERATE B. MICROTI ILLNESS
Atovaquone plus azithromycin, given orally for 7–10 days, is the recommended antibiotic treatment combination for mild to moderate babesiosis (Table 249-1). Clindamycin plus quinine is a second choice. Symptoms usually begin to resolve within 48 h of therapy initiation, but complete resolution may take weeks to months. An atypical or poor response to therapy should raise concern about the possibility of concurrent Lyme disease (Chap. 210) or human granulocytotropic anaplasmosis (Chap. 211). In the first prospective trial of antibabesial therapy, the combination of atovaquone plus azithromycin was compared with clindamycin plus quinine in adults. These two drug combinations were equally effective in resolving symptoms and clearing parasitemia. Adverse effects were reported in 15% of trial participants who received atovaquone plus azithromycin but in 72% of those who received clindamycin plus quinine. Adverse reactions were so severe that treatment had to be stopped in about one-third of participants taking clindamycin plus quinine but in only 2% of those taking atovaquone plus azithromycin. SEVERE B. MICROTI ILLNESS
Clindamycin given intravenously plus quinine given orally for 7–10 days constitute the recommended treatment for severe babesiosis. Intravenous quinidine may be used instead of oral quinine but requires cardiac monitoring because of the risk of QT prolongation and polymorphic ventricular tachycardia.
Standard antimicrobial therapy is sometimes insufficient to resolve symptoms and clear parasitemia, especially in patients with marked immunosuppression due to splenectomy, HIV/AIDS, malignancy, and/or immunosuppressive therapy (including rituximab for B cell lymphomas). In such patients, antimicrobial therapy should be administered for at least 6 weeks, including 2 weeks after parasites are no longer observed on blood smear. High-dose azithromycin (600–1000 mg/d) plus atovaquone have been successfully used in immunocompromised patients. Resistance to atovaquone plus azithromycin has occurred in a few cases. In patients who are unresponsive to atovaquone plus azithromycin or who do not tolerate clindamycin plus quinine, alternative regimens have been used (Table 249-1).
Partial or complete RBC exchange transfusion is recommended in patients with high-grade parasitemia (≥10%), severe anemia (hemoglobin, <10 g/dL), or pulmonary, hepatic, or renal compromise. Parasitemia and hematocrit should be monitored daily until symptoms recede and the parasitemia level is <5%. OTHER BABESIA INFECTIONS
The regimen for B. duncani infections typically consists of intravenous clindamycin (600 mg tid/qid or 1200 mg bid) plus oral quinine (600–650 mg tid) for 7–10 days. A regimen often used for B. divergens–like infections is intravenous clindamycin (600 mg tid/qid, 900 mg tid, or 1200 mg bid) plus oral quinine or quinidine (650 mg tid).
In Europe, B. divergens infection is considered a medical emergency. The recommended treatment is immediate complete blood exchange transfusion and therapy with intravenous clindamycin plus either oral quinine or intravenous quinidine. Some cases have been cured with exchange transfusion and clindamycin monotherapy. Anemia may persist for >1 month and require additional transfusion.