Successful prevention and treatment of babesiosis with atovaquone.

Atovaquone was evaluated for the prevention and treatment of babesiosis in hamsters. When atovaquone was administered before inoculation of 10(6) Babesia microti and continued for 8 days thereafter, 9 of 10 hamsters survived beyond 54 days, but all untreated controls died within 12 days after inoculation. Quantitation of parasitemia showed a mean of 75% erythrocytes parasitized by day 5 in controls, but atovaquone recipients never exceeded 0.7% of parasitized erythrocytes over 54 days of observation. Clindamycin plus quinine was also effective but less so than atovaquone. When treatment was not started until parasitemia became established, atovaquone in doses of 300, 150, and 80 mg/kg/day was effective in the recovery of all animals compared with 50% of those receiving 10 mg/kg/day and 10% of untreated controls. With its remarkable safety record, atovaquone offers promise for clinical trials in babesiosis of both humans and lower animals.