Therapeutic efficacy of atovaquone against the bovine intraerythrocytic parasite, Babesia divergens.

This study demonstrates the activity of the hydroxynaphthoquinone (HNQ), atovaquone, against Babesia divergens, the cause of a rare but lethal form of human babesiosis. In vitro studies showed that unlike other anti-malarial drugs, the HNQs studied have a high level of anti-babesial activity and atovaquone was more active than imidocarb, the most effective compound used so far for human B. divergens babesiosis and also used routinely for the treatment of bovine babesiosis. Atovaquone also proved to be extremely active against B. divergens in gerbils (Meriones unguiculatus). Acute fulminating infections were effectively treated with as little as 1.0 mg/kg with increasing effectiveness up to 10 mg/kg, which compares well with the activity of imidocarb. Although immunosuppression with dexamethasone slowed the decline of parasitemias after treatment with atovaquone, gerbil survival was unaffected. Pretreatment of gerbils with 4 daily low doses of atovaquone did not have any effect on the development of subsequent infections. However, if treatment was continued after infection, daily doses as low as 0.5 mg/kg effectively suppressed the parasites.