Activity of 10 naphthoquinones, including parvaquone (993C) and menoctone, in cattle artificially infected with Theileria parva.

Ten naphthoquinones, including parvaquone (993C) (Clexon; Wellcome) and menoctone, were tested for activity in cattle artificially infected with Theileria parva , the causative organism of East Coast fever (ECF). Parvaquone cured all 14 cattle treated with a single dose of 20 mg/kg intramuscularly and all five treated twice with 10 mg/kg intramuscularly. Menoctone cured seven of 10 cattle treated with a single dose of 5 mg/kg intramuscularly. Of 25 untreated control cattle, 22 died of ECF. None of the remaining eight naphthoquinones was as active as parvaquone. Three esters of active naphthoquinones, designed as ‘prodrugs’ of their parent compounds, showed little or no activity in infected cattle despite being highly active in vitro against T parva. These results were instrumental in the selection of parvaquone for development as the first specifically active remedy for ECF.