TIME DOSE-RESPONSE OF TRYPANOSOMA-CONGOLENSE BLOOD-STREAM FORMS TO DIMINAZENE AND ISOMETAMIDIUM

Trypanosoma congolense bloodstream forms were propagated in vitro axen ically in a simplified cultivation medium at 34-degrees-C. Viability o f a drug-sensitive and a drug-resistant clone were examined for 10 day s following exposure to 0.1, 1.0 and 10.0 mug ml-1 of diminazene acetu rate and 0.1, 1.0 and 10.0 ng ml-1 of isometamidium chloride for vario us time intervals. Drug-sensitive T. congolense were irreversibly dama ged after incubation with 10 mug ml-1 or 1 mug ml-1 diminazene acetura te for 30 min or 2 h, respectively, while drug-resistant trypanosomes were not affected. Exposure to 10 ng ml-1 isometamidium chloride elimi nated drug-sensitive trypanosomes after 24 h and drug-resistant trypan osomes after 96 h. The data obtained on in vitro time-dose responses o f T. congolense were related to pharmacokinetic data of diminazene and isometamidium in cattle plasma.