Sensitivity of animal-derived Trypanozoon stocks from sleeping sickness endemic foci of Nigeria to trypanocides and human plasma.

Twelve Trypanozoon stocks isolated from semi-nomadic cattle in known sleeping sickness foci of central and northern Nigeria were studied in terms of susceptibility to two trypanocides, diminazene aceturate (Berenil) and isometamidium chloride (Samorin) and human plasma. In infected small ruminants, three of the stocks were resistant to diminazene aceturate at does of 7.0 -14.0 mg/kg body weight (b.w.) while isometamidium chloride at doses of 1.0 mg/kg b.w. or higher failed to effect parasitological cure of infections with two of the diminazene-resistant stocks. The two isometamidium-resistant stocks were also consistently resistant to the trypanolytic action of human plasma. It is suggested that cattle are reservoirs of Trypanosoma brucei subspecies potentially infective to man and resistant to the therapeutic action of the known sanative pair (diminazene and isometamidium).