Multiple-drug resistant Trypanosoma congolense populations in village cattle of Metekel district, north-west Ethiopia

Investigations were carried out to determine the prophylactic activity of i sometamidium chloride in village populations of cattle naturally infected w ith trypanosomes in Metekel district, northwest Ethiopia. In a cross-sectio nal study in March 1997, 484 randomly selected cattle from four villages we re examined for trypanosome infections by the dark ground/phase contrast bu ffy coat technique (BCT). The trypanosome prevalence was 17.2%. Trypanosoma congolense was the dominant species accounting for 47.6% of the overall in fections. Fifty parasitaemic cattle from two villages were treated with iso metainidium chloride (Trypamidium(R)) at a prophylactic dose of 1.0 mg/kg b ody weight (b.w.) and thereafter monitored on a monthly basis for parasitae mia. Trypanosomes were detected in six cattle within 1 month and in 18 catt le within 2 months of treatment. Twenty three percent (6/26) of cattle infe cted with T. congolense at the time of treatment were detected parasitaemic with this trypanosome species 1 month after treatment. Mice were infected with three T. congolense isolates obtained from cattle which were detected parasitaemic within one or 2 months after isometamidium treatment. The mice were subsequently treated with ranges of doses of isometamidium chloride o r diminazene aceturate (Berenil(R)) and thereafter monitored for parasitaem ia for a period of 60 days. Isometamidium chloride at doses of 0.5-4.0 mg/k g b.w. and diminazene aceturate at doses of 3.5-28.0 mg/kg b.w. failed to c ure T. congolense infections in any of the animals. Three clones were deriv ed from one of the isolates; each clone expressed high levels of resistance to both trypanocides when tested in mice. Based on these results it is con cluded that the prophylactic activity of isometamidium is greatly reduced f or some of the T. congolense populations present in the area, and in additi on there is resistance to diminazene aceturate in this trypanosome species. (C) 2000 Elsevier Science B.V. All rights reserved.