Resistance to diminazine aceturate by Trypanosoma congolense from cattle in the Zambezi Valley of Zimbabwe

The susceptibility of 14 stocks of Trypanosoma congolense, recently isolated from cattle, to therapeutic doses of diminazene aceturate and to isometamidium chloride was assessed in laboratory mice. Eight isolates were readily susceptible to the normal therapeutic dose of diminazene, two were resistant to the drug at 14 mg kg −1, and four were totally resistant at 28 mg kg −1. All the isolates were susceptible to isometamidium chloride at 0.5 mg kg −1. These observations highlight the need for regular evaluation of drugs used in the control of trypanosomosis.