Berenil (diminazene aceturate)-resistant Trypanosoma congolense in cattle under natural tsetse challenge at Kibaha, Tanzania.

Twenty-nine cattle, naturally infected with Trypanosoma congolense Kibaha, were subjected to chemotherapy with diminazene aceturate (Berenil, Hoechst) at 3.5 to 14.0 mg/kg. Fourteen animals recovered while six were refractory to treatment at 7.0 to 14.0 mg/kg. Further treatment of the Berenil-resistant isolates with isometamidium chloride (Samorin, May and Baker) at 1.0 mg/kg, effected cure. Corresponding chemotherapeutic trials in mice showed that the isolates were resistant to diminazene aceturate at 56.0 mg/kg and sensitive to Samorin at 20.0 mg/kg. It is noted, that T. congolense infections that do not respond to treatment with Berenil at 7.0 mg/kg may indicate development of resistance; the use of Samorin at 1.0 mg/kg or Homidium may be the alternative. The paper calls for judicious use of Berenil and Samorin, as they are the only sanative pairs available for the chemotherapy of bovine trypanosomiasis.