Isometamidium-dextran complex: therapeutic activity against Trypanosoma vivax infection in Zebu cattle

Isometamidium-dextran complex was prepared by adding a 4% solution of dextran sulphate to an equal volume of a 4% solution of isometamidium chloride. The resulting 2% suspension was administered subcutaneously at 0.5, 1, and 2 mg/kg to three groups of Zebu bulls infected with Trypanosoma vivax Y58. The fourth group received isometamidium at 0.5 mg/kg intramuscularly. The parasite was cleared from all groups within 5 days, and recrudescence occurred to either preparation only at 0.5 mg/kg during the 90 day observation period. A firm movable subcutaneous nodule formed at the site of injection of the complex. The skin over the nodule appeared thickened due to oedema. Histologically, the nodule was characterized by diffuse connective tissue proliferation, with round cells and giant cell infiltration. There were focal areas of necrosis in the underlying granuloma associated with yellowish-brown staining drug deposits at the centre. The average growth rate of the treated groups was better than the non-treated group but inferior to the non-infected group. It was concluded that the complex at 1 or 2 mg/kg s.c. could be expected to protect cattle against trypanosomiasis and still yield good carcass and hide grading.