Therapeutic and prophylactic activity of isometamidium chloride in Boran cattle against Trypanosoma vivax transmitted by Glossina morsitans centralis.

Ten Boran steers were infected with Trypanosoma vivax, transmitted by Glossina morsitans centralis; five steers with a T vivax clone from Nigeria and five with a T vivax clone from Kenya. Eleven days after infection all 10 animals were treated with 0.5 mg kg-1 isometamidium chloride. Four steers infected with the Nigerian T vivax and all five infected with the Kenyan T vivax were completely cured. When different steers received a single prophylactic dose of 0.5 mg kg-1 isometamidium chloride and subjected to monthly tsetse-transmitted challenge with the same T vivax clones, complete protection was afforded for at least two months against challenge with the Nigerian T vivax, but for less than one month against the Kenyan T vivax. The findings indicate that the level of sensitivity of a T vivax population to the prophylactic activity of isometamidium chloride cannot be concluded from sensitivity studies based on the therapeutic action of the drug.