Comparison of the isometamidium-based trypanocidal drugs Samorin® and Veridium® in cattle under field conditions at Nguruman, Kenya

The trypanocidal activity of two commercially available isometamidium-based products, Samorin® (Merial, USA) and Veridium® (Sanofi Santé Nutrition Animale, France), used at a dose rate of 0.5 mg kg−1 bodyweight, was compared in a field trial involving groups of approximately 30 zebu cattle in a trypanosomosis endemic part of south-western Kenya. The trial took place between April 1997 and March 1998 during a time of higher than normal rainfall that resulted in periods of high trypanosome challenge. The trial consisted of five consecutive prophylactic cycles, each of approximately 10 weeks duration. It was demonstrated that there was no significant difference in the prophylactic activity of the two isometamidium-based products, and no significant difference between the relative activity of three different batches of the product Veridium® used during the course of the trial. There was some evidence that drug-resistant strains of trypanosomes may have been present, but it was concluded that isometamidium is still an effective trypanocidal drug in this location.