The efficacy of toltrazuril for prevention of oriental theileriosis (Theileria orientalis Ikeda genotype) in Friesian calves.

The aim of this non-blinded, randomised, controlled study was to determine the efficacy of toltrazuril for the prevention of oriental theileriosis in calves. Thirty calves were infected with Theileria orientalis Ikeda genotype through the application and retention of infected female bush ticks (Haemaphysalis longicornis). 15 Group 1 calves were treated with a single, oral dose of toltrazuril at the dose registered in Australia for coccidiosis (15 mg/kg), concurrently with tick infection, and 15 Group 2 (control group) calves were untreated. There were no significant differences (P > 0.05) in mean parasitaemia, packed cell volume (PCV) or bodyweight between the toltrazuril treated and untreated groups at any timepoint up to Day 64 after infection, apart from a higher mean PCV for the toltrazuril treated group at Day 20. In this study, the calves treated with a single oral dose of toltrazuril (15 mg/kg) at the time of infection were not prevented from becoming infected with oriental theileriosis.