Evaluation of the potential of systemic slow release chemical treatments for control of the cattle tick (Boophilus microplus) using ivermectin.

Stall and field trials with cattle infested with various acaricide-resistant strains of cattle tick, have demonstrated the potential of ivermectin as a systemic tickicide. A dosage of 200 micrograms/kg, administered subcutaneously to animals naturally infested in the field, gave satisfactory tick control for 21 days, after an initial lag period of 2 days immediately following treatment, during which significant numbers of ticks survived. Daily subcutaneous treatments, administered so as to simulate slow release, indicated that a dosage of 15 micrograms/kg/day should give complete tick control if the chemical could be released continuously from a subcutaneous implant. The potency of ivermectin assessed by in vitro tests against engorged adults, suggests that the tickicidal activity could be associated with the parent compound per se rather than a metabolite.