Persistent efficacy of topical moxidectin against Dictyocaulus viviparus and Ostertagia ostertagi

Abstract

The persistent activity of moxidectin topically administered at the dose rate of 0.5 mg kg −1 bodyweight was evaluated against experimental nematode infection in 30 calves randomly allocated to six groups. Five groups were treated on days −42, −35, −28, −21 and −14. The 6th group remained untreated as a control. On Day 0, the calves were infected experimentally with 1000 Dictyocaulus viviparus and 50 000 Ostertagia ostertagi larvae and killed 3 weeks later. The formulation of moxidectin showed excellent activity against both parasites up to 5 weeks (>99%). Six weeks after treatment the reduction in the number of D. viviparus was still high (>90%). No adverse reactions to moxidectin were observed in any of the animals.