Efficacy of Michel's ‘dose and move’ system against Dictyocaulus viviparus infections in cattle using moxidectin as anthelmintic

Abstract

Two grazing experiments were performed to study the effect of moxidectin in a ‘dose and move’ system on Dictyocaulus viviparus infections in calves. In the first experiment, three groups of four calves were experimentally infected with 20 larvae of D. viviparus 7 weeks before moxidectin treatment of two of these groups. A sufficient suppression of Dictyocaulus infections was observed in a ‘dose and move’ group, but also in a group which stayed on contaminated pasture after treatment. In contrast, high faecal larval counts and lungworm disease were observed in July-August in a non-treated pasture control group. Development of immunity against lungworm was sufficient in all three groups on pasture. In the second experiment, four out of 16 calves, including two groups of six calves and four tracer calves, were experimentally infected with 20 larvae of D. viviparus 7 weeks before moxidectin treatment combined with a move of one of the groups. No lungworm disease was observed in this ‘dose and move’ group. In a pasture control group high faecal larval counts and severe clinical disease were observed in August-September and one calf had to be euthanized. Although a mean burden of 129 immature lungworms was present at the time of treatment, development of immunity appeared to be low in the ‘dose and move’ group. In contrast, high levels of immunity had developed in the pasture control group.