Anthelmintic resistance in cattle

Parasitic nematode infections can affect all ages of cattle, but are mainly of clinical significance in young parasite-naïve calves in their first year at grass, or in second-year grazers (Figure 1). For these animals, several control and worming strategies have been advocated that have proved successful – particularly since the launch of the macrocyclic lactone (3-ML) class of anthelmintics, which now dominate the cattle “wormer” market.