Resistance of gastrointestinal roundworms to ivermectin in sheep, goats and cattle has been reported almost worldwide, including the USA, UK, Australia and New Zealand. Based on the very abundant and frequent use of ivermectin and other macrocyclic lactones (with cross-resistance to ivermectin) in livestock it must be assumed that resistance of these roundworms to thischemical class will continue spreading and strengthening in the future.
La resistencia de los nematodos gastrointestinales a la ivermectina y otras lactonas macrocíclicas está extendida en casi todo el mundo en ovinos y caprinos, algo menos en bovinos.