[Therapy and anthelmintic resistance]

Treatment against nematode parasites in sheep and goats is reviewed. The main risk factors for parasitic infection in these hosts are briefly outlined. The mechanism of action of the most important chemical groups (imidazothiazoles and pyrimidines, benzimidazoles/ pro-benzimidazoles and macrocyclic lactones) to which the modern anthelmintic drugs belong are illustrated and discussed with particular emphasis on possible selection of anthelmintic resistance. The need for strategic integrated control based also on the epidemiological patterns of parasitism, the composition and the production of the herd (milk, meat, wool) and the potency of the drugs are discussed. The importance of diet and potential alternative control measures (nematophagus fungi and natural compounds such as tannins) are illustrated.