Gastrointestinal nematodes (GIN) are an important cause of production losses in young grazing sheep, particularly in intensive production systems. The prevention of GIN infections and parasitic gastroenteritis relies on broad spectrum anthelmintic drugs. At present, the major classes of anthelmintics available for sheep belong to the families of the benzimidazoles (albendazole, febendazole, and oxfendazole) ,imidazothiazoles (levamisole) and macrocyclic lactones (avermectins).Anthelmintic resistance has been recognized in small ruminants worldwide, and this phenomenon has increased to become a major worldwide problem to livestock industry. A systematic review was conducted with the aim to measure the prevalence of sheep gastrointestinal nematodes (GIN) in Iran and potential management factors associated with development of anthelmintic resistance. Modern strategy for nematode control should not rely on sole use of anthelmintics.Targeted selective treatments attract the interest of parasitologists towards maintaining parasites in refugia, seems to be a key point in controlling and delaying the development of resistance. Therefore, it is needed to use novel non-chemical approaches that decrease the need for treatment.

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