Anthelmintic resistance of gastrointestinal nematodes in sheep grazing in irrigated and dry areas in the semiarid region of northeastern Brazil.

This study aimed to determine the AR of gastrointestinal nematodes (GIN) to commercial drugs in sheep flocks naturally infected, grazing in irrigated (IA) and dry (DA) areas of the semiarid region in northeastern Brazil. Fecal egg count reduction tests (FECRT) were performed at 10 farms. From each flock, 36 adult sheep were selected and divided into five groups (G1 (0.