Genomic signatures of selection associated with benzimidazole drug treatments in Haemonchus contortus field populations

•A genome-wide scan detected signatures of benzimidazole (BZ) selection in Haemonchus contortus field populations.•A ddRADseq panel of >49 k genomic markers was generated for population genomic studies in H. contortus.•Iso-1 β-tubulin is quantitatively the most important BZ resistance locus in the H. contortus genome.•There is evidence for two additional BZ resistance loci of secondary importance.•We provide a framework for detection of genomic signatures in parasitic nematode field populations.