Analysis of putative resistance gene loci in UK field populations of Haemonchus contortus after 6years of macrocyclic lactone use.

•Field populations of Haemonchus contortus were collected from UK sheep farms.•Farms with 6years of macrocyclic lactone (ML) use or avoidance were compared.•Parasites were genotyped at microsatellite loci and putative ML resistance loci.•No evidence of ML selection was detected at Hc-lgc-37, Hc-glc-5, Hc-avr-14 or Hc-dyf-7.•These loci are unlikely to be suitable for diagnostic marker development in the UK.