Liver fluke control on sheep farms in Northern Ireland: A survey of changing management practices in relation to disease prevalence and perceived triclabendazole resistance.

•Surveys on liver fluke control in sheep were conducted in N. Ireland in 2005 and 2011.•There was a progressive shift away from use of TCBZ; it was replaced largely by closantel.•Lowland sheep owners rotated drugs more often in 2011 than 2005.•The timing of treatments moved towards the start of the year.•At both time-points, almost one-third of farmers gave 3 or more treatments per year to ewes.•Few flock owners gave quarantine treatments in 2005. The percentage dropped further in 2011, from 31.0% to 15.2% and 25.9% to 13.9% for lowland and upland flock owners, respectively.