Suspected ivermectin resistance in a south-east Queensland Parascaris equorum population

BackgroundThere have been several international reports of macrocyclic lactone (ML)-resistant Parascaris equorum over the past decade, but the resistance status of Australian P. equorum populations is largely unknown. A case of apparent reduced efficacy of ivermectin against P. equorum in Australia was investigated. Methods and ResultsA faecal egg count reduction test carried out on a group of weanling foals in south-east Queensland showed the efficacy of ivermectin to be 65%. ConclusionThe case highlights the need to review current worm control strategies, especially for young horses.