Seasonal differences in the efficacy of pour-on formulations of triclabendazole and ivermectin or abamectin against late immature liver fluke (Fasciola hepatica) in cattle.

Three controlled studies were conducted to determine the efficacy against late immature (6 weeks) Fasciola hepatica of two currently available fasciolicides (Genesis Ultra and Coopers Sovereign) which are applied externally to cattle. Efficacy of the two products was assessed when application was made under winter, spring and summer conditions. Efficacies for winter, spring and summer respectively, based on arithmetic mean total fluke counts, were 78.9%, 91.7% and 99.6% for Coopers Sovereign and 73.4%, 89.7% and 99.6% for Genesis Ultra. Seasonal differences with treatment efficacy were indicated. The studies also confirmed previous observations that liver fluke egg counts overestimate the efficacy of fasciolicides and that total fluke counts is the most reliable method for assessing efficacy of such products.