Seasonal variation in the effects of Mediterranean plant extracts on the exsheathment kinetics of goat gastrointestinal nematode larvae

•Seasonal pattern for inhibition of larval exsheathment by the ethanolic extracts was observed.•P. lentiscus and I. viscosa with peaks of inhibition during fall and spring, but not in P. latifolia.•Peaks of exsheathment inhibition were associated with seasonal peaks of phenolics contents.•Not all the seasonal variation could be related to the content of phenolics in plants.•Seasonal variation in anthelmintic activity should be taken into account.