Seasonal variation in the effects of Mediterranean polyphenol extracts on the exsheathment kinetics of goat gastro-intestinal nematode larvae

Abstract

The use of chemical drugs for the control of Gastro-intestinal nematodes causes rapid development of resistance to anthelmintics in worm populations. The possible use of polyphenols from plants has been identified as a valuable solution. However, the concentration of these bio-actives in plants can be seasonal and we hypothesized that this may cause different anthelmintic bio-activity. Using two-species Teladorsagia circumcinta and Trichostrongylus colubriformis, we tested this hypothesis by using the larval exsheathment inhibition assay. We examined effect on L3 larval exsheathment kinetics and polyphenol content of ethanol 70% extracts of Pistacia lentiscus, Phillyrea latifolia, and Inula viscosa clipped during different seasons. Extracts of P. latifolia showed similar inhibition of larval exsheathment throughout the year; in contrast, the inhibition by both extracts of P. lentiscus and I. viscosa was affected by season, ranking fall>summer>spring=winter and spring>summer=fall>winter, respectively. The total polyphenol content in foliage of these plant species was highest in fall for P. lentiscus and in spring for I. viscosa, but did not vary significantly for P. latifolia. Differences in larval exsheathment inhibition did not completely fit differences in phenolics contents. Seasonal variation in anthelmintic activity should be taken into account where plants are integrated into anthelmintic strategies.