Anthelmintic efficacy of heather extracts against ovine gastro-intestinal nematodes

Summary

The use of anthelmintics in organic farming is regulated; however its limited use is permitted due to GI nematodes threatening the health and welfare of animals worldwide. There is a requirement for a reduction of contentious inputs in organic farming, such as anthelmintics, and the H2020 project RELACS focuses on developing alternatives for sustainable parasite control. One of such alternatives is the use of bioactive plants; this study focuses on the perennial shrub heather (Ericaceae family) as it is a plant rich in condensed tannins, which have been shown to have anthelmintic properties, and the plant is highly abundant across Europe. The objective was to compare the anthelmintic efficacy of heather acetone extracts from five European countries, across two seasons, against two of the most common GIN species in small ruminants: Teladorsagia circumcincta and Trichostrongylus colubriformis. A total of 11 heather samples were analysed to determine their polyphenol content, including type and amount of CTs, and tested in vitro with the aim of quantifying their impact on egg hatching and larval motility. Results showed the heather extracts reduced egg hatching in a dose dependent manner (P<0.001) and reduced larval motility at the highest concentration of 200µg/ml (P<0.05). The anthelmintic efficacy of the heather varied by season, country of origin and the species of heather tested on both egg hatching and larval motility, with variation also seen on the susceptibility of the two GIN species egg hatching rate. These variations in extract activity were not always consistent between the two in vitro tests indicating that the active compounds may target different parasite life stages. Results demonstrate heather does show anthelmintic ability when tested in vitro, so has promise as a sustainable parasite control method and should be investigated further.