In vivo anthelmintic activity of terpenes and essential oils in small ruminants

Terpenes and essential oils (EsOi) have a wide range of biological activities that could be explored in veterinary sciences. In this sense, their use has been proposed as a strategy to overcome the growing populations of gastrointestinal nematodes (GIN) resistant to the traditional anthelmintic (AH) drugs. In the present review, we analysed eleven scientific manuscripts aimed to evaluate the AH activity of terpene-rich plants (TRP) and EsOi in small ruminants by using the in vivo approach. The sheep species was used in the 81% of works. Brazil is the country leading this research line, followed by the United States of America and Benin. All the analysed manuscripts employed the faecal egg count reduction test, while five manuscripts employed the controlled test —or trial— methodology. The activity of TRP and EsOi on the faecal excretion of GIN eggs was variable, showing values between zero to 97%. Two manuscripts reported a reduction in the size of male GIN, as well as the fecundity of female GIN after administration of EsOi. It would be worth to perform more works aimed to understand the relationships between plants, their secondary metabolites and the ruminants consuming them. Through the understanding of such interactions, we will be allowed to use these natural products as elements that could contribute to improve the nutrition and health of sheep and goats under different productive systems