Plant-Based Solutions to Global Livestock Anthelmintic Resistance

Abstract

Anthelmintic resistance in livestock is increasing globally. Livestock intestinal parasites now develop resistance to synthetic anthelmintics within 2–10 years, collectively costing billions of dollars annually in lost revenue around the world. Over-reliance on commercial drugs and dips and changes in livestock management practices are key drivers of this trend. To date, current research has focused on identifying new anthelmintics from bacterial and fungal sources or even synthesizing new drugs that target parasite metabolism or reproduction. Plant-derived anthelmintics are a promising alternative, yet to date major research funders and scientists have overlooked this option. Until the mid-20th century, rural communities relied on plant-based methods of controlling livestock parasites. These methods include feeding livestock specific medicinal plants and trees, grazing livestock on herbal leys, and changing where livestock grazed based on ecological factors (e.g., flooding) that increased parasite burdens. Many historic texts and ethnological accounts record the ethnobotanical knowledge of rural communities and the plants they used to control livestock intestinal parasites. Some traditions persist today yet the farmers, graziers, and shepherds who hold this knowledge are rapidly disappearing and with them perhaps a potential long-term solution to anthelmintic resistance. This short perspective piece will cover recent research using ethnobotanical data as a means to identifying potential new anthelmintics; the morphological, physiological, and metabolic effect of plant secondary metabolites on parasites; and an overview of “best practices” which can reduce bias in assessments of plant bioactivity and increase reproducibility of test results. This will hopefully bring recent advances in ethnobiology, chemistry, and ecology to new audiences, and, potentially, spark new interest in using medicinal plants to improve livestock health.

Essential oil of Peumus boldus Molina against the nematode Haemonchus contortus (L3) and three stored cereal insect pests

“…The anthelmintic activity obtained from P. boldus agrees with a study against Ascaris suum (Delgado-Díaz and Jara, 2018). The activity of some of the constituents of P. boldus present in this study, such as ascaridol, 1,8-cineole, p-cimene, and methyl eugenol, among others, against H. contortus has been reported previously.…”

Disclosing the bioactive metabolites involved in the in vitro anthelmintic effects of salt-tolerant plants through a combined approach using PVPP and HPLC-ESI-MSn

“…Due to the constant diffusion of resistance to synthetic anthelmintics in worm populations, the search for plants with antiparasitic activities and their bioactive metabolites that can be used for integrated control approaches of GIN, has expanded over the last 20 years 63 . Extremophile plants, in particular salt-tolerant species, may represent an untapped reservoir of anthelmintic compounds for such purpose.…”

Natural Products Are a Promising Source for Anthelmintic Drug Discovery

“…The main target sites of the currently available anthelmintics are solely proteins and those are ion channels, microtubules and bioenergetics (Table 2) [40]. All the commercial anthelmintics included in Table 2 are non-plant derived chemicals and their activity is based on a single target species [41]. Most of these classes of drugs act on Cys-loop ligand-gated ion channels (LGICs) in invertebrates [42] and many were initially identified through low through-put approaches using either whole animal-based or phenotypic screening methods.…”