Ethnoveterinary Medicine for Livestock Ectoparasites: A Systematic Review of Plant-Based Treatments

Abstract

Farmers in many regions treat ticks, mites and lice on their animals with plants, and a large literature reports that extracts, oils and crude preparations kill or repel these parasites. This narrative review asks how much of that literature can be relied on when a farmer or veterinary adviser must decide whether to use a plant-based treatment. It draws on published work on livestock ectoparasites and acaricide resistance, on ethnoveterinary documentation, on the chemistry and stability of botanical products, and on the design and reporting of animal and laboratory studies, and it reports no new data. Three problems recur. Plant identity and preparation are often poorly specified, so that a result cannot be repeated or compared. Controls are frequently weak or absent, and laboratory assays on isolated parasites seldom predict what happens on a living animal exposed to weather, grooming and reinfestation. Safety, including toxicity to the host, irritation, and residues in milk and meat, is the least studied part of the chain. The review concludes that several plant products are credible leads, that none can yet be recommended on the strength of the evidence assembled here, and it sets out the minimum a study should report before a traditional treatment is promoted as a substitute for registered products.