Ivermectin in veterinary medicine: a narrative review of antiparasitic efficacy, resistance evolution, antiviral evidence, and One Health implications

Ivermectin is a common macrocyclic lactone that is proven to be active against a wide range of parasites in veterinary medicine. This article presents a narrative review that combines evidence on the antiparasitic effects of ivermectin, its therapeutic use in animals, the development of resistance, preliminary antiviral studies, and ecological consequences within a One Health framework. A comprehensive literature search was conducted through PubMed, Scopus, Web of Science, and Google Scholar for literature published between 1980 and 2025, and the evidence was synthesized qualitatively. Its main antiparasitic effect is mediated via glutamate-gated chloride channels in invertebrates, resulting in neuromuscular paralysis. Clinical benefit of established antiparasitic indications is best evidenced, but the results of treatment depend on the species of the parasite, the host species, the formulation, dosing conditions, and the baseline resistance condition. The antiviral effects reported are mostly exploratory, with most being the results of in vitro or preclinical studies, and are not a proven clinical activity in veterinary practice. Evidence on the environment also suggests that ivermectin residue may cause negative effects on non-target invertebrates, and thus stewardship-based dosing, resistance surveillance, and reducing ecological exposure should be considered in a One Health system.