Drug dose and animal welfare : important considerations in the treatment of wildlife

A recent article published in Parasitology Research describes the use of high-dose moxidectin (Cydectin®) by wildlife carers for the treatment of sarcoptic mange in bare-nose wombats (Vombatus ursinus). We provide additional perspectives on this topic, including consideration of the pharmacokinetics, mode of action and efficacy of moxidectin. The volumes of moxidectin applied by some carers exceeded the manufacturer recommended dose by up to 100-fold, although there appeared to be no association between dose and clinical efficacy. The safety of these extremely high doses has not been scientifically evaluated and we raise concerns regarding the potential for severe adverse events that may be undetected in free-living animals. The inadvertent spillage of large volumes of pour-on acaricides may also have ecotoxic impacts. Reports of treatment failure prompting the perceived need for higher doses are also concerning. The causal factors behind treatment failures should be investigated as a matter of priority, as it is possible that moxidectin resistance is emerging in Sarcoptes scabiei mites infesting wombats. We welcome the insights of individuals actively engaged in the treatment of this debilitating disease of wombats and encourage further discourse, reflecting both the lived experience and evidence-based practice.