Ethyl-Iophenoxic acid as a serum marker for oral baiting of Tasmanian devils

Abstract

Oral baits containing vaccines, medicants or toxicants have been delivered to a broad range of wildlife species to protect against or treat disease, or suppress populations. Ethyl-Iophenoxic acid (Et-IPA) is used as a biomarker to determine oral bait consumption by wildlife species to assess and refine baiting strategies. Et-IPA is a persistent biomarker in many eutherian mammal species but not in the two marsupial species, swamp wallaby (Wallabia bicolor) and brushtail possum (Trichosurus vulpecula), tested to date. Et-IPA has not previously been evaluated in carnivorous marsupials. The Tasmanian devil (Sarcophilus harrisii), the largest extant carnivorous marsupial, is threatened by devil facial tumour disease (DFTD). Development of an oral DFTD vaccine bait is underway. In this study, eight devils were fed between 1 mg and 50 mg Et-IPA via oral baits to assess the effectiveness of Et-IPA as a serum biomarker for this species. Using liquid chromatography with tandem mass spectrometry, serum Et-IPA was detected in the devils up to 206 days after ingestion. This study demonstrates the utility of Et-IPA for estimating oral bait consumption by devils, the first carnivorous marsupial species to which this applies.