Ethyl-Iophenoxic acid as a serum marker for oral baiting of carnivorous marsupials

<p><strong>Context:</strong> Ethyl-Iophenoxic acid (Et-IPA) has been widely used as a bait biomarker to determine oral bait consumption by vertebrate wildlife species. Oral bait vaccines have been delivered to numerous wildlife species to protect them from disease. The Tasmanian devil (<i>Sarcophilis harrisii</i>), the largest extant carnivorous marsupial species, is threatened by the transmissible cancers known as devil facial tumour disease (DFTD). Development of a protective DFTD vaccine is underway, and an oral bait has been proposed to deliver the vaccine in the wild. The bait delivery system requires a biomarker that can be detected for several months post-consumption in Tasmanian devils.</p> <p><strong>Aim: </strong>To determine the suitability of Et-IPA as a bait biomarker in the Tasmanian devil.</p> <p><strong>Method:</strong> Two Tasmanian devils were fed 50 mg Et-IPA (4.5 to 7.1 mg Et-IPA/kg bodyweight). Liquid chromatography with tandem mass spectrometry (LC-MS/-MS) was used to directly measure Et-IPA in baseline serum samples and samples collected on days 1, 14, 26 and 56 post-baiting.</p> <p><strong>Key result:</strong> Both devils retained serum Et-IPA concentrations at two orders of magnitude above negative control sera when this study concluded.</p> <p><strong>Conclusions:</strong> Et-IPA is a useful bait biomarker for Tasmanian devils and can be included in future DFTD bait vaccine field trials to determine bait vaccine uptake.</p>