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

Context: 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 (Sarcophilis harrisii), 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.

Aim: To determine the suitability of Et-IPA as a bait biomarker in the Tasmanian devil.

Method: 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.

Key result: Both devils retained serum Et-IPA concentrations at two orders of magnitude above negative control sera when this study concluded.

Conclusions: 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.