Identifying the toxin

Paul McNabb of the Cawthron Institute in Nelson describes how scientists identified the toxin in the sea slug that was responsible for the death of some dogs on Auckland beaches. Paul explains how they used liquid chromatography-mass spectrometry (LC-MS) to pinpoint the exact toxin.

Transcript

PAUL MCNABB Once we had discovered that the sea slug was the likely cause of the poisonings, then we were involved in much more dialogue with the Poisons Centre, MAF Biosecurity, the local council, DOC – so there was a number of agencies involved – but it was clear from the way that the dogs were dying that it was a highly potent poison that was fast acting and it appeared to have neurological capabilities, so the dogs were getting partially paralysed before they were dying. And the ability to block sodium channels and to cause neurological disruption is very common in marine toxins, and so the first thing we wanted to do was check out it wasn’t a toxin that we were already looking for in shellfish.

Our first stop was to do a series of tests, and we were able to say that it wasn’t a toxin we were currently looking for in shellfish regularly in New Zealand. We used an LC-MS – liquid chromatograph-mass spectrometer – as a scanning instrument, scanning for anything in the sample which was abundant and it would tell us what the mass of that compound was. We were able to identify something in the sample which had a mass of around about 300 and we knew the mass of tetrodotoxin

Tetrodotoxin was a compound that we knew a reasonable amount about. It was a marine toxin that had similar effects to some of the toxins that we were already dealing with. So what we then did was go and look at other scientific papers where they had analysed tetrodotoxin using an LC-MS, and we compared our sample to the results that other researchers elsewhere in the world had got and they were very similar. But we needed to confirm that and the only way to be confident about that was to have some tetrodotoxin of our own. The next day, we had the samples, and we were able to confirm by using the pure tetrodotoxin that the sea slug contained tetrodotoxin.

Acknowledgements: Biosecurity NZ Research, Investigations & Monitoring, Auckland Council