Toxic Sea Slugs Cause Dog Deaths

The Cawthron Institute is pleased to have been at the forefront of investigations into the deaths of dogs on Auckland beaches.

Cawthron, a world-renowned algae authority, sent two of its scientists to take samples from Narrow Neck and Cheltenham Beaches after water sent for testing failed to reveal the source of the fatalities.

The Institute was then able to confirm the toxin found in the vomit of one of the dogs that died was the same toxin found in a sea slug sample, and to also identify that toxin as tetrodotoxin, which is also found in tropical puffer fish.

Cawthron made the decision to fund the travel itself, in the interests of expediency.

Technical Manager, Paul McNabb, says given the volume of neurotoxins that can occur in marine and coastal environments, identifying the source was critical in defining the potential culprit, and this was best done in the environment where the problem was occurring.

The Institute has now been commissioned to further investigate how the sea slugs came to contain the toxin.

In puffer fish, symbiotic bacteria within the gut of the fish produce Tetrorodotoxin, and there are special mechanisms to transport the toxin to the skin to provide protection for the fish.

Paul McNabb says, "sea slugs are not known to be able to do any of these things, so it's unlikely it is doing this on purpose. It would appear they are ingesting something which is killing them and once dead they are washing up on the beach where they are being found by dogs."

He says it is also possible the slugs have always been toxic, but never tested before. But now that it is known, he says, people should consider them a possible danger.

Tetrodotoxin, also known as tetrodonic acid and frequently abbreviated at TTX, is common in many organisms.

This is the first time it has been seen in sea slugs, and this far south.

Tests at Cawthron's in-house laboratory in Nelson were able to confirm the presence of the toxin within days of taking samples from the beaches, further evidence of both its capability and expertise in this field.

The Institute recently also developed a new assay test for honey, which has meant the presence of 'tutin' toxin can be detected at much lower levels than previously.

In the past it was only possible to detect at 10 mg/kg, which is five times the acceptable New Zealand limit of 2 mg/kg.