Sea slug eggs likely cause of dog poisonings

Dogs on eastern bays beaches may have eaten toxic sea slug eggs. Photo / Dean Purcell.

Eggs laid by toxic sea slugs are the likely cause of seizures suffered by dogs walking on Auckland beaches, a marine ecologist says.

At least seven dogs have become sick after walking at beaches in the eastern suburbs and the Kohimarama Veterinary Clinic this week emailed clients saying symptoms suggested the animals had eaten slug bait.

However, Dr David Taylor of the Cawthron Institute, said they were much more likely to have fallen victim to sea slug egg sacs. Both the slugs and sacs contain tetrodotoxin, which has been found in high concentrations on beaches in Auckland and Coromandel and was blamed for the deaths of nine dogs in 2009.

"First of all, we've found sea slugs in those areas before and the symptoms that you get with tetrodotoxin poisoning are very similar to what's been described for slug bait poisoning," Dr Taylor said.

Symptoms included gums changing colour, vomiting and the dogs becoming very sick soon after a trip to the beach.

The sacs look like toothpaste squeezed from the tube in a circular motion, Dr Taylor said. The tubes are opaque with white flecks and tended to stick to objects like seaweed, pieces of ropes and shells.

"People don't necessarily see the slugs on the beach, but the dogs can pick up the sacs. They might ingest a little bit of egg sac and still get the quivering and vomiting and not actually die.

"[The idea that] people [are] going along and putting slug bait on the ground does sound a little bit far-fetched."

September and October is the danger season for slugs and their eggs, and it was during this period in 2009 that the dog deaths occurred.

Tetrodotoxin can shut down the human body to a state which imitates death, Dr Taylor said.

More than 2ml per kg of body mass could kill a person.