Every year dogs around Australia are poisoned and killed by dead puffer fish washed up along the coast, with many pet owners unaware of how quickly a pleasant beach walk can turn deadly.
While there are no collated national figures on the number of dogs that fall victim to puffer fish poisoning each year, veterinarian Andrew Byrne says he alone has treated "half a dozen or more" cases of such poisoning in dogs within the past 18 months at his clinic in northern Tasmania.
Each of those dogs had, according to their owners, come into contact with a dead puffer fish immediately before they fell sick.
Two of them had such dramatic reactions to the toxin of the fish that they died before they arrived at Dr Byrne's clinic in St Helens.
"By the time they got into the car and to the clinic from wherever they were … the dog was no longer with us," Dr Byrne said.
He said most dog owners were not aware of the "extreme" toxicity of puffer fish and all the owners of the poisoned dogs he had treated had been surprised by how easily their pets' lives had been threatened.
'Among the most toxic poisons known'
Puffer fish, also known as toadfish and blowfish, along with their longer-spined relatives the porcupine fish, are found all the way around Australia's coastline.
The potentially lethal toxin they contain — tetrodotoxin — is found on their skin and internal organs.
According to Animal Emergency Service, tetrodotoxin is approximately 1,200 times more poisonous than cyanide and a lethal dose of it is smaller than the head of a pin.
University of Tasmania marine ecologist Professor Graham Edgar says the toxin is "among the most toxic [natural] poisons known".
"That's across everything — snakes, spiders, whatever," Professor Edgar said.
"Within a toadfish, there are some parts that are actually edible and some parts that aren't.
Deadly 'tasty treats'
Dr Byrne says it is common for dogs in coastal areas to encounter dead puffer fish.
"If puffer fish are pulled up by anglers they tend to be dropped on the wharf or in the boat, or just discarded," he said.
They are also often seen washed ashore on beaches around the country, where many coastal residents walk their dogs.
"So they're there, they smell like fish [and] for a lot of animals that's a worthwhile tasty treat," Dr Byrne said.
He said some dog breeds seemed more likely to chew on a dead puffer fish than others when given the chance.
"The ones that I've seen tended to be English staffies, which tend to put their mouths on anything, and other curious dogs like labradors," he said.
Diagnosing 'in the dark'
For a vet, it can be difficult to diagnose puffer fish as the cause of a dog's poisoning, Dr Byrne said.
"So a lot of the stories [of poisoning by puffer fish] are straight from the owners' mouths regarding what the dog was doing just before it got itself into a lot of trouble … incoordination and breathing issues, and what have you.
"We treat those animals like we would treat any poisoning [when] we don't know what [poison] it is."
Treatment included giving the animals fluids and activated charcoal "to bind up any poisons internally".
This treatment worked for the "four or five" dogs believed to have been poisoned by puffer fish that arrived at Dr Byrne's clinic alive, as they all pulled through.
Puffer fish facts
In Australia, there are more than 60 species of puffer fish, which belong to the Tetraodontidae family.
But the term 'puffer fish' is also often used more generically, to include porcupine fish, which in some cases are also lethally poisonous.
Not all the puffer fish-poisoned dogs that Dr Byrne has seen actually swallowed tetrodotoxin.
While scientific reports of tetrodotoxin passing through a puffer fish's spines do not seem to exist, one scientific article describes the case of an aquarium curator who developed symptoms of tetrodotoxin poisoning after handling a dead porcupine fish's internal organs, and then being pricked by its spines.
With dogs, once the tetrodotoxin enters the body, it acts quickly and signs of poisoning — including vomiting, excessive drooling and panting — appear within minutes.
Symptoms may then progress to trembling, unstable walking, muscle tremors, paralysis, coma and then death.
Dr Byrne said dog walkers must to be on the lookout for puffer fish all year round and familiarise themselves with the symptoms of tetrodotoxin poisoning.
"It's not quite like snake bites where … they're definitely seasonal, and we know all there is to know about snake bites, virtually," he said.
For dog owners looking to keep their pets safe from puffer fish poisoning, Dr Byrne recommends keeping them on a lead.
"This is not a bad idea anyway because there's certain birds and wildlife in our sand dunes that don't really need dogs bothering them," he said.
And to dog owners who have already seen their pet chew, lick or roll on a dead pufferfish his advice is simple:
For further information call the Animal Poisons Helpline on 1300 869 738 or go to animalpoisons.com.au/news/pufferfish-and-your-dog
