Every year at Christmas, I write about seasonal hazards to pets. Sometimes I feel like a spoilsport, but a recent survey of vets has changed my mind: eight in ten companion animal vets (80%) saw at least one case of toxic ingestion over the Christmas break last year.
This fact makes me realise that I am actually the opposite of a spoilsport: by warning people of potential risks to their pet, I can make sure that they avoid the risks, resulting in a happier Christmas time for people and animals alike.
In the survey, chocolate treats were at the top of the list of edible hazards for dogs, with 72% of companion animal vets reporting seeing at least one case of this type of poisoning. This was followed by cases of toxic ingestion of raisins/sultanas (reported by 63% of vets) and onion or garlic (15%).
Cats also needed emergency trips to the vet at Christmas. The survey found that around one in six vets had treated a cat for antifreeze poisoning (17%) last year and around one in eight (12%) for poisoning by seasonal plants like lilies.
Poisoning is not the only seasonal hazard: festive decorations like tinsel and fairy lights can also be a hazard if hung within reach of a pet. More than a quarter of vets surveyed (28%) had seen at least one such case over Christmas last year.
Most pet owners are aware of most of these dangers to their pets (e.g. chocolate), but the two new ones that still catch people out are onions/garlic and grapes/raisins.
Onions and garlic contain chemicals that damage canine red blood cells, causing anaemia. However they only poison pets if a relatively high quantity is eaten: the amounts normally used in seasoning a human meal are unlikely to do any harm.. The toxic dose of onions is around 0.5% of body weight i.e. around 50g of onions (two ounces) for a 10kg terrier. A medium sized onion weighs 150g (six ounces). You can imagine that if a small dog ate a plateful of onion-rich turkey stuffing, there could be an issue.
As with most poisonings, the best way to deal with this kind of accidental ingestion is to take the pet to the emergency vet at once: drugs can be given that cause vomiting, and this effectively empties the stomach, removing the onions/garlic before they are absorbed. Time is of the essence: if you wait more than two hours between ingestion and vet visit, it's too late, because the onions will already have passed beyond the stomach to the intestines, where the toxic chemicals will be absorbed into the bloodstream.
Grapes and raisins are an even more surprising poison for dogs. How can this be? They're harmless to humans. And everyone has seen dogs occasionally eating foods containing grapes or raisins with no visible adverse consequences. So how can they possibly be poisonous?
The risk to dogs has only been identified in the past fifteen years, following studies of large numbers of dogs that seemed to spontaneously develop life- threatening kidney failure. This research found that a significant number of affected dogs had eaten grapes or raisins in the previous few days: far more dogs than would have happened by chance. This proved that there was a link.
However, not all grapes are poisonous to all dogs. Some dogs can gorge happily on some grapes and raisins with no ill effects while in other cases, a dog might eat just a few raisins and become dangerously ill. It's an intermittent, unpredictable poison.
Despite extensive analysis of the fruit, so far it has been impossible to identify the toxic ingredient in grapes and raisins. The best guess is that it's an intermittent mycotoxin (a poison produced by moulds or fungi when the grapes are damp at harvest). Dog kidney cells are far more sensitive to other mycotoxins than human ones, so this would explain why humans can gorge on grapes with no ill effects while dogs can die from eating a small bunch.
Like most poisons, grape and raisin toxicity is dose dependent, meaning that smaller dogs are more vulnerable. The question that everyone wants to have answered is this: when should they rush their pet to the vet? After a terrier scoffs a slice of Christmas cake? Or when a Labrador steals a few mince pies?
The old rule of thumb that vets used was when a 5kg terrier ate 10 grapes or raisins, or a 30kg Labrador ate 60 grapes, there would be a high risk of a problem. So if a pet ate half of these quantities, you should go to the vet to have vomiting induced. These days, vets are being even more cautious, suggesting that even if just a few raisins are eaten by any dog, the safest option is to empty the stomach.
So if a dog is seen to any food containing raisins, they should be taken to the emergency vet as soon as possible, even if it's lunchtime on Christmas Day or midnight on New Year's Eve. If it's left till later, intravenous fluids and other expensive treatments may be needed to lessen any risk to the pet, and even then, if a significant dose of toxic agent has been eaten, the kidneys could still be damaged irreparably.
Enjoy your Christmas, but don't forget that quick scan of your home to make sure seasonal hazards are out of reach of your pets. More than at any other time of year, preventing problems is so worthwhile.