Paws for Thought

EDITOR’S NOTE: Dr. Janice Mitchell is a veterinarian with the Island Animal Hospital and Little Current Veterinary Service.

The Dangers of Eating Mice

by Dr. Janice Mitchell

This article is unfortunately inspired by a turn of events that happened in late January. I was called over to my friends’ house as their ‘mouser’ cat was acting strange. This little girl looked inebriated, was vomiting (digested mouse body parts) and very lethargic. She passed away quickly (although not quietly) during the night. It was determined that she had been eating poisoned mice, and the two choices that it could have been are both deadly. I had written about rodenticides last year but after this event had happened, I think a re-visit of this topic is in order. 

The two toxins I wish to focus on are the rodenticide Bromethalin and the antifreeze ethylene glycol.

Bromethalin is downright terrifying. It is a potent neurotoxin that causes irreversible brain swelling, seizures and paralysis. There is no antidote. It is usually fatal if accidentally ingested. This is one nasty poison. What is interesting is that the company states that an animal cannot get poisoned if it eats the poisoned mouse—what they call a ‘relay’ toxicosis. However, as I was researching on our Veterinary Information Network, other clinicians have documented that this is false. Remember the “I know an old lady who swallowed a fly?” Well, the cat or dog that swallows a ‘bromethalined’ mouse will, like the old lady, die. I checked out quickly at our hardware stores to see what products are on the shelf. Sure enough, mixed in with the warfarin poisons (which surprisingly have an antidote), bromethalin is found in products such as TomCat bait blocks. As with most labels these days, you may need reading glasses to look at the ‘ingredient’ list, and remember that broMETHalin creates convulsions in mammals just like METHamphetamines do. Avoid this poison at all cost! It is too deadly to take a chance, knowing now that cats and dogs can be innocent bystanders by eating affected mice. 

I never thought I would talk about antifreeze, or ethylene glycol, as a rodenticide, and you may be wondering as well. Yes, we normally talk about animals getting poisoned by licking antifreeze from a leaking radiator or even broken snow globes. However, as I discovered, antifreeze is added to water to prevent its freezing in the bucket mouse trap set up.

Antifreeze is well known to be an extremely hazardous substance if ingested by dogs and cats.  Animals are attracted to its sweet taste. If veterinary treatment is not begun within a few hours of exposure, one teaspoonful of ethylene glycol can be fatal to a 10-pound cat, while one to two tablespoonfuls can kill a 10-pound dog. Thinking back to our sad scenario, it is possible that this avid mouser looked over into a bucket trap and saw a buffet of mice, laced with antifreeze, and either grabbed one or even licked her paws in the attempt to do. Again, one teaspoon of antifreeze is all it takes to kill a cat.  

What does one do? Rodent control is often necessary as mice are known carriers of hantavirus, a severe, sometimes fatal respiratory disease in humans. Plus, they can wreak havoc on electrical wires leading to fire hazards, and quickly populate out of control. As I have said before, the most effective and safest ways to take care of mice is either having a great mouser cat, using the classic Victor mousetraps, or the sonic mousetraps of which I have heard several anecdotal success reports. The bucket mouse trap is also very successful however without the antifreeze. 

Let’s make mouse eating safe again so that veterinarians can only be worried about the classic treatable tapeworm infections. Sautéed Souris anyone?