Bromethalin: The Invisible Killer Lying In Wait For Your Dog

There’s a hidden danger to your dogs that’s probably lurking around houses, apartment buildings, and offices and you may not even notice it. It’s extremely lethal in incredibly small amounts. Its name sounds rather innocuous: bromethalin — although it’s anything but. How did it get there? In an attempt to deal with one of humanity’s oldest nemeses: the rat.

A short history of rats

Rats have been a constant companion of humankind for as long as dogs have been, although a generally unwanted one. They have been associated with many diseases that can be transmitted to humans, were partly responsible for various plagues that ravaged Europe, and with the exception of space flights have wound up almost everywhere that humans have gone — including commercial airliners. The only landmass they have failed to conquer is Antarctica, for reasons that should be obvious.

They are considered an invasive species, and tend to have a detrimental effect on local wildlife when they move in, especially sea birds. They can multiply rapidly and seem the happiest living alongside us in our cities, lurking under our homes and in our walls.

The exterminators

This is why the extermination of rats has been such a big thing throughout human history, immortalized in the legend of the Pied Piper of Hamelin. In Canada, the entire province of Alberta has been rat-free for nearly sixty-five years, although that’s a distinction that requires the constant attention of a staff of full-time professionals. Elsewhere, the two most common approaches to eliminating rats have been traps and poison. Until recently, one of the most effective poisons used on rats was an anti-coagulant that is also used as human medication. It belongs to a class of chemicals called coumarins, and you may have heard the drug name, Warfarin.

While it can prevent strokes and blood clots in people, it kills rats by making them bleed internally. The key to how it functions is that it is odorless and tasteless, and accumulates in the rat’s body. Normally, rats will only nibble small samples of new food sources, then shun them if they taste anything rancid or poisonous. Because they can’t detect the anti-coagulant in the bait, they will return over the course of a few days to consume more, eventually building up a lethal dose.

Unfortunately, some rats were naturally immune to the effects of Warfarin at those otherwise lethal levels, so they survived and went on to breed more immune rats. In yet another example of unintended evolution in action, Warfarin stopped working, so researchers had to create a new class of anti-coagulants often referred to generically as “super-warfarins.”

Then, in 2011, the Environmental Protection Agency imposed a ban on the use of so-called “second-generation long-acting anticoagulants” in rat poison used in residential settings. Their intention was to protect children, pets, and wildlife from the chemicals used in them. As a replacement, manufacturers began using bromethalin, which is a neurotoxin that kills by damaging the nervous system. 

Unfortunately, it turns out the bromethalin can be fatal to dogs in fairly small amounts — less than 38 ten-thousandths of an ounce (108 mg) will kill a fifty pound dog, although it can take as little as one-fifth of that amount to kill a young dog of the same size. For perspective, that higher number is about one-tenth the weight of a one dollar bill.

There is no known way to test for bromethalin poisoning and no antidote. The only treatment, if caught early enough, is to induce vomiting and administer activated charcoal in a clinical setting. The keys words are early enough. You can induce vomiting yourself if you discover your dog has eaten bromethalin within about fifteen minutes. Otherwise, a fast trip to the vet is the only option.

Signs and treatment

Symptoms will vary depending on the size of your dog and the amount of poison he’s ingested, with smaller and younger dogs being more vulnerable. Signs to watch out for include unsteadiness, weakness, muscle tremors, over-excitability, paddling motions of the limbs, depression, vomiting, high fever, leg stiffness, and seizures.

Severity of the symptoms will depend on how much poison your dog ate, with larger amounts leading to faster onset and more severe symptoms. As mentioned above, there is no cure. The goal in treatment is to remove the poison from the dog’s system before it takes full effect, hence the induced vomiting and activated charcoal.

Keeping your dogs safe

Fortunately, there are alternatives to spreading rat poison all over the yard, depending on how humane you want to be about it. This list of suggestions calls itself humane, although only two of the methods they mention are non-lethal for the rat. If you don’t mind having to release a living rat, then no-kill traps are your best option — and based strictly on name alone, it’s hard to not like the idea of unleashing The Atomic Barbie Rat Trap on your infestation.

If, however, you’re a renter or don’t otherwise have control over the vermin eradication methods used in places where your dog will be, then it’s up to you to make sure that they don’t get into the poison. Try to avoid bait stations when you see them, and never let your dog get near any dead rats or other rodents if you see them.

If you have to use poison, then be sure to follow FDA guidelines, make sure that the container is marked child- and pet-proof, and store it and use it only in locations that your dog cannot possibly get to.

The ideal, of course, is to avoid using poisons at all. There are many other ways to get rid of rats with none of the risk to our faithful furry friends.

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