Rodent poison will kill rats…and possibly your dog

Micki McCabe(Feb. 29, 2024) — I have it on good authority that this has been a prolific season for mice in local communities.

Homes, garages, even schools and sidewalks, have proffered opportunities to have one-on-one encounters with these little rodents. This has led to an uptick in the use of mousetraps, sticky traps and rodenticides (poison).

This is an area that needs a little unpacking. First and foremost, be humane. Generally, mousetraps are a safe, effective and humane way to dispatch mice. The sticky traps require an additional step to humanely kill the little guy. Please don’t just throw the live, stuck mouse in your garbage can.

Both these methods are pretty effective in catching/killing rodents without a high risk to your own pets, as long as the traps are thoughtfully placed out of reach of your beloved animals.

On the other hand, poisons used to kill rodents of all kinds are all toxic to our own pets as well as to wildlife, including birds of prey. This is true whether the unintended animal eats the poison directly or eats a sufficient amount from dead or dying prey.

I can’t tell you how many times a client came to me with what I suspected was rodenticide toxicity and told me that yes, they have rat bait at home, but their pet had no access to it. You would be surprised how often they can find it. Rat baits are flavored to attract rodents, which also attracts other pets.

I do not utilize any rodenticides at our home for this reason, but I do occasionally use mousetraps when necessary.

The most common rodenticides are anti-coagulants. They work by blocking the animal’s access to vitamin K, a necessary component of several vital clotting factors made in the body. Lack of Vitamin K leads to severe blood loss and death.

Anti-coagulants are technically no longer available for purchase by the general public because of the unintended toxicity to pets and wildlife. They still can be utilized, however, by professional exterminators and on farms. In addition, people often have old boxes of these anti-coagulants somewhere in their garage.

Common anti-coagulants include warfarin (Coumadin) as well as longer-acting products such as diphacinone, brodifacoum and bromadiolone, among others.

On a slightly positive note, there is an antidote to anti-coagulant toxicity in the form of Vitamin K1 (phytonadione), as long as a diagnosis is made promptly. These patients often also require a blood transfusion to stabilize while waiting for the Vitamin K1 to start working. Vitamin K1 should be administered for 2-6 weeks, depending on how long acting the product is (if known).

The second category of rodenticides is Bromethalin, which causes severe neurologic signs including seizures, tremors and death. It has no antidote, and treatment is limited to decontamination by eliciting vomiting, repeated use of activated charcoal to “soak up” the remaining poison and supportive care. Severe clinical signs indicate a very poor prognosis.

The third category of rodenticides utilizes Cholecalciferol. This is a Vitamin D3-based poison that can lead to severely elevated calcium levels in the blood stream, tissue mineralization, cardiovascular injury and kidney failure. There is no known antidote for Cholecalciferol toxicity, and treatment is aggressive decontamination and intensive supportive care. Prognosis is very guarded in severely affected patients.

If a pet ingests a rodenticide, it is a medical emergency that warrants a veterinary visit. If you have the suspected rodenticide, bring the package with you. If you notice green or blue pellets, bring a sample as well.

If your pet is acting strangely, has developed sudden weakness, pale gums, tremors, etc., a toxicity is often the first thing vets suspect. Seeing a bright green or blue stool could also be the first indication that a pet has had rodenticide exposure. Time is of the essence, because that means the product has already traveled through the gastrointestinal tract.

Wildlife out there don’t have the luxury of a caring owner to get emergency care, so think twice about using these powerful poisons.

Dedicated to Lily and Frankie, two beloved kitties.

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Micki McCabe

Micki McCabe, DVM, DACVIM, FAAVA, is a long-time Clayton resident. The recently retired local veterinarian has an interest in internal and integrative medicine.