Rodenticides

Dear Dr. Jody:  We live in a rural area in an older home, and this winter we have had a lot of mice invade our garage and pantry.  We can’t have them continue to invade our food supply, so we are considering trying to poison them.  We want to make sure the product we choose is safe to use around our Lakeland terrier, “Octane”.  What advice can you give us?

Mouse and rat poisons are collectively known as rodenticides.  They were first developed in the 1940s by the Wisconsin Alumni Research Foundation (WARF).  This organization developed warfarin, the first anticoagulant rodenticide.  Warfarin was part of the group of “first generation” rodenticides, but rats and mice became resistant to the toxin in the decades that followed.  Since then, second generation products have become available.  These products are designed to work more quickly and to be more effective than the first generation products.  Active ingredients include brodifacoum, diphacinone, and bromadiolone.

Both first and second generation rodenticides work in the same way:  they are anticoagulants that inhibit the animal’s ability to clot blood by destroying the body’s supply of Vitamin K.  Vitamin K is a critical component of the complex biochemical chain reaction that produces a blood clot, and without this vitamin, clotting cannot occur.  Even in a healthy and uninjured animal, this inability to clot blood is extremely dangerous.  Without clotting factors, spontaneous bleeding can occur into any body cavity, including joints, lungs, gastrointestinal tract, eyes, and nose.  It is through spontaneous hemorrhage that these products result in the death of rats and mice.

Unfortunately, rodenticides are not species-specific toxins.  All animals, including humans, could suffer the same fate if they ingest enough of the toxin.  There are NO rodenticides that are considered safe for people or pets.

What makes the products especially dangerous to dogs is that they contain flavor enhancers to attract the mice.  Many dogs think that the products taste fabulous, and they are of course unaware that the bait is deadly poison.

If you suspect your pet has ingested even the tiniest amount of rodenticide, there are several important steps that must be taken immediately.  Firstly, bring your pet to your veterinarian immediately.  Bring the packaging with you, and try to estimate how much of the product your pet may have consumed.  Your veterinarian will need to know the name of the active ingredient and its concentration in order to calculate whether your pet consumed a potentially dangerous quantity of the toxin.

If the ingestion occurred in the previous four hours, your vet will induce vomiting to try to rid the pet of most of the product.  Activated charcoal is given to bind any remaining toxin in the gastrointestinal tract and prevent any more from being absorbed.  Your veterinarian may also recommend specific blood tests, called a PT/PTT panel, to be performed at both the 3- and 7-day mark.

Depending on the dose of toxin consumed, your veterinarian may also recommend supplementation with Vitamin K1 to help counteract the effects of any of the toxin that the pet did absorb.  Vitamin K1 supplementation is an extremely effective way to replace the body’s supply of Vitamin K that is being depleted by the anticoagulant.  The Vitamin K supplement must be administered at a carefully calculated dose once daily for several weeks.  Unfortunately, Vitamin K is a rather expensive product, but it is the only known antidote for rodenticide toxicity.

It is important to remember that cats and dogs that ingest poisoned mice are also at risk for toxicity.  If you choose to use rodenticides around your home, it is critical that you ensure the bait is inaccessible to pets, and that the pets have no access to the exposed mice.