Animals – Rat bait danger

Most of the domestic rodenticides used in NZ are baits containing anticoagulants, with the same mode of action in that they prevent the production of vitamin K, which is needed for blood clotting. Poisoning of dogs generally occurs through eating the baits directly rather than secondary poisoning (where the dog eats a rat that has died from the bait).

As vets, we see one of three scenarios when we get the call of rat bait poisoning in dogs:

• “My dog just ate some rat bait.” If you can get your dog to us within a couple of hours of ingesting the bait, we can cause vomiting and essentially stop the poison being absorbed into the body at all. Sometimes you observe your dog eating the bait directly, but another useful sign is finding blue or green colouration on the tongue, teeth or gums of your dog, as rodenticides are required to be dyed.

• “I think my dog ate rat bait, but I don’t know when. He seems fine though.” This is where you find the overturned bait bucket where the dogs were rummaging yesterday, or you notice that their faeces are an odd blue colour (see scenario 1). The poison has been ingested and absorbed into the body, so too late to make them vomit. It takes about three to five days from ingestion for the poison to disrupt the body’s ability to clot, so here we can usually time a blood test and look for delayed blood clotting. We then give the antidote, which is a vitamin K supplement that needs to be given daily for as long as the poison is active in the body (usually four weeks).

• “My dog is sick, could it be rat bait?” Some days after eating the poison the anticoagulant effect now means there has been a significant amount of bleeding (often internally) and the dog is in a serious condition. Signs can include weakness, lethargy, pale gums, difficulty breathing, coughing, vomiting, blackened tarry faeces, bleeding from the gums, bruising, shaking, abdominal distention, and eventually death. If there has been significant blood loss, your dog will need a blood transfusion in addition to the antidote and lots of supportive care to get them through.

You can see the scenarios increase in seriousness from one to three, and they also increase in cost moving up. My advice is to be vigilant! Know what your dogs have access to, know who uses rat bait around you, and store and use bats carefully if you have it yourself.

A side note – the other type of rodenticide available over-the-counter is cholecalciferol (Vitamin D). It essentially causes the body to take in too much calcium which leads to damage and dysregulation of multiple organs, then death. It acts fast, a fairly small quantity is toxic, and there is no antidote. I don’t recommend you ever use this bait.