We receive these phone calls year round. A dog (rarely a cat) has ingested poison left out for mice or rats. The owner is often frantic and usually wants to be seen right away. I am not generally in the habit of turning away people who are upset, scared and want me to look at their pet right away but this is one of the cases where I might encourage them to wait depending on when the poison was ingested and what i am going to be able to do for them.
While are several types of rodenticides available for home use the majority of poisons being used in our area are anticoagulants. They kill mice and rats by causing them to bleed to death. In order to understand how these poisons work we should first do a brief overview of clotting.
Everyday we suffer minor injuries that cause damage to the small blood vessels in our bodies. These small breaks in the vessel do not cause any harm because we have a mechanism set up to control blood loss. When a vessel is ruptured it spasms and constricts to minimize the blood lost. When the outside of the blood vessel comes into contact with blood it attracts platelets. Platelets are always circulating and they begin to accumulate at the site of injury. In order for the platelets to stick together and make a clot they need to produce a substance called fibrin. The formation of fibrin involves the activation of one of two clotting pathways. These pathways involve proteins called serine proteases that facilitate several reactions that eventually lead to fibrin formation. As long as vitamin K is available these serine proteases can do their job.
Anticoagulant rodenticides block the body’s ability to produce and utilize vitamin K. That means that once the vitamin K stores in the body are depleted clotting can not take place. If clotting can not take place then the bleeding that occurs everyday but typically goes unnoticed takes on a life threatening importance.
It takes a bit of time for the vitamin K stores to be depleted and most dogs don’t show any signs of toxicity until several days after ingesting the poison. This is why I typically don’t have my clients rush the dog right into the clinic. Especially if the dog eats the poison in front of the owner on a Saturday or Sunday evening. Most people can look up how to induce vomiting on the internet and can try this at home if they like. I always recommend that we induce vomiting as there are certain risks associated with inducing vomiting, including but not limited to breathing in vomit and setting up a terrible pneumonia. If it has been more than few hours since the dog ate the poison, our chances of getting it up with vomiting are pretty small. We can try but it is not likely to happen.
Treatment of anticoagulant rodenticide toxicity involves replacing the vitamin K. This is usually started with an injection of vitamin K given under the skin in the clinic. The injection is followed with oral vitamin K supplementation for several weeks. It is important to be using vitamin K1 (phylloquinone) and the use of vitamin K3 (menadione) as a substitute can be fatal. After two or three weeks the vitamin K is discontinued. 48 hours later we will test your dog’s ability to clot by performing a specific blood test called a Prothrombin Time (PT). If the PT is abnormal we can assume there is still rodenticide in the system and we will continue vitamin K for a few more weeks.
There are newer rodenticides on the market but if you are thinking about fixing your mouse problem with poison I recommend an anicoagulant as there is an antidote available to us should your pet accidentally get into it.
While it is possible for a pet to become poisoned by eating poisoned mice, it requires either the mouse to eat a lot of poison or the pet needs to eat a lot of poisoned mice. These are both possible in theory and have been seen, mostly in barn cats, but it is very unlikely.