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Rodenticide (Rat Poison) Toxicity


Let’s face it – although this image of a rat seems cute enough, not many people tolerate rats. Rats transmit disease, infest houses, and destroy crops. One of the most common way people attempt to get rid of rats is by using one of several commercially available rat poisons.

Every year, we see several cases of dogs and cats that have ingested rat poison (rodenticide). Usually, the pet’s owner has knowledge that the rodenticide was out, but did not know it could harm his/her pet. Although there are different types of rat poisons, most are anticoagulants which kill by causing an animal to bleed out internally or externally. Typical anti-coagulant rodenticides include one of the following active ingredients: brodificoum, diphacinone, warfarin, and bromadoline. Most of these rodenticides are dyed a green color and, in general, dogs and cats like to eat them.

How do rodenticides work?

The anti-coagulant rodenticides work by interrupting the normal sequence of events that results in clotting or the cessation of bleeding. An animal’s “clotting cascade” is a series of events that involves Vitamin-K clotting factors (specifically factors II, VII, IX, and X). These factors are made by the liver and circulate in the blood of normal animals. As long as there is enough Vitamin K, these factors can be activated and clotting can proceed normally. The anti-coagulant rodenticides essentially make Vitamin K unavailable to these factors, which render them useless in the clotting process. Without Vitamin K, blood clotting doesn’t happen. If clotting can’t happen normally, even the smallest jostle or trauma can lead to life-threatening hemorrhage.

What are signs my pet has ingested an anti-coagulant rat poison?

Because of the characteristic green dye in the rodenticides, sometimes a bright green vomit or stool may be noticed by the owner shortly after ingestion. Once an animal ingests a rodenticide, it generally takes approximately 3-5 days before clinical signs develop. Clinical signs result from bleeding. If an animal begins to bleed externally (or outside the body), you may notice bloody urine, bloody stool, or nose bleeds. More commonly, animals bleed internally (or inside the body), and one of the first signs owners notice is weakness and lethargy. Bruising may be evident on the mucous membranes or area where skin is visible. On a physical examination, we generally notice pale mucous membranes, harsh lung sounds, and signs of fluid or blood accumulation in body cavities (chest, abdomen, even joints).

How do we diagnose rodenticide toxicity?

Diagnosis is made with a combination of physical examination findings, history, and diagnostic tests (x-rays, blood tests (complete blood count, clotting panel, etc.).

How do we treat animals with rodenticide toxicity?

If you know or suspect your pet has ingested a rodenticide, seek veterinary attention immediately! If it has been 4 hours or less since the animal ingested the poison, we will attempt to decontaminate with inducing vomiting and administering activated charcoal. We supportively treat them with Vitamin K supplementation and monitor their clotting with blood tests. If an animal is actively bleeding, we first attempt to stop the bleeding. Decontamination at this point is useless because it has been greater than 24 hours after ingestion. Vitamin K supplementation is started, and blood/plasma transfusions are used to restore clotting factors and red blood cells. Some rodenticides can stay in the body for several weeks. We always try to figure out, if possible, which type of poison was ingested. Either way, treatment with Vitamin K lasts at least 3 weeks (or longer depending on the type of rodenticide ingested), and clotting tests are performed 48 hours after Vitamin K supplementation is stopped to verify that clotting is working properly. Although there are three types of Vitamin K, ONLY VITAMIN K1 is used therapeutically.

What is my animal’s chance of survival if he/she ingests a rodenticide?

If the animal presents shortly after ingestion, the prognosis is excellent. If the animal has bled into the chest or central nervous system, the prognosis is guarded to poor.

Can my pet be poisoned by ingesting a rodent who ate the poison first?

This is a common question we encounter. The answer depends on which type of anticoagulant rodenticide the rodent ate. For example with the newer generation anticoagulant rat poisons, such as diphacinone, the risk is very real. A very greedy rat can eat enough poison to kill 20 rats, although usually rats don’t overindulge to this degree. Animals most at risk would be barn cats that ingest large quantities of rodents which may have been poisoned. In our experience, ingestion of rodenticides by pets is common when animals have access to the poison.

The best bet in preventing an accidental poisoning is keeping your pet away from the poison. To be on the safe side, no poison should be on the premises where your pet lives. If you believe your pet has ingested a rodenticide, seek veterinary care IMMEDIATELY! Call us with any questions about this post 406-255-0500.