Despite the name, mouse and rat poisons can kill more than just that. While these products are designed to kill problem rodents, we also see them resulting in accidental poisoning to our pets (e.g., dogs and cats), and "relay toxicity" to wildlife (e.g., mountain lions, bob cats, birds of prey, etc.) that eat the dead rodents.
 

There are several types of mouse and rat poisons out there, and they are often sold under the same brand name while having different active ingredients. The important thing to keep in mind is that these poisons all work by different mechanisms of action, and many veterinarians aren’t even aware of these different types!

Unfortunately, there’s no way to physically tell which type of rat poison was ingested without seeing the label or box — after all, most of these come in a green, blue, pink, or tan color, and in pelleted or block form. When in doubt, have the box with the active ingredients and the EPA-REG number listed  on it (the latter is required to be on the original container) and readily available at all times; this will allow your veterinarian or Pet Poison Helpline to know the exact active ingredient in the mouse and rat poison.

The four common mouse and rat poisons include types that cause:

• Internal bleeding (e.g., warfarin, bromadiolone, brodifacoum, etc.)
• Brain swelling (e.g.,  bromethalin)
• Elevated calcium and secondary acute kidney failure (e.g., cholecalciferol or Vitamin D3)
• Gastrointestinal bloating and potential organ failure (e.g., zinc phosphide)

Internal bleeding: long-acting anticoagulants (LAACs)

The current, most readily available mouse and rat poisons are what we call long-acting anticoagulants (LAACs). This type affects the body’s ability to clot due to vitamin K₁ antagonist and results in internal bleeding. This active ingredient is similar to warfarin, a blood thinner often used in human medicine. (People who are undergoing hip surgery or knee replacements, or those who have a pulmonary embolism may be on these types of medications.)

Fortunately, when pets ingest this type, there is an antidote: Vitamin K₁, a prescription medication readily available from your veterinarian. Unfortunately, due to new EPA mandates, this type of rat poison will soon be less readily available. In other words, more deadly types of mouse and rat poisons will be on the market, and the ones with an easy, inexpensive antidote (LAACs) will be taken off the market.

Not quite sure what the government was thinking when they made this decision!

With LAAC toxicity, animals will bleed internally within 3-5 days of ingesting the poison. Clinical signs include acting lethargic, coughing (with or without blood), having a decreased appetite, developing bruising or swellings on the body, having difficulty breathing, bleeding from the gums, etc.

If you notice any signs, bring your dog or cat to a veterinarian immediately to have a clotting test done — specifically a platelet count and prothrombin test (or "PT"). Further treatment may include a blood or plasma transfusion, oxygen therapy, and oral vitamin K₁ capsules for 4-6 weeks duration.

Brain swelling

With the ingestion of bromethalin, tremors, weakness, seizures, or paralysis can be seen within a few hours of ingestion. Treatment includes decontamination (e.g., inducing vomiting and giving activated charcoal to bind up the poison) and treatment for cerebral edema. This may include IV fluids, blood pressure monitoring, drugs that decrease brain swelling (e.g., mannitol, furosemide, etc.), anti-seizure medication (e.g., phenobarbital, diazepam, etc.) and symptomatic and supportive care.

Unfortunately, this type of mouse and rat poison has a narrow margin of safety, which means that only a small amount needs to be ingested before clinical signs can be seen.

Elevated calcium and secondary acute kidney failure

This is my most hated type of mouse and rat poison. Not only does this type have a narrow margin of safety (again, it only takes a tiny amount to poison a pet), but it requires very expensive, long-term treatment — with any amount of poisoning. With cholecalciferol or Vitamin D3 toxicity, a sudden, life-threatening increase in calcium levels occurs, and can result in severe acute kidney failure within 2-3 days of ingestion.

Treatment includes aggressive IV fluid diuresis (with a type of IV fluid called 0.9 percent saline), electrolyte monitoring, drugs that increase calcium excretion from the body (e.g., furosemide and prednisone), expensive drugs that decrease calcium absorption from the body (e.g., pamidronate), and chronic blood work monitoring (typically for 4-6 weeks). Typically, pets affected by this poison need to be on chronic, oral medications — from weeks to months — to prevent secondary chronic kidney failure.
 
Gastric bloating and potential organ failure

Phosphide poisons are often found in slightly different forms: poisoned peanuts, gummy moles, or even blocks of poison. This particular type of mouse and rat poison results in severe vomiting, bloating, difficulty breathing, and potential organ failure when ingested. When the poison mixes with the gastric acid of the stomach, phosphine gas is produced, which results in the severe clinical signs.

Feeding your dog when he is poisoned by this can actually make his signs worse, as it increases the amount of potential gas production in the stomach. (Again, reiterating that you should never administer a home remedy — even milk, bread, water, or food — without consulting your veterinarian or Pet Poison Helpline first!).

More importantly, this type of mouse and rat poison is poisonous to you, too — particularly if you inhale the gas from your dog’s vomit! If you or your veterinarian induce vomiting, make sure you aren’t exposed to the gas; ventilate the room well. Or, on the way to the clinic, roll down the car windows and turn on the air conditioner, as the phosphine gas can cause nausea, headache, and asthmatic-like bronchial reactions in you!

When in doubt, always contact your veterinarian, emergency veterinarian, or Pet Poison Helpline (1-800-213-6680) to find out what to do if you think your pet just ingested mouse and rat poison. We can calculate if the amount ingested is poisonous or not, and discuss treatment options as needed. Like most toxicities, mouse and rat poisoning should be 100 percent curable if detected early enough, and treatment is always less expensive and less invasive when treated earlier than later!

To be on the safe side, it’s best to keep mouse and rat poisons out of your yard and house, particularly if you own pets. While it seems more "cruel," using a traditional mouse trap (where it snaps their neck) is actually the most humane — there’s no poison involved, it’s a quick humane death, and worst case scenario, you really hurt your finger in the process.

Dr. Justine Lee

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