Anticoagulant Rodenticide Poisoning in Cats

What are anticoagulant rodenticides?

Anticoagulant rodenticides are poisons used to kill mice, rats, and other rodents by preventing blood clotting. They are commonly found in hard bait blocks, soft baits (firm play dough consistency), and pellets, but may also be in powder, grain/meal, and liquid formulations.

There are several different active ingredients that may be used in anticoagulant rodenticides, including chlorophacinone, brodifacoum, bromadiolone, difenacoum, difethialone, diphacinone and warfarin. The active ingredient and bait formulation depend on the rodenticide’s intended use and federal regulations.

What is anticoagulant rodenticide poisoning? 

Anticoagulant rodenticide poisoning occurs when a cat ingests a rodenticide containing an active ingredient that prevents blood clotting. This usually occurs when the poison is placed, without protective bait stations, in and around buildings, allowing access to the poison by cats and other non-target animals.

"Anticoagulant rodenticide poisoning occurs when a cat ingests a rodenticide containing an active ingredient that prevents blood clotting."

When an animal is poisoned after it eats a rodent killed by the rodenticide, it is called secondary, or relay, poisoning. This can occur, but is rare, because a cat would need to eat many rodents that died from the poison. Outdoor cats or cats living on farms/stables/ vineyards that use rodenticides are at higher risk for secondary poisoning, especially if they subsist on a diet of rodents.

How does poisoning occur?

Anticoagulant rodenticides cause excessive bleeding by interfering with vitamin K1, which is needed for the body to make certain clotting factors that enable blood to clot and help to control bleeding. Anticoagulant rodenticides decrease vitamin K1 to levels that are too low to produce the needed clotting factors, resulting in uncontrolled bleeding. 

What are the clinical signs of anticoagulant rodenticide poisoning?

Initially, cats do not show signs of anticoagulant rodenticide poisoning. After ingesting this type of bait, it takes 1–2 days for clotting factors in the body to be used up. Next, it takes 3–7 days before signs of poisoning occur due to blood loss. Bleeding is not always obvious as it often occurs inside the abdomen, chest, lungs, joints, and gastrointestinal tract. In some cases, bleeding may be visible from the mouth, nose, or even ears.

Signs of internal bleeding may include weakness, depression, difficulty breathing, pale gums, lack of appetite, distended abdomen, vomiting, bloody or dark tarry stools, unexplained swelling, and bruising. If bleeding occurs within the brain or spinal cord, cats may have neurologic signs. If bleeding is not recognized and treated, death may occur.

If you suspect your pet ingested an anticoagulant rodenticide, it is important to contact your veterinarian or Pet Poison Helpline, a 24/7 pet poison control center, at 1-800-213-6680 right away to help determine the risk of poisoning to your pet.

How is anticoagulant rodenticide poisoning diagnosed?

Most cases of poisoning are diagnosed in pets that have signs of bleeding and a known or suspected exposure to anticoagulant rodenticides. Blood work is often performed to assess for abnormalities. X-rays (radiographs) and ultrasound may be used to check for blood in the chest or abdomen.

How is anticoagulant rodenticide poisoning treated?

Early decontamination and treatment decrease the risk of serious toxicity. If an anticoagulant rodenticide ingestion occurred within a few hours of treatment, the veterinarian may induce vomiting. Inducing vomiting at home in cats should never be attempted because it may cause severe damage to the esophagus and stomach lining. 

"Early decontamination and treatment decrease the risk of serious toxicity."

Once vomiting is controlled, medical-grade activated charcoal may be administered to decrease absorption of the anticoagulant rodenticide by the gastrointestinal tract. Activated charcoal should only be administered by a veterinarian. Otherwise, aspiration into the lungs and life-threatening changes in the blood sodium level may occur.

The antidote to anticoagulant rodenticide is vitamin K1, a prescription medication. This is given to increase vitamin K1 levels in the body and prevent bleeding.

Depending upon the time since ingestion and clinical signs present, hospitalized care may be needed. Cats developing more serious signs may require intensive therapy as they have an increased risk of death. 

What care will my cat require after treatment?

When anticoagulant rodenticide poisoning occurs, vitamin K1 supplementation must be continued for several weeks. During the early stages of recovery at home, limited activity is recommended to prevent injuries that could cause bleeding. Once vitamin K1 supplementation can be discontinued, the cat can return to regular activities.

Pet Poison Helpline, a pet poison control center based out of Minneapolis, MN, is available 24/7 for pet owners and veterinary professionals that require assistance treating a potentially poisoned pet. The staff provides treatment advice for poisoning cases of all species, including dogs, cats, birds, small mammals, large animals, and exotic species. As the most cost-effective option for animal poison control care, Pet Poison Helpline’s per-incident fee includes follow-up consultations for the duration of the poison case. Pet Poison Helpline is available in North America by calling 800-213-6680. Additional information can be found online at www.petpoisonhelpline.com.