Anticoagulant Rodenticide Poisoning in Dogs

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 depends on the product's intended place of use and federal regulations.

What is anticoagulant rodenticide poisoning?

Anticoagulant rodenticide poisoning occurs when a dog ingests rodenticide. This usually occurs when the poison is placed in and around buildings without protective bait stations, allowing access to the poison by dogs and other non-target animals. Poisoning after eating rodents killed by the rodenticide is called secondary or relay poisoning. This can occur but is rare because a dog would need to eat many rodents that died from the poison.

How does poisoning occur?

Anticoagulant rodenticides causes excessive bleeding by interfering with vitamin K1 recycling in the body. Vitamin K1 is needed for the body to make certain clotting factors which enable blood to clot and help control bleeding. By preventing vitamin K1 recycling, anticoagulant rodenticides decreases vitamin K1 to levels that are too low to produce the needed clotting factors. Since the clotting factors cannot be produced, the body can no longer form clots needed to keep blood within its vessels and uncontrolled bleeding may occur.

What are the clinical signs of anticoagulant rodenticide poisoning?

Initially, dogs do not show signs of anticoagulant poisoning. After ingesting this type of bait, it takes 1-2 days for vitamin K1 and 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 such as from the mouth or nose.

"If bleeding happens within the brain or spinal cord, dogs may have neurologic signs."

Signs of internal bleeding may include weakness, depression, increased respiratory rate, difficulty breathing, coughing (which may produce blood), pale gums, lack of appetite, enlarged abdomen, vomiting, bloody or dark tarry stools, swelling or pain in the joints and bruising. If bleeding happens within the brain or spinal cord, dogs 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 animal 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 to assess blood clotting times, red blood cell and platelet counts are often performed. Radiographs (x-rays) and ultrasound may be used to check for blood in the chest or abdomen.

Measuring amounts of specific rodenticide active ingredients in the blood can be performed at a specialized veterinary diagnostic laboratory. Since the results may not be returned quickly, testing is uncommon. Treatment is often started without testing if poisoning is suspected.

How is anticoagulant rodenticide poisoning treated?

Early decontamination and treatment decrease the risk for serious toxicity. If an anticoagulant rode ingestion occurred within a few hours of treatment, the veterinarian may induce vomiting. Once vomiting is controlled, activated charcoal may be administered to decrease the absorption of 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 blood sodium levels may occur.

The antidote to anticoagulant rodenticide is vitamin K1, a prescription drug. This can be given via injection or by mouth to increase the vitamin k1 levels in the body and prevent bleeding.

Depending upon the timing since ingestion and signs, hospitalized care may be needed. Fluids may be administered intravenously. Dogs developing more serious signs may require intensive therapy as they have an increased risk for death. In addition to vitamin K1, blood or plasma transfusions, oxygen therapy or removal of blood from the chest and/or abdominal cavity may be needed. Blood work to monitor blood clotting times, red blood cell counts, and platelet counts are commonly performed.

What care will my dog require after treatment?

When anticoagulant rodenticide poisoning occurs, vitamin K1 supplementation must be continued for several weeks. Approximately 48 hours after discontinuing the vitamin K1, blood clotting times will be evaluated to assure no further supplementation is needed. 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 dog can return to regular activities.

Pet Poison Helpline, an animal 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