10/05/2017
What symptoms should I look for if my dog ate mouse bait?
Dr. Colleen Lewis / May 10, 2017
Mouse and rat baits come in many block and loose grain forms that are very attractive to our dogs and to a lesser extent, cats. The most common products that I have come across in accidental dog ingestions include the first-generation anti-coagulants such as warfarin, second generation anti-coagulants such as brodifacoum and bromadiolone and a newer neurotoxin called bromethalin.
The first-generation anti-coagulant products have been around awhile on both the human and animal side. There are still a few on the market labeled as mouse and rat bait, but more often dogs and cats are coming into the veterinary clinic due to accidental ingestion of a human product. According to our local pharmacist, the most common first generation anti-coagulants on the human side are still warfarin and coumadin: human blood thinner prescriptions. Once eaten, the anti-coagulant will inhibit the production of vitamin K, therefore, preventing the liver from making necessary blood clotting factors for 4 to 6 days. Without vitamin K, the body loses its ability to adhere platelets together, resulting in poor clot formation. Luckily, the liver stores a few days’ worth of clotting factors, so repeated ingestion is often necessary to cause a problem. When just one pill has been eaten or “lost” I do not get too excited. If someone was feeding their warfarin to their dog because they thought it was the dog’s medication, they have captured my attention. Repeated ingestion of a first-generation anti-coagulant can definitely lead to subsequent problems.
According to Dr. Tina Wismer at the ASPCA Animal Poison Control Center in Urbana, IL, anticoagulants in use as rodenticides today are almost all second-generation derivatives. This class is longer acting than the first-generation. Second-generation products can inhibit vitamin K production for up to 30 days and are potentially fatal after just one incident of ingestion. Symptoms may include lethargy, blood in the urine or feces, exercise intolerance, a non-productive cough, and nose bleeds. Pale gums and bruising can be seen in the later stages as blood loss becomes severe. Bleeding into the brain can cause seizures and other neurologic problems. The cause of death is often by fatal hemorrhage. The bleeding can occur so quickly that you may not see any symptoms at all, only sudden death. All animals suspected of exposure should be evaluated by a veterinarian. Vitamin K is the antidote for the anticoagulant types of rodenticide toxicity. Injectable vitamin K can be absorbed quickly and used in emergency situations, but because of the lingering effects of the second-generation products, oral vitamin K will be prescribed for up to 30 days.
The third class of rodenticide is a newer product, Bromethalin, does not work as an anti-coagulant but as a neurotoxin. Young dogs are very sensitive to this neurotoxic class of rodenticides, causing swelling around the brain. Leading to a completely different set of symptoms, animals may be unable to stand due to rear limb deficits. Extreme hyperexcitability can cause a fever. Hypersensitivity to touch and sound may be present with excessive vocalization. Seizures and coma are common as well. Unfortunately, there is no antidote for bromethalin. Because it is not an anti-coagulant, vitamin K is not effective. Dr. Wismer at the Poison Control Center warns that “treatment of clinical signs is directed toward controlling cerebral edema, and is mostly frustrating and non-productive.” The death rate in dogs and cats following ingestion is high. Fortunately, pets with lower toxicity levels can survive with supportive care. My first experience with bromethalin was heartbreaking as two family dogs at a hog confinement unit got into bait and died within a few hours of each other.
To prevent the devastating effects of rodenticides, make sure that baits are secured in dog-proof boxes or up out of your pets’ reach. Prevent your pets from eating any rodents that have ingested the bait, to avoid “relay” toxicity. Don’t wait for symptoms; call your veterinarian immediately if you suspect ingestion. Take the packaging with you to help your veterinarian determine the class of rodenticide consumed. Depending on the product, inducing vomiting, preventing absorption with charcoal, immediate vitamin K therapy, blood transfusions and measures to decrease cerebral inflammation can potentially save your pet’s life.
About the Author
Dr. Colleen Lewis is a 1996 graduate of Kansas State University, College of Veterinary Medicine. Her career has taken her to many places as a practice owner, consultant, embryologist, and mentor. She enjoys mixed animal practice, teaching, traveling, farming and high school sports with her husband, Andrew and their three boys.
