It’s getting cold outside and everyone is starting to spend more time inside. Unfortunately this includes rodents. At my house, the barn becomes a warm place for the local rats and mice to hide. However, my barn cat, Buster, is ever vigilant and has no intention of letting these uninvited guests stay in his barn. I often have a “present” waiting for me in the morning, the carcass of an unlucky visitor that Buster has left for me as a trophy.
I have always said the safest form of rodent control is a good cat, especially since rodenticides cause so many problems in my patients. Poisoning with rodent baits is one of the top 10 poisonings reported to the ASPCA Animal Poison Control Center. In 2013, there were 6,803 reports of rodenticide poisoning, almost 20 per day!
Treatment of rat bait ingestion used to be fairly straightforward, most rodenticides contained anticoagulant, or warfarin type drugs. This class of drugs has an antidote, Vitamin K. So our standard protocol would be to make the animal vomit if ingestion has been very recent, and then put the pet on vitamin K for 2 weeks. After treatment, we check a blood test to make sure clotting was normal.
Newer regulations from the U.S. Environmental Protection Agency (EPA) require discontinuing the longer acting (second generation) anticoagulant chemicals in rodenticides. Short-acting (first generation) anticoagulants. The first generation anticoagulant drugs have the advantage of still having an antidote, Vitamin K, but the disadvantage is that some strains of rodents have developed a resistance to the drug, making it less effective.
Many rodenticides contain bromethalin, which affects the nervous system and doesn’t have an antidote. This is very concerning to veterinarians because treatment has to be started immediately after ingestion to reduce absorption of the toxin and prevent symptoms. Symptoms are seizures caused by brain swelling. Once seizures start, unfortunately, mortality is 100%. For dogs, the lethal dose of bromethalin is fairly large, 36 times the amount of an anticoagulant rodenticide. Cats, however, are more sensitive to intoxication than dogs. 2 mg of bromethalin can be lethal to a 10-pound cat, whereas a similarly sized dog’s toxic dose is close to 10 times that amount, or 21 mg.
The newer regulations from the EPA does require all bait is in more secure containers or stations. So the days of leaving out green pellets or wafers are going away. However, the containers aren’t impossible to get into if the dog is motivated by the smell of the bait. Also, cats are more frequently poisoned by eating rodents that have eaten the bait, most cats won’t eat the bait on its own.
A less common ingredients in rat baits are cholecalciferol, which causes kidney failure and zinc phosphide which forms a toxic gas when mixed with stomach acid and water. Just like bromethalin, neither has an antidote.
Overall, pet owners need to be aware of what the active ingredient is in any product they put in their pet’s environment. It is also important to keep packaging available, because if a pet does get into a product, it is very important to know what the toxin is and if specific treatment is available. Ideally, pet owners will either put any toxin well out of reach of their pets or better yet, use more pet-friendly options. As I mentioned previously, a cat is an excellent option, or mouse traps strategically placed with a safe luring agent (my father had the best success with peanut butter).
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