The main ingredient in these frequently used blue-green pellets, bars and poison packs has changed. For many years, these products used anti-coagulants to kill pests. They contained products that used up Vitamin K-dependent clotting factors in animals and caused them to bleed to death. As gruesome as this sounds, these products took several days after ingestion to cause harmful bleeding in dogs and cats that accidentally ingested them. If an owner had a question about potential exposure, an animal could have its clotting time tested. If the clotting time was abnormal or if the pet owner was certain that exposure had occurred, then we could give the pet Vitamin K pills, and the pet would likely make a full recovery.
But in 2008, the U.S. Environmental Protection Agency mandated a move away from anti-coagulants. And since 2011, an ingredient called Bromethalin has replaced anti-coagulants in newly manufactured rat and mouse poison. These new Bromethalin-containing products are packaged identically to their predecessors, so they can’t be distinguished based on looks alone.
According to the national Animal Poison Control Center, Bromethalin causes fluid build-up and increased pressure in the brain within four to 36 hours after it is ingested. Signs that pet owners might see in their animals include unsteadiness, depression, vomiting, muscle tremors and seizures. The signs can progress for one to two weeks, and death may occur due to respiratory failure or complications secondary to prolonged seizure activity. Cats tend to be even more sensitive than dogs and will often develop paralysis with only small exposures.
Because there is no test for Bromethalin exposure, this kind of poisoning can be difficult for veterinarians to diagnose. The best remedy is early and aggressive treatment, including emptying the stomach and providing multiple doses of activated charcoal over several days to try to bind the toxin.
Animals having complications associated with brain swelling would be hospitalized and intensively managed as long as their symptoms warranted. The degree of clinical symptoms and the management of rodenticide ingestion is dependent on the type and amount ingested. Since it is impossible to tell from the color and appearance of the mouse or rat poison what the active ingredient is, owners who suspect a problem should bring in the label from the packaging if it is available.
Rodents certainly can be a problem as the weather cools and they try to get indoors. If you have to take measures to control rodents, consider humane traps, traditional mouse traps or products with an active ingredient other than Bromethalin.