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Unintended consequences: Change to safer formula of rodent poisons may be unexpectedly deadly for dogs

An array of rodent poisons fills the shelves at the Running’s store in Willmar. Local veterinarians are urging the public to be aware of recent changes in rodenticide formulas and to take steps to reduce the risk of accidental pet poisoning. (Tribune photo by Rand Middleton)

WILLMAR — A new form of rodent poison, aimed at reducing the health risk to children, pets and wildlife, is appearing on store shelves nationwide and locally.

But worries are mounting among veterinarians about the unintended consequences. Although the rodenticide is meant to be safer, it’s fast-acting and doesn’t have an antidote, and veterinarians fear it could increase the number of dogs who become severely sick or die from accidental poisoning.

Because the appearance and packaging also are similar to those for older rat poisons, it’s especially challenging for pet owners and veterinarians to know what they’re dealing with.

It’s something the public needs to be aware of, said Dr. Gregg Laurence, a veterinarian with the South 71 Veterinary Clinic.

“The game has changed,” he said. “We have seen it already and we know it’s going to get worse.”

Rat and mouse poisons sold for home and farm use have traditionally contained an anticoagulant that prevents blood from clotting and is lethal to rodents that consume it.

Dogs that accidentally get into one of these rodenticides can get sick but are treatable with Vitamin K, Laurence said.

The new rodenticides are the result of a U.S. Environmental Protection Agency decision in 2008 that phases out household use of rat poisons containing so-called second generation, or long-acting, anticoagulants as their active ingredient.

The EPA decision was prompted by concerns over secondary poisoning, which can happen when a rat or mouse poisoned by a second generation anticoagulant is then consumed by wildlife or pets.

Manufacturers began complying in 2011 with the new regulation and reformulating their rodenticides. New rodent poisons containing bromethalin, a toxin that affects the central nervous system and causes swelling of the brain, are now becoming widespread in the market.

What has raised concern among veterinarians is the unexpected risk to pets.

Since 2011, Pet Poison Helpline, a national hotline, has documented a 65 percent increase in bromethalin poisoning in pets.

Unlike accidental poisoning with older rodent control products, which took up to five days before symptoms became evident, a dog that ingests bromethalin can become seriously ill within two to 24 hours, Laurence said.

Symptoms include hyperexcitability, twitching and seizures and are often frightening and distressing to both the animal and the owner, he said.

Immediate veterinary treatment is necessary. There’s no antidote to bromethalin, so treatment generally consists of supportive care.

The similarity in appearance and packaging for bromethalin-containing products and older rat poisons makes it especially challenging for veterinarians to provide the correct diagnosis and treatment.

Laurence has this advice: If you suspect your pet has accidentally ingested rat poison, seek prompt veterinary care and bring along the poison container with the label to ensure accurate identification.

“The sooner we treat, the better the success,” he said.

Although farm dogs are the most frequent victims of this type of poisoning, any dog that comes into contact with rat poison in a garage, shed or other outbuilding is at risk, said Laurence. “It’s very, very rare that we see cats get into it. It’s almost always dogs.”

For property owners who need to control the rat and mouse population, one way to reduce the risk is to place the poison inside a tamper-proof bait station. Both disposable and refillable stations are on the market and are designed to resist tampering by children and dogs.

Veterinary professional organizations have been working to educate practicing veterinarians about the changes in rodent control products but it’s also important for the public to be informed, Laurence said. “People are going to get caught off guard. … Be aware of it.”

Anne Polta

Anne Polta covers health care, business/economic development and general assignment. Her HealthBeat blog can be found at Follow her on Twitter at @AnnePolta.

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