This post was originally published in November of last year. But as autumn weather closes in, our homes once again become tempting homes for rodents looking to get out of the cold—which is why we want to remind folks to protect their pets from rodenticides.

by Dr. Cheryl Smith

As the winter weather and temperatures return and make us all wonder why we do not move to warmer climates, the native rodents consider moving into our homes. This is the time of year mice and rats start leaving evidence that they

Bengal looking down and pawing at a rat

are trying to take up residence indoors. The modern human response is to buy traps and poisons to keep our personal environments free of these pests (which are also potential carriers of zoonotic diseases).

There are two basic types of rodenticides available in our area. They are either the type that results in abnormal and poor blood clotting, or Bromethalin– a relatively new chemical used in preparations for around the house, that acts by interfering with intracellular sodium balance.

The dicoumarin type results in signs associated with inadequate blood clotting, such as bleeding. This can range from mild to severe enough that the patient can die; however, this is very treatable if recognized in time. Fresh frozen plasma transfusions and vitamin K1 can be used to treat these pets and sometimes red blood cell transfusions are needed if significant bleeding has occurred prior to treatment.


A natural way to control the rodent population around your home is to get a good mouser cat

The Bromethalin type poses a different set of challenges. This type acts by interfering with sodium balance within cells. There are no specific tests that can be used to know if it has been ingested, nor specific antidote to give to prevent clinical signs. The treatment is based on: 1) known ingestion, 2)getting it out of the patient( inducing vomiting), 3) trying to prevent absorption (give serial doses of activated charcoal) and 4) vigilant observation for early neurological signs and then assertive treatment if it does occur.

Bromethalin is also fast acting– so any delay in action after suspicion of ingestion may result in serious compromise to the patient. Unknown ingestion is likely to result in serious patient compromise before suspicion of exposure to this agent is even considered.

If a pet is showing neurologic signs, effective treatment is difficult and costly.


Do not use these agents anywhere a pet (yours or your neighbor’s) could get to the product. Better yet, don’t use these agents at all and consider other methods of control of rodents: consider live trapping and humane death; lethal snap traps placed where no pets could be harmed; or get a cat to use for more natural limitations of a local rodent population.

Make your house less inviting and available to rodents: block entry sites and clean up where potential food sources for rodents might be (contain all wild bird seed, livestock feeds, pet foods, grass seeds, etc).

Know about all the dangerous agents in your house/home/garage/barns/sheds/property to protect your pets from rodenticides. Manage materials to prevent accidental ingestion or exposure.

Have phone numbers for poison control handy if any accidents do occur.

And one last time, consider getting a cat!


ASPCA National Animal Poison Control: (888) 426-4435 A $65 consultation fee may be applied to your credit card.

Pet Poison Help Line: (855) 764-7661  A $39 per incident fee applies

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Ann Arbor Animal Hospital is a locally-owned animal hospital operating for over 90 years in Ann Arbor, MI.