Rat Poison is Risky: Is it worth the danger?

Any amount of rat poison in your house puts your pets at risk!

My son thought this was a mouse drinking a beer.

As the weather gets colder, the rodents move inside.  Unfortunately, we often move out rat poison to follow.  This leads to a surge in rodent-poison-associated exposures throughout the winter months.

Rodent poison never stays put.

The problem with placing out bait stations is that once they’re placed, we feel safe.  With “chew proof” boxes and baits placed in unreachable areas, people feel confident that their pets cannot access the bait.

But mice and rats are hoarders. When they find a reliable cache of food, they gather more of it than they can eat in one feeding, and they stash it in various other places in your home for later consumption.  More often than not, they store blocks and pellets in places your pet can reach. This habit makes all the care put into safe placement pointless.

The scent of bait is designed to attract the rodents and encourage them to eat.  The result is a cheese or peanut-butter-scented chunk of poison laying around, tempting your pet.

There are more types of poison that people realize!

Even vet clinics can be guilty of assuming that all rat poison contains the same type of chemical.  While the poison that causes internal bleeding is one of the more common poisons on the market, there are several other types.  Not all of them have antidotes.

They are all virtually indistinguishable my looking at the bait block or pellet itself, so it is important to keep the label if you do place poison down in your home.

1. Anticoagulant rat poison

This rat poison is the only one on the market that has an antidote.  There are many, many brand names that carry baits that cause internal bleeding.  The active ingredients considered to be “anticoagulant” are warfarin, brodifacoum, bromadiolone, difenacoum, flocoumafen, diphacinone, chlorophacinone, pindone, and difethialone. They all range in concentration, which is presented in a percentage form.

Anticoagulants are the most potent rat poison available.  Doses as small as 0.02 mg/kg will lead to bleeding disorders and death.  The smallest concentration of poison is around 0.005%, or 0.05 mg per gram of bait. A ten-pound dog would have to ingest only 2 grams of the lowest concentration bait to ingest enough to cause death.  This is equal to about 1/14th of a one ounce bar.

Signs and treatment:

• These baits cause an animal to be unable to properly clot their blood.
• Within 3-5 days, we start to see signs of bleeding and blood-loss:
  • Bleeding from orifices
  • Blood loss
  • Bruising of the belly and extremities
  • Weakness
  • Lethargy
  • Pale gums
  • Lack of appetite
  • Changes in heart rate
  • Death
• Treatments vary depending on the amount of time that has passed since the ingestion:
  • Some recent exposures can have vomiting induced.
    • This should never occur in a pet more than a few hours past the original ingestion.
  • Dogs showing clinical signs may require a blood transfusion.
  • Blood testing will determine how well the blood is clotting.
    • Successful testing can occur at 48 and 72 hours after an ingestion.
  • Vitamin K is started as an antidote, and continued daily for 21 or more days.
    • Another blood test at the end of treatment will determine if it is safe to stop the antidote.
    • Without the antidote, this poison is deadly.

2. Neurotoxins

Many states have been making a push towards using a different type of rodenticide to prevent death in local wildlife.  The upside about the neurotoxin is that it takes more of the bait to cause signs, but the downside is that it has no antidote.  The active ingredient of the neurotoxin rat poison is bromethalin.  The dose where we may start to see signs is still relatively small at 0.1 mg/kg.  As the concentrations of bromethalin bait average at around 0.01%, there are 2.83 mg per one-ounce bar.  This means we may start to see signs in a ten pound dog who eats about 1/5th of a bar (cats are much more sensitive, and may start to show signs at half the dose for a dog).

Signs and treatment:

• Smaller doses may not be lethal, but severe signs could still occur.
• As doses increase, so do the severity of the expected signs:
  • Hind-limb weakness
  • Stumbling (ataxia)
  • Vomiting
  • Lethargy
  • Lack of appetite
  • Tremors
  • Paralysis and stiffness
  • Eye flicking (nystagmus)
  • Differently sized pupils
  • Seizures
  • Coma
  • Respiratory failure
  • Death
• Any exposure, even if believed it will cause fewer signs, should receive treatment:
  • Vomiting can sometimes be induced within 4 hours of the ingestion.
  • Repeated doses of activated charcoal can help prevent absorption.
  • Supportive care and drugs may be administered to control signs.
  • Hospitalization may be required for several days.

3. Zinc Phosphide

Zinc phosphide baits are more commonly used for infestations of gophers and moles, but you can still find mouse baits containing zinc phosphide.  This is the scariest poison, as an exposure to the family pet can also affect the people in the home as well as the vet staff treating the pet.  Due to the highly dangerous nature of zinc phosphide, and exposure needs to be treated as an emergency.

If your pet gets hold of zinc phosphide, drive your pet to the nearest clinic immediately, and make sure to roll down your windows on the way to the clinic.

Signs and treatment:

• Zinc phosphide is extremely irritating to the stomach and causes quite a bit of vomiting.
  • In stomach acid, zinc phosphide is converted to phosphine gas.
    • Phosphine gas is extremely toxic to both animals and humans!
    • When the animal vomits, it releases the gas into the surrounding air, leading to respiratory failure for both the pet AND the humans who inhale it.
    • Phosphine gas is reported to smell like spoiled fish or garlic.  If you can smell it, it is affecting you.
• Other signs may include:
  • Bloody vomit
  • Diarrhea
  • Lethargy
  • Stumbling (ataxia)
  • Seizures
  • Paralysis
  • Coma
  • Kidney damage
  • Liver Damage
  • Death
• Much of the treatment given at your vet will be symptomatic, since there is no antidote.  Because of the extremely deadly nature of this poison, be prepared for extensive vet care.

If you expect an exposure to a zinc phosphide bait, don’t hesitate to go in.  Time is of the essence, and is important to your own health as it is to your pet’s.

4. Cholecalciferol (Vitamin D)

This bait is not as commonly found in stores anymore, but there are still rat poisons designed to affect the kidneys. Higher in concentration than your average multivitamin, about 0.5 mg/kg of bait can cause signs of kidney damage in a pet.  In a 10-pound dog, this is equal to about 3 grams of bait, or roughly 1/10th of a one-ounce bar.

Signs and treatment:

• The signs seen after an exposure typically occur within 12-48 hours of exposure:
  • Vomiting
  • Diarrhea
  • Lack of appetite
  • Increased thirst
  • Increased urination
  • Kidney failure
  • Heart arrhytmias
  • Muscular dysfunction
  • Death
• Treatments are similar to any poison that causes damage to the kidneys:
  • Inducing vomiting, if possible
  • Administration of charcoal
  • IV fluid therapy for 48 hours or more
  • Checking and re-checking blood work to determine kidney health
  • Medications to help flush the toxins from the body
• Since this bait can last in the body for a very long time, treatment may need to be followed up or continued for weeks after exposure.  If the kidneys sustain damage, life-long adjustments may need to be made to your pet’s lifestyle.

What happens when my pet eats a poisoned rodent?

A common fear of many pet owners is when they find their pet eating the remains of a mouse in a house that has mouse poison.  The transmission of a poison between a rodent and an animal is called a “relay toxicosis”.  In the majority of cases, this is not an issue, as the amounts of bait that linger in the blood and tissues of a dead rodent are going to be far smaller than the amount that is needed to kill a pet.

The exception to this is when a pet digs into the guts of a dead rodent.  In some cases, there will be pellets or bait left undigested in the stomach of a rodent, and this could potentially be enough to cause damage to a pet.  However, a rodent that has died from rat poison will very likely have already digested and absorbed the poison before it dies, so this also is not a very high risk.  When in doubt, seek treatment from a veterinary professional.

Prevention, Prevention, Prevention

As always, the key to keeping your pet from dying of rodenticide poisoning is simply by keeping it off of your property.  If the bait is not there, your pet cannot have access.

Since we can never be 100% sure when it comes to ingested baits (as amounts are very difficult to judge), it is always better to treat as recommended by a vet rather than to hope everything turns out okay.  The hording behavior of rodents makes it hard to keep track of placed baits, and the flavorings make them extremely tasty to your household pets.

If you need some sort of rodent control, snap traps, humane traps, or cellulose baits are a far better option.