The poison-proof dog: Part two

The most frequent intoxication seen by emergency room veterinarians is in dogs that have eaten rodenticides

By Kevin T. Fitzgerald, PhD, DVM, DABVP
Police K-9 Magazine

In our last issue, we began a discussion of how best to protect working dogs in law enforcement from accidental poisoning. We put particular focus on the dog, especially on normal vital signs, in hopes that by recognizing normal values we could more swiftly identify the abnormal ones. In this segment we will look at the most common poisons themselves: how they work, what they do to the dog, and what owners and veterinarians can do to treat the dogs and remedy the situation.

In the United States, far and away the most frequent intoxication seen by emergency room veterinarians is in dogs that have eaten rodenticides. Rodents are incredibly competitive with man for food stores, can be tremendously destructive to buildings, and have the potential to carry life-threatening diseases. The United Nations has estimated that each year one fifth of the world’s food supply is consumed, contaminated, or condemned due to contact with rodents. As a result, since the time of the pharaohs, people have been trying to develop the perfect mousetrap.

Photo courtesy Police K-9 Magazine

In 1944, the anticoagulant rodenticide Warfarin was first produced. It caused rodents who ingested it to bleed into their body cavities. It was primarily sprayed onto grain and then spread as bait. Warfarin was a cumulative toxin. The rodent had to go back a number of times to achieve levels high enough to start bleeding. In the early 1980s, newer, more powerful anticoagulants (brodifacoum, bromadilone) were developed that were first-feeding killers. They killed the rats faster but they also were more toxic to non-target species (children, dogs, wildlife, etc.) that also will readily ingest the bait.

Dogs that eat anticoagulant rodenticides typically bleed into a body cavity — the chest, in most cases. The dog becomes anemic due to hemorrhage, develops pale gums, and pants since it no longer has enough blood to carry oxygen. There is a two- to four hour window in which animals can be made to vomit if they have ingested a toxic substance. Always check with your veterinarian before you make your dog vomit to determine whether it is necessary.

For anticoagulants, a simple blood test establishing clotting times can help document the poisoning. For the anticoagulant rodenticides, there is an effective antidote. Your veterinarian will prescribe Vitamin K1 to improve clotting. If the condition is detected early enough, clotting times are elevated, and the dog is anemic — prompt treatment with Vitamin K1 for an appropriate length of time is almost always successful.

Two newer rodenticides — cholecalciferol (which causes dystrophic calcification of the kidneys) and bromethalin (which causes cerebral edema) — are likewise in widespread use. Recognize that these are not anticoagulants, do not cause bleeding, and are not receptive to Vitamin K1 therapy. If your dog is poisoned, bring in any original containers that the toxin was in (even if they have been chewed up). The original package will give you the active ingredient, the amount, and the concentration of the poison. It may also contain 1-800 numbers that might give manufacturer’s information about poisonings, treatment, and any potential antidotes.

Ethylene Glycol
Pound for pound, the most toxic substance we most frequently deal with is ethylene glycol (antifreeze). Antifreeze also has the highest fatality rate of any poison in animals. It is used everywhere, not only as antifreeze but also as rust remover, in photographic developing labs, and as ice-melt. The molecule is tremendously harmful in small amounts. A shot glass is enough to kill a 20-pound dog and a tablespoon will kill a cat. It has a sweet taste, so animals (and children) may drink it.

The first signs of ingestion are that the dog appears drunk and wobbly, but this stage stops after the first six hours and the animal then appears better. From six to 18 hours, the drug works to damage the kidneys, resulting in renal failure. If detected in the first five or six hours, an effective antidote (fomepizole) can be given and the animal can be saved. Unfortunately, the prognosis is grave for animals presenting after six to nine hours.

A variety of insecticides (organophosphates, carbamates, pyrethrins, and pyrethroids) are used in agriculture to kill destructive pests. Unfortunately, our dogs can blunder into these substances too, particularly puppies that are still teething, younger animals that are more active, and unneutered males that wander more.

The majority of these poisonings present with neurologic symptoms; stumbling, tremors, or even seizures. Know what pesticides are in seasonal use in your area and protect your dog from any exposures. Don’t forget that bathing a dog after any dermal exposure is a very effective decontamination procedure and also prevents dogs from licking potentially toxic material from their coats and ingesting it. Your dog should be bathed immediately following any toxic exposure (powder, liquid, or vapor) that can end up on their fur.

Poisons in the Home
Many veterinarians believe that the bedroom nightstand is the most dangerous place in the home. Here the dog may jump up on the bed and eat human medications, many of which are pleasantly flavored and potentially toxic. Again, bring in the original bottle that contained the medication. The container will tell the active ingredient in the medication, the strength, and how many pills or tablets were in the bottle.

Remember — in poisonings, time is of the essence. We only have a few hours to make the dog vomit and empty the stomach to prevent absorption of the poison. If you think your dog has ingested a harmful substance, call your veterinarian immediately or go right to the animal emergency room. It is better to be safe than sorry concerning toxic ingestion.

The methylxanthines are theobromine (found in chocolate), caffeine (found in cola, coffee, etc.), and theophylline (found in tea). These molecules are in a variety of human foodstuffs and have been recognized as stimulants for centuries. They work by increasing the amount of ATP available to the cell, opening up cellular calcium channels, and releasing epinephrine and norepinephrine. They cause excitement, increase the heart rate, and can cause panting.

The half-life for these molecules in humans is minutes to hours, but in dogs the molecules’ half-lives are long and their effects can last nearly 24 hours. Death can occur as a result of cardiac arrest. Unsweetened baking chocolate contains the highest concentration of theobromine and recently was seen to cause the death of two dogs that were less than 20 pounds.

There is no known antidote for methylxanthines. All we do is attempt to support these dogs, hasten theelimination of the poison, and stabilize the heart rate. Caffeine is often seen in tablet form as Vivarin and No-Doz and used as a study aid or sleep retardant. Dogs that eat these medications should be closely monitored.

Indoors and Outdoors
It is most surprising to me that people don’t know what plants they have — even in their own homes! People frequently bring me pieces of chewed-up leaves and ask me what the plant is. Familiarize yourself with the plants you have and know which ones can be toxic.

April showers bring May flowers but the moisture also leads to the growth of mushrooms. Certain species can cause vomiting, seizures, and even death in dogs. Familiarize yourself with the toxic mushrooms in your area and never allow your dog to eat wild mushrooms.

We still have much to cover in our review of potential toxins for our dogs. In the next issue, we will discuss snakes, bees, spiders, ants, and other creepy things that can bite or sting us and our canines. Future discussions will focus upon poisonous substances that only recently have been recognized as poisonous. Pay attention to the environment your dog works in and be aware of any possible poisons. He depends upon your good judgment. Always be vigilant!

Kevin T. Fitzgerald, DVM, is a staff veterinarian at the Alameda East Veterinary Hospital in Denver, Colorado. He also appears on the television show “Emergency Vets,” seen on Animal Planet.


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