Earlier this year, there was a well-publicized case of several dogs dying after consuming mushrooms.Though it occurred on Vancouver Island, the threat exists anywhere that mushrooms grow, and dog owners must safeguard against it.

Documented cases of mushroom toxicity – poisoning due to the deadly effects of toxins contained in the mushroom itself – are rare in veterinary literature. However, they do occur.

The reason they are missed is because a dog may die and a post mortem never carried out. As well, if an examination is done, testing for a mushroom-derived toxin is infrequently requested.

To understand what mushrooms can do is best illustrated by a few examples.

The mushroom Amanita phalloides, also known as “death cap,” accounts for most cases of mushroom poisoning in people. The toxin it contains causes abdominal cramps, vomiting, watery diarrhea and if enough is ingested, liver and kidney failure. One fresh mushroom cap of this species can contain enough toxin to kill a full-grown human. Higher death rates are recorded in children because of their smaller body size. This would be analogous to a dog.

Cortinarius mushrooms target the kidneys specifically and cause the organs to fail. Other species of mushroom produce toxins that disrupt the nervous system. These mushrooms, which include Amanita muscaria, are grouped under the moniker “magic mushrooms.” After ingestion, even after cooking, the toxins cause people to feel spacey and experience trips.

The mushroom identified in the B.C. poisonings was Amanita pantherina, known as “panther cap” (photo opposite). It is regarded as another magic mushroom and is very poisonous. Interestingly, an article on this mushroom on Wikipedia.org states that “Pantherina is extremely dangerous for pets. Dogs appear to be attracted to it and will feed on it. Brain death can result in as little as one hour.” These effects could not be verified in the veterinary literature, but they seem to reflect what happened in the cases seen by Dr. Longair.

Unfortunately, unless you are a mushroom expert, you can’t tell if the mushrooms growing on your lawn or between your trees are poisonous or safe. Your dogs can’t tell, either. Because dogs, and especially puppies, are inquisitive, it’s easy for them to find a mushroom and nibble on it. And, because some breeds or puppies are so small, it takes very little mushroom to poison them.

With mushrooms, clinical signs may appear immediately or start a long time after ingestion. In the latter case, the link between mushrooms and the symptoms may be lost. Also, mushrooms contain a plethora of poisons that generate a staggering number of symptoms – symptoms that can resemble other diseases and other toxicities.

Making a diagnosis of mushroom poisoning is difficult. For some mushroom species, the toxin has been identified and can be tested for, but for many others, the toxin is unknown. This means that testing is not available. The only way to make a presumptive diagnosis is to have a mushroom specialist (mycologist) identify any remaining mushrooms and match them with the symptoms.

Because mushrooms can be toxic, you already know not to eat one unless you are positive that it is safe. Take the same precautions for your dogs. If there are mushrooms where they play, remove them. This may mean a daily walk so you can find and eliminate any that erupted overnight.

The facts in the mushroom poisonings – Alan Longair, D.V.M.
When the panicked client called, saying her two puppies were crashing, Dr. Alan Longair of the Prevost Veterinary Clinic in Duncan, B.C., got ready.

In a short half hour from the first signs, one puppy was in a coma and the other was seizuring. The team went into action – intravenous lines were set up and the convulsing puppy was given Valium. This stopped the muscle contractions, but then the breathing stopped. The puppy was intubated and provided with artificial respirations.

By the time an hour had passed, the puppies were unresponsive with fixed, dilated pupils, and being kept alive through resuscitation procedures. Even if they survived, chances were their brains would not function properly. The difficult decision was made to euthanize them.

In 31 years of practice, Longair had never seen a case like this. He did manage to find in the stomach contents, remnants of what resembled mushrooms in the owner’s backyard. The diagnosis was confirmed when the mushrooms were identified as Amantina pantherina (panther cap mushroom).

A surprising fact revealed by Longair is that mushroom spores can remain dormant for 100 years and then pop up when conditions are suitable (usually spring or fall). This means that they can suddenly appear where there have been none seen before.

There are no specific antidotes or cures for mushroom poisoning. All a veterinarian can do is treat and hope for the best. Owners can help by preventing poisonings. If you see mushrooms, remove them as soon as they pop up.

Handling poisonings
If you suspect that your dog or puppy has been poisoned, try to tell the veterinarian what the toxin was. If that information is not available, the veterinarian might be able to make an educated guess based on the clinical signs.

When a poisoned dog is presented to a hospital, the veterinarian usually institutes general ‘detox’ treatment. If the dog is seizuring, diazepam (Valium) is administered to stop the violent muscle contractions. If it’s soon enough after the exposure (the dog only recently ate the poison), the stomach may be emptied, by pumping it out or making the dog vomit.

Activated charcoal is often given to absorb any toxins that may persist in the intestines. If the dog is suspected of developing liver or kidney damage, supportive care such as intravenous fluids and other medications are necessary.

In some cases, there is a specific treatment for the poison. This can be done with antifreeze or insecticides. Unfortunately, there is no antidote for mushroom poisoning. The dog can only be helped and supported while the toxin’s effects wear off.

By Jeff Grognet, D.V.M.
A multi-published writer, Jeff Grognet, D.V.M., B.S.c.(Agr.), runs a veterinary practice in Qualicum Beach, B.C., along with his wife, Louise Janes, D.V.M.

(Appeared in August, 2008 issue. To learn more about our print edition click here)