Mushroom Toxicity

After rains, the East Bay hills come alive with mushrooms. Sprouting in an array of dazzling colors, these fungal fruit bodies can be beautiful – but some of them are deadly poisonous. The Bay Area is home to two of the world’s most toxic mushrooms – Amanita phalloides (the Death Cap) and Amanita ocreata (the Western Destroying Angel). Both are robust, handsome mushrooms that grow near oak trees and contain lethal toxins.
 

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Dogs and cats are curious creatures. When outside, they wander around with their noses to the ground... sniffing a lot of things, licking several things, and eating a few things. Unfortunately, their curiosity sometimes gets them into trouble, especially if they decide to nibble on mushrooms. Dogs and cats are natural scavengers, but many mushrooms are toxic and can cause serious or even life-threatening illnesses. Here are a few things you need to know about mushroom toxicity.

Where do toxic mushrooms grow?

Mushrooms grow best in warm, wet weather and flourish in many places in Canada and the United States. They grow in wooded areas, rocky terrains, grassy parks, and even your backyard. They may grow year-round in warmer climates, but spring and early fall are the prime growing seasons in most areas. This year we are seeing an increase in mushrooms due to the very wet weather we have been having. A good habit is checking your yards daily before giving your pets access. Mushrooms grow very quickly, and many dogs will quickly eat mushrooms without you knowing, especially young dogs.
 

What do toxic mushrooms look like?

Some mushrooms look like the umbrella kind with woodland creatures hiding under them depicted in children’s books. Others look entirely different. Many different species of mushrooms have various characteristics, making the identification of individual types quite complicated. If you aren’t a “mushroom expert, " it’s best to assume that any mushroom you find could be poisonous. Knowing the name of every mushroom species is unnecessary if you avoid them all.
 

How serious is mushroom poisoning?

The severity of mushroom-induced illness depends on the type and number of mushrooms ingested. Sometimes a pet may have mild gastrointestinal (GI) upset that resolves at home. Other times, pets become extremely sick and require hospitalization. Unfortunately, some pets die despite therapy.
 

What does mushroom toxicity look like?

Just as there are many types of mushrooms, there are many types of toxic reactions to mushrooms. Signs vary with the mushroom species and the amount of mushroom ingested by the pet. The toxins can be broken down into four categories to simplify the complexity of mushroom poisoning.

1. Gastrointestinal toxins. Many mushroom varieties cause upset stomachs. Pets may become ill within 15 minutes of nibbling on these mushrooms, or symptoms may be delayed for up to 6 hours. The muscarinic mushroom is a noted variety that causes vomiting and diarrhea. Pets may become weak and dehydrated. Out-patient treatment may suffice, but hospitalization is often required to stop vomiting and diarrhea and restore fluid balance. These mushrooms can also cause a slow heart rate (bradycardia) and respiratory problems.

2. Hepatotoxic. These mushrooms affect the liver. With names like death cap or death angel, Amanita mushrooms sound really ominous, and they are! Amanita mushrooms cause liver failure, which can be deadly. Owners may see their dog or cat nibble this type of mushroom but do not become concerned because their pet looks fine immediately afterward. Then 6-24 hours later, GI symptoms start to occur. Some pets appear to get better for a while, giving owners a false sense of security; however, the underlying liver failure continues to progress. The pet becomes jaundiced, weak, lethargic, and sometimes comatose. What starts as mild GI upset quickly progresses to full-blown liver failure that can result in death in a matter of days. If not treated quickly and aggressively, the liver failure is irreversible.

3. Nephrotoxic. Mushrooms in this category affect the kidneys. Symptoms include nausea, vomiting, and dehydration. Fortunately, these mushrooms are not as plentiful in North America, so cases of toxicity in pets are rare. When illness does occur, signs can be delayed for 12 hours up to a week or longer, so the damage is done by the time treatment is sought.

4. Neurotoxic. There are three main groups of mushrooms that cause neurological signs, including hydrazines, isoxazole, and psilocybin (hallucinogenic or “magic”) mushrooms. The onset of illness is fast, with signs occurring in thirty minutes to six hours. Signs include weakness, lack of coordination, tremors, hallucinations, vocalizations, disorientation, agitation, and seizures. These toxins can also affect the kidneys and liver, causing many problems. Unlike other cases of mushroom toxicity in pets, the source is often inside rather than outdoors. Pets are curious about mushrooms in your home and may find their owner’s private stash of hallucinogenic mushrooms.
 

How is mushroom poisoning diagnosed?

Evidence of exposure to mushrooms is the first factor in an accurate diagnosis. Tell your veterinarian if you even suspect that your pet ate mushrooms and when it may have occurred. Be specific when describing symptoms and their time of onset. This information is vital for accurate diagnosis and prompt treatment.

"To help with identification, bring a mushroom specimen with you to the emergency hospital."

After taking a thorough history, your veterinarian will perform a complete physical exam. Next, blood and urine samples will be taken to determine organ function. A sample of stomach contents may also be retrieved to help identify the mushroom ingested. Since some mushroom toxins have a delayed effect on organs, liver and kidney function tests may be repeated every 24-48 hours to monitor function.

To help with identification, bring a mushroom specimen with you to the emergency hospital. Wrap the mushroom in a damp paper towel rather than a plastic bag. This will preserve the integrity of the specimen and make identification easier. You can also take a picture of the mushroom, but make sure to capture all aspects, including the gills, cap, and stem.
 

What is the treatment for mushroom poisoning?

As with most cases of poisoning, prompt treatment is critical to a successful outcome. Minimizing the toxin's absorption is also critical, so identifying the mushroom in question may take a back seat for a while. Once your pet is stable, mushrooms can be identified by a mycologist at a local college or by visiting the North American Mycological Association website.

"As with most cases of poisoning, prompt treatment is critical to a successful outcome."

Decreasing the amount of toxin that enters the bloodstream may be accomplished by several methods. If your pet sees your veterinarian soon after ingestion, your pet’s veterinarian may induce vomiting to remove mushrooms from the stomach. A GI medication such as activated charcoal will bind with the toxin and prevent its absorption. Sometimes, the doctor may perform a gastric lavage to eliminate any remaining mushrooms from the stomach.

Your pet will also be given intravenous (IV) fluids to combat dehydration and flush toxins from the body. Fluids also support kidney and liver function while already absorbed toxins are processed.
 

How can I prevent mushroom poisoning?

First, assume that all mushrooms growing in the wild are harmful until proven otherwise. If your pet wanders outside unsupervised, remove all mushrooms in your yard. Patrol the yard regularly - mushrooms spring up quickly! If you have trouble eliminating all the mushrooms from your yard, consult an expert.

Curiosity is a good personality trait for a pet. Inquisitive cats and dogs are usually bright and entertaining. But to keep your curious pet safe, avoid mushrooms to prevent mushroom poisoning!