Visiting Veterinarian

Poisonous mushrooms and your pet

By Michele Gerhard Jasny V.M.D. - August 2, 2007

In the mid-1990s a grandmother living in the Gulf Coast area of the United States collected wild mushrooms for a special Sunday brunch dish. The self-taught woman had been selecting and cooking wild mushrooms for more than 30 years. This time she goofed. Four people including herself were poisoned. Three recovered but one, a three-year-old child, died of liver failure.

Mushrooms. They come in all shapes, sizes, and colors. There are gilled mushrooms, tube mushrooms, pore or bracket fungi, teeth fungi, and puffballs. There are coral fungi, jelly fungi, flask fungi, and cup fungi. I love their names. Showy Flamecap, Red Pimply Fungus, Old Man of the Woods, Delicious Lactarius, Stinkhorn, Witches' Butter, Big Laughing Mushroom, Destroying Angel, Death Cup.

Wait. Read those last two names again. They're not kidding. Although wild mushrooms come in delicious varieties, like morels, there is also a wealth of deadly varieties - like the Amanita species commonly known as Destroying Angel and Death Cup. So how do you know which of the fungi in your forest are the dangerous ones? You don't. There are a number of folk tales about how to differentiate poisonous from nonpoisonous mushrooms. "It's safe to eat if it doesn't tarnish a silver spoon." "It's edible if it peels easily." Don't believe these. Instead, believe the more cautionary ditties such as "If it's reddish, you might be deadish," and "There are old mushroom hunters, and bold mushroom hunters, but there are no old, bold mushroom hunters." "Even experts make mistakes," says Suzan Bellincampi, Sanctuary Director at Felix Neck Wildlife Sanctuary. I agree. My rule is simple. Only eat mushrooms you buy at the grocery store.

Bad-news 'shrooms

Unfortunately dogs don't always follow my rule. So what happens if your pup, Truffle, munches on the mushrooms when you're walking in the woods? First of all, if you see the ingestion, immediately collect a sample. Wrap the mushroom in a paper towel and put it in a paper bag. Do not use a plastic bag. That keeps things too damp and moist mushrooms rapidly disintegrate into, well, mush, making identification difficult. Next, call your veterinarian and discuss how to induce vomiting. Not every wild mushroom is poisonous, and not every poisonous mushroom is deadly, but until proven otherwise by an expert mycologist, any wild 'shroom should be assumed to be potentially lethal. Don't wait to see if Truffle gets sick. Some of the more deadly varieties will not cause illness for 12 hours or even longer after ingestion, and by then it is too late. Why take chances? Get the mushroom out of Truffle's gut. After that, your veterinarian will probably recommend a dose of activated charcoal to lessen absorption of any potential toxin remaining in Truffle's tummy.

Luckily, although some common backyard mushrooms may cause significant illness, they rarely result in death. In these less-than-lethal cases, onset of clinical symptoms will usually occur within an hour or so of ingestion. Truffle may exhibit vomiting, diarrhea, depression, salivation, excessive tearing, urination, and lethargy. His heart rate may be too fast - or too slow. His pupils may be constricted - or dilated. It all depends on the specific type of mushroom. If it's a "funny" mushroom with psychotropic properties, Truffle may be restless, anxious, have hallucinations, appear disoriented, and seizure.

The most dangerous group is the Amanita species, which account for the majority of mushroom-related fatalities in both people and dogs. Mushrooms in this group contain toxic cyclopeptides. If Truffle eats one of these "death caps," clinical symptoms may not develop for up to 10 to 12 hours later, or longer, giving owners a false sense of security. "Relax," you say. "He ate that funny white mushroom in the woods and nothing happened all day. See? He's fine."

Not. Eating Amanita mushrooms in any significant quantity is almost always fatal. After that delay of 12 hours or so, symptoms begin with abdominal pain, profuse bloody diarrhea, vomiting, nausea, dehydration, elevated heart rate and blood sugar. This may continue for a day or more. Then Truffle may appear to feel better for a day or two but he will eventually go into acute liver failure, with jaundice, sepsis, and clotting problems leading to hemorrhage. Once Truffle is showing clinical signs, there is little known effective treatment. Children and pets tend to be more susceptible than adult humans due to their smaller size, as the unfortunate grandmother on the Gulf Coast tragically learned. There are suggested protocols for aggressive supportive care, but none are scientifically proven to consistently increase the chance of survival. People often end up having emergency liver transplants. Dogs? They usually die within a week.

Don't mow mushrooms

The only definitive case of mushroom poisoning I have ever seen was a youngish pup from up-Island. While mowing the lawn, his father noticed a bunch of little mushrooms and ran them over with the mower. The pup then went and scarfed down the resulting grass clipping-chopped mushroom salad. By the time the dog arrived at my office, he was definitely showing some unusual signs, mostly neurologic in nature - twitching, trembling, and acting disoriented. Clearly whatever type of toadstool he had eaten had central nervous system toxins. The pup's symptoms passed with supportive care and his dad vowed not to mow the mushrooms ever again.

There have been other times I was suspicious of possible mushroom toxicity but couldn't prove it. Unless you witness Truffle eating the mushroom, or we find bits in his feces or vomit to confirm exposure, it is hard to know for sure. Even then, odds are that your veterinarian is not an expert mycologist, and that definitive identification of the species ingested will be elusive. Even if we think we know exactly what Truffle ate, we still determine our protocol based on the specific clinical symptoms, not just the botanical specimen, following another old adage: "Treat the patient, not the mushroom."

What about other pets? For the most part, it is young, curious dogs that eat weird things in the woods. Cats have a more discriminating palate. Horses generally seem to eschew chewing mushrooms (although there is one curious case reported in the veterinary literature of an 18-year-old horse with a benign brain tumor that altered his grazing behavior, resulting in the horse ingesting an Amanita mushroom and dying.)

Obviously, the best cure is prevention. Never intentionally feed wild mushrooms to your pets. If you see them growing in your yard, do your best to get rid of them. This isn't an easy task. Things that may reduce mushroom proliferation include removing animal waste, rotting mulch, and old tree stumps. Some sources suggest that reducing the lawn thatch may also help, but everyone agrees it's tough to tame the mushrooms. I try to pick the ones I see when pooper-scooping the yard and dispose of them. Fortunately, most dogs prefer chewing on a nice stick or tennis ball to a deadly mushroom and cases of serious toxicity in pets are rare. For me, well, I'll occasionally indulge in a few local fiddlehead ferns or even spring dandelion greens, but when it comes to my mushrooms, I'll stick to the store-bought varieties.