New test quickly detects poisonous mushrooms

A simple, portable test to detect the deadliest of mushroom poisons in minutes has been developed by California-based U.S. Department of Agriculture scientists and their colleagues.

USDA said eating toxic mushrooms causes more than 100 deaths a year, globally, and leaves thousands of people in need of urgent medical assistance, with a toxin called amanitin causing the most serious issues.

The new test can identify the presence of as little as 10 parts per billion of amanitin in about 10 minutes from a rice grain-sized sample of a mushroom, or in the urine of someone who has eaten a poisonous amanitin-containing mushroom, USDA said, adding that the test also works with dog urine, as dogs are known to eat mushrooms indiscriminately.

"We developed the test primarily for mushrooms as food products," said microbiologist Candace Bever of the USDA Agricultural Research Service laboratory in Albany, who worked on the development. "Serendipitously, it was sensitive enough to also detect the toxin in urine."

No definitive point-of-care clinical diagnostic test currently exists for amatoxin poisoning, USDA said, and early detection of amanitin in a patient's urine would help doctors trying to make a diagnosis.

"Our hope is that doctors and veterinarians will be able to quickly and confidently identify amatoxin poisoning, rather than having to clinically eliminate other suspected gastrointestinal diseases first," Bever said. "We also hope that will give patients a better chance at recovery, even though there are no clearly effective, specific treatments right now."

USDA said the test also could be a practical and definitive way for mushroom foragers to identify and avoid eating mushrooms with amanitin toxin, if the agency can find a commercial partner to produce and market a test kit.

Although mushroom experts can identify deadly mushrooms just by looking at their appearance, experts cannot see the toxic chemicals that lurk inside, USDA said.

Still, the agency said, the test identifies only the presence or absence of this specific class of toxin; it does not detect other compounds such as hallucinogens or toxins that cause other gastrointestinal or neurological symptoms—so it cannot determine if a mushroom is edible.

Mushroom hunting has gained in popularity in the last several decades. USDA said distinguishing toxic from nontoxic mushroom species is based on first correctly identifying the mushroom and then using a mushroom field guide to determine if it is known to contain toxins or not. But mushrooms of the same species can vary in appearance, especially at different life stages and habitats, the agency said, making them very difficult to identify.

"This test can provide more information about a wild mushroom beyond physical appearance and characteristics, and detect something we cannot even see—the presence of amanitins," Bever said.

If an affordable product like this was available, she said, foraging could become even more popular and possibly safer.