Toxic Fungi of Western North America

by Thomas J. Duffy, MD

General overview of mushroom poisonings

The mushrooms that cause almost all deaths worldwide contain amanitins. Amanita phalloides (Fr.:Fr.) Link and Amanita ocreata Peck are the usual amatoxic species in western North America. These two Amanitas have caused all of the recorded deaths in California (which leads the nation in mushroom fatalities) and nearly all of those in the West. The majority were patients who had ingested Amanita phalloides. Amanita ocreata has caused a large number of California deaths and at least one death in Oregon. (10) Two serious poisonings have occurred with amatoxic lepiotas--Lepiota helveola Bres. and Lepiota josserandii Bon & Boiffard in California. There has been one fatality with Lepiota josserandii in Vancouver, British Columbia. (9) There was one death in Washington state caused by an amatoxic Galerina species. Other serious cases of Galerina poisoning have occurred in the PNW.

Unfortunately, there are no simple tests for these amatoxins or for any other toxins in mushrooms, such as silver turning black or rice turning red. Any supposed benefit is the result of pre-selection—making a distinction between “toadstools” and “mushrooms” in the home area of the collector. Since these local, non-systematic distinctions have no scientific basis, collecting in an unfamiliar area may lead to serious poisoning. For example, Americans of Asian heritage may ignore the deadly significance of a volva, since the paddy straw mushroom of east Asia is both very edible and decorated at the base of the stalk with a volva; the spores, however, are pink in contrast to those of the deadly amanitas.

Because of the delay from gastrointestinal symptoms to organ failure in some poisonings, instructions should be given to have emergency room patients return if symptoms are continued or if new symptoms occur. These instructions should be noted on the chart. If the mushroom is known to contain amanitins, the patient should be closely monitored even if initial laboratory studies are negative. Unless it is reasonably certain that the patient can and will return in 4-8 hours, it is probably best to keep the patient in the emergency room.

The consumption of wild mushrooms in the West became increasingly popular in the 1960's because of the rush to natural foods, mushroom fairs, a return to ethnic roots and later the need of loggers to move to another forestry industry. Poisonings, however, have leveled off. Both poisonous and highly edible mushrooms are rare compared to those that are simply inedible.