Mushrooms are the fleshy fruiting bodies of fungi. They typically shoot up from growing vegetative (mycelium) portions, and they contain spores as reproductive units. Fungi lack chlorophyll; their nutritional requirements are met by using organic material from saprophytic, parasitic, or mycorrhizal life cycles.
Physical Characteristics of Common Poisonous Mushrooms of North America
Genus and Species | Color of Cap | Habitat | Season | Range |
|---|---|---|---|---|
Amanita muscaria | Red to orange-red, sometimes yellow or white | Ground-pine, spruce, birch, poplar, hemlock, and oak trees | June–Nov, Nov-Feb (California) | Widespread, common in eastern US, California, and Pacific Northwest |
Amanita ocreata | White or cream-colored | Sandy soils under oaks or pines | Winter and spring | Pacific Coast from Baja California to Washington |
A pantherina | Brow with white warts, margins with short white striations | Ground under conifers (Douglas fir) | June, Sept–Oct, Nov–Feb (California) | Rocky Mountains and west coast; rare in the eastern US |
A phalloides | Greenish-yellow, yellow or sometimes brownish green | Ground under conifers, hardwoods; junipers and oaks | Late summer, fall, and winter | Maine to Virginia west to Ohio; Pacific Northwest to California |
A bisporigera | Stark white to ivory | Ground under oaks and other hardwoods | Summer and fall | Eastern North America from Texas to the northern Maritime provinces |
Chlorophyllum molybdites | Initially smooth and brown but soon breaking up into brown scales or patches | Lawn, pastures, meadows, fairy rings | Fall | Florida to California, common in Denver, reported in New York and New Jersey |
Clitocybe spp | White, whitish gray, or buff | Ground | Year round (but depending on species) | Widespread in North America |
Cortinarius orellanus | Tawny-brown to reddish-orange | Ground under conifers, birches, and oaks | July–Nov | Widespread in North America |
Galerina marginata | Yellow-brown to brown | Moss, well-decayed conifers and logs | Summer and fall | Throughout North America |
Gyromitra esculenta | Yellow-brown, reddish brown, or dark-brown, cerebriform with lobes | Ground under conifers | Spring: April–early June | Throughout North America |
Inocybe spp | White, yellow to brownish-yellow | Ground under conifers | Summer and fall: May–Nov | Widespread in North America |
Lepiota spp | White to yellow-brown with brown scales | Ground conifers, grass, leaf litter, oak and mixed woods | July–Oct (Michigan, Ohio); July–Nov (Florida); Nov–Feb (California) | Throughout North America |
Paxillus involutus | Yellow-brown, brown, or reddish-brown | Ground: single or numerous on wood in mixed woods | July–Nov | Widespread in North America |
Psilocybe cubensis | Reddish-brown to golden-brown | Dung (cattle ranching), decaying wood chips | Year round | Gulf Coast |
Russula emetica | Red | Single or group; on sphagnum moss, rarely on very rotten wood, conifers, or mixed woods | July–Sept | Widespread in North America |
Exposure is by ingestion. Dogs are particularly susceptible to mushroom toxicosis because of their indiscriminate eating habits and a tendency to roam. Although many mushrooms are edible and safe, some contain toxins (eg, cyclopeptides, gyromitrin, orellanine, muscarine, ibotenic acid and muscimol, and psilocybin as well as unknown toxins) that, on ingestion and absorption, result in mild to severe illness and even death. The mushroom species most frequently implicated in human and animal mushroom fatalities globally is Amanita phalloides.
Poisonous Mushrooms: Onset of Action and Organs Targeted
Mushrooms | Toxin | Onset Time | Organ/System Affected |
|---|---|---|---|
Latent Period >6 hr After Ingestion; Life-threatening | |||
Amanita phalloides,A ocreata, A bisporigera | Cyclopeptides, alpha, beta, and gamma amanitins | 6–24 hr, rarely >24 hr | Primarily liver, kidney secondarily |
Conocybe filaris | Alpha and beta amanitins | 6–24 hr, rarely >24 hr | Primarily liver |
Cortinarius orellanosus, C rubellus | Orellanine | 3–14 days | Primarily renal |
Galerina marginata | Alpha and beta amanitins | 6–24 hr, rarely >24 hr | Primarily liver |
Gyromitra esculenta | Monomethylhydrazine | 6–24 hr | CNS |
Lepiota spp | Alpha and beta amanitins | 6–24 hr, rarely >24 hr | Primarily liver |
Latent Period ≤3 hr After Ingestion; Not Life-threatening | |||
Amanita muscaria, A pantherina | Isoxazoles: ibotenic acid and muscimol | 30 min–2 hr; recovery 4–24 hr | CNS |
Chlorophyllum molybdites | Unknown | 15 min–3 hr; recovery 1–2 days | Gastrointestinal |
Clitocybe spp, Inocybe spp | Muscarine | 15 min–2 hr; recovery 6–24 hr | Autonomic nervous system |
Paxillus involutus | Unknown | 1–3 hr; recovery 2–4 days | Gastrointestinal, immune system (rare) |
Psilocybe spp, Conocybe spp, Gymnopilus spp, Panaeolus spp | Psilocybin and psilocin | 30–60 min; recovery 6–12 hr | CNS |
Russula emetica | Unknown | 30 min–3 hr; recovery 1–2 days | Gastrointestinal |
Most Amanita species are typically identified by their physical characteristics: veil (ring or skirt) or partial veil (annulus) around the upper part of the stem, smooth yellowish-green to yellowish-brown cap or pileus, white gills (spore-bearing structure under surface of pileus), spores (reproductive structure—white to black and other shades of color), stipe or stalk (cap support), volva (cup-like structure at the base of the stem), and mycelium. Other characteristics helpful in the identification of some poisonous mushrooms are listed in . Visual identification can be difficult, even for experienced mycologists, especially considering that the appearance of the mushrooms can be distorted by mastication, gastric secretions, or orally administered treatments such as activated charcoal. For a spore print and spore identification, a mycologist must be consulted. In cases of human poisoning, PCR assays have been used to identify ingested mushrooms when visual identification is inconclusive or impossible.
The latent period between mushroom ingestion and observed clinical signs in exposed animals largely dictates the prognosis. A long delay of 6–12 hours often occurs with exposure to amanitins, with often fatal outcomes (). However, short latent periods do not necessarily indicate a favorable prognosis, in that the animal may have ingested a combination of nonlethal and lethal mushroom species growing in the same location. Generally, for mushroom species that produce clinical signs ≤3 hours after ingestion, effects are self-limiting and not life-threatening, whereas those that produce clinical signs>6 hours after ingestion are life-threatening.
The rapid emergence of mushrooms and their short lifespan within the environment, coupled with the indiscriminate eating habits of many animals, creates diagnostic challenges. History, time after ingestion at which clinical signs occur, and, when possible, mushroom identification determine the treatment approach and prognosis. Establishing the time of ingestion may be difficult or impossible. With no proven antidotes to treat mushroom toxicosis, treatment is primarily directed at decontamination and intensive supportive care.
