Naturally Occurring Toxins 2

This is the sixteenth post based upon educational sessions and syllabus material presented at the Wilderness Medical Society Annual Meeting & 25th Anniversary held in Snowmass, Colorado from July 25 to 30, 2008. It includes information from a lecture entitled “Beautiful But Deadly: Naturally Occurring Toxins,” delivered by Edward J. (“Mel”) Otten, MD, FACMT, FAWM, who is Professor Of Emergency Medicine and Pediatrics, as well as Director of the Division of Toxicology in the medical center at the University of Cincinnati. Mel is also a past President of the Wilderness Medical Society.

Plants

Plants represent a huge reservoir of medicinal and toxic substances available to man since the dawn of history. There are thousands of known poisonous plants and probably thousands more potentially poisonous and medicinal plants awaiting discovery in the rain forests and other wild territories.

Plants can affect every human physiologic system, and many do so in a deadly fashion. Fortunately, although quite common, most plant ingestions lead to:

° Mild to moderate gastroenteric symptoms
° Mucous membrane irritation
° Contact dermatitis

The most common ingestions fall into one of three categories:

° The herbalist or forager who mistakes a toxic plant for a nontoxic species
° The toddler who tastes everything in his or her immediate environment
° The abuser who is trying to get high by smoking, eating or drinking
whatever might cause the desired effect

The Rule of Plants: Most ingestions are insignificant in volume and not usually harmful, but in large ingestions the plant must be identified.

Most treatment is supportive. The only specific antidote is digoxin Fab fragments (Digibind) to treat some of the cardiac glycoside plants, including oleander, convallaria, and aconitum.

Plant dermatitis
Hundred of plants may cause dermatitis either by antigen formation; irritating sap or latex; phytophotodermatitis; or irritating raphides, hairs or needles.

Poison ivy, oak and sumac

The most common cause of poisoning and the leading cause of work related illness in the United States is a dermatitis caused by species of the genus Toxicodendron (formerly Rhus) known as poison ivy, oak and sumac. A substance known as urushiol, found in all parts of the plant, is a potent antigenic resin that penetrates the dermis and causes cell mediated allergic dermatitis. The dermatitis may be prevented if the resin is removed within 10 minutes by washing with soap and water.

Other

Other common causes for contact dermatitis are daffodils, pineapple, ragweed, chrysanthemum, mistletoe, tulip, creosote, mesquite, mango, lime and Brazilian pepper. Seaweed dermatitis is caused by the blue-green algae Lynbya majuscula and is common during the summer months. These and hundreds of other plants may cause a dermatitis either by antigen formation;
irritating sap or latex; phytophotodermatitis; or irritating raphides, hairs or
needles.

Mushrooms

Fungi have been collected for food since time began and many animal species have developed a tolerance for many of the toxins found in mushrooms. Man, unfortunately, is not one of these species - it has been commented that, “There are old mushroom hunters and there are bold mushroom hunters, but there are no old, bold mushroom hunters.” Most mushroom poisonings are a case of mistaken identity. Amateur mushroom collectors sometimes mistake a poisonous species for a similar appearing edible species. If they ingest a large amount it can cause fatal toxicity. The case fatality ratio for Amanita phalloides poisoning for children is 50%.

The toxic mushrooms are divided into eight groups based on their toxin or clinical presentation.

Group I

Cyclopeptide-containing mushrooms. These are the most toxic of all the
mushrooms. This groups contains Amanita phalloides (death cap), Amanita virosa (destroying angel), and Galerina species. The Amanita species contain amanitins, which are heat stable polypeptides that inhibit RNA polymerase. The victim may exhibit gastrointestinal signs, along with liver and kidney failure and death. While Group I mushrooms usually do not induce symptoms for at least 6 hours and up to 36 hours after ingestion, the case fatality rate may be 50% or more.

Group II

Monomethylhydrazine-containing mushrooms. Monomethylhydrazine inhibits pyridoxal phosphate reactions. Seizures are the most common serious clinical finding and may be treated with pyridoxine. Included in this group are Gyromitra species, including the false morel Gyromitra esculenta.

Group III

The muscarinic mushrooms. These include Amanita muscaria (fly agaric), Amanita pantherina, Clitocybe species, and Inocybe species. As the name would indicate, the symptoms are mainly muscarinic (nausea, vomiting, and diarrhea, among others) and may be treated with atropine.

Group IV

Coprine-containing mushrooms, such as Coprinus atramentarius (inky cap). The toxin blocks acetaldehyde dehydrogenase in a manner similar to disulfiram (Antabuse) and thus only causes toxicity when consumed at the same time as alcohol.

Group V

The ibotenic acid- and muscimol-containing mushrooms. The clinical effects are variable and include hallucinations and an anti-cholinergic syndrome.

Group VI

The hallucinogenic mushrooms, some of which contain psilocybin. These produce an LSD-like hallucinosis and have been used for religious purposes by Native Indian tribes and for recreational purposes by others.

Group VII

These are the most common poisonous mushrooms. They produce gastrointestinal symptoms of nausea, vomiting, and diarrhea. Group VII mushrooms may cause symptoms within 1 hour of ingestion. The symptoms are commonly self limited.

Group VIII

Orelline-containing mushrooms of genus Cortinarius. The toxins in this group have been known to cause interstitial nephritis weeks after ingestion.

The Rule of Mushrooms: The longer it takes for symptoms to begin (after ingestion), the more toxic the mushroom.

To be continued…