FAMILY: Ascomycetes—the Ascomycete Family
"Sac fungi" produce spores in asci, or sacs. Some economically important fungi in this family include yeast and the edible morels. Each ascus produces a definite number of spores, usually eight, and the fungal threads have cross walls (septae) with a central perforation. The fungi are responsible for Dutch elm disease, Chestnut blight, and a variety of human lung disorders as are all ascomycetes.
OCCURRENCE: Claviceps parasitizes the ovary of grasses, especially rye, wheat (durum is most susceptible), barley, and some wild species. Infection occurs when host flowers begin to open.
DISTRIBUTION: Ergot occurs on pasture land grasses or hay and cereal grains from cultivated fields.
POISONOUS PARTS: The poisonous part is the sclerotium (ergot body), a grain-shaped mass that replaces the grass ovary. This varies in size from the same as the grain to 4 times larger. The fungal mass, homogeneous and white when cut open, is shed with the grass and acts as the overwintering phase of the fungus. Federal law prohibits use of cereal grains containing more than 0.3% sclerotia by weight.
SYMPTOMS: Two syndromes are produced by ingestion: 1) gangrenous and 2) convulsive. Ingestion of small amounts daily over a short period results in necrosis of tissues in the extremities, producing dry gangrene. Gangrene is caused by constriction of the blood vessels with blockage of circulation. This results in lameness, coldness, and insensitivity to pain of the affected part. In some instances, serum seepage can cause secondary infection, which may be associated with nausea, vomiting, abdominal pain, and constipation or diarrhea. Pregnant animals spontaneously abort. Mucus membranes of the oral cavity may be inflamed or damaged. In humans gastrointestinal distress and headache may be present. Fowl may lose their combs and beaks. Convulsive ergotism results from ingestion of large quantities of ergot. In addition to the above syndrome, nervous symptoms appear, which are characterized by hyperexcitability, paranoia, rapid pulse, and belligerence. In livestock, death may result from dehydration or starvation within a few days or a month. In humans, whole body spasms and delirium may be present.
Postmortem: gross lesions: dry gangrene of ears, limbs, and tail; moist gangrene of feet and phalanges; inflammatory zone between gangrenous and living tissue; visceral organ congestion and hemorrhage may be present; histological lesions: dry gangrene shows coagulated blood, bacterial infection; moist gangrene shows coagulation and liquefaction necrosis in which large bacilli are evident.
POISONOUS PRINCIPLES: Alkaloids, amines, and other organic compounds are present in ergot. The antihemorrhagic alkaloids probably are the major problem. Chemical formulas are known for two dozen alkaloids, derivatives of lysergic acid. Compounds include ergocryptine, ergocornine, ergocristine, ergotamine, ergosine, and ergonovine.
CONFUSED TAXA: Identification of parasitic fungi should be made by trained specialists.
SPECIES OF ANIMALS AFFECTED: Ergotism in animals other than cattle and humans is rare.
TREATMENT: (11a)(b); (26)
OF INTEREST: The scientific and herbal literature contains much material on ergot, including the natural history and biology of the fungus, chemistry and physiology of its alkaloids, disease symptoms, and use of ergot in medicine. The mode of action of ergot is to stimulate smooth muscle. Because of the persistent contraction of smooth muscle blood vessels, dry gangrene of the extremities occurs.
The infection of grain seed heads by fungus is not uncommon. Cultivated barley, Hordeum vulgare L.. is subject to infection by Gibberella saubinetti (imperfect stage is Fusarium graminearum) and becomes toxic to certain species of animals. The severity ranges from vomition and listlessness in pigs to no apparent effects in ruminants.
Festuca arundinacea Schreb. (=F. elatoir var arundinacea (Schreb.) Wimmer) may cause ergotlike poisoning in livestock, especially cattle (horses appear to be immune). The toxicosis may be due to parasitic fungus rather than the grass itself. The cattle disease "fescue foot" resembles gangrenous ergotism. Postmortem: gross lesions: edema followed by necrosis, distal to a line of demarcation, in extremities; extremities dry, shriveled, and separate; histological lesions: arterioles at the coronary band have thickened walls and constricted lumens.