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Historical Significance

Although ergot causes yield reductions, concern about the disease is primarily related to the various toxic alkaloids present in the ergots. The alkaloids can cause severe health problems in both humans and animals. In the Middle Ages, a frightening disease of humans known as "holy fire" or "St. Anthony's fire" was common but unpredictable. Its history is unclear because diagnostics were primitive and symptoms could be attributed to a number of diseases. Symptoms also varied depending on which toxins, called alkaloids, were present in the ingested ergots and at what concentration. Common symptoms included strange mental aberrations, hallucinations, a feeling of burning skin or insects crawling under the skin. Women frequently miscarried, and fertility was generally reduced during outbreaks. Some victims developed gangrene due to constriction of blood vessels in the extremities; many victims lost hands and feet. (Figure 9). Patients with ergotism were cared for in hospitals dedicated to St. Anthony until their painful and prolonged sufferings ceased (Figure 10).

Figure 9

Figure 10

People under the influence of ergot alkaloids may have convulsions, become manic, appear dazed, be unable to speak or have other forms of paralysis or tremors, and suffer from hallucinations and other distorted perceptions. These strange behaviors have been linked to ergotism during the French Revolution and witchcraft in Europe and the U.S. (Salem, MA, in particular). Peter the Great was stopped at the mouth of the Volga River in 1722 in his quest for a warm-water port at Constantinople (Istanbul) by an ergot outbreak that poisoned both his soldiers and their horses.

Ergots are so commonly associated with rye that they were included in early botanical drawings of the plant species (Figure 11). This may be one reason that it took a long time for people to make the association between St. Anthony's fire and ingestion of the ergots. The discovery of the cause of ergotism in 1670 is attributed to a French physician, Dr. Thuillier. Ergotism could then be reduced by separating the ergots from the healthy grains before milling.

Figure 11

Thousands of people have died of ergotism, and mortality rates averaged 40% in some documented epidemics in the 1800s. Even after the cause of ergotism was known, many poor people did not have alternative food sources in years when ergot was severe. Many lives have probably been saved by the adoption of the potato, which originated in South America. As the potato became a peasant staple, production of rye and its accompanying ergot disease declined in many areas.

Fascination with C. purpurea has resulted in its appearance in various fictional works. Robin Cook based his 1994 novel, Acceptable Risk, on an ergot-like fungus isolated in Salem, Massachusetts. A character in an episode of the television series, X-Files, develops strange behaviors after receiving a tattoo colored with a rye extract.

Current Significance

Ergot reduces yield because seeds or kernels are replaced by sclerotia. The disease is of greater significance because of the toxic alkaloids produced by the fungus. Modern cleaning methods remove ergots from grain before it is milled or used for animal feed, but the process is costly and may leave toxic residues. The legal limit of ergot is 0.3 per cent by weight for rye or wheat and 0.1 per cent for barley, oats, or triticale. Grain is classified as "ergoty" if it exceeds this level and is of lower value. Ergot toxins are not destroyed by baking.

Modern management practices reduce ergot infections in most cereal crops. Occasionally, animals released into fields for grazing are poisoned by ergot in wild grasses, particularly following prolonged cool, wet weather in the spring. Ergot can also be a problem where cattle producers rely on grass hay for feed during the winter. When fed to cattle, levels of ergot greater than 0.3 per cent by weight can cause them to lose ear tips and other extremities during very cold weather. Ergot remains a significant problem in grass seed production by reducing yields, creating harvesting problems because of honeydew residues, and causing restrictions on shipment of contaminated seed to other countries.

Midwives and doctors have used extracts from ergots to hasten childbirth or to induce abortions for centuries. Ergot is now deliberately cultivated in the field and laboratory for medicinal purposes. Chemists have intensively studied the more than 40 alkaloids produced by the fungus, including the infamous lysergic acid diethylamide (the hallucinogen, LSD) which was synthesized in 1938. Various compounds have been isolated and modified for medicinal uses, such as treatment of migraine headaches, post-partum bleeding, and various psychological disorders.

Additional Related Fungi

Sorghum ergot. Several Claviceps species cause ergot disease in sorghum (Figure 12). In 1995, Claviceps africana was discovered in Brazil, the first report outside Africa and Asia. It rapidly spread worldwide in most sorghum growing areas including the U.S. It has been found in the Texas high plains where 90% of the U.S. and 35% of the world sorghum hybrid seed is produced. The life cycle is similar to that of C. purpurea with the addition of a second, airborne conidial stage on the surface of the honeydew droplet, in addition to the sticky conidia, which contributes to its rapid spread. The toxicity to animals appeared minimal in previous feeding studies, but the sudden threat of the disease worldwide has led to new studies to determine if the fungus is a health threat to animals in the new areas of disease occurrence. (See additional information in the APSnet Feature Article http://www.apsnet.org/online/feature/ergot/top.html.)

Figure 12

Endophytes in grasses. Pasture grasses with superior drought and insect tolerance and competitivenss have made grazing animals sick. Investigation revealed the presence of fungal symbionts, that were named endophytes (Figure 13). These were fungi from the same family as the ergot fungus (Clavicipitaceae).

Figure 13

Figure 14

The endophytic fungi produce alkaloids similar to those produced by the ergot fungus, resulting in animal diseases such as "fescue toxicosis" and "ryegrass staggers." Symptoms are similar to those of ergotism. Because the fungi are usually transmitted only by seed, care must be taken that endophytes are not present in seed used for forage plantings. On the other hand, endophytes are beneficial in some turfgrass species because they confer disease and drought tolerance and are used as a biological control for leaf-feeding insect pests (Figure 14).

Figure 15

One species of grass endophyte, Epichloë typhina, sometimes produces an external sexual stage that halts the development of grass seed, causing a disease called "choke" (Figure 15). "Choke" disease sometimes limits the production of endophyte-enhanced grass seed.

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