|Victims of ergotism by Peter Bruegel|
Geoffroy du Breuil of Vigeois was a Benedictine who recorded events from 994-1184 in his Chroniques. He mentions preparations for the First Crusade and the Cathar heresy. He also talks about an outbreak in France of an illness that caused rampant gangrene. This is believed to be a case of St. Anthony's Fire.
St. Anthony's Fire was so-called because it was most successfully treated by monks of the Order of St. Anthony. The order was founded in 1095 by Gaston of Valloire and his son, because the son had been cured from the symptoms by the relics of Saint Anthony the Great. The symptoms of St. Anthony's Fire were not only gangrene that caused limbs to fall off but also convulsions, diarrhea, psychosis, headaches, nausea, vomiting, and an uncontrollable itching feeling.
Now we equate St. Anthony's Fire with ergotism, caused by the fungus Claviceps purpurea which infects rye, barley, and other grains. Ergotism also explains a plague in 857, mentioned in the Annales Xantenses. It is also a proposed explanation for anecdotes of bewitchment found in the Middle Ages and later, including in Puritan New England.