In 1451, a landowner in Switzerland noticed that one of his ponds was choked with leeches so great in number they threatened his fish stocks. On the advice of his local clergyman, the landowner contacted the Bishop of Lausanne, Georges de Saluces, who immediately convened a hearing. Saluces ordered several of the leeches to be brought into Lausanne, to stand as representatives for the others and receive his ruling.
The outcome of the proceedings is recorded in Saluces’ memoirs and by other chroniclers, who report that the leeches were ordered:
“…to leave the district within three days. The leeches, however, proving contumacious [wilfully disobedient] and refusing to quit the country, were solemnly exorcised.”
Saluces’ decision to exorcise the leeches, while unorthodox and lacking any kind of precedent, was heartily endorsed by academics in Heidelberg. It also seemed to work:
“Immediately after its delivery the leeches began to die off, day by day, until they were utterly exterminated.”