Borna disease was first described in 1885, when all horses belonging to a cavalry regiment stationed near the city of Borna in Saxony, Germany, died from a hitherto unknown disease, then termed hitzige Kopfkrankheit ("hot-tempered head illness"). In 1909, Ernst Joest and Kurt Degen discovered distinctive inclusions in the nerves of horses that had died of Borna disease, which were named Joest-Degen inclusion bodies. This histopathological feature remains in use today to confirm the presence of Borna disease. In 1924, the Austrian virologist Wilhelm Zwick suggested a virus as the cause of the disease.
