In the original italian book, is a kind of illness called "donkey fever". When a boy does not study, read, be kind and gentle, listen to his parents, and has bad habits and behaviour, he falls ill and turns into a donkey. Pinocchio has been in the "Paese dei Balocchi" for several months before turning. Of course, the Benigni's version of the story is a horrible thing, I'm talking about Collodi's book.