Porcine intestinal spirochaetosis is a notifiable pig disease caused by certain spirochetal bacteria (Brachyspira hyodysenteriae and Brachyspira pilosicoli. Infection causes mild gastrointestinal signs in young pigs and can also be transmitted as intestinal spirochetosis in humans, as it is a zoonosis.
The disease is widespread in pig-rearing countries and may be referred to as PIS, spirochaetal diarrhoea and porcine colonic spirochaetosis.