Brachyspira are gram-negative anaerobic bacteria which, however, have a certain tolerance to oxygen. Reproduction takes place in the goblet cells of the large intestine where Brachyspira can persist after surviving infection (intermittent shedding!). Pig dysentery, which is caused by B. hyodysenteriae, is a highly contagious multifactorial diarrhoeal disorder that leads to high economic losses in pig production worldwide. The main sources of infection are infected pigs without clinical signs and rodents as reservoir hosts. B. pilosicoli causes a milder disease, spirochete diarrhoea in pigs, which usually occurs directly after weaning.