Swine dysentery (SD) is caused by a small, spiral shaped bacterium called Brachyspira hyodysenteriae.
If it takes hold in your herd it can be one of the most expensive and possibly impossible diseases to eradicate especially in the growing pigs, causing a severe, red blood cell destroying (haemolytic), mucus producing, bloody diarrhoea with a severe inflammation of the large intestine (colitis).
There are four other Brachyspira species in pigs:
Brachyspira innocens which is considered non-pathogenic.
Brachyspira pilosicoli which is often associated with a less severe colitis and may also cause disease in chickens and humans.
Brachyspira intermedia which is commonly found in poultry and its significance in pigs remains unclear.
Brachyspira murdochii which was thought to be commensal (normal inhabitant) to the intestine but is now considered to be a low-pathogenic species that interestingly has also been isolated from chickens and rodents – who infects who remains unclear.