First identification and characterisation of Brachyspira hyodysenteriae in pigs in Hong Kong

Swine dysentery (SD) is an important endemic disease of pigs throughout the world. The most common aetiological agent is the anaerobic intestinal spirochaete Brachyspira hyodysenteriae. The related spirochaete Brachyspira pilosicoli causes a milder form of colitis. We report the first isolation of B. hyodysenteriae and B. pilosicoli from a pig farm in Hong Kong. Faecal samples containing mucus or fresh blood were collected from the ground where finisher pigs had just been loaded into a truck for transport to the abattoir. The samples were subjected to selective anaerobic culture and PCR for B. hyodysenteriae and B. pilosicoli, and two isolates of both species were obtained. The B. hyodysenteriae isolates showed clinical resistance to tylosin and lincomycin, whilst the B. pilosicoli isolates were resistant to tylosin and showed intermediate susceptibility to lincomycin. The B. hyodysenteriae isolates were subjected to multilocus sequence typing and a single previously undescribed sequence type (ST250) was identified. Disease was not recorded in other pigs on the farm, but it may have been masked by the use of antimicrobials. Further work is required to examine the distribution of these two pathogens in this and other farms in Hong Kong and in adjoining mainland China.