Swine dysentery (SD) is an important cause of mucohemorrhagic diarrhea in pigs. Swine dysentery is associated with infection by Brachyspira hyodysenteriae which has historically been the only recognized strongly beta-hemolytic Brachyspira sp. However, in recent years, not all strongly beta-hemolytic isolates have been identified as B. hyodysenteriae using PCR assays specific for this species. Several reports have described putatively novel strongly beta-hemolytic Brachyspira spp. including "Brachyspira hampsonii" associated with SD. A pig inoculation study was used to compare lesions and colonic mucin expression associated with infection by B. hyodysenteriae or "B. hampsonii." Diagnosis of SD commonly includes culture which while sensitive is time-consuming and PCR which while rapid can be limited by fecal inhibition. Due to the limitations of these assays, a same-day fluorescent in situ hybridization (FISH) assay was developed to detect B. hyodysenteriae and "B. hampsonii" in pig feces and the threshold of detection was compared to PCR and culture. Little is published about the pathogenesis of SD; yet the interaction between the colonic microbiota and diet seems to be important. Recently, distillers dried grains with solubles (DDGS), a source of insoluble fiber, has been increasingly included in swine diets. A randomized complete block experiment was used to examine the effect of DDGS on the incidence of Brachyspira-associated colitis in pigs.

Gross and microscopic lesions are similar following infection with "B. hampsonii" or B. hyodysenteriae. Histochemical and immunohistochemical evaluation of the colon revealed decreased expression of sulphomucins and mucin 4 and increased expression of mucin 5AC in diseased pigs compared to controls.

The FISH assay effectively detected both Brachyspira spp. in formalin-fixed feces from pigs with SD. Spirochetes were also readily detectable in pen level samples from clinical pigs. Although culture remains the diagnostic assay of choice for surveillance, clinically affected pigs may be identified in a timelier manner using either qPCR or FISH.

Pigs receiving 30% DDGS shed on average one day prior to and developed SD nearly twice as fast as pigs receiving 0% DDGS. These data suggest a reduction in insoluble fiber should be considered a part of any effective disease elimination strategy for SD.