New insights into swine dysentery: faecal shedding, macro and microscopic lesions and biomarkers in early and acute stages of Brachyspira hyodysenteriae infection.

Background: Swine dysentery (SD) is a severe mucohaemorrhagic colitis in pigs caused classically by Brachyspira hyodysenteriae. Although several aspects of B. hyodysenteriae infection dynamic are already described, further research in the early stage of this infection is required. In this study, 7-week-old pigs were orally challenged with B. hyodysenteriae to obtain information about faecal shedding, macro and microscopic intestinal lesions and serum acute phase proteins in pigs at the onset of B. hyodysenteriae shedding (early infection group, n = 8), in pigs with mucohaemorrhagic diarrhoea (acute infection group, n = 8) and in non-infected controls (n = 16).

Results: First B. hyodysenteriae detection by q-PCR and first loose stools with blood and mucus occurred both at 8 days post-inoculation. The lapse between a positive q-PCR and observation of mucohaemorrhagic diarrhoea ranged from 0 to 3 days, except in a single pig in which this period lasted 5 days. Macroscopic lesions were observed in the large intestine from both infected groups although more frequent and severe in acute infection group. Microscopic observation of the apex mucosa revealed that in early infection only higher ulceration values were observed compared to healthy controls. In contrast, the acute infection group exhibited higher ulceration, neutrophils infiltration and increased mucosal thickness compared to the other two groups. Among the serum biomarkers tested, only haptoglobin, C-reactive protein, and creatine kinase showed a significant increase in pigs in the acute infection period compared to controls, whereas haptoglobin was the only factor with a significant increase at the early infection compared to non-infected animals.

Conclusions: This study provides new insights about SD and remarks the complex and limited options to perform an early detection of infected animals beyond PCR diagnosis.