Pathological observation on experimental swine dysentery.

Experimental swine dysentery caused by 4 cultured strains (S73/2, DJ183, DJ70 and DK762) of Treponema hyodysenteriae was studied pathologically. The distribution and quantity of treponemes were examined on tissue sections stained by the Warthin-Starry method. Of the organs the colon contained the largest number of treponemes and the cecum and rectum the second largest number. Histopathological lesions were restricted to the large intestine. They ranged from mild catarrhal colitis in the mild case to desquamative, hemorrhagic colitis in the severest case. The severity of lesion was closely associated with the quantity of treponemes present. There was no difference in quality of the lesion between any two of the strains used in this study. Electron microscope revealed a large number of free treponemes present in the intestinal lumen and crypts. Treponemes were seen more frequently in the cytoplasm of goblet cells than in that of intestinal epithelial cells. They were also observed in desquamated degenerative epithelia. A small number of them were found in intact epithelia. Morphologically, the treponeme had a granular protoplasmic cylinder at the center which was surrounded by a thin envelope. Between the cylinder and the envelope there were axial fibrils.