Experimental infection of young broiler chicks with Treponema hyodysenteriae.

In young broiler chicks which were inoculated with 108 cells of Treponema hyodysenteriae within 24 hr after hatching, numerous treponemes were observed by scanning electron microscopy on the surface of the cecal mucosa 7 and 14 days after the inoculation. However, in the groups inoculated with 107 cells, treponemes were not observed on the cecal mucosa 14 days after the inoculation, and the isolation rate from the cecal contents was lower than that from cecal contents of chicks inoculated with 108 cells. While the cecal mucosa of noninfected chicks had a smooth surface, that of the chicks infected with treponemes was generally roughened and the epithelium was eroded. Numerous treponemes were also observed within the eroded epithelium.