Enteropathogenicity of Treponema hyodysenteriae in young chicks.

Observation by scanning electron microscopy served to demonstrate that Treponema hyodysenteriae colonized the cecal mucosa of young chicks on day 3 after inoculation and produced lesions from 9 days after inoculation. Severe and clearly visible lesions were present on the cecal mucosa of all chicks necropsied 18, 21, and 24 days after inoculation. Severe lesions such as roughness of mucosal surface and disappearance of the mucosal foldings were observed at low magnification. The lesions were characterized by a destruction of superficial epithelial cells and dilation of crypt orifices. The dilated orifices of crypts were clearly observed, and the number of the crypts increased as compared with that of the crypts on the cecal surface in non-infected chicks. At high magnification, mucosal epithelial cells were found to be desquamated and the surface of the lamina propria mucosae had appeared. Numerous treponemas became visible on the surface of damaged epithelial cells and on the surface of the lamina propria mucosae.