Observations on avian intestinal spirochaetosis.

Three SPF-laying hens were inoculated into the crop with avian intestinal spirochaetes which previously had been passaged in broiler chicks by oral inoculation (isolate 1380). Mild persisting gastrointestinal disorder developed; at nine months post inoculation spirochaetes were readily demonstrated in caecal faeces. Histologic examination of the caecal mucosa revealed many spirochaetes covering the mucosal surface and filling up the crypts lumina. Spirochaetes were found in intra- and subepithelial locations and in gaps running through the epithelium. These gaps often opened into subepithelial cavities crowded with spirochaetes ('gaplike lesions'). These lesions were seen mostly on the tips of the villi and in the deeper parts of the crypts. Massive erosion or desquamation of epithelium heavily infested by spirochaetes occurred. These findings indicate colonisation of the mucosal surface and of the crypts, penetration of the mucosa and colonisation of subepithelial compartments with spirochasetes in poultry suffering from intestinal spirochaetosis.