Differentiation of Treponema hyodysenteriae from T innocens by enteropathogenicity testing in the CF1 mouse.

Fourteen isolates of Treponema hyodysenteriae and 11 isolates of T innocens from eight different countries were evaluated in the CF1 strain female mouse for virulence. Mice were fasted for 24 hours and inoculated intragastrically with 1 ml of culture for two consecutive days. Mice were killed and necropsied at 12 to 15 days after inoculation. Caecitis was detected in mice from each of the groups receiving T hyodysenteriae (67 per cent) but not in mice receiving T innocens or sterile broth. Lesions consisted of hyperaemia, mucosal oedema, catarrhal inflammation and occasional haemorrhage. These studies suggest that the CF1 mouse may be an inexpensive in vivo means of differentiating T hyodysenteriae from T innocens.