Toshiyuki Aohag*
Toshiyuki Shibahara
Laboratory Animal Research Center, Faculty of Medicine, Tottori University, Yonago 683, Japan.

*Present address:
Kurayoshi Livestock Hygiene Service Center, 597-10 Ohtsuka, Kurayoshi 682, Japan.

Katsumoto Kagota
Department of veterinary Internal Medicine, Faculty of Agriculture, Tottori Unversity, Yunago 680, Japan