Takashi Oyamada
Takeaki Kawagoe
Tsuyoshi Matsunaga
Noboru Kudo
Takashi Yoshikawa
Department of Veterinary parasitology, School of Veterinary Medicine and Animal Science, Kitasato Unversity, Towada-shi, Aomori 034, Japan.

Hiroyasu Yoshikawa
Department of Veterinary Pathology, School of Veterinary Medicine and Animal Science, Kitasato Unversity, Towada-shi, Aomori 034, Japan.