[1] Yamaguchi Prefectural Res Inst Publ Hlth, Yamaguchi 7530821, Japan
[2] Natl Inst Infect Dis, Infect Dis Surveillance Ctr, Tokyo 2010011, Japan
[3] Gunma Prefectural Inst Publ Hlth & Environm Sci, Maebashi, Gunma 3710052, Japan
[4] Kagoshima Univ, Dept Vet Hyg, Kagoshima 8900065, Japan
[5] Yamaguchi Univ, Dept Vet Hyg, Yamaguchi 7538511, Japan