1. College of Veterinary Medicine; Huazhong Agricultural Univ.; Wuhan 430070 P.R. China
2. Univ. College of Veterinary & Animal Sciences; Islamia Univ. of Bahawalpur; 63100 Punjab Pakistan
3. Laboratory of Detection and Monitoring of Highland Animal Diseases; Tibet Agricultural and Animal Husbandry College; Linzhi 860000 Tibet P.R. China