부산대학교 도서관

Because they are a major source of virus spread in a herd, cattle persistently infected (PI) with the bovine viral-diarrhea virus (BVDV) must be identified and removed. PI cattle generally show various clinical manifestations and are often identified on the basis of mucosal lesions. Some, however, demonstrate no mucosal disease. The present study involves surveillance of BVDV infection in diseased cattle. Examinations for persistent infection were performed on 157 head of cattle demonstrating such clinical manifestations as stunted growth, diarrhea, and pneumonia and others failing to respond to treatment. Of 157 animals demonstrating clinical manifestations, 27 (17.2%) were identified as PI. Next, 14 head of cattle with the same pedigrees as the PI animals but demonstrating no clinical manifestations were examined; 4 of them were identified as PI. It is therefore practically impossible to detect all PI cattle on the basis of clinical manifestations because some demonstrate none at all. Consequently, to determine disease prevalence, examining the whole herd is more important.