Analysis of bovine viral diarrhoea virus in Korea dairy farms

A total of 2, 194 bulk-tank milks from dairy farms were investigated, and of which 842 dairy farms (55, 263 cattle) were assessed to detect persistently infected (PI) individual cattle by performing ELISA. Reverse transcription (RT)-PCR and immunohistochemistry (IHC) were used to develop a rapid screening test for detecting Bovine viral diarrhoea virus (BVDV) in ear tissues. Testing for the bulk-milk tank from dairy farms showed that 2, 007 (91.5%) out of a total of 2, 194 farms were determined to be positive for BVDV, while only 187 bulk-milk tanks (8.5%) were negative. A total of 55, 263 cattle were tested for BVDV, of which 669 (1.2%) cattle from 387 farms (46%) were identified as PI. The distribution of PI was 178 (65.4%) of 272 herds under 14 months. A 220 (80.9%) herds were found in less than 23 month ages. Four infected herds were identified as PI based on RT-PCR analysis. BVDV protein was shown to be localized within epidermal hair bulb cells. This approach of targeted testing of dairy herds using ELISA and RT-PCR for pre-diagnostic testing proves to markedly reduce BVDV-infected herds in Korean dairy farms and in Korean Native Cows.