COMPARISON OF DIFFERENT BVDV-STRAINS FOR THEIR USE IN DIFFERENTIAL-DIAGNOSIS OF CLASSICAL SWINE-FEVER - AN ATTEMPT TO STANDARDIZE THE NEUTRALIZATION TEST

Six bovine virus diarrhoea (BVD) virus strains were tested in the neut ralization test for their use in the differential diagnosis in classic al swine fever (CSF) serology. The aim of the investigation was to fin d a suitable BVD virus strain guaranteeing a safe differentiation of C SF- and BVD virus induced antibodies using permanent cell cultures (PK -15, MDBK). For test purposes the neutralizing antibody titres of 73 d efined test sera were titrated against the CSF virus strain Alfort/187 as well as the BVD virus strains Grub, Paplitz, NADL, 1138/69, Stenda l, 10421/Han 94). Tests were repeated fivefold. The level of mean anti body titres, the differences in titre to the homologous pestivirus str ain, the standard deviation and the variation coefficient served as te st criteria. The BVD virus strains Grub and NADL yielded the best resu lts. In view of harmonization and standardization the BVD virus strain NADL in connection with a standard protocol for neutralization tests is recommended for the differential diagnosis in CSF serology. Due to the adaptation of the permanent cell-lines PK-15 and MDBK to horse ser um a further source of contamination with non cytopathogenic BVD virus es under routine conditions can be excluded.