[Differential diagnosis of classical swine fever and border disease: seroepidemiological investigation of a pestivirus infection on a mixed sheep and swine farm].

During recent years neutralizing antibodies against Border Disease Virus (BDV) were found repeatedly in German pig herds. Consequently there was a demand for a differential diagnostic system. A permanent sheep cell line and BDV reference strain Moredun were chosen and were applied in a could be used case study. A pestivirus could be isolated from piglets on a mixed farm and was characterised as 'non-Classical Swine Fever' (CSF) by using monoclonal antibodies. Due to a CSF suspicion the pig herd was destroyed immediately. Serum samples of sheep from the same farm were used for further characterisation of the new virus isolate. A neutralization test of the sheep sera was performed against different pestiviruses and the new isolate. Neutralizing antibody titres against the new virus pig isolate were significantly higher than against all other pestiviruses. BDV strain Moredun recognised the antibodies clearly, whereas CSF viral strain Alfort 187 and several isolates of bovine viral diarrhoea virus (BVDV) strains scored the lowest cross reaction.