Serologische Differentialdiagnostik der Klassischen Schweinepest (KSP) mit Border Disease (BD)

Pestiviruses have a broad host spectrum and can also infect other species besides their specific hosts. In these cases clinical signs are rare but production of neutralising and other virus-specific antibodies usually occur. These antibodies show variable cross reaction with other pestiviruses. Classical Swine Fever (CSF) is the economically most important pestivirus infection of pigs. Serological investigation of pigs for antibodies against Classical Swine Fever Virus (CSFV) consequently requires a differential diagnosis for antibodies against Bovine Viral Diarrhoea Virus (BVDV) in order to avoid ‘false CSF positive’ results. Comparison of the CSFV and BVDV antibody titres do allow conclusious concerning the origin of the antibodies. Reference viruses to perform the appropriate neutralisations test have been recommended for CSFV and BVDV, respectively. During recent years antibodies against Border Disease Virus (BDV) have been detected in several pig herds in Germany and other EU member states. This caused considerable problems for the serological diagnosis of CSF because the cross reaction of these antibodies with CSFV was more pronounced than with BVDV. The need of an additional differential diagnosis for BDV antibodies was obvious and became the objective of this study. For this purpose 16 pestiviruses from sheep and pigs were tested on different cell culture systems, in order to select the most suitable one. Neutralisation tests of porcine sera were performed with the pestiviruses chosen above. The majority of these sera were produced experimentally with BDV and BVDV in pigs at the EU reference laboratory for CSF. A comparison between homologous and heterologous pestivirus antibody titres could be performed. Furthermore, field sera from pig herds in different countries were also investigated for pestivirus antibodies. These sera yielded doubtful results during routine serological CSF diagnosis and antibodies to other pestiviruses were suspected. The results were evaluated taking into account the value of the antibody titres and the differences between homologous and heterologous titres of the experimental sera. The preliminary results could be tested for suitability in a recent BDV infection of pigs in Germany. For the serological differential diagnosis of CSFV and BDV the permanent sheep cell line SFT-R and the BDV strain Moredun were recommended. BDV strain Moredun does detect the majority of pestivirus antibodies in experimental sera as well as in field sera. However, due to the wide range of antibody titres it is difficult to determine one BDV as reference strain only. Due to geographical localisation one of the remaining BDV strains 137/4, Frijters or Aveyron might be used as well. The decision should be taken by the respective national reference laboratory for CSF. Recent pestivirus field isolates from pigs are not suitable for the differential diagnosis because they occurred sporadical and are individual events.