Reduction of singleton reactors against swine vesicular disease virus by a combination of virus neutralisation test, monoclonal antibody-based competitive ELISA and isotype specific ELISA

Pigs which are serologically positive for swine vesicular disease virus (SVDV) but which show no clinical signs and for which there is neither a relevant history of the disease on the holding nor contact with a known outbreak are considered as singleton reactors. False positive serological results for an epizootic disease, like SVD, in a non-vaccinated population or in imported animals are of great concern to international trade. For the virus neutralisation test, the gold standard for SVD, singleton reactors are found at a level of 1–3/1000. Singleton reactors also occur when other serological testing methods are used. The number of animals finally considered as singleton reactors can be reduced considerably by performing three different serological tests (virus neutralisation test, monoclonal antibody-based competitive ELISA and isotype specific ELISA) on the same serum. A serological profile of the animal can be derived by analysing the results in greater detail. This procedure can reduce considerably the number of pig holdings on which a prohibition of movement and trade needs to be imposed without requiring analysis of supplementary samples.