A seroepizootiologic study of vomiting and wasting disease virus in pigs.

Neutralizing antibodies to Vomiting and Wasting Disease virus were found in 95 per cent of the sera collected from Belgian sows at slaughter. Piglets suckled by immune sows and kept in isolation acquired maternal antibodies; these had disappeared in all the animals at the age of 15 weeks. Most pigs had lost their maternal antibodies at the age of 11 or 12 weeks (respectively 57 per cent or 86 per cent). A serologic study on two conventional breeding farms showed that this passive immunity was replaced by active immunity between the ages of 8 and 16 weeks. No clinical disturbances appeared to be associated with the infection. The present data indicate that Vomiting and Wasting Disease virus persists on the majority of the conventional breeding farms.