Pseudorabies virus antibodies in swine slaughtered in Iowa.

Sera from butcher swine (1,246 total) were evaluated qualitatively by the microimmunodiffusion test and quantitatively by the virus neutralization test for antibody to pseudorabies virus. Ten percent of the sera had antibody to pseudorabies virus. Follow-up contact with veterinarians whose clients included the farms from which the positive swine originated revealed that few feeder swine are vaccinated against pseudorabies and that most infections with pseudorabies virus are subclinical.