Epidemiologic monitoring following an episode of pseudorabies involving swine, sheep, and cattle.

In April 1978, an episode of pseudorabies involved swine, sheep, and cattle on a farm in north-central Missouri. The herd of 48 farrowing sows was vaccinated, then separated from the sheep and cattle by double fencing. Within 4 days, death losses in sheep and cattle ceased, indicating that separation by double fencing is an effective means of controlling interspecies virus spread. Monitoring of pseudorabies in sows and their vaccinated offspring was done by serum neutralization testing and virus culturing of pharyngeal swabs for the following 12 months. Pseudorabies virus carriers were in the sow herd 6 months after the initial episode. The serologic response to vaccination of the offspring from immune sows was poor, but pigs segregated from their dams at weaning remained free of detectable infection. It was concluded that segragation at weaning may be useful when expensive breeding lines must be salvaged from an infected herd.