Eradication of Aujeszky's disease virus from a Swedish pig herd using gI-/TK-vaccine.

An attenuated glycoprotein I-negative (gI-)/thymidine kinase-negative (TK-) constructed vaccine was used to eradicate Aujeszky's disease virus from a large farrow-to-finish herd in Sweden. The herd had had problems every year for seven years and two attempts to eradicate the virus without vaccination had failed. At the start of the vaccination programme 86 per cent of the 396 breeding animals were seropositive to the virus. In spite of evidence of virus circulation in the fattening units, no fatteners were vaccinated. The breeding stock was vaccinated every four months and monitored serologically. Seropositive sows and boars were culled at an economic rate. During the programme, four breeding animals seroconverted to gI. Another seven animals which seroconverted to gI were suspected to have been infected shortly before the first test and vaccination. When all the seropositive breeding animals had been culled, the fattening units were sampled and no seropositive animals were found. The herd was declared gI-negative 39 months after the start of the programme. Monitoring of the herd for another four years, until all the vaccinated animals had been culled, showed that the herd remained free from Aujeszky's disease virus.