Preliminary survey of pseudorabies virus prevalence in swine herds of Thailand and comparison of the relative efficacy of gI indirect and blocking ELISAS.

A survey of 15 swine herds ranging in size from approximately 200 to 2,000 head in central Thailand was conducted to determine the prevalence of pseudorabies (PR) in the region and to determine the infection rate within herds. All swine in the survey had been routinely vaccinated with gI deletion mutant modified live virus PR vaccines. Sera from individual pigs were tested for PR virus specific antibodies with both the gI blocking ELISA and the gI indirect ELISA. Fourteen (93.3%) of the herds were found to be infected with wild type PR virus. The infection rate within these 14 herds was more than 20% in 10 (71.0%) herds and ranged from 2.1 to 15.6% in the remaining 4 herds. The per cent agreement between the gI indirect and blocking assays was 99.3% for all field sera tested. This high level of agreement between the epitope specific gI blocking ELISA and the multiple epitope specific indirect gI ELISA indicates that both tests can be used with equal efficacy and that it is unlikely that field strains that could go undetected by the gI blocking ELISA exist in central Thailand.