Aujeszky's disease vaccination and differentiation of vaccinated from infected pigs.

In this paper, the use of a glycoprotein E (gE)-deleted vaccine to eradicate Aujeszky's disease virus (ADV) or pseudorabies virus in swine is described. In regions where there is a dense population of swine, ADV is highly prevalent and intensive vaccination with such a marker vaccine has resulted, in several countries, in a decrease of the field virus prevalence to a sufficiently low level so that culling becomes economically feasible. The evolution in the reduction of circulating field virus can be followed at herd and/or population level by serological monitoring for antibodies against gE, using commercially available enzyme-linked immunosorbent assays. To be successful, other measures besides the vaccination in itself are important, such as the proper use and administration of the vaccine, repeated boosters, prevention of introduction of gE-positive animals and restriction in the movement of animals from gE-positive herds. When pockets of infection remain, intensifying the vaccination may be needed. Culling of remaining gE-positive animals, particularly breeders, is usually necessary. Some European Union (EU) member states have become ADV-free using this approach. Others are still working at it. The success is often dependent on whether or not a good discipline exists. The disease situation in the different EU member states is described. In ADV-free regions with dense swine populations at risk, it is advisable not to stop the vaccination too soon, particularly when the infection status in neighbouring countries or trade partners is not equally good.