Experimental studies with a gE-deleted live BHV1 vaccine

A study to compare a conventional BHV1 vaccine with a gE-deleted live BHV1 vaccine revealed that duration and extent of virus excretion and reactivati on following immunosuppression are similar. The main advantage of a marker vaccine is the ability to differentiate antibodies induced by field virus f rom those induced by the marker vacine. Vaccination with the marker vaccine also leads to a latent infection and the virus can be isolated after immun osuppression. It is also impossible to prevent a subsequent infection with field virus or an excretion of a latent field virus from an earlier infecti on, even in cases where the animal appeared serologically negative. The loc al application of the marker vaccine onto the mucous membranes of the respi ratory tract leads to the formation of local antibodies (immunoglobulin cla ss A), which are not produced after parenteral vaccination. Necessary are further studies concerning vaccination intervals. The propert ies of BHV1 deserve special attention in eradication programmes.