IS RECOMBINATION OF PRV VACCINE STRAINS A REAL PROBLEM

Simultaneous inoculation of 50 doses of two modified live pseudorabies vaccines with either functional (strain Bartha) or inactivated (strai n Begonia) thymidine kinase into piglets of 1 week of age did not indu ce any clinical signs of Aujeszky's disease. In only 3% of the cases c ould virus be re-isolated from organ specimens, namely from trigeminal ganglia or tonsils. In all samples only Bartha strain was recovered. By using a nested set of gII-specific primers viral DNA was found in 9 2% of the 135 samples. A deletion of 72 bp in the inverted repeats was used to differentiate Begonia from the Bartha strain. The genomes ide ntified represented 12 times the Bartha, and 11 times the Begonia type , the remaining genome types could not (yet) be identified. We found n o indications for the presence of the genomes of both viruses at the s ame time, nor for recombinants. The results suggest no selective press ure for recombinants by using vaccines with the same marker, i.e. gI-n egative vaccines. Thus, when using gI-minus vaccines only, there are n o indications that any real problems of recombination should arise.