[Training of the immune system of foals against ERP virus infections by frequent vaccination with presently available commercial vaccines].

During 3 foaling seasons around 150 Lipizzaner foals were vaccinated against ERP with commercial vaccines and groups thereof were serotested in CF and SN for their humoral immune response. In addition, 6 horses of cheaper common breeds were vaccinated on the University premises, were continuously serologically screened and subjected to virulent nasal test infection. The live-virus vaccine Prevaccinol interfered so profoundly and up to the 20th week of life with maternal antibodies that its further use was discontinued. The inactivated vaccine Pneumabort-K proved to be of impressive immunogenicity, but without any doubt must be used 4 times instead of 3 times only during the first year of life as recommended by its manufacturer. Proofs that the vaccination intervals as recommended on the packing slips are too far-spaced and that 3 basic doses of vaccine induce unsatisfactory protection became apparent under two aspects. Firstly, yearling mares experienced an enzootic field infection by subtype 1 of EHV 1 while on summer pasture. Secondly, experimental nasal infection of horses of the University herd gave takes certified clinically, virologically, and serologically. Data as well as arguments are brought forward which shed doubt on the merits of CF-titers as indicators of immunity as recommended by other authors; SN-titers were shown to be more dependable parameters. With regard to the frequently needed revaccinations there is an absolute "must" for the producer of Pneumabort-K to purify this product before marketing it.