Live attenuated strains of Salmonella spp. make excellent vaccines against salmonellosis in experimental animals, eliciting a cell-mediated, mucosal and humoral immune response. In addition, new recombinant DNA technology permits the expression in Salmonella strains of protective antigens from unrelated bacterial, viral or parasitic pathogens. Exciting possibilities exist for a single live vaccine which could provide protection against two or more infectious agents. Recently, attenuated strains of the chicken pathogen Salmonella gallinarum have been considered as the basis of a live multivalent poultry vaccine and work is progressing on the expression of coccidial and herpes viral antigens in strains of Salmonella.
