A live bacterium, having a DNA construct stabilized against transduction of other bacteria, having a promoter sequence and encoding a fusion peptide, comprising a bacterial secretion peptide portion and a non-bacterial immunogenic polypeptide portion, having a nucleotide sequence coding for the non-bacterial immunogenic polypeptide portion which has at least one codon optimized for bacterial expression. The bacterium has a secretion mechanism which interacts with at least the bacterial secretion peptide portion to cause a secretion of the fusion peptide from the bacterium, and a genetic virulence attenuating mutation. The bacterium is adapted to act as an animal vaccine, to transiently infect a tissue of the animal, and cause an immunity response to the non-bacterial immunogenic polypeptide portion in the animal to a non-bacterial organism associated with the non-bacterial immunogenic polypeptide portion.
