Bactericidal effect and serological response of blood and secretions in bovine vibriosis.

Udder infection of vaccinated heifers with Vibrio fetus var. venerealis led to an early and severe reaction consisting of local swelling, hyperthermia, and increased blood leukocyte counts. This reaction was absent or less pronounced in heifers not previously vaccinated. This was interpreted as an immediate hypersensitivity reaction elicited in the vaccinated heifers. Specific antibodies were found in udder exudate from vaccinated heifers. Immune serum and udder exudate were moderately bactericidal and had a strong immunosuppressive and opsonophagocytic effect in rabbits. Immune cervicovaginal mucus was neither bactericidal nor opsonophagocytic or immunosuppressive. This would suggest that antibodies found in cervicovaginal mucus are not protective. It appeared that the immediate hypersensitivity observed and the subsequent transfer of antibodies from serum to udder exudate would provide by analogy a possible explanation of the mechanisms of immunity to bovine vibriosis.