Efficacy of a commercial bacterin in protecting Strain 13 guineapigs against Bordetella bronchiseptica pneumonia

Bordetella bronchiseptica is known to be endemic in many guineapig (Cavia porcellus) colonies, and periodically is the aetiological agent of fatal epizootics of bronchopneumonia. A commercial, non-adjuvant B. bronchiseptica bacterin, which is approved for use in canines, was evaluated for induction of a protective immune response in Strain 13/N guineapigs against an airborne challenge of virulent B. bronchiseptica in small-particle aerosol. Seronegative animals were vaccinated on days 0 and 21 with intramuscular injections of 0.2 ml of bacterin. Humoral antibody titres of the vaccinated animals, as determined by ELISA, ranged from 128-1024 on day 49. On day 30 following the second dose of bacterin (study day 51), 12 vaccinated and 12 PBS sham-vaccinated animals were exposed to an inhaled dose of 4.3 X 10(5) CFU of B. bronchiseptica (325 LD50). Vaccinated, challenged animals remained clinically normal, although each guineapig did develop a localized upper respiratory infection. The rate of weight gain as well as rectal temperature of these animals were analogous to those exhibited by the control groups. Examination of 4 of the vaccinated, challenged animals on day 7 after exposure showed bacteria present in moderate to high numbers in the larynx and trachea but only minimally detectable in the lungs; by 30 days after exposure, the numbers of bacteria in the larynx and trachea were diminished, with none being detected in the lungs. Pathological alterations induced by B. bronchiseptica were not detected at either day 7 or day 30 after challenge in any of the vaccinated, challenged animals. Protection induced in Strain 13/N guineapigs by the commercial canine bacterin was sufficient to preclude the development of pulmonary disease, even in animals presented with a massive challenge of virulent bacteria in a small-particle aerosol.