Efficacy of an Oral Bordetella bronchiseptica Vaccine 13 Months Postvaccination

Canine infectious respiratory disease complex (CIRDC) involves many viral and bacterial pathogens,¹ with Bordetella bronchiseptica being a common bacterial organism associated with CIRDC; thus, B bronchiseptica is a component of mono- and multivalent vaccines.^2,3

This blinded, placebo-controlled study* evaluated the effectiveness of a single-dose oral monovalent B bronchiseptica vaccine in dogs when challenged with 2 strains of B bronchiseptica 13 months after vaccination. Tracheal and nasal swabs for B bronchiseptica culture were collected at specific points during the study, including monthly during the prechallenge period, the day prior to challenge, and 14 days postchallenge. Blood was collected monthly during the prechallenge period and weekly postchallenge to test for the presence of B bronchiseptica antibodies. Patients in both the control (n = 17) and vaccinated (n = 17) groups were exposed to aerosolized B bronchiseptica and then observed for clinical signs of disease (defined as development of a spontaneous cough of 2 or more consecutive days duration) during the 14-day postchallenge period.

Although 76.5% of dogs in the placebo group developed signs of disease, no dogs in the vaccinated group had a cough noted on 2 consecutive days. In the vaccinated group, 17.6% of dogs developed a cough of 1-day duration. Dogs in the placebo group had a significantly higher rate of positive tracheal (88.2%) and nasal (64.7%) swabs as compared with vaccinated dogs (5.9% for each), suggesting reduced shedding of organisms with vaccination. In addition, 4 dogs in the placebo group (and 0 dogs in the vaccinated group) developed a fever. No dogs in either group developed other upper respiratory signs. Serum titers as measured by microscopic agglutination testing were consistently higher in vaccinated groups; however, the serum antibody levels needed to provide protection are currently unknown.

These results suggest that a single dose of the oral vaccine used in this study may be effective in preventing cough, reducing the duration of cough, and reducing shedding in dogs when administered annually.

Key pearls to put into practice:

Although there are many viral and bacterial organisms involved in CIRDC, vaccination for commonly associated organisms (eg, B bronchiseptica) can reduce severity of clinical signs and the frequency of coinfections.

In patients presented with clinical signs of CIRDC that have been vaccinated against B bronchiseptica, other testing (eg, molecular assays [PCR]) could be considered to determine a causative agent. This may reduce the use of antibiotics if a viral component is identified.

Cough is the primary clinical sign associated with B bronchiseptica infection. Presence of other clinical signs of respiratory disease should raise suspicion for other CIRDC-associated organisms.