Evaluation of the efficacy of an autogenous whole bacterin Streptococcus suis serotype 9 vaccine in pigs

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     In intensively raised production animals vaccination is an important tool in on-farm disease management. Vaccination helps to limit the preventive and therapeutic usage of antimicrobials. However, for some bacterial animal diseases effective licensed vaccines are still not available. When no approved vaccine is available, it is allowed by law and under strict conditions, to prepare and apply autogenous whole bacterin vaccines. These vaccines are based on inactivated farm-specific isolates from clinical cases. For the control of Streptococcus suis (S. suis) infections in pigs, these autogenous vaccines are widely used in The Netherlands. S. suis is an important pathogen in pigs worldwide, causing arthritis, meningitis, endocarditis or sudden death in young pigs. S. suis can also cause severe infections in humans. Of the 33 known capsular serotypes of S. suis, serotypes 2 and 9 are worldwide most often associated with clinical signs in commercial pig farms. Serotype 9 is responsible for most cases in The Netherlands. Although widely used, the efficacy of autogenous S. suis vaccination against serotype 9 infections is, however, unknown. The aim of our study was to determine the effect of vaccination with an autogenous whole bacterin vaccine containing S. suis serotype 9 on mucosal colonization, on clinical signs, and on transmission of this serotype among pigs after homologous challenge.

    Materials and methods

    Animal experiments were performed with caesarean derived, colostrum deprived pigs (N = 50), housed pair-wise. Thirteen pairs were intramuscularly vaccinated at 3 and 5 weeks of age with 2–3×109 colony forming units formalin inactivated S. suis serotype 9 and α-tocopherolactetaat as adjuvant. Twelve pairs served as non-vaccinated controls. At 7 weeks, one pig of each pair was intranasally inoculated with 1–2×109 colony forming units (CFU) of the homologues strain; the other pig was contact exposed. Saliva swabs and tonsil brushings were collected for 4 weeks, and tested for the presence of S. suis by quantitative bacteriological culture. In the same period clinical scoring was performed daily. Blood samples taken at 3 and 7 weeks were tested for S. suis serotype 9 specific IgG in an indirect ELISA.

    Results and discussion

    Despite specific systemic IgG antibody responses in vaccinated pigs, no differences in quantity of S. suis in tonsilar or saliva samples were observed between vaccinated an control pigs. Mean values in vaccinated pigs were 2.71x105 and 1.18x106 CFU per saliva or tonsil sample, respectively. In control pigs this was 2.39 x105 and 0.73 x106 CFU for saliva (P=0.99) or tonsil (P=0.95), respectively. In all pairs, transmission between inoculated and contact exposed pigs occurred, and no difference was observed in transmission rate between the groups. The estimated transmission rate parameter β was 5.27/day among vaccinated pigs, and among non-vaccinated pigs 2.77/day (P=0.18). No differences in clinical signs were observed between vaccinated and control pigs, which is in contrast to published S. suis serotype 2 studies. Conclusion. Vaccination against S. suis serotype 9 under experimental conditions did not reduce transmission, nor colonization and there were no indications that protection against clinical signs was induced.

    Original languageEnglish
    Number of pages1
    Publication statusPublished - 16 Apr 2012
    EventScientific Spring Meeting KNVM & NVMM 2013 - Congrescentrum Papendal, Anrhem, Netherlands
    Duration: 16 Apr 201217 Apr 2012


    ConferenceScientific Spring Meeting KNVM & NVMM 2013


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