Abstract
BackgroundStreptococcus suis is an important pathogen that causes severe diseases mostly in weaned piglets. Only available vaccines in the field are those composed of killed bacteria (bacterins) but data about their effectiveness are missing. We report here a field study on the immunological response induced by an autogenous vaccine applied in pre-parturient sows. Using a farm with recurrent S. suis serotype 7 problems, the study was divided in three experiments: (I) Sows received the vaccine at 7 and 3 weeks pre-farrowing. (II) Replacement gilts introduced to the herd received the vaccine at 4 and 7 weeks after their entry in quarantine and a boost 3 weeks pre-farrowing. (III) Gilts from experiment II received another boost 3 weeks pre-farrowing at their 3rd/4th parity. Levels, isotype profile and opsonophagocytosis capacity of the serum antibodies induced by vaccination were evaluated in sows and maternal immunity in piglets.ResultsIn sows (I), the vaccine induced a slight, albeit significant, increase in anti-S. suis total antibodies after 2 doses when compare to basal levels already present in the animals. These antibodies showed a high opsonic capacity in vitro, highlighting their potential protective capacity. A gilt vaccination program of 3 doses (II) resulted in a significant increase in anti-S. suis total antibodies. Levels of maternal immunity transferred to piglets were high at 7 days of age, but rapidly decreased by 18 days of age. A gilt vaccination program ensued a higher transfer of maternal immunity in piglets compared to control animals; nevertheless duration was not improved at 18 day-old piglets. The vaccine response in both gilts and sows was mainly composed of IgG1 subclass, which was also the main Ig transferred to piglets. IgG2 subclass was also found in piglets, but its level was not increased by vaccination. Finally, a recall IgG1 response was induced by another boost vaccination at 3rd/4th parity (III), indicating that the vaccine induced the establishment of a lasting memory response in the herd.ConclusionsOverall, an optimal gilt/sow vaccination program might result in increased antibody responses; nevertheless duration of maternal immunity would not last long enough to protect post-weaned piglets.
Highlights
Streptococcus suis is an important pathogen that causes severe diseases mostly in weaned piglets
Experiment 1: sow vaccination Antibody levels induced by the autogenous vaccine increased in vaccinated sows, with an isotype response dominated by the IgG1 subclass In Experiment 1, the antibody response induced by a 2-dose vaccination program in pre-parturient sows with an autogenous vaccine was evaluated
The S. suis vaccination program, for all sows pre-farrowing of the herd, had just started when the study was initiated; a control non-vaccinated group could not be included
Summary
Streptococcus suis is an important pathogen that causes severe diseases mostly in weaned piglets. We report here a field study on the immunological response induced by an autogenous vaccine applied in pre-parturient sows. Using a farm with recurrent S. suis serotype 7 problems, the study was divided in three experiments: (I) Sows received the vaccine at 7 and 3 weeks pre-farrowing. (III) Gilts from experiment II received another boost 3 weeks pre-farrowing at their 3rd/4th parity. Streptococcus suis is an encapsulated bacterium which causes numerous pathologies, such as meningitis, arthritis, endocarditis, polyserositis and septicemia with sudden death. It is responsible for important economic losses in the swine industry [1]. S. suis has been reported to be an emerging zoonotic pathogen with the greatest risk for people who have close contact with pigs or unprocessed pork [4]
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