Streptococcus suis autogenous vaccines in French farms: Benefits of the vaccination of sows on mortality and antibiotic use in their offspring

Streptococcus suis (S. suis) is a major bacterial pathogen in pigs. Vaccination is a foremost strategy to reduce the impact of the infection and the antibiotic consumption due to this pathology. In France there is no available vaccine and autogenous vaccines are widely used, but there are no accurate and repeatable criteria for evaluating the efficiency of the vaccination. Field clinical observation on several farms is thus a tool for veterinarians to monitor Streptococcus suis vaccination.

In a French producer group, an evaluation of the vaccination was based on the comparison of the mortality rate during the weaning period, from 3 to 12 weeks of age and the oral amoxicillin and TMP Sulfa consumption from weaning to slaughter, before and after vaccination of the sows. The periods before and after vaccination were variable, depending on the date of implementation of the vaccine, varying from 9 (3 farms) to 12 months (4 farms). No changes in the vaccination program or in the management system were noticed during these periods. Among the 19 farms vaccinated, 7 were able to show reliable data. This represented 1700 sows and 47883 piglets before vaccination and 46144 after vaccination. The vaccination protocol was the same: 2 injections of an oil-adjuvanted autogenous vaccine 6 and 3 weeks before farrowing and then one booster 3 weeks before each farrowing. The symptoms of the disease occurred during the post-weaning period and were caused by S. suis serotype 2 for 6 farms and S. suis serotypes 7 and 9 for 1 farm.

Mortality rate during the weaning period was 4.53% before vaccination and 2.25% after, which represented a decrease of 50%. Statistical analysis was performed on GraphPad Prism 6. A Wilcoxon matched-pairs signed rank test was used and showed a p value of 0.0156.

Antibiotic consumption: despite the fact that there was no statistical difference because of a high variation among farms, the total Amoxicillin and TMP Sulfa consumption in g/100 kg from weaning to slaughter decreased by 85%, from 22.637 to 3.39. Among 6 farms which used amoxicillin or TMP Sulfa in feed at weaning, 4 completely stopped and 2 divided by 2 their consumption.

Even if evaluation of the efficiency of a Streptococcus suis autogenous vaccine is difficult in the field, good feedback from farmers is the first among criteria to be observed. It was not possible to monitor the average daily weight gain, a potentially excellent tool while waiting for the results of monitoring the protective immune response.

Disclosure of Interest: None Declared.