Streptococcus suis autogenous vaccines in Dutch farms: effect of sow vaccination on total mortality and antimicrobial usage in piglets after weaning

Streptococcus suis infections have a huge impact on animal welfare and economical performance in pig farms. Furthermore, they hinder the restrictive use of antimicrobials (AMB) because oral treatment is an important tool to control the disease.

Epidemiological studies have shown a high level of diversity in S. suis serotypes (st) between geographical regions and within farms. This has hampered the development and availability of effective commercial vaccines. Therefore, veterinarians also prescribe autogenous vaccines.

Only few experimental and even less field trials have been performed to study the efficacy of autogenous vaccines, and the results are inconsistent.

Extrapolation to an expected effect in a new field case is difficult because of the great variabililty in production methods, adjuvants, methods of isolation and selection of strains and vaccination protocols. In addition most studies concern st2 strains, while st9 strains are most prevalent on Dutch farms.

The objective of this multicentre retrospective cohort study is to investigate the effects of autogenous S. suis sow vaccines on total mortality (TM) and AMB use in weaned piglets, using a fixed protocol.

We included 8 farms (4158 sows) that were attended by vets from one clinic. These farms satisfied for all inclusion criteria. They started vaccination due to high mortality and high AMB use after weaning and were willing to participate. At least one st9 strain was present in the o/w adjuvanted vaccines which were produced at Biovac, France. Strains were isolated from piglets with typical signs. Sows were vaccinated 6-7 weeks prepartum and boostered 4 weeks later. In the next cycle sows received only 1 booster 2-3 weeks pre-partum.

An avg. of 2.4 vaccine strains were selected out of 3-11 serotyped strains per farm. We investigated the results of TM and AMB treatment (amoxicillin and tmp/s p.o.) after weaning (4-10 weeks of age) during 6 months after the moment that piglets born from vaccinated sows reached the age of 10 weeks. These data were compared to data from 12 months earlier. For TM and AMB use we performed ANOVA analyses with month (nested in period), farm and period (pre and post) as categorical variables (SYSTAT for WINDOWS, Version 13.00.05).

Mean TM after weaning was 4.05% pre- and 2.03% post-vaccination. This is a decrease of 50% (p< 0.001). Oral AMB use in piglets was calculated as kg BW that could be treated/sow (present at the farms)/month. This resulted in 16.5 kg pre- and 6.90 kg post-vaccination, which is a reduction of 58% (p=0.016).

In this study, it was shown that autogenous S. suis sow vaccines play an important role in reduction of TM and AMB use in piglets after weaning.

Disclosure of Interest: B. Engelen Conflict with: Dopharma Research, B. Meyer Conflict with: Dopharma Research, V. Shankar: None Declared, V. Minten: None Declared.