Development of novel Streptococcus equi vaccines with an assessment of their immunizing potentials and protective efficacies.
Authors: Soliman Rafik, Yousef Mohamed, Gelil Sara Abdel, Aboul-Ella Hassan
Journal: BMC veterinary research
Summary
# Editorial Summary Strangles remains one of the most economically significant infectious diseases in equine populations, yet effective vaccination strategies remain limited. Rafik and colleagues developed four inactivated vaccine formulations against *Streptococcus equi* using locally isolated strains, testing two different oil-in-water adjuvants (MONTANIDE GEL and MONTANIDE ISA-70) in both monovalent and bivalent (combined *S. equi* and *S. zooepidemicus*) configurations. Immunogenicity was assessed in mice and rabbits using passive haemagglutination assays, with antibody titres subsequently tracked in vaccinated foals via ELISA, whilst protective efficacy was evaluated through challenge studies in both laboratory and field models. The combined vaccine formulation with MONTANIDE ISA-70 adjuvant demonstrated superior performance, achieving 75% protection rates and generating significantly higher antibody responses compared to single-strain formulations or the MONTANIDE GEL-adjuvanted vaccines. Given the persistent management challenges posed by strangles outbreaks and the limitations of current vaccines, these findings suggest a potentially valuable alternative approach, though practitioners should note that efficacy data derived from laboratory models and foals will require validation in diverse field populations and age groups before widespread adoption.
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Practical Takeaways
- •A new combined vaccine against strangles shows promising 75% protection in trials, potentially offering better disease control than current single-strain vaccines
- •The choice of adjuvant matters significantly—ISA-70 outperformed GEL formulation, so vaccine selection should consider this detail when available
- •Bivalent vaccines covering both S. equi and S. zooepidemicus strains provide better protection than single-organism vaccines, relevant for herds with exposure to both pathogens
Key Findings
- •Combined S. equi and S. zooepidemicus vaccine with MONTANIDE ISA-70 adjuvant achieved 75% protection rate in challenge tests
- •Combined bivalent vaccine formulation demonstrated superior efficacy compared to monovalent S. equi vaccine alone
- •MONTANIDE ISA-70 adjuvant provided significantly better protective efficacy than MONTANIDE GEL adjuvant
- •Antibody titers were successfully induced in foals, mice, and rabbits, confirming immunogenicity of developed vaccine formulations