(E35) Safety of Strangvac, a Vaccine Against Streptococcus Equi, in European Horses

Abstract: Background – Strangvac, a new vaccine against strangles, contains eight important proteins of Streptococcus equi. Thousands of horses across Europe have been vaccinated with Strangvac since its launch in 2022.Hypothesis/Objectives – We hypothesised that the vaccination of horses with Strangvac induced side effects that were similar to other vaccines.Animals – Feedback on the clinical signs experienced by 451 horses at four leading equestrian centres in Sweden were reported by the responsible veterinarians.Methods – Horses in this case series were vaccinated on three occasions with Strangvac via intramuscular injection and then monitored for clinical signs.Results – 145, 96, 60 and 150 competition horses were vaccinated at farms 1, 2, 3 and 4, respectively. Body temperatures increased in some horses for 1 day. Thirty-nine horses had stiffness/swelling in their neck that resolved after 2 to 7 days. Some horses were dull for a few days post-vaccination. None of the vaccinated horses developed signs of purpura haemorrhagica or strangles. The veterinarian at farm 3 noted that vaccinated horses were unaffected during an outbreak of S. zooepidemicus infection.Conclusions and clinical importance – Three of the four farms reported that clinical signs post-vaccination with Strangvac were similar to those observed following the administration of other vaccines. Although the vet at farm 2 felt that Strangvac led to more side effects, they believed it was safe and continue to use this vaccine to protect their horses. Our data provide further evidence of the safety of Strangvac for the vaccination of horses.