Peer-reviewed veterinary case report
Horses vaccinated with Strangvac showed no strangles after natural
By Gröndahl, Gittan et al.·Published in Equine veterinary journal·2026·Department of Animal Health and Microbial Strategies·View original on PubMed →
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Original publication title: Reining in strangles: Absence of disease in horses vaccinated with a DIVA-compatible recombinant fusion protein vaccine, Strangvac, following natural exposure to Streptococcus equi subspecies equi.
- Species:
- horse
Plain-English summary
A group of 17 healthy horses was vaccinated with a new vaccine called Strangvac after an outbreak of strangles, an infectious disease caused by Streptococcus equi. The horses were monitored for signs of illness, and none of them developed strangles, even though some showed evidence of exposure to the bacteria. Blood tests indicated that all vaccinated horses produced antibodies in response to the vaccine. This suggests that Strangvac can help protect horses during an outbreak, keeping them healthy despite potential exposure to the disease.
Abstract
BACKGROUND: Strangles, caused by Streptococcus equi subspecies equi (S. equi), is a prevalent infectious disease of horses. This is the first report on the use of a new vaccine, Strangvac, in a natural outbreak of strangles. OBJECTIVES: To measure the effects of Strangvac vaccination during an outbreak of strangles at a Swedish farm. STUDY DESIGN: Longitudinal cohort study. METHODS: Healthy horses (n = 17) were vaccinated on day 0, which occurred 23 days after strangles was first confirmed in three unvaccinated horses on the same farm. Blood serum samples were collected on day 0, day 28 and day 489. A combined iELISA was used to measure total antibody titres towards the components of the vaccine. Specific antibody levels in blood sera to S. equi were also quantified using the antigen A/C iELISAs, which can differentiate infected from vaccinated animals. Clinical signs were monitored. RESULTS: All vaccinated horses had increased total antibody titres to CCE, Eq85 and/or IdeE from day 0 (2.50 ± 0.28) to day 28 (3.63 ± 0.31; p < 0.0001). Seropositivity in the antigen A/C iELISA was noted in 8/17 healthy horses on day 0 (prior to vaccination), in 9/16 vaccinates on day 28, and in 3/3 unvaccinated clinical cases on day 28. None of the vaccinated horses developed strangles, but 5/7 of the original vaccinated horses tested seropositive in the A/C iELISA on day 489, which was 377 days after their third vaccination. MAIN LIMITATIONS: Aside from the three unvaccinated clinical cases, no unvaccinated control group was available. CONCLUSIONS: Despite adherence to recommended biosecurity measures, serological evidence of exposure to S. equi was demonstrated in half of the vaccinated horses. Notably, all horses vaccinated during the outbreak responded to the vaccine components and remained healthy, suggesting a protective effect of vaccination of healthy horses with Strangvac in outbreak situations.
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Search related cases →Original publication on PubMed: https://pubmed.ncbi.nlm.nih.gov/41276995/