New strangles vaccine candidate advances in U.S. horse studies

A familiar equine disease may be getting a new prevention option in the United States. In a July 2026 Equine Disease Quarterly article highlighted by The Horse, University of Kentucky investigators and collaborators outlined ongoing U.S. work on Strangvac®, a recombinant strangles vaccine already sold in Europe, as part of the regulatory pathway for possible U.S. use. The authors position it as a potential advance for a disease that still routinely disrupts breeding farms, boarding barns, training centers, veterinary hospitals, and equine events. (gluck.mgcafe.uky.edu)

That context matters because strangles remains stubbornly difficult to control. The disease, caused by Streptococcus equi subsp. equi, spreads readily when horses are moved and commingled, and clinically normal carriers can keep it circulating long after an outbreak appears resolved. The Kentucky group notes that persistent guttural pouch infection and chondroid formation can allow some horses to harbor viable bacteria for months or years, helping explain why farms can see re-emergence after long quiet periods. AAEP and ACVIM guidance similarly emphasize that identifying and managing carrier horses is central to outbreak control. (gluck.mgcafe.uky.edu)

The key change is not that U.S. veterinarians suddenly have a new licensed product, but that a different vaccine platform is moving through U.S.-relevant testing. According to the Equine Disease Quarterly article, Strangvac is being evaluated by the Helmy Laboratory at the University of Kentucky, together with Drs. Beatrice and Brett Sponseller, in collaboration with Intervacc and outside investigators. Parallel safety studies are underway in Kentucky, Pennsylvania, Iowa, and Texas. The authors say those studies are important because performance has to be assessed against locally relevant S. equi strains and within the U.S. regulatory framework, and they state plainly that the vaccine is not currently licensed for routine commercial use in the United States. Intervacc’s 2025 year-end report also said U.S. safety studies were part of the approval process. (gluck.mgcafe.uky.edu)

What makes Strangvac different, at least on paper, is its design. The Kentucky article says the vaccine targets eight S. equi proteins, does not contain a living infectious organism, and was designed to allow differentiation of infected from vaccinated animals, or DIVA. That could be useful in outbreak investigations, where distinguishing natural exposure from vaccine response can complicate management decisions. The article also notes that the vaccine does not include M protein, which has been associated in some contexts with immune-mediated adverse reactions such as purpura hemorrhagica following infection or immunization. (gluck.mgcafe.uky.edu)

That positioning addresses real concerns with the current U.S. landscape. Existing guidance describes strangles vaccination as risk-based rather than universal, and both AAEP and ACVIM materials caution that vaccination decisions should be individualized. Merck’s veterinary manual notes that the modified-live intranasal product can reduce disease risk, but reported complications include vaccine-associated clinical disease, local abscessation tied to handling errors, lymphadenopathy, nasal discharge, and purpura hemorrhagica. A 2026 case report added a fresh reminder: investigators traced a focal intramuscular abscess to transfer of vaccine strain after intranasal vaccine administration, underscoring how technique and workflow still matter. (aaep.org)

For veterinary professionals, the bigger takeaway is that vaccination alone still won’t solve strangles. The Kentucky authors stress that effective control requires early detection, rapid isolation, diagnostic testing, identification of persistent carriers, strong biosecurity, and vaccination working together. That lines up with established guidance recommending isolation of new arrivals, fever monitoring, movement controls, and testing of recovering horses before release from quarantine. In practice, a safer and more diagnostically useful vaccine could strengthen prevention programs, but it would complement, not replace, the basics of outbreak management. (gluck.mgcafe.uky.edu)

Why it matters: If Strangvac ultimately clears U.S. regulatory review and performs well in domestic field conditions, it could give equine practitioners another option for barns with repeated commingling risk, sales and show populations, referral settings, and operations where the downsides of live intranasal vaccination have limited uptake. Its non-live design and DIVA potential are especially relevant for veterinarians trying to balance prevention with cleaner outbreak investigation and communication. Still, until licensure happens, the practical message for clinicians is unchanged: risk-based vaccination, disciplined biosecurity, and aggressive carrier detection remain the core of strangles prevention. (gluck.mgcafe.uky.edu)

What to watch: The next milestones are publication or presentation of U.S. safety and efficacy results, any formal USDA licensure progress, and whether professional guidance evolves if the vaccine reaches the U.S. market. Intervacc continues to report expansion of Strangvac in Europe, but U.S. adoption will hinge on domestic data, regulatory review, and how equine veterinarians judge its fit alongside existing strangles control protocols. (intervacc.se)