Intramuscular vaccination with Strangvac a new Strangles vaccine

Safe and fairly effective, particularly following the yearly booster. Better than the intranasal seems uncertain.
DrO

Vaccine. 2020 Jun 2
Intramuscular vaccination with Strangvac is safe and induces protection against equine strangles caused by Streptococcus equi.
Robinson C1, Waller AS1, Frykberg L2, Flock M3, Zachrisson O4, Guss B2, Flock JI5.

Author information:
1. Department of Bacteriology, Animal Health Trust, Lanwades Park, Kentford, Newmarket, CB8 7UU, United Kingdom.
2. Department of Biomedical Sciences and Veterinary Public Health, Swedish University of Agricultural Sciences, P.O. Box 7036, SE-750 07 Uppsala, Sweden.
3. Department of Microbiology, Tumour and Cellbiology, Karolinska Institutet, P.O. Box 280, SE-171 77 Stockholm, Sweden.
4. Intervacc AB, P.O. Box 112, SE-129 22 Hӓgersten, Sweden.
5. Department of Microbiology, Tumour and Cellbiology, Karolinska Institutet, P.O. Box 280, SE-171 77 Stockholm, Sweden; Intervacc AB, P.O. Box 112, SE-129 22 Hӓgersten, Sweden. Electronic address: jan-ingmar.flock@intervacc.com.
Abstract

The equine disease strangles, caused by Streptococcus equi, remains a major cause of welfare and economic cost to the global horse industry. Here we report the safety, immunogenicity and efficacy of a novel multi-component chimeric fusion protein vaccine, called Strangvac, when administered to ponies via the intramuscular route. Across the four studies, Strangvac was safe and induced robust antibody responses towards the vaccine components in blood serum and the nasopharynx, which were boosted by revaccination up to 12 months after a primary course of 2 vaccinations 4 weeks apart. The vaccine response did not cross-react with a commercial strangles iELISA, which identifies horses that have been exposed to S. equi, demonstrating that it was possible to differentiate infected from vaccinated animals (DIVA). Following challenge with S. equi strain 4047 (Se4047), all 36 control ponies that had received an adjuvant-only placebo vaccine developed clinical signs of strangles. In contrast, intramuscular vaccination with Strangvac protected ponies significantly from challenge with Se4047 at two weeks (5 of 16 ponies protected (31%), P = 0.04) and two months (7 of 12 ponies protected (58%), P = 0.0046 (including pooled control data) after second vaccination. Optimal protection (15 of 16 ponies protected (94%), P < 0.0001) was observed following challenge at two weeks post-third vaccination. Our data demonstrate that Strangvac is safe, has DIVA capability and provides a rapid onset of protective immunity against strangles. We conclude that Strangvac is a valuable tool with which to protect horses from strangles, particularly during high-risk periods, whilst maintaining the mobility of horse populations as required by the global equine industry.