Ask the Vet: Equine Vaccinology

Question: What part of the horse’s body do you administer the strangles vaccine? Is intranasal better than the injection?

Answer: Strangles vaccine is referring to vaccination to prevent a highly contagious disease caused by Streptococcus equi infection. This bacterial disease is also referred to as ‘distemper’ and/or ‘shipping fever’. This is an upper respiratory disease with associated lymph node swelling and abscessation, high fevers, inappetance and very easily spread from one equid to another.

There are two products available for prevention of Strangles infection. One is an injectable product called Strepvax II marketed by Boehringer-Ingelheim. The other product is an intranasal product called Pinnacle marketed by Zoetis. These two products MUST be administered according to label directions. By interchanging the administration methods, serious adverse side effects may and have occurred.

*Strepvax II is a Streptococcus equi bacterial extract. Label directions are as follows:

Shake well. Using aseptic technique, inject 1 mL intramuscularly preferably in the hind quarters. For primary vaccination give 3 doses at intervals of 3 weeks. Foals vaccinated when less than 3 months of age should receive an additional dose at 6 months. Revaccinate annually and prior to anticipated exposure, using a single 1 mL dose. Use a separate needle for each injection.

*Pinnacle is Streptococcus equi vaccine, Live Culture. Label directions are as follows:


DOSE: Aseptically rehydrate with the entire contents of the accompanying sterile diluent. Instill the entire rehydrated vaccine into one nostril using a syringe with applicator tip. Administer a second dose 2 to 3 weeks later. Annual revaccination is recommended.

As to the question which is a better product?

**Vaccination against S. equi is recommended on premises where strangles is a persistent endemic problem or for horses that are expected to be at high risk of exposure. Following natural infection, a carrier state of variable duration may develop and intermittent shedding may occur. The influence of vaccination on intermittent shedding of S. equi has not been adequately studied.

**Killed vaccines like Strepvax II are an adjunct to the prevention of strangles. Vaccination with these products should not be expected to prevent disease. However, appropriate pre-exposure vaccination with these products appears to attenuate the severity of clinical signs in affected horses, should disease occur, and has been shown to reduce the incidence of disease by as much as 50% during outbreaks.

**An intranasal product like Pinnacle has been shown to stimulate a high level of immunity against experimental challenge. The vaccine strain of Strangles may vary from the active field strain in circulation. This can account for reduction in vaccine effectiveness.

Strangles is a multi-factoral disease that vaccine alone will not address. There are many other cooperative decisions that need to be made by an active veterinarian-client-patient relationship. These include identifying best preventive methods, isolation and treatment and biosecurity measures prior to entry of this disease. Please contact your local veterinarian to identify the most appropriate product and plan for your horse’s needs.

Supporting documents used for this response include:

*Compendium of Veterinary Products

**AAEP website, vaccination guidelines for Strangles

ACVIM Consensus Statement: Streptococcus equi Infections in Horses: Guidelines for Treatment, Control, and Prevention of Strangles.

Courtesy of AAEP