Introduction

Since humans first relied on horses for work and recreation, strangles has been a source of frustration. Caused by the bacterium Streptococcus equi (Strep. equi), it is one of the most common equine respiratory infections in the world. It can affect horses of all ages and types.

Strangles is a common threat

The disease causes major economic losses to the equine industry worldwide due to its prolonged course, extended recovery period and associated serious complications. According to International Collating Centre reports, strangles is responsible for 30% of infectious disease episodes. Reliable UK statistics are not available, but in Sweden, where strangles and equine flu are notifiable diseases, there are approximately four cases of strangles for every case of flu (see table).

A dangerous and contagious disease

Strangles itself can kill (in simple cases there is a one percent mortality rate), but the major reason for its concern is the speed with which strangles spreads among horses, especially in a stable setting. In large horse populations, established outbreaks may last for months, essentially shutting down stabling premises.

Moreover, some “recovered” horses (carriers) can harbour Strep. equi with no outward clinical signs. Consequently, new or recurrent outbreaks are likely unless costly diagnostic procedures and aggressive quarantine measures are used.