The aim of this information sheet is to inform you of the clinical signs of strangles and how the bacteria is spread between susceptible horses. It also contains information on how to control the infection if it does enter your yard and finally some information on vaccination against strangles.


Strangles is a highly contagious, bacterial, respiratory infection caused by Streptococcus equi, which affects horses, ponies and donkeys of all ages. The symptoms include high temperature, coughing, nasal discharge and swollen and abscessed lymph nodes of the head and neck The disease may be fatal if it spreads to other parts of the body. However, a nasal discharge without swelling of the glands, is frequently all that is seen and a carrier state without any obvious clinical signs is also possible.

The incubation period is usually about one week but may be longer. The organism is shed from draining abscesses and from the nose. It survives in the environment and in water troughs.

The most important means of transmission is through direct contact with infected horses. Good hygiene is essential to controlling the disease.

Infection can be controlled by isolation of infected horses and shedders until they are free of infection. Shedding usually ends rapidly after recovery but some may shed intermittently.


All horses entering a yard should be monitored closely during the period soon after arrival. Any horses that develop a nasal discharge should be segregated and swabbed for the presence of Streptococcus equi.


All infected horses and their in-contacts should be placed under veterinary supervision in strict isolation with the highest possible standards of hygiene.

Horses should not enter an affected yard unless they can be kept in strict isolation from all sources of infection.

No infected or in-contact animal should be released from isolation or veterinary supervision for a minimum of 2 weeks following full recovery of the last infected horse unless 3 consecutive negative swabs have been taken over a 3 week period. Recovered cases may retain the potential for carrier status in spite of undergoing 3 negative swabs and it is recommended that guttural pouch, sinus openings and trachea are examined carefully with reference to carrier status.


All confirmed cases of Strangles and Streptococcus equi infection in Thoroughbred horses or animals in contact should be notified to the relevant official bodies. (HRA, TBA etc)

Scott Dunn’s Equine Clinic is part of CVS (UK) Limited, a company which owns over 300 veterinary practices in the UK. Company Registration Number 03777473. Registered Office CVS House, Owen Road, Diss, Norfolk, IP22 4ER