Strangles in horses

What is strangles?

Strangles is caused by the bacterium Streptococcus equi. The infection is highly contagious and is transmitted by objects that an infected horse comes in contact with, e.g. the water buckets and by persons handling an infected horse. Usually, all horses in a stable will be infected if they are not immune to the disease from having had the disease recently or due to residual maternal antibodies. The disease lasts typically for a month and affected horses need to be isolated for an extensive time. Horses can be carriers for a very long time, even after the symptoms have disappeared.

Global increase of strangles

Globally, the number of cases of strangles is rising. Sweden reports about 100 outbreaks annually and the UK about 1000. One case affects not only a single horse as several horses usually are quarantained. In Sweden, strangles is a notifiable disease to the Agriculture Department.

This means that the financial ramifications of strangles are usually severe. An affected breeder, stable or riding school may have to close for decontamination and horses are forced into quarantine and banned from attending events.

The infection begins with the bacteria binding to the surface of the tonsils and subsequently spreading into the lymphatic system. Symptoms begin with fever and after another few days swelling of the submandibular lymph nodes. The horse has difficulty eating and drinking and, needless to say, suffers badly from this. The lymph nodes finally burst and bacteria are released into the upper airways with purulent nasal discharge as a result. If untreated, as the lymph nodes burst the skin ruptures and bacteria are released into the open, contaminating the floor, bedding, proximate objects, etc.