What is Strangles?
Strangles is a highly contagious upper respiratory tract infection caused by the bacteria Streptococcus equi. It affects horses, donkeys and ponies of all ages, breed and sex. The bacteria often infect the lymph nodes around the jaw, causing them to become swollen. In severe cases they can become so swollen that horses struggle to breathe properly, hence the name ‘Strangles’.
What are the signs of Strangles?
The signs of strangles can vary enormously between cases, with some horses only exhibiting very mild signs, such as mild nasal discharge, which can be mistaken for other less serious respiratory diseases. More typical signs of Strangles include the following:
- Loss of appetite/ Difficulty eating
- Raised temperature
- Nasal discharge, often thick and yellow (purulent or pus like).
- Swollen lymph nodes (glands) around the throat
- Drainage of pus from the lymph nodes around the jaw
The incubation period (the time between infection and clinical signs) is between 3 and 14 days and most horses will recover fully within 6 weeks. However, roughly 10% of horses will remain carriers of the disease at this point. This means that they will no longer show clinical signs but they still harbour the bacteria in their guttural pouches, meaning they can intermittently spread the disease to other horses.
Complications of Strangles
Occasionally (in about 1% of cases) abscesses will develop within other body organs, this is known as ‘bastard strangles’ and can be fatal.
Another rare, but also potentially life threatening, complication of Strangles is ‘Purpura haemorrhagica’. This condition causes bleeding from the capillaries and fluid accumulation (oedema) in and around the limbs and the head. This accumulation of fluid can become so severe that there is circulatory collapse and death.
Diagnosis of Strangles
Sometimes Strangles can be diagnosed on clinical signs alone but often your vet will take a nasopharyngeal swab for confirmation of the disease. This is taken from the throat by passing the swab up the horse’s nose. Alternatively your vet may take a blood test from your horse which can help to identify not only infected horses but also carriers and those that have previously been exposed. Another method of diagnosis is guttural pouch endoscopy, during which the inside of the guttural pouch can be visualised and samples can be taken for testing. Your vet will advise you on the most appropriate method of diagnosis for your horse as this depends upon the individual case.
Treatment of Strangles
The mainstay of treatment for Strangles is supportive care. This involves treatment such as anti-inflammatory medication in order to treat the raised temperature and make horses feel well enough to eat. Feeding wet, sloppy food from the floor also makes it easier for infected horses to swallow and encourages the abscesses to drain. Hot compressing of the abscesses will also help to bring them to the surface, allowing them to rupture.
Very occasionally vets will treat infected horses with a course of antibiotics but this depends on the individual case.
Infected horses must be isolated, please see the article ‘Strangles Management’ for more information on this.
The treatment for carriers involves the removal of any chondroids (dried pus) from the guttural pouches via endoscopy and the use of topical antibiotics (usually penicillin) within the guttural pouches.
How does Strangles spread?
Strangles is a highly contagious disease which can spread quickly through a yard via direct horse to horse contact or indirectly through tack, shared drinking water and on clothing.
The bacteria can survive in water for up to four weeks.
Strangles within the UK
Strangles is endemic within the UK. This means that it is relatively common within the horse population. Outbreaks cause major economic problems, particularly on big yards, as affected yards should not allow horses to leave or enter the premises during this period. This means that horses are unable to go to competitions etc.
How can Strangles be prevented?
Prevention relies on good yard management and biosecurity, which will be discussed in the article ‘Strangles Management’.
There is also a vaccine available for at risk horses. This vaccine is a submucosal injection given into the inside of the upper lip. It should be used in conjunction with good biosecurity. Please contact your vet for more information on this.