January 2021

Strangles is one of the most common diseases diagnosed in horses worldwide, with over 600 outbreaks estimated to occur throughout the UK each year. Strangles can affect any age, sex or breed of horse and remains a widely feared disease because of its debilitating effects and its potential economic impact on equestrian businesses.

Strangles is a disease caused by a bacteria called Streptococcus equi that can be easily spread directly through horse to horse contact and indirectly through contaminated equipment, handler clothing and boots etc.

Whilst strangles is not spread through the air (airborne), the bacteria can spread when a horse with strangles coughs or snorts.



clinical signs of stranglesClinical signs

  • High temperature, above 38.5°C
  • Lethargy/dull and depressed
  • Reluctance to eat/drink, difficulty swallowing and/or a lowered head and neck
  • A cough (although not always present or as common)
  • Thick and discoloured nasal discharge
  • Swelling of the glands under the jaw (lymph nodes), in the space between the head and neck, or on the head or neck which may lead to the formation of abscesses

The abscesses which cause the lymph nodes to swell can burst, discharging highly infectious, thick, creamy-yellow pus. In some cases the glands swell so much they restrict the airway, hence the name strangles.

Not all horses with strangles will show the same signs and some horses may only show mild signs such as a mild fever, other forms of nasal discharge, a slight loss of appetite or even no signs at all. This is called ‘atypical strangles’. Horses with atypical strangles may go unnoticed but they can still shed the infection to others. If you do notice your horse is showing mild signs it is always sensible to isolate them as a precaution and contact your vet for advice.

It normally takes 3-14 days after the horse has been in contact with the strangles bacteria for signs to develop (incubation period). However, there have been times where it has taken up to 21 days.

A high temperature is often the first indicator that your horse is unwell, often before they show any clinical signs. This is certainly the case for strangles.

Steps to follow if you suspect strangles:

  • Isolate the horse that is showing signs of strangles and any other horses that have had direct contact with that horse. Also isolate those which have/may have had indirect contact with the horse
  • Call your vet out for advice and to examine the horse showing signs. Your vet is likely to take samples that will be sent off to the lab to diagnose whether the horse has strangles or not
  • Contact owners of the affected horse and owners of all other horses on the yard to explain the situation and what procedures must be followed to help prevent the spread
  • The yard should be on ‘lock down’- no horses moving on or off the yard to help prevent the spread of disease
  • Keep a very close eye on all other horses on the yard for any sign of strangles. It is vital to check their temperatures at least twice a day as any rise in temperature could be an early sign of strangles. Keep your vet informed of any suspected new cases. Learn how to take a horse’s temperature here
  • It’s important to let people know, such as your farrier and neighbouring equine property, that you have a suspected or confirmed case of strangles. Strangles can have an unjustified and unhelpful stigma associated with it which may cause people to keep an outbreak to themselves. This can increase the risk of spread. Let’s break down the stigma surrounding strangles, help prevent the spread and do the responsible thing by speaking out!

clinical signs of strangles


Most horses recover from strangles in 3-4 weeks but it can sometimes take longer. Treatment of strangles is decided on a case-by-case basis and usually depends on the stage of the disease and how severe the signs are. The main treatment for strangles is to allow the disease to run its course on its own with supportive care and potentially medication depending on what the vet advises is best for your horse. In circumstances where multiple vet practices are involved e.g., a DIY livery yard, it is important they work together to put a plan in place for the whole yard.

A horse that has had strangles but is no longer showing any signs should not be automatically thought of as free from the disease and removed from isolation. This is because the horse may still be able to spread the bacteria to others for around 4 weeks after their nasal discharge has stopped. Testing is the only way to make sure the horse is no longer infected with strangles, is not a carrier, and able to be removed from isolation. Due to a possible incubation period of 21 days, it is recommended to conduct testing 21 days after the last infected horse has stopped showing clinical signs of strangles – speak to your vet for further advice.



Every horse has two air pockets called guttural pouches located at the back of their throats, one on the left and one on the right. The abscesses in the lymph nodes usually burst into the horse’s guttural pouches which then drain out through the nostrils. This is why you see nasal discharge as a sign of strangles.

In most cases all of the pus in the abscesses will drain away as the disease takes its course but infection can remain in the guttural pouches in around 10% of strangles cases. This leads to a horse becoming known as a ‘carrier’ of strangles. This means they have fully recovered from strangles and do not show any signs of the disease but are still infected and are able to spread the bacteria to others. You will not be able to determine whether your horse is a carrier following strangles by visibly looking yourself. 


Treating Carriers

Horses identified as carriers can go on to living a normal life once treated by a vet. Usually, the pus from abscesses dries and forms balls called chondroids, these will be identified by your vet through a guttural pouch endoscopy. Chondroids are removed from the guttural pouch and antibiotics may be required to kill any remaining bacteria. Horses are re-examined after two weeks to check if they are then free of infection.


bio security welfare

Here are a number of additional steps you can take to help prevent the spread of disease:

  • Quarantine new horses for a minimum of three weeks. Quarantine means no direct or indirect contact between a new horse and other animals, or equipment used by other horses. Take their temperature twice a day to help identify an illness as quickly as possible
  • To help prevent a strangles carrier from entering a yard, speak with your vet to arrange to test all new arrivals. This could either be, a guttural pouch endoscopy or a blood test depending on what your vet advises in your individual circumstance
  • Wash your hands after handling any horse
  • There is a strangles vaccine currently available for use in the UK. The vaccine should be seen as an additional measure and not a replacement for good hygiene and disease prevention measures. Your vet will be able to advise whether the vaccine would be suitable for your horse and individual situation

The Surveillance of Equine Strangles

The Surveillance of Equine Strangles (SES) project, first launched by the Animal Health Trust in 2019 and now funded by the Horse Trust, aims to raise awareness of this very common and contagious disease. SES collaborates with veterinary laboratories across the UK, who report to SES when they have a positive diagnosis of strangles. These findings are published on their website, which provides vital information of where outbreaks are occurring across the UK. A report highlighting the findings for each quarter of the year is also published in an easy to read and sharable format. This will help to encourage more rigorous disease prevention measures and enable horse owners and vets to know when they are in or travelling to an area of higher risk. Ultimately helping to reduce the spread!



1) Durham A, E & Kemp-Symonds, J. (2020) Failure of serological testing for antigens A and C of Streptococcus equi subspecies equi to identify guttural pouch carriers. Equine Veterinary Journal. 53(1) PP 38-43.

2) Pringle,J. Venner, M. Tscheschlok, L. Waller, A & Riihimaki, M. (2020) Markers of long term silent carriers of Streptococcus equi ssp. equi in horses. Journal of Veterinary Medicine. 34(6) PP 2751-2757.


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