Strangles: what is it and how to prevent it?

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By BHS Welfare Education Coordinator, Louise Nicholls

Strangles is one of the most common, highly contagious and debilitating diseases diagnosed in horses worldwide. It is caused by a bacterium called Streptococcus equi that can be easily spread through direct horse-to-horse contact and indirectly for example, via contaminated equipment, handler clothing and boots.

Whilst strangles is not spread through the air, the bacteria can still spread if an infected horse coughs or snorts.

Clinical signs

High temperature – it’s important to know what is normal for your horse

Dull, depressed or lethargic

Reluctant 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 that can swell and burst, discharging highly infectious pus

Some horses may only show mild signs or even display no signs at all; this is known as atypical strangles. This risks infected horses going unnoticed, but they can still shed the bacterium and cause an outbreak.

It normally takes 3-14 days after the horse has been in contact with the strangles bacteria for signs to develop but it can also take up to 21 days. A high temperature will often be the first indicator that your horse is unwell, and this is usually before they show any clinical signs.

What to do if you suspect your horse has strangles

Isolate the horse that is showing any signs of being unwell as well as any other horses that have had both direct and indirect contact with the infected horse and immediately call your vet out for advice.

Further information on isolation procedures is available in the BHS Strategy to Eradicate and Prevent Strangles (STEPS) which is available at www.bhs.org.uk/strangles.

Strangles: what is it and how to prevent it?

Treatment

Most horses typically recover from strangles in three to four weeks but it can sometimes take longer. Treatment is decided on a case-by-case basis; usually, the vet will recommend allowing the disease to run its course with supportive care and potentially anti-inflammatories such as phenylbutazone (“bute”).

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 at least six weeks after their nasal discharge has stopped. Testing is the only way to make sure the horse is no longer infected with strangles and is not a carrier, and is therefore, able to be removed from isolation; speak to your vet for advice.

Carriers

Every horse has two air pockets called guttural pouches located at the back of their throats. The abscesses in the lymph nodes usually burst into the guttural pouches which then drain out through the nostrils.

In most cases of strangles, all of the pus will drain away but infection can remain in the guttural pouches in around 10% of cases – leading to a horse becoming 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 therefore, able to spread the bacteria to others. A vet can determine whether a horse is a carrier through testing.

Prevention

Make sure you don’t share water sources when away from your yard as a horse with strangles can spread the bacteria into the water as they drink. The bacteria can then survive for up to six weeks with the potential to infect other horses.

To help prevent a strangles carrier from entering a yard, speak with your vet to arrange to test for all new arrivals. This can usually be done by a blood test. Further tests may then be required depending on the result. Avoid allowing your horse to graze away from their yard as they could pick up the bacteria indirectly from a diseased horse that has grazed there previously, for example when attending a show.

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