Strangles (Streptococcus equi. subspecies equi.), can be a cause of major concern to horse and pony owners. Misinformation and unsubstantiated rumour spread via social media only serves to exacerbate the worry, unnecessarily causing widespread panic and fear. So it is important to understand the facts.
Strangles is caused by the bacteria Streptococcus equi. subspecies equi. It is a common, highly contagious infection of a horse’s upper respiratory tract. Strangles can cause large abscesses to form, making swallowing difficult, restricting breathing and is both painful and distressing for the infected horse or pony. Whilst the disease often causes considerable suffering to affected horses and ponies, most will make a complete recovery. However, it is important to note that up to 20% of infected horses are at risk of serious or life-threatening complications.
‘Bastard strangles’ (metastatic abscessation) and purpura haemorrhagica
‘Bastard strangles’ is the development of abscesses in parts of the horse’s body beyond the upper respiratory tract and is usually fatal. Also life-threatening is ‘purpura haemorrhagica’, which is a rare complication associated with the horse’s immune system as it fights strangles bacteria.
How does strangles spread?
Strangles can be passed by direct contact from horse to horse, even if they only touch briefly. Importantly, it is also spread by indirect contact, where bacteria is picked up from stables, field shelters, paddocks, water tanks, troughs, buckets, yard equipment, transport and people’s hands, boots and clothing. Yard dogs and cats can act as fomites for the disease. Strangles is not airborne, but the bacteria can be ejected, as an infected horse coughs and snorts, into the environment in huge quantities, landing on the ground, on fences, clothing, equipment and other horses as an infected horse coughs and snorts.
Recognising the signs of strangles
Clinical signs include:
- A fever temperature of above 38.5 degrees Celsius.
- The horse or pony is dull and depressed.
- There is nasal discharge.
- The horse or pony displays a loss of appetite, has difficulty eating and/or extending the head due to pain from a sore throat or abscess around the head.
- Lymph node swelling under the jaw, behind the jaw or below the ears. These can become abscesses, which produce thick pus when they burst.
- Cough.
The incubation period from infection is up to 21 days and the first clinical sign is often a fever, frequently appearing before bacteria are shed.
Diagnosing strangles
Your veterinary surgeon will examine the horse, taking swabs and samples for laboratory testing and analysis. Guttural pouch endoscopy may be undertaken with a lavage taken from both guttural pouches. Nasopharyngeal swabs may also be taken from all infected horses and any others who may have been in contact with them. These swabs are submitted for PCR (polymerase chain reaction) tests at the laboratory. Occasionally bloods may be taken to test for the presence of antibodies.
Strangles carriers
It is important to understand that some 10% of horses who have suffered from strangles will continue to carry live bacteria in their guttural pouches for months or even years. These strangles carriers appear perfectly healthy, making them difficult to identify, but they have the potential to infect other horses. Carriers are believed to be the most common source of strangles outbreaks and until they are treated, can repeatedly trigger outbreaks. A carrier can shed strangles bacteria at any time, but the likelihood of shedding increases during periods of stress, such as travelling, moving home, being introduced to other horses or suffering injury or illness. Strangles carriers can be identified by testing (see above) and once diagnosed and treated by a vet, can go on to live healthy, normal lives.
Treatment of strangles
All horses testing positive for strangles and those sharing the premises and in close proximity, and who are sick are likely to require medication. Each affected animal will need individual care. Medication depends on abscess development and progression, and must be considered on a case-by-case basis. Treatment includes medication to reduce the fever and pain associated with the lymph node abscessation. Anti-microbials are administered for the infection at certain stages of the disease.
Nursing care of the individual animals is essential. It is important to ensure they can eat by soaking feed to make it easier to swallow, by raising the feed bowl so the horse does not have to bend its neck, and by applying a hot compress to any developing abscesses and bathing burst abscesses.
Strangles and biosecurity
Biosecurity is covered in greater detail elsewhere on this site. Many horse owners enjoy transporting their horses to participate in shows, events, competitions or even just for an enjoyable hack with friends in new surroundings. Implementing effective biosecurity will reduce the risk of picking up strangles whilst away from home:
- Don’t allow direct contact between your own horse and others.
- Avoid touching other horses, or wash/sanitise your hands before and after handling others.
- Discourage contact between your horse and people who have been handling other horses.
- Only use your own tack, rugs and equipment.
- Provide your own food and forage, and carry a container of your own water.
- Avoid using communal water sources where horses immerse their muzzles, such as troughs.
- Avoid communal grazing areas; when resting keep horses stabled or with your vehicle.
Biosecurity on returning home from travelling your horse or pony
When returning home from shows and competitions, horses and ponies should ideally be treated as new arrivals and quarantined. Of course, this isn’t always practicable, but the animals should, at the very least, be closely and regularly monitored. It is therefore important to familiarise yourself with your horse’s clinical signs and through twice daily temperature-taking, understand what the normal baseline is.
Managing and controlling strangles
Strangles has an incubation period of between 3 and 21 days. Horses become contagious just before they exhibit symptoms, so by the time a horse has nasal discharge, it may already have passed the disease on to others. Fever normally precedes infectivity by 2 to 3 days, and spotting fever is the best way to catch strangles early.
Immediately you suspect strangles, contact your vet and request an urgent examination for your horse for strangles. If strangles is confirmed you should ensure movement of horses and ponies on and off the yard stops immediately. Clear signage should be placed at every access point to the premises, warning of the enforced quarantine and the bio-security measures to be followed. If there are footpaths across the site, consult the relevant authority about closing them and erect warning signs. Work with your vet to implement the traffic light system – this will enable you to contain the disease effectively, even on a large yard.
Prevention and mitigation of the effects of strangles
A separate detailed article on the prevention and management of strangles can be found here on this website.
Rely on your veterinary practice for support and guidance. Your vet will offer sound professional advice, taking into account the facilities at your yard, the number of people available to help you and any other relevant factors. Do not be afraid to discuss the financial aspects of a strangles management plan, right at the outset, your vet will want to help. Remember – do not be frightened or misled by misinformation and scaremongering spread on social media – instead ask your vet for qualified, science-based advice
Consider vaccination. The costs of sensible precautions against the disease are significantly less than the cost of treatment once it takes hold. A course of the Strangvac® vaccine for a typical, normally healthy horse or pony requires an initial vaccination, followed by a second vaccination four weeks later. Booster vaccinations are required every six months to one year, ask your vet for details of the vaccine.
Find out more about taking precautions against infection from Streptococcus equi subsp. equi. Ask any of our clinical team or ‘phone the office on 01462 414008 between 0830hrs and 1700hrs, Monday to Friday.
And, of course, should you suspect your horse or pony has an infection from Strangles, call your vet immediately.
