Strangles is a bacterial infection of the upper respiratory tract of the horse caused by the bacteria Strepticocci Equi. These bacteria are highly contagious and are infamous within the equine community!
Common clinical symptoms
- High temperature (above 38.5°C)
- Depressed, quiet horse
- Large swellings at the top of the neck or under the horse’s jaw, which may turn into open abscesses.
- Thick nasal discharge
Spread of disease
The bacteria is passed from horse to horse through respiratory secretions, which can be passed through direct nose to nose contact, and through a carrier, such as an owner, visitors, transport, grooming kit, shared water bucket etc.
Strangles will often be suspected in a horse showing the above clinical signs, but a diagnosis is made by detecting the bacteria’s DNA either through sampling the contents of a burst abscess, swabbing the back of the horse’s throat, or by washing the Guttural Pouches.
Guttural Pouches are an extension of the tube which connects the ear to the back of the throat and are almost exclusively only found in the horse. There are many theories about their purpose; to warm air before it hits the lungs; to help with balance; but most importantly, they are the place where the strangles bacteria can lie dormant, and cause a horse to become a CARRIER. Bacteria are only intermittently shed into the nose and throat.
Another way of detecting exposure to the strangles bacteria is to measure antibodies the horse has made by taking a blood sample. This can be helpful to identify carriers and identify horses that may need further investigation, but has limitations.
- The first limitation is that if a horse has only recently been exposed to the bacteria when sampled, then a blood sample will not indicate exposure, as the body will not have made antibodies yet.
- The second limitation is that you cannot tell whether a horse is recently infected, or has antibodies left from an old exposure.
Both these limitations are overcome by taking repeat samples. These are known as paired samples and are usually taken 10-14 days apart. This will identify horses with a rising value (indicating recent exposure) or a consistently high value (indicating possible carrier status). In both these situations, it is then wise to perform a guttural pouch inspection and flush, to ensure there are no bacteria within the pouches.
Once all the horse is clinically better, horses need to have a negative guttural pouch wash (or three consecutive nasopharyngeal swabs, each 2 weeks apart), or 2 negative blood tests 2 weeks apart, to be considered negative for strangles.
Treatment of Strangles
Most horses require very little treatment for the disease, and will clear the infection on their own, however, 1 in 10 horses will not effectively clear the disease by themselves, and can go on to become a carrier.
Diagnosis and treatment are often combined via guttural pouch endoscopy. If large solid balls of pus (known as chondroids) are seen when examining the pouches, these can be removed using small grabbing forceps. If there is pus seen then, after the sample is collected, the pouches may be washed with a large volume of saline. In some cases, an antibiotic may be put into the pouches.
It is rare that a horse requires any other antibiotics, but may benefit from pain relief. Horses require careful nursing, to ensure they are comfortable, can eat and drink easily and are comfortable. If the horse has open abscesses, they should be cleaned and flushed with poviodine to kill the bacteria enclosed. The treatment can vary massively depending on the severity of disease, and the horses own immune response.
Control of an outbreak
- Yards should have an isolation procedure in place, which should include a plan for new arrivals and horses that show signs of disease. If you would like help designing a plan, please contact the office.
- Any suspect cases should be examined immediately by a vet.
- Once a case is diagnosed, that horse should immediately be isolated. The yard should immediately be closed- no new horses in, and no horses out (even for hacking or competition)
- The yard should be divided into “red horses” – those who have been diagnosed, or showing signs of strangles; “amber horses” – those who have been in contact with red horses; and “green horses” those that have not been in contact with the symptomatic horses. It can be helpful to label stables with these identifications- so that everybody on the yard is clear on a horse’s status.
- All horses should have their temperature taken twice daily, these should be recorded. Any horse with a temperature above 38.5ºC should be isolated, and treated as a red horse
- There should be one person designated to the care of the sick horse(s) this person should ideally only handle the sick animals, but if they have to handle other horses, they look after the healthy horses first, and do not handle healthy horses after sick horses.
- The sick horses should have their own equipment, grooming brushes, rugs etc. This should not be shared between horses.
- Owners should only handle their own horses, and everyone should disinfect using hand sanitiser and foot dips, when moving from their area to the communal area, and then again when leaving the yard.
- All equipment should be cleaned using a ‘horse-safe’ disinfectant, such as Safe 4 on a daily basis.
- Attention should be paid to where water is tipped out and changed. For example, do not run a hose from a safe area into an isolation area, or tip a bucket out in an isolation area, for it to run into a clean area.
The control of an outbreak will vary from yard to yard, and therefore it is essential to work closely with us (and each other) to get the quickest resolution.
The strangles bacteria can, in normal conditions, survive for 3 days in the soil, 7 days on fence posts/ stables, and as long as 30-40 days in water. These times will be longer when it is cold and frosty, and shorter if bright and hot. In basic terms, the bacteria love moisture. The bacteria are killed by direct sunlight or disinfectant.
It is unclear how long the bacteria will survive in muck- as this is a mixture of factors mentioned above! Therefore, with this in mind, it is advisable to bag all muck from infected horses, and either burn, or store at a location far from any horse contact, and then spread only after at least 3 months.
How to prevent Strangles being introduced into your yard
- Blood test all horses prior to moving to your yard
- Isolate all new arrivals for a minimum of 3 weeks
- Encourage owners not to borrow food/water containers and only use their own equipment on and away from yard.
- Do not touch other peoples horses at shows or borrow/lend any equipment.
Last reviewed March 2023