We are a Royal College of Veterinary Surgeons (RCVS) approved equine hospital.
Strangles is a very common but unpleasant bacterial disease that can affect horses and ponies of all types. The best way to minimise its spread is through early detection and implementation of appropriate bio-security. Signs differ between individuals and can range from very mild (e.g. a transient fever) to dramatic (severe throat swelling causing asphyxia) in appearance.
Strangles can cause great distress to both the horse and its owner. It can be difficult for the vet to treat and can become a management nightmare for yard owners.
NB: It is important to recognise that not all horses show all of these signs. Some may simply have a high temperature and seem off colour, so the disease can remain unrecognised until another horse is infected and shows more typical signs.
Strangles spreads principally by direct contact from horse to horse or horse to object to horse i.e. rubbing noses and sharing drinking troughs etc. Even horses kept together do not always all contract the disease, in the same way that not all members of a family all catch the same cold.
Just as important as horse-to-horse contact is spread of the infection by poor hygiene amongst handlers i.e. spread on clothes, buckets, tack and other contaminated kit. The bacteria that cause strangles can linger for several weeks in the environment so may persist in dirty stables.
Fortunately this infection is not airborne so, unlike influenza, it will not spread long distances without some kind of direct contact. Horses may shed bacteria while they are ‘incubating' the disease a few days before they show any signs or for a few weeks after all their symptoms have resolved. Some horses become ‘carriers' and harbour the infection in their respiratory tract. These carriers may shed bacteria for years without showing any overt signs.
Diagnosis is not easy to confirm. Presumptive diagnosis may be made if horses have a contagious respiratory disease with very high fevers and abscess formation in the throat area, and rapid spread between different in-contact animals. However, NOT ALL cases can be PROVEN to be caused by strangles, even when all clinical signs are highly suspicious; strangles may be confused with viral respiratory diseases.
Confirmation of the disease can only be made from laboratory tests on swabs of the nose or draining abscesses. Endoscopy is sometimes used to check inside the throat where the guttural pouches may be lavaged. This is especially useful to check for carriers.
Isolation is important, but often difficult to maintain, for up to a month after the last case occurs; other precautions include:
Actual veterinary treatment of strangles is limited. Anti-inflammatory medication such as phenylbutazone ("bute") or Danilon (which is more palatable) as directed by your vet may be used. Sometimes other injections may be given intravenously by the vet when affected strangles case will not eat.
Use of antibiotics in cases of strangles is contraversial:
Complications are unusual but can be very serious:
Respiratory distress: Swelling at the back of the throat may cause difficulty swallowing and, in more severe cases, difficulty breathing
Bastard strangles: Severe illness with spread of abscesses to other areas of the body
Purpura Haemorrhagica: Serious illness of the immune system that can follow on about a month after - 1-2% of strangles cases can be affected. The clinical signs of purpura haemorrhagica vary, but can include:
It is not a disease that will sneak up on you without you being aware something is wrong with your horse. It is unpleasantly obvious that something serious is wrong.
The most obvious sign is the oedema; even spindly thoroughbred legs will appear as thick as tree trunks. This oedema is caused by fluid leakage within the body and can have other serious effects; eating and breathing can be impaired. Severe cases can show signs of colic or kidney disease. In the early stages or milder cases, the muscle stiffness and reluctance to move may be confused with laminitis.
Overall there are limitations to the current control measures available to prevent the disease. As well as watching for signs of sickness and testing horses these include:
In the real world many anti-strangles precautions may seem impractical, but they should still be followed as far as possible. There is a vaccine against strangles and is available for use where necessary. If the vaccine is given it is best given to all the horses on a yard and requires regular boosters. If you are considering this option call, Bell Equine on 01622 813700 to talk to one of our vets who can advise you on what is the best course of action for your particular situation. The best advice has to be to talk to Bell Equine for guidance relating to your individual situation.
How long should a new horse be separated from the others to know that it is not ‘brewing' strangles?
Incubation period is 3-10days from exposure. If a horse has not spiked a fever or shown any signs of ill health in 2 weeks it should be safe to introduce to the herd. A horse may, however, be a silent ‘carrier' and bring strangles into a yard without showing signs.
How do I know if a horse is a ‘carrier' that is new to the yard or after an outbreak?
In theory vets can test if a horse is a carrier by taking swabs from the back of the airway or by collecting samples via an endoscope. In most (but not all) cases if three swabs (usually taken at 5-7 day intervals over a two week period) are negative, the horse is clear. This involves effort, expense and cannot guarantee a horse is free from infection so vigilance is still required.
There's a horse on the yard that is showing signs that might be strangles but it has not been proven by the vet. Do we have to shut down the yard?
The mere mention of the word ‘strangles' can cause a lot of bad feeling and worry on a yard. Strangles can be unpleasant and painful for the horse, difficult for the vet to treat and a management nightmare for yard owners.
Once one horse has been diagnosed with this infectious disease, all other horses in contact are at risk. Ideally the affected horse should be isolated and the stable yard should be closed to prevent spread. Within reason, until you are given the all clear, it is best to start taking precautions. Delay in preventing further spread of the disease results in more horses being exposed and a more serious and longer lasting problem. Isolate horses that are showing signs and those that have been in direct contact. If it turns out to be strangles this will significantly reduce spread through the yard.
It is also worth considering cancelling excursions from the yard to avoid spreading the disease to other horses that may take it back to their yards, just as you would appreciate others showing the same consideration, so that your horse does not ‘catch something' at a show.
One difficulty is that there is no legal notification requirement for strangles. If individuals elect to carry on regardless despite persisting infection they cannot be prevented from so doing! All this does is increase the potential for further spread.
How do I know which of the healthy horses to isolate?
Horses that have been in direct contact with a horse that has developed strangles may be ‘incubating' strangles and may be infectious to others. This includes contact in the few days before the horse may have started showing signs. Taking rectal temperatures twice daily of all horses (if it is safe to do so) may allow earliest detection of a horse not yet showing other symptoms. This allows early isolation and reduces spread.
Does the vet have to examine my horse if I think he has strangles?
It is advisable to speak to a vet and describe your horse's symptoms and yard situation to decide whether you need a visit. If you are not sure whether it is strangles, it is a good idea for a vet to come and examine the horse in case there is another disease involved.
If the vet thinks that it is suspicious of strangles they can take swabs from some affected horses. It is a good idea to try to confirm or disprove the diagnosis so that a yard is not ‘shut down' unnecessarily.
If your horse develops difficulty breathing or very noisy breathing, a vet needs to examine your horse to make sure that there is not a risk that the airway will become blocked requiring emergency treatment. If your horse refuses to eat or swallow, the vet may need to inject "bute" to start to reduce the swelling in the throat and make your horse more comfortable so that you can then administer "bute" in the feed.
If you already know that your horse has been exposed to strangles and the situation is under control, telephone advice may be sufficient.
My horse has had strangles before, can he get it again?
Most horses will be fully protected from catching strangles again for up to 5years. It is unusual for horses to catch strangles more than once.
How should I clean abscess discharges?
Wipe and flush daily with very dilute iodine or Hibiscrub or salt water. The horse may resent this and warm water may help. It is not worth a battle if the horse will not allow it.
There is a massive hole where the abscess burst, is that ok?
The wound may appear distressingly large but this is very common and will fill in and heal remarkably quickly.
What disinfectant should I use in footbaths or to clean stable, headcollars etc?
Virkon or Trigene are effective.
How long until the paddock is safe for other horses?
A paddock (especially fences, gates, water troughs, etc) can remain contaminated for up to two months (less in hot weather).
It is recommended that all horses are tested 28 days after the last horse has shown clinical signs of strangles. To be considered free from strangles a horse must EITHER have three negative nasopharyngeal swabs one week apart OR one negative guttural pouch wash.
Guttural pouch washes are very useful in finding carriers of strangles.