Disclaimer: The following is only general information. If you believe that your horse has a problem please call your veterinarian as soon as possible.
Strangles is a highly contagious, bacterial infection of the upper airways and lymph nodes. This respiratory infection is caused by Streptococcus equi and it can affect horses, ponies and donkeys of all ages.
Foals and young horses are particularly susceptible because of their underdeveloped immunity. The bacteria usually invades the tonsil tissue first, then migrates to the lymph nodes in the neck and along the lower jaw.
There is an increased risk of Strangles in Autumn/Fall and Winter, when the weather is cooler.
In many countries, Strangles is a notifiable disease and you are legally required to report it (check with your vet about the requirements in your state or country).
Signs and Causes
Within three to eight days of becoming infected your horse will develop some or all of these symptoms:
A high temperature (up to 41°)
Become depressed and go off its food
Within days the lymph nodes around the throat may enlarge (abscesses are forming within them)
A discharge from both nostrils (this can start as a clear discharge, which then becomes thick and yellow, and lots of it).
If the glands at the throat are swollen the horse will find it hard to swallow (it may be so painful that he will stretch his neck down and forward to relieve the pain)
If abscesses have formed in the lymph nodes at the throat and/or jaw line they may burst and start draining pus
Note: Not all horses show all of these symptoms. Some horses only get a nasal discharge without glandular swelling. Young horses are more likely to show all or extreme symptoms.
To know whether your horse has Strangles your veterinarian will look for clinical signs and may or may not take a swab from the back of your horse’s nasal cavity. If a swab is taken a pathologist will try to culture the discharge to see if the Streptococcus equi bacteria are present (culturing bacteria isn’t easy, so even ‘no bacteria present’ does not mean your horses is clear of Strangles). Sometimes it is extremely difficult to diagnose, when a horse only has a nasal discharge and doesn’t develop swelling and abscessing of the lymph nodes.
Streptococcus equi can survive in the environment for several weeks if it is not exposed to sunlight or soil flora. It is spread in the pus discharge from an infected horse’s nose and from draining abscesses.
The most common sources of infection are:
Introducing new horses to your property or stables
Attending shows or activities were there are a number of strange horses
Nose to nose contact with an infected horse or ‘carrier’ horses (some horses are ‘carriers’, regularly shedding bacteria without showing any symptoms)
Using infected stables, bedding material, troughs, rugs, grooming gear or horse tack.
Horses that have had Strangles will keep shedding the bacteria for weeks after the symptoms have passed.
Carrier horses can shed the bacteria for months, or even years, after infection.
Call your vet immediately, if you see any of the above symptoms
Immediately isolate your horse from other horses
Your vet will probably give your horse a non-steriodal anti-inflammatory drug, such as Butozone (this will reduce the horse’s temperature, swelling and pain)
Your veterinarian may or may not prescribe antibiotics (many vets believe that administering antibiotics can actually delay recovery)
If abscesses are present and have not burst, your vet will probably make a small cut, with a scalpel, so that the abscess can drain (this will also alleviate some of the pain)
When abscesses are draining you should flush them out with an antibacterial solution such as a diluted iodine solution (a 25cc syringe, without the needle, can be used to draw up the diluted solution and then flush out the abscess)
Follow strict hygiene measures by disinfecting all equipment and tack as well as your own clothing after every use or contact, so that you do not infect other horses (you can use either a diluted chlorine or iodine solution, depending on the equipment or tack you are disinfecting)
Good nursing care may include warm compresses to relieve the pain from swollen lymph nodes
The majority of horses will recover within 7 to 10 days from the onset of symptoms. However, they will still be shedding bacteria for many weeks after their recovery.
In a small number of cases the following complications may occur:
Non-fatal complications can include inflammation of the heart (myocarditis), inflammation of the skin tissue (cellulitis), roaring (a noise caused when the airways are damaged), anaemia and pus-filled guttural (throat) pouches
A small number of horses will develop Chronic Carrier Status, were they harbour the bacteria in the guttural pouches and continue to shed the bacteria for months or even years after infection
In a very small number of cases infected horses can go on to develop fatal complications. These include Bastard Strangles and Purpura Haemorrhagica:
Bastard Strangles. Infection spreads to involve lymph nodes and organs in other parts of the body causing abscesses to form internally. This is nearly always fatal.
Purpura Haemorrhagica. Infection causes bleeding of the small blood vessels under the skin, causing red spots on the skin and mucous membrane as well as swelling (oedema) of the legs and head. This complication mainly affects younger horses and is often fatal.
All new horses should be isolated and monitored over a two to three week period to see if a nasal discharge develops
Take their temperature every day (at the same time), as an early indication of infection – call your vet immediately if the new horse’s temperature moves outside the normal range (see ‘Vital Signs’ for information on taking your horse’s temperature)
Find out as much as you can about the new horse’s history – medical and immunisation history as well as any recent events that they have attended
If you know that the new horse has had Strangles in the past it may be a ‘carrier’ – your vet may suggest taking a endoscope/swab or endoscope/flush to identify genetic material (DNA) from the bacteria
You should use good hygiene over this period – do not share equipment with other horses, disinfect all your equipment and tack as well as you own clothing
Wash your hands regularly and attend to your isolation horse last not first
When you go to events or activities do not share water troughs or equipment – take your own water, buckets and equipment
Try to avoid ‘nose to nose’ contact with other horses, either at an event or at home, or with neighbour’s horses hanging over boundary fences
Do not take horses with a nasal discharge or cough to any event or activity
At the first sign of illness – temperature, nasal discharge, swollen lymph nodes or cough – isolate the horse and call your vet immediately
Immunise all your horses, however do not rely solely on immunisation as it does not provide 100% immunity
Not all countries have approved vaccines, so check with your veterinarian about your options. Where Strangles vaccines are available they usually involve an initial course of three injections, with each injection given two weeks apart. Maximum immunity occurs two weeks after the last injection. This will need to be followed with an annual ‘booster’ injection to maintain some immunity.
Immunisation is not a replacement for good horse management practices.
The above information is only general in nature. If you believe that your horse has a problem, please call your veterinarian as soon as possible.
Strangles in horses