Updated: Feb 25, 2022
Debatably one of the most feared words amongst horse people is strangles. This disease, caused by the bacterium streptococcus equi subsp. Equi, is incredibly contagious so as with many contagious diseases, it can easily cause panic. Today we will delve into the details of strangles so that the next time you hear the word you'll be able to put fact over fear!
So what is it?
As previously mentioned, Strangles is an infectious bacterial disease in horses. It Initially affects mainly the upper respiratory tract however, complications can lead to other body systems being affected. Due to its infectious nature, it is seen most commonly in horses that have been in contact with other unknown horses; for example at horse shows, auction sites and other gatherings. Transmission of the disease is through both direct (horse to horse) and indirect (contaminated equipment, feed or handlers) contact, making biosecurity and good hygiene key! the Tricky part is that a horse does not need to be showing symptoms to spread the disease through their nasal secretions as there is an initial incubation period prior to signs, and some horses can become carriers after they recover and still spread the bacteria, Luckily the bacteria do not survive long in the environment so as long as appropriate measures (Discussed below) are put in place it is fully possible to return a facility to being Strangles-free, even after an outbreak.
How do I know if my horse has it?
Clinical signs of strangles are fairly characteristic, making a presumptive diagnosis is relatively easy. If any of the following symptoms are noted at your barn, take immediate action to halt the flow of horses in and out and to call a veterinarian. Strangles tend to start like any other infectious diseases with fever, lethargy and decreased appetite. A clear nasal discharge that then becomes thicker and yellow in colour will follow. From there, it is common for breathing and swallowing to become more labored as the lymph nodes that lie in the throat-latch area become enlarged and abscessed. Over the next few days these lymph nodes will begin to burst and drain pus which is very infectious. Ideally drainage should be preformed by a veterinarian to decrease the risk of shedding through pus and prevent any of the abscess draining backwards into the throat area. It must also be noted that other lymph nodes within the body can become infected without being outwardly noticeable (View complications below). Nasal swabs and bloodwork are recommended to verify the severity of the case and the potential need for more aggressive treatments.
In approximately 25% of cases the infection will spread from the lymph nodes in the head and neck down into those located deeper within the body such as the abdomen and the chest. This is a condition known as Bastard strangles. Due to the likelihood of abscess rupture into the body the prognosis in these cases is much lower. The other complication that is occasionally seen in strangles cases is an immune-mediated reaction known as Purpura Hemorrhagica. With this condition blood vessels all over the body become enlarged and allow fluid leakage out of the cells and pinpoint hemorrhages. This can lead to skin sloughing and open wounds.
Prevention leads the way!
As with many diseases, prevention far outweighs treatment when it comes to Strangles. As previously discussed strict biosecurity and hygiene methods are very effective in reducing the risk of Strangles. Some examples of this include quarantine periods for any new horse on the property, using your own water buckets, brushes etc while at shows, and minimizing contact with other horses that you don't have a medical history on. If you have returned from a show where exposure was possible it is also recommended to quarantine any horse that attended the show from those who stayed behind. Finally a vaccine is available for strangles. In the past an intra-muscular version of the vaccine was associated with vaccine reactions however over the past few years an intra-nasal version has been developed that is both more effective and has a lower likelihood of reaction.
What does treatment entail?
Treatment of Strangles is mainly based on restricting contact and having good hygiene as detailed above. In some cases that are caught early enough (Prior to lymph node enlargement) antibiotics can prevent furthering of the disease however once there is enlargement antibiotics are unable to access the bacteria within the abscess and so will only be warranted in complicated cases. Clean drainage and supportive care such as pain medications and soft mashes for feed are the mainstay in most cases.
Take Home Message
Strangles is a relatively preventable but potentially fatal disease. Even without complications the affected horse will experience decreased quality of life due to social isolation, pain and difficulty eating. By far the most effective method to deal with strangles is to prevent it and to manage outbreaks. Immediately and aggressively. If you are concerned about the potential for strangles at your facility or in your horse. Please do not hesitate to reach out to your veterinarian.
Written by Dr. Emily Zakrajsek