13/05/2026
🦠🔷Strangles - Streptococcus equi equi🔷🦠
We have had an influx of clients concerned about the risk of strangles to their horses. The following information is to answer many of the common questions we've been asked and allow a resource for clients to digest at their own pace.
A broader understanding in the equestrian community of the infection, the signs and how it spreads in the equine population ultimately leads to a reduced risk of outbreaks by safer behaviours and practices.
Strangles is a highly contagious disease caused by a bacteria, Streptococcus equi equi. It is ubiquitous in the UK equine population, and should be considered a constant risk whenever you attend shows or events with your horse, buy in new horses from other areas, or have high traffic of different horses near your fields or the facilities you use for training.
The bacteria is spread between horses through contaminated discharge/ secretions from an infected individual to an uninfected (naive) individual. It can also be spread indirectly between infected and non-infected horses; if discharge from an infected horse comes into contact with clothing, feed buckets, grooming kits, water troughs, licks etc, and a naive horse then comes into contact with these items. Outside of the host, the bacteria does not survive long (~3 days) in hot dry🌞 environments, but in warm wet conditions🌦 can live for up to 30 days e.g. water trough in summer months.💦
The bacteria enters through the oral or nasal mucosa and invades the local lymphatic tissues (lymph nodes) of the head and upper neck (USUALLY!). It then incubates here for a number of days before eventually creating an abscess that swells and ruptures producing more infectious discharge and the cycle repeats. Sometimes the infection can cause more unusual signs like abscess in lymph nodes elsewhere in the body or cause immune reaction affecting the blood vessels or muscle tissue.
Incubation:📅 A horse, after being exposed to strangles, may take up to 28 days to show the first clinical symptoms of the disease.
Clinical signs: these start with a fever 🤒(>38.5C in horses and ponies, >37.8C in donkeys), which causes dullness and inappetence. After several days swellings may appear between the jaw, on the head or around the throat area that are hot and painful, the horse may have difficulty chewing and swallowing, and possibly breathing, as swellings in the throat/pharynx area reduce the space for airflow. When an abscess in the lymph node ruptures, discharge will appear thick, creamy yellow and malodourous, and may come from the swellings on the head/neck or down the nose (draining from the guttural pouches, a structure at the back of the horses throat, where the retropharyngeal lymph nodes rupture into). Coughing may or may not be observed and is associated with inhalation of
discharge and secondary inflammation in the airways, reduced airflow and irritation, and/or as a result of ineffective swallowing due to the inflammation/swelling and discomfort. A small number of cases may go on to develop more severe airway/lung infections. Unfortunately, some horses with very severe swelling can suffer from respiratory distress (hence the name, STRANGLES). Some horses will die from severe symptoms, or severe complications of the infection.
Clinical signs can last several weeks, we generally treat symptomatic horses with supportive care - anti-inflammatories 💊, fluid therapy if they are dehydrated 💦, sloppy feeds that are easy to swallow and cleaning abscesses, hot compresses etc. The majority of horses recover from the infection, and without the need of antibiotic treatment during the symptomatic phase. Many horses harbor the infection for a short period (4-6weeks) AFTER clinical signs have resolved, therefore they must remain in isolation and barrier nursed. If they are allowed to mix too early in the group, they may cause ongoing outbreaks. After quarantine they will then be tested for the bacteria, and if negative can return to normal routines. A few individuals are unable to clear the bacteria entirely and need assistance from us with antibacterials and require prolonged periods of isolation.
❗IF YOUR HORSE HAS BEEN EXPOSED❗
Isolate your horse for 28 days, and monitor the re**al temperature, 🌡 demeanor and appetite/drinking, and for any swellings.
Avoid any movement of the horse, 🚛or group of horses during this time, avoid mixing of individuals on your property, do not take your horse to any competitions or events. Some horses will be exposed but do not develop disease. If the horse had contracted the bacteria the clinical signs above will develop in some form (this can be mild or severe) during the 28 days. As your horse is in quarantine, it will not cause spread to other horses in the area/community.
When a horse/group of exposed horses are in quarantine/isolation, it should be barrier nursed: this means a separate grooming/feed buckets/headcollar/water bucket/mucking out equipment, and designated clothing for that individual handling them. Ideally the horse is dealt with last before the handler changes clothes and washes hands boots etc, or there is someone designated only to come into contact with those quarantined and not the rest of the group. There should be a 10metre buffer zone between quarantine paddock and other fields. Avoid isolating horses in a stable block which has a shared airspace with non exposed horses: sneezing/coughing can allow transmission of infectious discharge!
If a horse develops signs of strangles and is managed in a group of horses currently being monitored, isolate that horse immediately from all the other horses, and manage as described above - separately, with different equipment and clothing, a buffer zone etc.
It is always better to be safe than sorry, if you are concerned about your horse's demeanor, and especially if you have identified a fever or other clinical signs, isolate the individual, and wash your hands/clothes before touching another horse or shared equipment. Call us, and we will talk you through what to do next and come prepared with barrier clothing ourselves to avoid further spread.
Testing: 💉The blood samples many people are familiar with are a test of the antibody levels i.e. recent exposure to the bacteria, they are NOT a test for the infection itself. In the face of an outbreak paired blood samples over 2 weeks can identify a rising antibody level and suggests recent exposure. Horses receiving this monitoring should be isolated if the antibodies have risen, but they have not shown any clinical signs.
Horses with clinical signs will have a sample of discharge taken: swab, wash/lavage, sent away for PCR which detected bacterial DNA, this gives a positive or negative result for infection. These samples can also be cultured to grow the bacteria, which takes longer and has some limitations (sample age/handling). If a horse is still incubating the bacteria the guttural pouch lavage or swabs taken can be negative as the bacteria has not burst out and contaminated their mucosal surfaces yet. These tests are only used when there are symptoms or at the end of a quarantine period looking for asymptomatic carriers.
In an acute outbreak, with a known exposure event e.g. a horse attended the yard for one day with clinical signs, those horses exposed that have not developed clinical signs after 28 days may be released from quarantine. However, the gold standard would be to, at the end of the quarantine period perform a guttural pouch lavage. Again, we are looking for bacterial DNA/or the absence of DNA. The allows identification of asymptomatic carriers in the group. These carriers don't tend to occur during an acute outbreak without developing any signs but are horses that have been infected previously but have been unable to clear the bacteria and carrier it for months to years. They shed the bacteria often at low levels/intermittently and continue to expose other groups of naive individuals. If a strangles outbreak on your yard does not have a known source, we would insist that a guttural pouch lavage is performed for all horses ending their quarantine, as there may be a carrier in the group causing the outbreak.
It is unidentified asymptomatic long-term carriers, horses showing clinical signs and horses that have recently (4-6weeks ago) been infected but have resolved symptoms, but have not been quarantined for long enough, that cause the continuous spread and threat of outbreaks in our equine population. We as humans also contribute to that ongoing spread through indirectly passing infected material between horse groups.
If you are going to a show: bring your own water/water bucket/hay net/hay and do not allow nose to nose contact or shared grazing between horses, don't speak to other horses or wash your hands if you do, avoid other people touching/feeding your horse. Monitor your horse following events for fever or inappetence or swellings. Quarantining after every event is unrealistic; we advise monitoring and quarantining at the first sign of concern. However, quarantine is essential if you KNOW your horse was exposed to avoid further spread.
If you are buying a new horse onto your yard, or have new liveries joining, please follow a 28 day strict quarantine as above. Your horses may not enter the yard /other horses for any reason- farrier/vet. We will attend the horses in their quarantine paddocks, or if not essential visits, delay the appointment until safe. At the end of this quarantine PLEASE test your horse via a guttural pouch lavage & PCR method to identify if they are clear of the bacteria before releasing them. You cannot tell who is or isn't a carrier by looking at them, and absence of symptoms does not mean absence of disease
