Equine strangles is a disease caused by the bacteria Streptococcus equi equi. The bacteria enter the nose and mouth and then make their way to the lymph nodes at the back of the throat and head of the horse. They infect the lymph nodes and cause them to swell. When the lymph nodes become so swollen, they can actually interfere with the horse’s breathing – hence the name strangles!
Equine strangles is a disease that is seen worldwide and in many countries is classified as endemic ie always present somewhere in the population.
Infectious horses shed bacteria in nasal discharge and in pus from ruptured abscesses, which can infect other horses. This can happen from direct horse to horse contact, via transmission on fomites (tools) and also from drinking from contaminated water troughs/feed troughs.
Once the horse is infected they can start showing a number of signs. The incubation period of the disease is 3-14 days. The variety and severity of signs often depends on the immune status of the horse. Very young and very old horses tend to show more severe disease due to compromise of their immune systems. The main symptoms seen in the horse are:
- Nasal discharge (snots)
- Swollen lymph nodes (glands)
- Abscesses under the jaw and around the head
- High temperature (over 38.5C or 102.5 F)
- Off feed/anorexia
A high temperature is usually the first sign seen and occurs within the first couple of days after infection. This high temperature can often cause lethargy and anorexia. Nasal discharge can then appear followed by abscessation of lymph nodes approximately a week later. When these lymph nodes are swollen and painful the horse can find it difficult to eat and breathe. Think how sore your throat was if you have ever had tonsillitis! The abscesses will eventually rupture and the horse will begin to feel better and start to recover.
Horses that have encountered the disease before can be infected again but tend to show less obvious signs such as a mild nasal discharge, and sometimes don’t even have any significant enlargement of their lymph nodes.
How is strangles diagnosed?
Vets can take a sample from the horse and send it to a laboratory for culture. They can also send the same sample for a PCR test (this is the same type of test used for looking for covid-19). This test looks for the genetic material of the bacteria. Samples can usually be taken from the nasal discharge or a ruptured abscess. Sometimes a swab will need to be inserted up the nose to get a sample from the throat if no pus is present.
How is strangles treated?
Equine strangles is a self-limiting disease in most horses and usually the only treatment required is supportive. Quite often painkillers and anti-inflammatories are given to treat the high temperature and sore throat. Antibiotics are not commonly used in treating the disease as the use of them is controversial. It is known that if a horse can be supported without antibiotics then they will mount a great immune response that will significantly reduce their chances of reinfection or severe disease in the future. Some cases will require antibiotics and your veterinary surgeon will be able to guide you as to whether it is necessary for your horse.
Quite often poultices and hot packs are used to help encourage lymph node abscesses to rupture. Once ruptured they can be cleaned with an antibacterial solution. The painkillers such as bute or finadyne can be used to help provide pain relief for your horse during this time.
Supportive care is equally important. Feed your horse small and often soft feeds if they are having problems eating. Always feed them from the ground as this helps encourage drainage of nasal secretions and abscesses.
In very severe cases of equine strangles, some horses will require hospitalisation with constant veterinary supervision. Most uncomplicated cases will recover with no issues at home.
Horses that have apparently ‘recovered’ from the disease can continue shedding bacteria from their noses for up to 6 weeks!
Consequences of equine strangles infection
Unfortunately approximately 10% of infected but recovered horses will still be infectious to other horses. They are known as carriers and can infect horses despite showing no outward signs. These horses usually have pus and bacteria trapped in their guttural pouches therefore providing a reservoir of infection. These horses need to be identified so that they can be treated before being released from their isolation. This treatment involves removing the pus from the guttural pouch using an endoscope. In very severe/difficult cases surgery is sometimes required to remove the pus from the guttural pouches.
In about 1% of cases there can be more serious complications of the infection. The bacteria can reach lymph nodes elsewhere in the body such as in the abdomen. This is called ‘bastard strangles’ and can be fatal.
Another significant but rare complication is that some horses can develop a syndrome known as purpura haemorrhagica. This is caused by the immune system reacting to the infection and damaging small blood vessels. This complication can also be fatal.
Prevention of strangles
The mainstay of preventing strangles infection and on your yard is good biosecurity. Recommendations are :
- Don’t share equipment between horses
- Quarantine new arrivals for 3 weeks and take daily temperatures in this period
- When away at shows with your horse avoid direct contact with other horses and sharing any equipment
- Regularly clean water troughs that are shared
If an outbreak occurs it is important to do the following:
- Isolate all affected horses
- Close the yard
- Separate the herd into groups of
- Red – infected horses and horses with signs of strangles
- Amber – horses that have been in contact with infected horses
- Green – horses that have had no contact with horses from red or amber group
- If a green or amber horse begins to show any signs then they need to be moved into the red group
- Contact your vet and inform all owners of horses
- Daily temperature taking of all horses
- Deal with in contact and infected horses last
- Place foot dips and protective clothing outside stables
- Ideally have separate staff to deal with each group
- Infected horses require testing in the form of either a guttural pouch wash or 3 consecutive negative swabs 5-7 days apart before they can be classified as no longer infectious
In all circumstances it is vital that you keep communication open and keep in contact with your vet for guidance. A great place for useful information is here
Should you have any questions, please don’t hesitate to contact us at [email protected]