Strangles is a serious and highly contagious respiratory disease of horses and donkeys caused by the bacterium Streptococcus equi equi. Strangles commonly affects foals and younger horses, however, horses of any age can be infected.


Infection occurs when susceptible horses have direct contact with infected horses through coughing or eating and drinking from a source contaminated by a sick horse. Infection can also be spread by indirect contact with things infected horses have contaminated such as stables, bedding, feed and water buckets, vehicles, hands and clothing. Outbreaks can occur when large numbers of horses are held in close contact.


Strangles affects the upper respiratory system and lymph nodes of the head. Signs of disease include:

  • Depression and fever within 3-8 days of becoming infected
  • Lack of appetite and painful swallowing due to throat inflammation
  • Swollen and painful lymph nodes, especially those of the head
  • Burst lymph nodes that discharge thick creamy yellow pus
  • Breathing difficulties, nasal discharge and a cough
  • Occasionally infection may spread to other parts of the body (‘bastard strangles’) – this form is very difficult to cure and is often fatal

Signs may persist for days to months depending on how many lymph nodes are affected.


Yes. Affected horses remain infectious for at least four weeks after clinical signs have disappeared. Some horses may even retain the infection in the guttural pouch and shed bacteria intermittently for months afterwards.


Diagnosis is based on clinical signs as listed above. Often your veterinarian will collect swab samples from the nose and/or abscesses and send them to a laboratory for bacterial culture.



Strangles is a very painful disease and veterinary treatment should be sought immediately to alleviate the symptoms. Anti-inflammatory medications are often given and then an assessment is made as to whether antibiotics are required or not. Transportation should be limited as this is stressful for the sick horse and also risks spreading the disease.

All affected horses should be isolated for 6-8wks following the onset of signs to prevent spread to other horses. Strict hygiene practices should be implemented on the property and all areas where sick horses have been held should be disinfected as soon as possible. The strangles bacterium is very hardy and can remain active in the environment for weeks to months in moist conditions.


Hendra virus is an emerging disease that has only been found in Australia. It can be transmitted from flying foxes to horses though contaminated urine, faeces or foetal fluids. Humans and other horses have become infected though close contact with infected horses. Despite Hendra being a rare disease, there is a sixty percent fatality rate for humans if the disease is contracted making it a big concern for horse owners and veterinarians alike. The signs of Hendra virus are extremely variable in horses making it particularly difficult to diagnose in the field. Any neurological, respiratory or colic signs including a spike in temperature could all be caused by Hendra virus infection.

For this reason, to protect ourselves and to protect you as a horse owner, we may take particular precautions in cases of respiratory disease (i.e. strangles) in certain horses. If your horse appears to be presenting with any number of the above signs and has not been Hendra or Strangles vaccinated, your veterinarian may choose to wear Personal Protective Equipment (PPE) prior to examining your horse. They may also ask you to dress in PPE if they require assistance and a surcharge may be applied if the use of PPE is required. If your vet is particularly concerned, they may want to take samples to exclude Hendra virus as being the cause of the current illness. If this is the case, your veterinarian will provide you with a clear action plan as to what will happen with your horse until test results return.

Your equine companion’s health and comfort is very important to us however we also feel that the value of a human life is more important. We strongly suggest that all horses be Hendra vaccinated as soon as possible to avoid the chance of treatment being minimised due to the associated human risk. Please contact your local veterinarian if you have any further questions or would like to book an appointment to get your horse vaccinated.


Regular vaccinations can help avoid contracting strangles and also aid in control of outbreaks. Vaccinations are recommended for any horses that go to shows, competitions, studs or those agisted with other unknown horses. Vaccination is not 100% but will significantly reduce the severity of disease should your horse contract the disease. Strangles vaccination can be given alone (Equivac S) or combined with tetanus vaccination (Equivac 2in1).

There is always a risk of infection if you are sharing water sources, feed bins, tack and grooming gear at horse events. Always use your own equipment and thoroughly clean your boots and outer clothing after each event.

New Horses
If new horses are being introduced to a property without having up to date vaccinations, they should ideally be quarantined for two weeks away from all other horses. This will allow for close monitoring for any signs of ill health.

Boundary Fences
Nose-to-nose contact between your horses and those on neighbouring properties can be a source of infection. Manage this risk by keeping horses away from boundary fences or use double fencing.

This information sheet is not intended as a substitute for a veterinary consultation. It is recommended that a consultation be arranged with a Veterinarian if you have any concerns with your herd’s health.