What is Strangles?

The disease commonly known as “Strangles” is an upper respiratory disease caused by the bacteria Streptoccocus equi var. equi. This bacterium is not a normal inhabitant of the respiratory tract. Bacteria are shed into the environment via nasal secretions or abscess material. Exposure often occurs when a horse comes into contact with an infected horse that is shedding the bacteria but looks clinically normal. Other sources of exposure are contaminated water, feed and other fomites (inanimate objects like halters, shoes, clothes, buckets, etc.) that have been in contact with the infected nasal secretions or abscess material from an infected horse.


What does a horse with Strangles look like?

Classical signs of this disease that most people think of when they hear the word strangles is swollen abscessed lymph nodes in the throatlatch area (submandibular lymph nodes), copious amounts of thick, green nasal discharge and coughing. However, those clinical signs are often only seen in young naïve yearling or foals. Healthy adult horses, or vaccinated horses, may only present with only a mild nasal discharge that you think nothing of and blow off as an insignificant “cold”. Signs may also include fever, cough, severe swelling of the limbs and inability to swallow due to swollen retropharyngeal lymph nodes (you can’t see them externally). Horses can continue to shed the bacterial for up to 6 months after all other clinical signs have disappeared.


How do I know if my horse has Strangles?

If your horse presents with a nasal discharge (no matter how small), cough and fever, you should call your veterinarian right away. Exposure is often determined in the history. They will ask you if your horse or any other horse has left the property and returned or if a new horse has been added to the farm within the past 2-4 weeks. If the answer is yes, then a culture should be taken of the sick horse to determine if Strep. equi is present. There are many bacteria that can cause similar signs, but Strep. equi. is a serious disease that would result in you needing to quarantine your farm for up to 6 months after all horses stop showing signs of disease. Your veterinarian may need to perform repeat cultures to determine if all affected horses are no longer shedding the bacteria.


Can I protect my horses from getting Strangles?

There are two different types of commercially available vaccines. There is a killed injectable vaccine that is given intramuscularly and a modified live vaccine that is given intranasally. Where no vaccine is 100% effective, it is generally accepted that the intranasal vaccine is most effective in preventing disease. Note that any vaccination can carry risk of side effects including mild to severe allergic and anaphylactic reactions, this vaccination can have a unique reaction process called purpura hemorrhagica. Horse that have recently undergone severe, naturally occuring clinical disease and get vaccinated, carry a risk of developing purpura. Purpura hemorrhagica is a severe reaction process marked by mucosal hemorrhage, severe swelling of the limbs, face, and ventral abdomen. The swelling can be so severe that serum leaks out of the animals pores.

Treatment of purpura is often difficult and lengthy and involves supportive care, high doses of steroids, hydrotherapy, and in some cases tracheostomy to allow horses to take in adequate amounts of oxygen due to severe swelling in the upper airway passages.

For this reason, horses with a known history of clinical disease (of strangles) or previous vaccine reaction (of strangles) should NOT be vaccinated.


What do I do if my horse/farm comes down with Strangles?

Once your veterinarian has diagnosed this disease (or while you are waiting for the test results to come back), they will discuss with you the appropriate treatments for the sick horses and biosecurity protocols to keep the other horses from getting sick. Treatment is usually effective with antibiotics that have good gram-positive coverage (example: penicillins). Treatment depends of the severity of the disease and whether there are external lymph nodes abscessing. Drainage of the external abscesses is often necessary and can alleviate a lot of discomfort for the horse and allow for better breathing and aid in swallowing. Some veterinarians will not instigate the use of antibiotics until the abscesses have drained. Hot packing or pollticing of the external abscesses is often helpful. Anti-inflammatories to reduce fever and pain is often helpful as well. In any case, it is essential that you try to limit the spread of the disease on and off the farm. Do not move horses. You can segregate the sick horse to an isolated area that has is well away from all other horses, but do not move unaffected horses. Even apparently normal looking horses in the same pasture with the sick horse have potentially already been exposed and you could be spreading the disease to another part of the farm. You are a source of contamination now. When you are feeding or doing daily farm chores, be diligent to feed all healthy high-risk animals first like pregnant mares and foals. Then move to down along the line until you get to the sick animals last. Do not allow healthy animals to drink out of the same buckets or troughs as sick animals. Change your clothes and shoes and be sure to wash your hands before starting the next round of feedings.

Your veterinarian will also discuss with you the need to quarantine your farm. This will limit the disease to just your farm. Do not bring in new animals that could be exposed or send animals off to shows, sales or on trail rides where other horses can get exposed. Even if your horse now looks perfectly normal, it could be shedding the bacteria and be a source of exposure for some time (potentially 6 months or more). Two negative cultures a week apart is usually acceptable to release the farm from quarantine.