Strangles, a bacterial disease caused by Streptococcus equi, is a highly contagious disease of horses.  Horses, aged 1-5 are most commonly affected by the disease, however horses of all ages can be affected.  Immunity to strangles following a natural infection is not lifelong.  In fact, these horses are usually immune for up to 4 years.

Strangles can be spread by horse to horse contact and the spread of nasal discharge or lymph node drainage.  It can be transmitted by fomites (for example, you!).  Animals recovered from strangles can continue to shed the organism for weeks after clinical recovery.  Shedders are diagnosed by a culture and PCR of a nasopharyngeal swab.  M protein titers of the blood can also be used to monitor clinical course of the disease.

After a horse is exposed to strangles, they usually develop clinical signs within 2-6 days.  Clinical signs include fevers, nasal discharge, lethargy and submandibular lymph node enlargement/abscessation.  The disease usually runs its course in approximately 3 weeks.

An ounce of prevention is worth a pound of cure.  Vaccines against strangles do exist in both modified live and killed preparations.  Modified live, intranasal vaccines stimulate the best immunity by simulating natural infection.  Although vaccination does not guarantee protection, vaccinating your horse can decrease the severity of clinical signs should they come in contact with the organism.  After vaccination, allow 7-10 days before adequate immune response is mounted.