Strangles is a highly contagious respiratory disease especially in foals and younger horses. The causative organism is Streptoccus equi and it is spread from horse to horse very easily.
Horses suffering from strangles may have a purulent discharge from the nostrils and enlargement of the lymph glands under the jaw. These lymph glands can abscess and burst exuding a thick yellow pus. Fever, depression and a lack of appetite are common symptoms associated with infection. Most horses will eventually recover but they may need to be out of work and quarantined for long periods of time. Once infected, horses can shed the bacteria for many months.
The disease can be very debilitating in some animals, but by adhering to a regular vaccination program the severity and frequency of the disease can be controlled.