Strangles is a highly contagious disease that causes horses to have swollen and painful lymph nodes that block their airway and can cause difficult breathing. The name was coined because these enlarged nodes sometimes (but rarely) suffocate affected horses.

The first reported case of strangles in a horse was made in Europe in 1251 by Jordanus Ruffus. Convinced of its contagious nature, Ruffus recommended isolating affected animals and pointed out that the most common source of infection for horses was water buckets previously used by infected animals. This advice remains valid today