Strangles is an upper-respiratory infection caused by the bacterium Streptococcus equi. Which of the following statements about strangles is not true?

a. Younger horses, particularly yearlings, are most at risk for developing the disease.

b. A strangles victim can infect other horses only when clinical signs of the disease, including nasal discharge, swollen glands and high temperature, are present.

c. Shared water sources are the most common strangles reservoirs.

d. All horses with strangles develop painfully swollen glands between or just behind the jaw bones.

Answer:

b. Looks can be deceiving in this highly contagious disease. Even after a horse seems to have recovered completely from strangles, he may continue to shed bacteria in normal-looking nasal secretions for several subsequent weeks. In fact, researchers believe that some horses remain carriers for life, capable of spreading infections to susceptible contacts. Strangles can infect horses of any age, sex and breed, but once exposed, horses usually recover completely and develop lasting immunity. Thus the most at-risk population includes young, immunologically “naive” horses.

The infection is spread through direct horse-to-horse contact or by intermediaries, including flies, human handlers and, most commonly, communal watering troughs. Nasal discharge is variable among infected horses, but victims always run very high fevers and always develop painful abscesses in the lymphoid tissues behind or between the jaw bones, where they may impede swallowing, hence the name “strangles.” Once these abscesses burst and drain, the horse usually recovers without incident.

This excerpt originally ran in the article “Germ Midterm” in EQUUS 282, April 2001.