After exposure a horse will begin to show signs of the disease in two to six days. Untreated horses will develop abscessed lymph nodes which open and drain within one to two weeks after the onset of the disease. Although most horses recover, about 10 percent of untreated horses die. Death most commonly occurs due to a secondary infection causing pneumonia. To control strangles, if the health history of any horse new to the stable is vague or unknown, it should be isolated, as much as practical, for four or five weeks.
Vaccinations are another useful control.
Although current vaccines are more effective and cause less reaction than those of the past, they do not always prevent the disease. Still, the severity of the disease is lessened if the horse has received the inoculation. One myth is that horses can get strangles from the vaccine. This cannot happen since the vaccine is made from only parts of the bacteria.