There may be a fever and loss of appetite. The swellings eventually mature into abscesses, then break open and drain pus. Sometimes they break open into the throat or larynx and the horse may have a snotty nose and a cough. Dr. Rustebakke said sometimes, after they are mature, distemper abscesses should be lanced, to reduce the swelling and make sure the pus drains to the outside. The best antibiotic is penicillin, but it is important to not use penicillin or any antibiotic until all the abscesses are open and draining.
Most horses make a complete recovery in a couple of weeks.
The horse should be rested completely and given antibiotics, at the correct dosage, until four or five days after all the symptoms are cleared up. Preventing contact with infected horses will help avoid the disease. That may be difficult, because many horses who have distemper have only mild symptoms, and some show none at all. There are also other bacteria that can cause swellings and abscesses that look like distemper, but are not as serious, and not contagious. Distemper can be positively identified by a simple lab culture.