Fever is a common symptom of many equine diseases caused by viruses or bacteria. Fever per se is nothing bad, it is a defensive reaction of the body. It becomes problematic when the fever rises too high, because irreversible damage can occur. It is advisable to wait at least one hour after exertion before taking a temperature.
Symptoms are, of course, fever, i.e. a body temperature above 38.5 °C, as well as sweating, loss of appetite and exhaustion.
With the help of the veterinarian, the cause of the fever should be sought, as fever in itself is only a symptom. Besides that, box rest and cooling the legs with leg wraps will help. You should offer your horse fresh water and if necessary cover it thinly, e.g. with a sweat blanket, if it is wet and cold outside. In addition, if the cause of the fever is still unclear, the horse should be separated from the other horses.