The clinical signs of EPM vary widely among horses. This is because the protozoa can cause damage at various locations in the CNS. The most common signs are: incoordination, weakness, muscle atrophy, and cranial nerve damage. The incoordination and weakness, characteristic of spinal cord disease, are common findings in horses with this disease. The signs involve only one side of the body. Many times what is seen is a weak spastic, swaying, and possibly stumbling gait. Horses can exhibit what appears to be a low-grade lameness. In severe cases, the horses may fall and are unable to get up. The muscle atrophy associated with EPM is not symmetrical and is most apparent over the hindquarters. Cranial nerve damage is manifested by facial paralysis, drooping ear, lazy eyelid, head tilt, and difficulty eating and drinking. Horses with EPM appear bright and alert with no fever. They have a normal appetite, even though they may have problems eating.
Foals are more likely to get a respiratory disease in their first six months than any other disease. They are more prone to respiratory diseases than adults. In one study, about one-quarter (22.2 percent) of all foals had a respiratory disease. Pneumonia was responsible for most deaths (16 percent) up to six months of age in one study. Foal pneumonia is the major respiratory disease causing economic loss due to death, poor growth and treatment cost. Pneumonia, an inflammation of the lungs, is a common disease in foals of all breeds up to six months of age. A complex disease, pneumonia has many predisposing factors.
Cows that milk largely and test richly are always susceptible to milk fever, and the more fleshy, vigorous, and strong the condition in which they freshen, the more liable they are to be attacked with milk fever, which usually makes its appearance at some time during the first 48 hours after calving. Where this disease was formerly greatly to be dreaded in that 98 per cent of the cows which were attacked by it died, little is thought of it nowadays, so seldom does a cow die because of it.