Equine Protozoal Myelitis is a devastating illness. There are several things you can do to prevent EPM. Do not allow your horse to closely interact with opossums. Secure feed in places where opossums and birds have no access. Trap and remove opossums to distant locations. Minimize vermin and insects (cockroaches), which may potentially act to spread the infective sporocysts.
If possible, horses should not be allowed to drink from slow-running streams or stagnant ponds (especially in wooded areas). Preventive measures should also include strategies to minimize the numbers of rats and mice in barns and in places where horse feed is stored.
For more information, please read the article Equine Protozoal Myeloencephalitis