|
|
Understanding Equine Protozoal Myleoencephalitis (EPM) (Part
1) Source: American Association of Equine Practitioners/Bayer |
|
|
|
|
EPM often presents with the same symptoms as other diseases, often making diagnosis very difficult. The causative agent is a protozoal parasite by the name of Sarcocystis neurona. EPM is not transmitted from horse to horse. The disease is spread by opossums, who obtain the parasite from infected birds. The infective stage of the parasite, the sporocyst, is then passed in the opossum’s feces. Horses come into contact with these infective sporocysts by consuming infected grass, feed, or water. After the parasites have entered the body, they migrate from the intestine to the bloodstream. Once there, they begin to attack the horse’s central nervous system. |
|
|
|
|
| The symptoms associated with EPM vary based on the location and the severity of lesions within the central nervous system. Symptoms may include the following: | |
|
v Ataxia (incoordination); stiff, stilted movements; abnormal gait or lameness v Incoordination or weakness, which may worsen when going up or downhill v Muscle atrophy, usually of the hindquarters v Paralysis of the muscles of the eyes, face or mouth. This is manifested through drooping eyes, ears, or lips. v Difficulty swallowing v Seizures or collapse v Abnormal sweating v Head tilt with poor balance; these horses may stand splay-footed or lean against stall walls for support. v Fatigue or narcolepsy
|
|
|
The progression
of EPM seems to be influenced by the number of parasites consumed by the
horse, how long the horse is infected prior to treatment, and the location
of damage caused by the parasites to the central nervous system. So which horses are at risk? The incidence of EPM is much lower in the western United States, especially in those regions with few opossums. However, because horses and feed are transported to different parts of the country on a daily basis, all horses should be considered to be at risk.
|
|
| It is important to realize that not all horses who come into to contact with Sarcocystis neurona will become ill and be diagnosed with EPM. Some horses are able to mount an effective immune response to the parasites and do not become ill. Other horses become infected and succumb rapidly, usually those that are under stress and/or have a weakened immune system. Still other horses may have the parasites present in their bodies for months or even years and show no sign of illness. These animals can then slowly or suddenly develop symptoms. A horse that has been successfully treated for EPM may begin to show clinical signs again later in life when they are under unusual amounts of stress (foaling, competing, etc.) | |
