Polioencephalomalacia (PEM or Polio) is a common disease in sheep. Unlike the human form of Polio, it is not a viral infection, but a neurological disease characterized by brain swelling that, if left untreated, progresses to degeneration of brain tissue due to pressure necrosis. Early treatment is critical to lamb survival. A deficiency in thiamine (vitamin B1) is the most common cause of Polio and is usually induced by a disruption in normal rumen function, especially acidosis.
Thiamine plays a key role in glucose metabolism and proper brain function. Since thiamine is produced from rumen microbes, lambs at greatest risk are those transitioning from milk to a solid diet, especially a high grain diet due to changes in the rumen flora.
Ingestion of thiaminase producing plants like bracken fern has the same effect. Another cause of Polio is excessive dietary sulfur from by-product feeds like DDG’s, forage brassicas (turnip, rape, mustard) or excessive sulfur in the water. It can also be triggered from a cumulative exposure to sulfur rather than from any one source.
Symptoms of Polio present as mostly neurological: dilated pupils, blindness, star gazing, uncoordinated or exaggerated gait, depression, and excessive salivation.
Polio can be successfully treated with Thiamine if detected early. Thiamine should be given at a dose of 5mg/pound via intramuscular injection every 12 hours for 2 days and then once daily for another 3-5 days. The addition of an anti-inflammatory may help reduce brain swelling and aid with recovery. The rumen may take up to 2 weeks to return to normal function. Thiamine is a prescription drug, so make sure to consult with your veterinarian before you have a problem. The earlier you can start treatment, the better the outcome so make sure to always have a fresh bottle on hand.
Other diseases, like listeria can present with similar symptoms. Early treatment is very important. If given as instructed above, thiamine is safe and should be initiated regardless of the cause.
By: EAPK Communications Committee