Livestock Disease Summaries नेपाली भाषा

Polioencephalomalacia (PEM, “Polio”)

Polioencephalomalacia, often called PEM, is a disease of the nervous system that occurs in cattle, buffalo, goats and sheep, but can affect any ruminant, including deer and camelids. This is not an infectious or transmissible disease and not the same as polio in humans. This disease is seen most commonly in young rather than adult ruminants.

Causes of PEM

There are three causes of this disease:

  1. Deficiency in thiamine (vitamin B1). Young ruminants depend on thiamine in the diet (usually milk) and if the diet is deficient in thiamine those animals can suffer from that deficiency. Once the rumen is functional, microbes in the rumen make thiamine, but sudden changes in diet can change the types of ruminal microbes, resulting in decreased thiamine production or actual destruction of thiamine, resulting in deficiency of that vitamin.
  2. Decreased thiamine production in the rumen or destruction of thiamine. Sudden changes in feed, including changes in composition of the pasture due to heavy rains can change the microbial population in the rumen resulting in production of enzymes that destroy thiamine, which is another way to get thiamine deficiency.
  3. Excess ingestion of sulfur. This can occur in a number of ways. Some plants have high concentrations of sulfur, including mustard and turnips. Also, some by-products of plant processing can sometimes be high in sulfur content. It is often difficult to predict whether a given forage will have high sulfur content without laboratory analysis.

Clinical Signs of PEM

PEM is a disease of the nervous system. The most common clinical signs of acute disease include:

These clinical signs can be seen below in videos of an affected goat and calf.





PEM can also occur less dramatically as a subacute disease, where animals show apparent blindness and such signs as “stargazing” or muscle twitching.

Diagnosis of PEM

A tentative diagnosis of PEM is based on seeing typical clinical signs of this disease: sudden development of blindness, muscle tremors, arched back and staggering. It is often also associated with a change in feed such as switching from to low roughage and high amounts of grain.

Be aware that several other diseases can look like PEM, including tetanus, salt poisoning (excess salt or water deprivation), ketosis, pregnancy toxemia, various poisons (lead, mercury, pesicides) or rabies.

Treatment of PEM

The standard treatment for PEM is to give thiamine: a dose of 10-20 mg/kg given subcutaneously or intramuscularly twice daily and repeated once daily for several more days. Thiamine can also be given intravenously but you have to be careful to inject it very slowly.

If thiamine solution is not available, give the animal ten times the normal dose of B-complex vitamins.

Improvement after treatment with thiamine is often very rapid. The images below show a sheep with obvious clinical signs of PEM (left) and up and eating 20 minutes after receiving a subcutaneous injection of thiamine (right) (Courtesy of Dr. Joan Bowen).

For PEM due to sulfur toxicity, thiamine treatment may also be useful, but also remove the source of excessive dietary sulfur.

Prevention of PEM

Prevention of PEM is difficult. Avoiding rapid changes in diet and providing a diet with sufficient roughage to promote synthesis of thiamine in the rumen is the most common recommendation.

Back to Index

Send comments to Richard.Bowen@colostate.edu