Polioencephalomalacia (Pem Or Star Gazing Disease)

Caused by a deficiency of thiamine (vitamin B1) in sheep of all ages and both sexes. May occur in sheep on high grain diets, and diets that include plants high in thiaminases (e.g. bracken).


• The first signs are listlessness and a loss of appetite, affected sheep will separate from the rest of the mob, appear blind and either wander aimlessly or stand still.

• Sheep will adopt one of two stances: - Head lowered to the ground; or - ‘Star gazing’ with a fixed stare into the sky over the horizon.

• Later, affected sheep will go down and if startled may start galloping leg movements and have convulsions.

• A sheep that is down will generally have its head and neck arched back stiffly.

• If not treated sheep will get weaker, sink into a coma and die within 2-3 days.


• Based on clinical signs and response to treatment in cases found early.

• Post mortem examination of the brain can be used to diagnose PEM.


• Sheep respond to thiamine or B1 injections which are available from most rural stores.

• Mildly affected sheep will improve within 6-8 hours of treatment.

• Sheep that are down will have irreversible damage to the brain and should be destroyed on welfare grounds.


Thiamine or B1 injections will prevent more cases of PEM if multiple cases are occurring.

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