or Cerebrocortical necrosis (PEM or CCN)
- Polioencephalomalacia or CCN is most commonly seen in weaned lambs aged 4 to 8 months but disease does occur in adult sheep.Individual lambs are usually affected approximately two weeks after movement to another pasture or other dietary change. The change in diet alters the bacterial make-up in the rumen allowing production of byproducts by some bacteria which have toxic effects on the brain.
- During the early stages of CCN affected sheep are blind and become isolated from the group and may wander aimlessly. There is ‘star-gazing’ when stationary. The condition deteriorates within 12 to 24 hours to lying flat out with seizure activity during handling. Without treatment, death follows within 3 to 5 days in untreated sheep.
- Thiamine deficiency produces polioencephalomalacia.
Treatment and control
- The treatment response during the early clinical stages of CCN to high doses of thiamine (vitamin B1 at 10 mg/kg twice daily) administered intravenously for the first occasion, is generally good. Successfully treated sheep are able to stand and commence eating within 24 hours although normal vision may not return for 5 to 7 days. Treatment should be continued for three consecutive days.