Nigropallidal encephalomalacia
Nigropallidal encephalomalacia or Chewing disease is a neurological condition that affects horses. Affected animals are unable to swallow easily and the food remains in the mouth where it is persistently chewed.
The principal cause is a diet high in Centaurea solstitialis or Yellow star-thistle or Creeping Knapweed which leads to the development over months of Parkinson's disease like symptoms.. The development of the disease typically occurs when Yellow Star-thistle is more than 50% of the horse's diet over a protracted period. The causative agent for Creeping Knapweed is believed to be repin. a Sesquiterpene lactone.Occurrence
The disease appears to be restricted to areas where the causative plant species have become invasive and may represent the only food available. Most evidence from published data relates to the western US and to Victoria, Australia.
