Muscle trembling Prolapse of the third eyelid — this means that the third eyelid flickers across the eye or covers more of the eye than normal Generalized weakness Weakness in the hind end — the horse may look as though it is 'dog-sitting' Complete collapse Abnormal whinny — because the muscles of the voicebox are affected as well as other muscles Death — in a severe attack the diaphragm is paralyzed and the horse can suffocate