Clinical signs vary with the severity and extent of the disease and include anorexia, marked weight loss, stertorous respiration and conjunctivitis with marked chemosis.
When they're frozen, the creatures enter a state called cryptobiosis, in which their metabolic processes shut down, and they show no visible signs of life.
They are one of the classic signs of untreated disease, but can also be seen in other illnesses as well including shigellosis and nontyphoidal salmonellosis.