Cats are being struck down by a mystery disease that turns them into 'living robots'. Their legs become rigid, giving them an odd, stiff gait, their personality changes and their tail stiffens and sticks out. There is no known treatment or cure. The symptoms become progressively worse and the animals are put down when their suffering becomes too much. The condition has baffled vets, as tests for numerous viruses have come back negative. Their best guess is that the pets caught the disease while out hunting.