-The cats had outdoor access and lived in the same rural area of Scotland -Now cats with a similar condition have been found in Sweden and Austria By Fiona Macrae 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. Scroll down for video Vets at two surgeries in the Highlands have recorded 21 cases of 'staggering disease' where afflicted cats walk with a rigid legs and with a stiff, extended tail. An unknown cat is pictured with the condition Victims become over affectionate, their movement becomes stiffer and they are increasingly disorientated with difficulty grooming All the cats with the condition appear to have a slowly progressing neurological disease had outdoor access and lived in the same rural area of Scotland 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. Around 50 cases have been spotted in Scotland in the past decade, along with one in Liverpool, but researchers believe more may have gone unreported elsewhere. The outbreak appears to be centred in a rural area between Inverness and Aberdeen. Vets there have treated around 20 'robotic' cats, including two that have only recently become ill. Jeannette Andrew, of the Strathbogie Veterinary Centre in Aberdeenshire, said: 'They look like robots. 'They get a bit lost and get stuck in corners and don't know how to reverse and turn round.' Danielle Gunn-Moore, a professor of feline medicine at Edinburgh University, said: 'Their head is forward, their chin is slightly down, their ears are forward and they have a very stiff walk and a stiff tail … They walk like robots.' The condition also affects personality, with most of the sick animals becoming more affectionate. Some, however, become aggressive. As it doesn't seem to spread between cats and all the sick animals are avid hunters, experts believe the most likely source to be a mutant virus carried by mice or voles. Professor Gunn-Moore said: 'We have looked in the blood, in the brain fluid and in brain sections. 'We have looked for the presence of viruses in the brain and so far we've been able to rule out vast numbers but can't find the one that's causing it.' Vets have tried treatments including painkillers, vitamins, antibiotics and drugs normally given to multiple sclerosis sufferers, but none has held the disease at bay. The animals, which are usually elderly, gradually become more disabled and when they start to find it hard to swallow, they are usually put down – normally within a year of falling ill. So far the 'robotic cat' in Liverpool is the only one treated outside Scotland, and it is believed it may have caught the disease while living in the Highlands. A similar condition, known as 'staggering disease' has been seen in Sweden and Austria. However the cats there do not develop stiff tails. Experts are now looking to find a cure as most of the cats had to be humanely put down after about 11 months of developing the disease source: dailymail