Grouse shoots are being urged to adopt strict biosecurity measures after it emerged that at least half of grouse moors in the North of England are infected with a new form of ‘bulgy eye’. The disease is resistant to disinfectants, has no effective treatment and is spreading rapidly. The infection currently sweeping through wild grouse is different to the ‘bulgy eye’ found in other game and poultry, which is caused by Mycoplasma galliseptum.

The new disease is caused by another species of bug, known as Cryptosporidium baileyi, which had not previously been recorded in grouse. GWCT scientists say the disease is highly contagious, and estimate it affects at least 80 per cent of grouse moors in the North Pennines. Last year it was also recorded in the Lammermuirs in Scotland.

Scientists are baffled as to why and how the disease has suddenly appeared in wild red grouse. There are no effective treatments available for birds infected with cryptosporidiosis. There are products that can be used to reduce the shedding of oocysts in captive birds, but these are not practical to use in wild grouse owing to their toxicity. The disease is thought to be specific to birds and is not thought to affect dogs or humans.

Helen Errington, BVMS Cert SHP MRCVS, a specialist avian vet with St David’s Game Bird Services, is researching the disease on moors in the North of England. She said: “People should be aware of the problem, and seek professional advice.”

She added: “Personally I suspect that this problem has been around in grouse for a long time, at background levels, and increased bird density is causing it to show up. The research work we are doing on clean moors will help us to understand what is going on.” She is keen to hear from any member of the shooting industry who encounters birds apparently suffering from ‘bulgy eye’ in a previously unaffected area. If you have an account to share, the contact details are available online at


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