A possible new outbreak of the bluetongue virus is being investigated in animals in north-west England.
Bluetongue can be fatal to cattle and especially sheep
The suspected cases have been found in north Shropshire and Greater Manchester and two of the animals are sheep.
If tests prove positive, it will mean new restrictions for thousands of livestock farmers in large parts of the UK previously free of the disease.
Bluetongue is a non-contagious virus spread by a midge species, affecting ruminants including sheep and cattle.
The first case in the UK was detected last September. The disease spread to other parts of south-east England and protection and surveillance zones remain in place.
According to the Department for Environment, Food and Rural Affairs website, as of noon on 11 January there were 66 confirmed premises affected by bluetongue.
Scotland's first and only case to date was discovered on 28 December.
If tests on the new suspect cases show that the midges which carry the virus are active in the area, the restricted zones will be extended to cover most of Wales, north-west England and farms around the Bristol Channel.
Mark Holdstock from BBC Radio 4's Farming Today said: "This would limit animal movements, and would be a huge blow to livestock farmers stuggling to cope with existing bluetongue restrictions, and last year's foot-and-mouth outbreak."
All ruminants, such as cattle, goats, deer and sheep, are susceptible, although symptoms are generally most severe in sheep.
Signs of the disease in species vary, but key indicators include a high fever, excessive salivation, swelling of the head and neck, lameness and sometimes discolouration of the tongue.