The warning came following a meeting between key industry stakeholders and Christianne Glossop, the chief veterinary officer for Wales.
It was suggested that too many farmers appeared to be sitting back waiting for the first case to appear to register with their vets for vaccine.
Gareth Vaughan, Farmers Union of Wales president, admitted he would be very concerned if this really was the case, as it seemed likely that the current restricted zone in south east Wales would be declared a protection zone within weeks.
Farmers should be ready to start vaccination immediately this happened. Also the disease-free status of farms in the rest of Wales would change very rapidly should an actual case of bluetongue be confirmed within or near the border.
“I would therefore urge farmers who have not registered with a vet to do so immediately rather then risk being left out,” Mr Vaughan said.
“Those within the current restricted zone may only have a very short time to do this before vaccination starts,” he said.