BOURNEMOUTH, Christchurch and East Dorset have all been placed in the government's bluetongue protection zone.
Now farmers and animal keepers are restricted by DEFRA livestock movement controls.
DEFRA says it has extended the existing protection zone following a new case of bluetongue in Sevenoaks.
The zone now includes Bournemouth, Christchurch and the area covered by East Dorset District Council.
DEFRA has written to all recorded owners of animals within these districts advising animal keepers and farmers of this change.
This affects farmers with ruminant animals such as cattle, sheep, goats and deer.
Farmers with animals in those areas may not move them to premises outside the bluetongue protection zone, except to slaughter.
Vehicles used to transport animals to slaughterhouses outside the protection zone must be sprayed with approved insecticidal.
The movement controls do not apply to pigs.
Richard Herringshaw, the county council's principal trading standards officer, is urging farmers to remain vigilant.
"The extension of the protection zone does not mean the disease is in Dorset," he said.
"It is a measure designed to slow the spread of the disease.
"The countryside remains open for business and the disease does not affect humans or food safety."
But he does stress that animal keepers must check their stocks regularly. "If keepers have any concerns they should report them to Animal Health on 01823 337922.
"The county's Trading Standards Service's role is to enforce the movement controls. However we recognise that the situation is changing regularly.
"If anyone has any questions about what the controls on movements are they can telephone us on 01305 224475.
"For those who have access to the internet I suggest they look at the DEFRA website," he added.
Bluetongue is a non-contagious virus spread by a species of midge and is most commonly seen in the late summer and autumn.
The outbreak started last month and has so far been confined to the South East.
A total of 52 premises are affected by the disease.
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