Farmers could face fines or jail for moving livestock as cases of the potentially fatal bluetongue virus rise.
Defra, the Department for Environment Food and Rural Affairs, enforced the new rules as the total number of confirmed cases has reached six.
It means farmers cannot move cattle, sheep, goats, deer or camelids to or from the zone unless they are given a licence by a veterinary inspector.
If found to be breaking the rules, farmers could face either a fine, up to three months in jail, or both.
The first case emerged in Canterbury while the next four were discovered within the six-mile temporary control zone at two separate premises.
All infected animals have been put down in a bid to reduce the risk of spreading the disease.
The virus is transmitted by midge bites and affects cows, goats, sheep and other camelids such as llamas.
The insects are most active between April and November and not all susceptible animals show immediate, or any, signs of contracting the virus.
Chief veterinary officer Christine Middlemiss said: “Bluetongue does not pose a threat to human health or food safety, but the disease can impact livestock farms, and cause productivity issues.
“This detection is an example of our robust disease surveillance procedures in action and it is also a clear reminder for farmers that the disease remains a threat, despite coming towards the end of the midge activity season.
“Farmers must remain vigilant and report any suspicions to APHA.”
The UK’s chief veterinary officer from the British Veterinary Association, Anna Judson, added: “Whilst the confirmed case of Bluetongue in a cow in Kent is deeply concerning, it’s positive to see that routine veterinary surveillance to identify potential disease risks is working.
“This is now a critical moment and BVA urges UK farmers, particularly those in the Southeast of England, to remain vigilant for any signs of Bluetongue in their animals.
“Vets are there to support farmers in protecting the health and welfare of their livestock.
“We’d recommend farmers speak to their vet about the benefits of vaccination where one is available and especially if farmers have any concerns about their livestock.”