The bluetongue virus has been confirmed on three more Norfolk cattle farms, following surveillance into an earlier case in the Broads.
Animal health officials identified the dangerous animal disease at three new sites within the 10km temporary control zone (TCZ) established earlier this month around a farm near Cantley - which became East Anglia's first case since 2007.
Defra says all the infected animals "will be humanely culled to minimise the risk of onward transmission".
The TCZ will not be extended, and movement restrictions continue to apply to cattle, sheep and other ruminants within the zone.
It is worrying news for East Anglia's livestock farmers. Defra says the midge-borne disease does not affect people or food safety, but outbreaks "can result in prolonged animal movement and trade restrictions".
However, it says there is "still no evidence that bluetongue virus is currently circulating in midges in Great Britain" - although surveillance is ongoing.
The virus is transmitted by biting midges which are usually most active between April and November, and it has been spreading rapidly in continental Europe.
Two of the new cases were in cattle on two separate premises within the ownership of a single family business.
This brings the total number of cases in England to 27 infected animals on 16 premises, with 11 different keepers in Norfolk and Kent.
Bluetongue affects ruminants including sheep, cattle, deer and goats as well as camelids such as llamas.
Norfolk farmers have been warned to "remain vigilant" and report any suspicions of the virus immediately.
Livestock producers within the TCZ can only move animals out of the zone with a specific licence, which will only be granted if there is an "urgent and genuine welfare need to move the animals" - or if they need to move animals to another premises or abattoir within the TCZ; from outside the zone to permanently within the TCZ; or to to go directly to slaughter at a designated abattoir.
Bluetongue is a notifiable disease, and suspected cases must be reported to the APHA (Animal and Plant Health Agency) on 03000 200 301. For more guidance on symptoms and prevention measures, see www.gov.uk/guidance/bluetongue.
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