Defra has announced that the UK is now in a seasonally low vector period when midge activity is reduced, leading to some changes to disease control measures for bluetongue.
BTV-3 is the new strain of bluetongue currently being found in northern Europe and UK, transmitted via biting midge, affecting cattle, goats, sheep and camelids such as llamas.
As of 2 February, there are 70 bluetongue cases in England on 43 farms and premises, spread across three counties - Kent, Norfolk and Suffolk.
The counties are still in a temporary control zone (TCZ) since the initial outbreak of bluetongue in mid-November, which was the UK's first case since 2007.
But the current weather conditions and time of year mean that Culicoides – the type of midge able to spread viruses - are unlikely to transmit the virus to livestock, Defra said today.
Because of the reduced risk of transmission, it has taken the decision not to cull infected animals where test results indicate older infection and the presence of BTV-3 antibodies.
Infected animals may still be restricted at their current locations and other disease mitigation measures taken as appropriate.
The reduced risk from midges means that some restrictions on movements of live animals from the TCZ can now be eased.
However, this is only if they meet certain conditions, including testing negative in a pre-movement test. A licence is required.
A statement by Defra said: "Due to a decrease in temperature, we are now in a seasonally low vector period, when midge activity is much lower, and they are not actively feeding.
"Low temperatures also mean that the virus cannot replicate in the midge, so even if a midge does feed on an infected animal, the risk of transmission to another animal is low.
"The reduced risk from midges means that some movements of live animals out of the zone can now be temporarily permitted subject to pre-movement testing and that they meet certain licence conditions.
"These relaxations will only apply during periods of low vector activity and will not apply to animals that test positive in a pre-movement test."
Dr Marion England, institute fellow in vector ecology at the Pirbright Institute, said midges previously infected with BTV-3 were currently highly unlikely to transmit the virus.
“The most active period for midges is during the warmer months in spring, summer and autumn, and midges can become newly infected with bluetongue virus and spread disease when the weather is above 12°C for a sustained period.
“Midges infected in late autumn 2023 are now not likely to be a risk for spreading disease because they usually die off during winter, and are not actively biting when temperatures are below 4°C."
Surveillance of susceptible animals and epidemiological assessments within the TCZs in Kent and Norfolk will continue, Defra said.
Farmers can call the dedicated bluetongue hotline to get advice or ask questions linked to the current situation – on 024 7771 0386.
In the UK, bluetongue is a notifiable disease, meaning anyone suspecting the disease must take action and report it to the Animal and Plant Health Agency (APHA).