BTV-3 is the new strain of virus currently being found in northern Europe and UK. The virus is mainly transmitted via biting midges and affects cattle, goats, sheep and camelids, such as llamas.
Dr Marion England, Institute Fellow in Vector Ecology at The Pirbright Institute, said: “The current weather conditions and time of year mean that Culicoides – the type of midge able to spread viruses, such as BTV-3, are highly unlikely to transmit the virus to livestock.
“Under these conditions, midges previously infected with BTV-3 are 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,” adds Dr England.
Because of the reduced risk of transmission between midges and animals, Defra 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 Temporary Control Zones (TCZ) can now be eased if they meet certain conditions, including testing negative in a pre-movement test. A licence is required.
Some restrictions on movements of animals into and within the TCZ have also been eased.
Surveillance of susceptible animals and epidemiological assessments within the TCZ will continue and Defra will keep the situation under review.
In the UK, bluetongue, including BTV-3, is a notifiable disease, so anyone suspecting the disease must take action and report it to the Animal and Plant Health Agency (APHA).
Article adapted from Ruminant Health and Welfare.