Farmers must be aware of the facts and avoid misinformation to prevent unnecessary actions and costs when combatting the 'very high' threat of bluetongue, experts say.
This is according to a recent technical meeting by the AHDB and Ruminant Health & Welfare, which looked at the bluetongue situation in the UK.
Government vets have concluded there is a 'very high' probability of new bluetongue virus serotype 3 (BTV-3) infections due to the arrival of biting midges from northern Europe.
There have been over 120 bluetongue cases in England across 73 premises in four counties since November 2023, with the last case confirmed on 8 March 2024.
Lesley Stubbings, sheep consultant and adviser for Sustainable Control of Parasites in Sheep, who attended the meeting, said farmers must understand the current facts surrounding the disease.
“The fact is, a single bite from a single infected midge will reliably transmit BTV-3," she explained.
“This means that trying to control midges is futile and is not going to impact on the risk of BTV-3 transmission. It is crucial that we 'ACT' with this knowledge in mind.”
At the meeting, farmers and the industry were told to remain Aware, apply Caution and use evidence-based Tactics to 'ACT' and mitigate against BTV-3.
Speaking as a spokesperson for Ruminant Health & Welfare, Ms Stubbings said the group was recommending farmers to be aware of the facts and avoid misinformation.
She said: “As an emerging new strain of bluetongue, with no vaccine currently available, the industry is taking learnings from research, science and our EU counterparts, who experienced clinical cases during 2023, to provide the most up-to-date advice and guidance.
“Many have questioned the role of insecticides in controlling midges and in controlling BTV-3 transmission. They are not the same. There needs to be clear distinction between midge control and BTV-3 control.
“There is no evidence that insecticides can prevent infection as they do not kill Culicoides midges (the specific type of midge that transmits bluetongue) fast enough to prevent the first bite."
Similarly, the technical meeting heard that there is no evidence that insecticides prevented onward transmission of bluetongue.
There is also no evidence that insect repellents - which deter insects - have any effect on the transmission of BTV-3.
“Therefore, the use of insecticides or repellents to try to prevent BTV-3 infection is not recommended," Ms Stubbings said, adding that they could have detrimental effects on the environment as well as being an unnecessary cost.
“Farmers will not be able to significantly reduce the number of midges in a specific area, nor for long enough to prevent BTV-3 transmission.”
When it comes to tactics for midge control, air movement is key, the technical meeting heard, as midges are most active during dusk and dawn.
Farmers should act to maximise natural ventilation, particularly by taking advantage of hills, wind and rain.
Farmers in the Netherlands favoured housing animals with powerful fans, providing air flow of more than 3m/s, for example.
Ms Stubbings said: “Midge control through increased wind speed may reduce midge biting rate but it won’t eliminate all biting and therefore won’t necessarily prevent bluetongue transmission.
"As we know, it only takes a single bite from a single infected midge to reliably transmit BTV-3,” she explained.
“This small practical insight from the Netherlands feels better than doing nothing and will be a tactic farmers can act on to potentially help midge control on-farm.”
Currently, there are no products licensed for Culicoides midge ‘control’, the meeting heard, meaning that any products sold for this purpose would be off licence.
What is the current advice?
Ruminant Health & Welfare and AHDB brought together experts, including scientists, research and veterinary professionals, to ensure the right information is available for farmers.
They are advising farmers to ‘ACT’ on BTV-3 by being aware of how bluetongue is transmitted as a vector-borne disease, while providing caution against misinformation, and promoting evidence-based tactics on-farm.
• Awareness of how BTV-3 is transmitted as a vector-borne disease
• Caution against any misinformation, but instead view the latest facts
• Tactics on-farm to help with midge control must be evidence-based
