A sheep consultant has warned that trying to control midges is “futile” and is not going to impact the risk of bluetongue transmission.
Sustainable Control of Parasites in Sheep (SCOPS) advisor, Lesley Stubbings, said farmers should be aware of the facts and avoid misinformation to prevent unnecessary actions and costs when it comes to serotype 3 of the bluetongue virus (BTV).
According to Stubbings: “The fact is, a single bite from a single infected midge will reliably transmit BTV-3.
“This means that trying to control midges is futile and is not going to impact on the risk of BTV-3 transmission.
“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.”
Stubbings said many farmers have also questioned the role of insecticides in controlling midges and in controlling bluetongue transmission.
“They are not the same. There needs to be clear distinction between midge control and BTV-3 control,” she said.
“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, there is no evidence that insecticides prevent onward transmission of bluetongue and there is also no evidence that insect repellents (which deter insects), have any effect on the transmission of BTV-3.”
Stubbings said the use of insecticides or repellents to try to prevent bluetongue infection is not recommended.
“They may 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,” she added.
Midge control
The Department of Agriculture, Food and the Marine (DAFM) recently urged livestock keepers to be vigilant as increasing temperatures have brought about increased midge activity.
When it comes to midge control, Stubbings said air movement is key, as well as noting that midges are most active during dusk and dawn.
“Farmers should act to maximise natural ventilation, particularly by taking advantage of hills, wind and rain,” she said.
“Farmers in the Netherlands favoured housing animals with powerful fans, providing air flow of more than 3m/s, for example.
“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,” the advisor explained.
The small practical insight from the Netherlands feels better than doing nothing, Stubbings added, and will be a tactic farmers can act on to potentially help midge control on-farm.
‘ACT’ on BTV-3
Ruminant Health and Welfare (RH&W) and the Agriculture and Horticulture Development Board (AHDB) have brought together experts from across the UK to ensure the right information on bluetongue 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.
The Department for Environment, Food and Rural Affairs (Defra) has said it is planning for a “possible increase of bluetongue virus” over the coming months as the weather warms.
The seasonal low vector period has ended, meaning biting midge activity has increased with the warmer spring weather.
The risk of infected biting midges blowing over from northern Europe has increased, the department said.
Defra said there is currently no evidence that there is circulating bluetongue virus.
“Surveillance of susceptible animals and epidemiological assessments will continue. We will keep the situation under review,” the department said.
The last confirmed case of bluetongue was on January 19. It was confirmed in a cow on the Norfolk/Suffolk border as part of ongoing surveillance at the time.
