Bluetongue (BTV) is a non-contagious, infectious viral disease transmitted only by biting midges, which affects all ruminants (e.g. sheep, cattle, goats and deer) and camelids. The latest strain to affect the UK is BTV-3 which has been an issue on mainland Europe since 2023, the first UK case was reported in November 2023 with a lull in cases over the winter and further cases identified from August 2024.
BTV is spread by adult-infected midges biting a susceptible animal. An uninfected adult midge bites an infected animal, taking in blood and the virus. The virus replicates within the insect when average daily temperature exceeds 15oC and moves to the salivary glands. The infected adult midge then bites an uninfected ruminant, transmitting the virus.
A single bite from a single infected midge is sufficient to transmit the virus. This ruminant animal will be infectious within 2-4 days. Additional bites will not result in greater levels of infection or worse clinical signs.
Generally, vets in Europe and those seeing cases in the UK are reporting that sheep appear to be more severely affected than other species, with clinical signs in cattle being particularly subtle.
| Sheep | Cattle | |
| Lethargy, reluctance to move | x | |
| Crusty erosions around the nostrils and on the muzzle | x | x |
| Discharge of mucus and drooling from mouth and nose | x | Nasal discharge |
| Swelling of the muzzle, face and above the hoof | x | |
| Reddening of the skin above the hoof | x | x |
| Redness of the mouth, eyes, nose | x | x |
| Breathing problems | x | |
| Erosions on the teats | x | x (possibly just reddening) |
| Low milk yield | x |
Calves/lambs can be infected with bluetongue before birth if the mother is infected while pregnant. Signs of infection include being born small, weak, deformed or blind or death within a few days of birth or abortions.
You can check whether you are in the current BTV Restricted Zone (RZ) by searching for the BTV Interactive Map online. Movements of animals are allowed within the RZ under a general movement license, but there is a risk movement will cause further spread of the virus by unwittingly moving infected animals or transporting infected midges to a new area. Please take precautions when moving animals – checking your stock for possible signs of disease and spraying the inside of vehicles with an insecticide approved for use against flying insects prior to loading. Avoid moving during dawn and dusk when midge biting activity is highest. Please only move animals when absolutely necessary. Animals can also be moved from a free area into the RZ. Movements of animals out of the RZ to live requires a specific license and testing that must be applied for from APHA in advance – there is no guarantee these licenses will be granted.
Total elimination of midges on farm is not feasible, reducing the risk is therefore the aim. Midges are not able to fly in high winds or rain, using the windiest location for stock can help reduce midge exposure. Midges breed in damp soils with high organic content, such as muckheaps – keeping these distant from susceptible stock and housing may reduce biting frequency and transmission. Whilst topical insecticides do kill insects, there is no evidence that use of insecticides on animals reduces bluetongue virus transmission in the field. These products have a poor retention/efficacy time (especially in the rain) so would require frequent repeat administration.
As you know there are now 3 vaccines available Bultavo-3, Bluevac-3 and Syvazul BTV – originally these were only freely available to those in the high-risk counties but this has now been extended to the whole of England. If you wish to vaccinate you will need to obtain a general license, follow strict rules regarding recording which animals receive the vaccine and fill in a form within 48 hours of vaccinating. The vaccines are only licensed in cattle and sheep but we have guidance from the camelid and goat vet societies with best advice for these species. Please be aware these vaccines do not claim to prevent infection, but to reduce viraemia and clinical signs.
Please contact our farm team if you wish to discuss any concerns or you require further information on Bluetongue.
