Bluetongue Update: Where Are We Now and Should You Be Vaccinating?

By Will Gratwick

Bluetongue continues to be a concern for UK livestock farmers, but the situation this spring is quite different to what we experienced last year. Here is a clear update on where things stand and what actions we should be taking now.

At present, the risk of new bluetongue infection is low. The cases we are seeing on farm now are largely the result of infections that occurred last summer and autumn, rather than recent spread.
One of the most noticeable outcomes has been the birth of so-called “dummy calves.” These result from infection of the dam during the first trimester of pregnancy, when the virus can affect foetal brain development.
The predominant strain circulating is BTV-3, with a small number of BTV-8 cases reported in the south of England.
The UK is currently operating under England and Wales-wide restriction zones, but importantly, there are no movement restrictions within these zones. Scotland remains officially free of bluetongue and movement rules are expected to come into force from June.

The key factor in bluetongue spread is the activity of biting midges (Culicoides species), which act as the vector.
Last year, the “vector high-risk period” began around 1st July, but this could shift depending on weather conditions. A warm, wet early summer could bring this forward.
This means that while things feel quiet now, risk will increase significantly as we move into summer.

Although current infection risk is low, this is actually the ideal time to vaccinate.
Vaccination works by reducing:

• The level of virus in the blood (viraemia)
• Clinical signs, particularly in sheep

Transmission risk within and between herds/flocks
It’s worth remembering:

• Cattle often show mild signs of disease. However, there can be a major impacts due to reduced fertility, abortions, birth of ‘dummy’ calves and significant and prolonged milk drop.
• Sheep are much more severely affected, with high mortality.

To ensure protection before midge activity increases:

• Animals need to have completed their vaccine course at least 3–4 weeks before vector activity rises.
• This means vaccinating now (spring) is the optimal window

Delaying vaccination until mid-summer risks leaving animals unprotected during peak exposure. Unlike last year when the disease was moving gradually across the country, this year we know that it is already present so is likely to spread as soon as sufficient numbers of midges are present.

Although movement within England and Wales is currently unrestricted:

• Recording of vaccine prescription and administration is still required
• Future movement rules (particularly involving Scotland) may require:
• Vaccination at least 3 weeks prior, or
• Pre-movement testing

Planning ahead will help avoid disruption later in the season.

Key Take-Home Messages

• Current cases reflect last year’s infections, not active spread
• Risk is low now, but will increase with midge activity
• Vaccination is the most effective tool we have
• Spring is the best time to vaccinate

If you would like to discuss a vaccination plan tailored to your herd or flock, please get in touch with the practice.