Farmer’s Newsletter – March 2024

It all seems to have gone quiet on the eastern front for now, a relief to the rest of the team who’ve managed to wriggle out of being deployed to the delights of Norfolk to blood sample sheep in the rain. Do David, Ollie and I deserve medals for bravely answering the call of duty? Maybe.

So, what’s next? Did we get away with it?

This new strain of Bluetongue (BTV-3) popped up last September in the Netherlands, ripping through the sheep and cattle populations, with a 30% mortality rate in sheep. Between now and September, they saw an estimated loss of 5% and 0.2% of the Dutch national flock and herd respectively. This is on top of the devastating production losses from sick animals and movement restrictions. BTV-3 was also found in neighbouring Belgium, Germany, France and, in early November, the UK.

Since arriving here, most likely with infected midges being blown across the channel from North Holland, we’ve had a total of 123 confirmed cases to date in the Kent and Norfolk areas. What’s interesting is that none of these 123 cases have been symptomatic or ill, with no deaths yet linked to BTV-3 here. All cases have been found with antibodies, indicating that they were exposed to bites from infected midges, though none have had active virus found in their blood. Positive-testing animals were euthanised not so much on welfare grounds but due to the small risk that they could be a potential source of virus for other midges.

The working theory is that, because the virus only replicates inside the midges above a certain ambient temperature, by the time they arrived in November it was too cold for them to be carrying a high viral load per bite. This meant that there was enough virus per midge for some animals to be exposed and develop antibodies, but not enough to cause symptomatic disease (or at least only very mild disease that appears to have gone unnoticed). As we proceeded further into the winter, the midge populations would have died off and entered a low activity period. Right now, the midges are mostly waiting as larvae in the soil to emerge in the spring as it warms up again.

Unfortunately, a vaccine is possibly not going to arrive in time for this next midge season, which starts picking up from the spring onwards, typically peaking in autumn. Some are estimating that a vaccine may not be here before early 2025. So, we are at the mercy of the midges until then.

Will it have managed to overwinter here in our midge populations, or will it have faded away with the winter die off? Will it blow back over from northern Europe earlier into this midge season or will we get lucky again? Only time will tell.