Bluetongue surge strains vaccine supplies as test delays double

A rapid rise in bluetongue cases has strained vaccine supplies and doubled some laboratory turnaround times, despite millions of additional doses being imported and testing facilities deploying five times their usual staffing levels.

The Animal and Plant Health Agency (APHA) and Veterinary Medicines Directorate (VMD) have detailed the pressures facing the disease response in a letter published by the Environment, Food and Rural Affairs Committee.

The response followed concerns raised by the Committee over preparedness for the latest BTV-3 outbreak.

The first positive case of the 2026 outbreak was confirmed on 9 July, with weekly submissions then rising before quadrupling towards the end of the month. This prompted a wider response involving APHA, Defra, the Pirbright Institute and the VMD.

There have since been over 1,800 cases of BTV-3 or unspecified bluetongue serotype across the UK in the 2026-27 season.

Officials said prolonged hot weather helped BTV-3 spread more quickly than expected. In high temperatures, the time before an infected midge can transmit the virus can fall from around 20 days to as little as three days.

The agencies said the hot summer, combined with high livestock density in south-west England, may also have contributed to the relatively large number of sheep cases seen early in the season.

Pressure also developed around vaccine availability as disease levels and demand increased. BTV-3 vaccine uptake had been relatively low during 2025 and the first half of 2026, reflecting the lower incidence and severity of disease at the time.

Manufacturers therefore did not maintain substantial excess stocks in Great Britain because of the risk of vaccine wastage. As cases and demand increased, supplies of GB-authorised vaccines became constrained by mid-August.

Defra and the VMD subsequently worked with manufacturers to bring in EU-authorised products, with approximately 4.85 million doses imported into Great Britain during August and the first two weeks of September.

A further 1.68 million doses, including replenished stocks of GB-authorised vaccines, were expected to arrive between September and December. Another 1.33 million doses of GB-authorised vaccine are expected to become available in January and February 2027 ahead of the next vaccination season.

Testing laboratories were also put under significant pressure by the volume and nature of submissions. The Pirbright Institute tested 10,878 samples from 3,825 submissions from 9 July, with turnaround times for some samples increasing from five to as many as 10 working days.

Higher-priority tests needed to support disease-control decisions were generally returned within three working days. However, the agencies said overall weekly testing capacity had not been exceeded.

Instead, the unusually high number of individual clinical submissions created additional pressure because samples had to be separately packaged, labelled, received, processed and reported. Those requirements had the potential to create bottlenecks in the system.

Pirbright responded by redirecting trained staff and laboratory space towards the outbreak. “Five times the usual number of staff” were working on sample processing, testing and reporting at the peak, while laboratory staff worked evenings and weekends to tackle the backlog.

APHA staff and its Weybridge laboratory were also brought in to provide additional capacity.

The agencies continue to put vaccination at the centre of the disease response, stating: “Vaccination is the most appropriate way to control this disease”.

Farmers and veterinary surgeons have been encouraged to place vaccine orders promptly so demand is visible and available supplies can be allocated more effectively.

The outbreak has also raised wider questions about the resilience of the animal disease response system. APHA said lessons from BTV-3 would feed into further work to improve its processes, while identifying its capacity and capability to handle simultaneous disease outbreaks as the most significant remaining risk.