Germany’s Bluetongue Case: Outbreak Reports Don’t Match the Midges

Germany’s bluetongue evidence points to a regulatory surveillance problem rather than genuine winter circulation, with only one of 1,581 midge pools carrying BTV-3 RNA in November 2024 despite nearly 13,200 reported outbreaks the previous month. The disconnect suggests that animal case detection and vector monitoring operate in separate silos, raising questions about whether reported outbreaks reflect true virus transmission or detection artifacts.

Anja Voigt and colleagues reported in Parasites & Vectors that weekly barn trapping over four winters found blood-fed Culicoides still active above the EU vector-free threshold, yet winter circulation appeared “hardly existent” based on RNA detection. Germany logged 3,628 animal detections during winter 2024/25, but field sampling tells a different story: a 2019-23 national programme at 79 sites found no BTV or EHDV in 19,521 pools from 511,788 female midges.

The earlier 2024 outbreak pattern supports this gap. The first BTV-3 sheep case appeared in Kleve on 12 October 2023, with one infected midge pool detected the same day and 55 further cases by 18 April 2024. By contrast, Schmallenberg virus appeared in 534 pools in 6.5 weeks—suggesting SBV circulates far more readily in midge populations than BTV.

The regulatory outlook remains uncertain. Friedrich-Loeffler-Institut says the 2024 BTV-3 wave eased in 2025 after infection and vaccination, but lower-level BTV-3 persisted through 2025/26 and BTV-8 reappeared in October 2025 in two strains. Pirbright researchers found Culicoides eggs survived to −18°C, offering one mechanism for overwintering, while WOAH still describes vaccination as the most practical control strategy globally.