Usutu Virus Detected in Wild Birds in Scotland for First Time
Usutu virus RNA was detected in two Eurasian Blackbirds found dead on the Isle of Arran, Scotland, in summer 2025, marking the first confirmed detection of the virus in wild birds in Scotland. Phylogenetic analysis traced the strain to the Africa 3.2 lineage, closely related to existing UK detections, suggesting geographic spread within the country rather than a new introduction from abroad. The finding is significant because it indicates the virus is expanding its range northward within the UK, and surveillance confirmed the presence of potential mosquito vector species on the island.
In summer 2025, multiple Eurasian Blackbird (Turdus merula) deaths were reported on the Isle of Arran, Scotland, prompting veterinary investigation including post-mortem examination, which initially yielded no diagnosis. Subsequent laboratory testing for Orthoflavivirus and avian paramyxovirus identified Usutu virus RNA in two of the birds via reverse transcription-PCR. Phylogenetic analysis placed the strain within the Africa 3.2 lineage, clustering closely with previously identified UK detections, pointing to northward geographic expansion of an established UK strain rather than an independent introduction. Follow-up surveillance on the island confirmed the presence of several mosquito species capable of acting as potential vectors for the virus. Usutu virus, a mosquito-borne flavivirus related to West Nile virus, has been associated with mass mortality events in Eurasian Blackbirds across Europe and has been detected in the UK in recent years. The Scottish detections raise concerns about the continued spread of the virus and its potential impact on wild bird populations, particularly blackbirds, which are known to be highly susceptible.
What's missing
The study does not specify the exact mosquito species confirmed as present on Arran, nor whether any mosquitoes tested positive for Usutu virus. The total number of bird deaths investigated and the proportion that tested positive are not fully detailed. Long-term surveillance plans or public health risk assessments for humans are not discussed. As a preprint, these findings have not yet undergone formal peer review.
What different sources said
- bioRxivCenter
First Usutu virus detections in wild birds in Scotland, 2025
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