The mosquito-borne Usutu virus, lethal to Blackbirds, is sweeping through the southern regions of England, causing alarm among wildlife enthusiasts. Spotted on UK shores as of 2020, the pathogen has swiftly spread as far west as Dorset and northwards to Cambridgeshire.
Originating in Southern Africa, the virus appeared in Europe three decades ago, prompting significant die-offs in Blackbird populations, as reported by Bird Guides.
The British Trust for Ornithology has issued a call to action, urging those with gardens frequented by blackbirds to participate in a crucial survey aimed at assessing the damage and identifying areas in need of aid.
Although the Usutu virus poses a negligible threat to humans, with no cases in Britain, the avian fatalities are severe. Greater London reports suggest Blackbird numbers have dropped by as much as 40% since the virus’s incursion following 2020’s heatwave.
Dr Arran Folly from the Animal and Plant Health Agency warned about the swift advance and persistence of the virus in the UK, hinting at the potential for other mosquito-transmitted diseases to emerge in the country. “It gives an indication that in the future we might get other viruses that are transmitted by mosquitoes emerging in the UK,” he expressed concern.
Attributed to climate change, mosquito populations are booming due to warmer temperatures, extended summers, and increased rainfall, creating perfect breeding grounds for the insects and their pathogens.
In collaboration with the British Trust for Ornithology (BTO), APHA scientists are investigating the effects of Usutu virus on Britain’s birds. The BTO is calling on the public to report Blackbird sightings to help monitor the situation.
“Blackbirds are currently nesting and are a common sight in gardens and parks. With public help, we can better track population trends and the virus’s impact,” said a spokesperson from the BTO.
Despite stable Blackbird numbers in rural and northern regions, the unpredictable nature of Usutu virus calls for continuous monitoring. The partnership between APHA and BTO is crucial for gathering data to shape conservation efforts and anticipate future diseases.
The BTO commented: “We are trying to better understand the extent and spread of Usutu virus and what the potential impacts of the virus might be on Blackbirds. In particular, as Blackbird numbers were already decreasing in London, a large urban area, we want to know if anything similar is happening in other urban areas, or whether these changes are specific to the capital, and how this compares to smaller urban and more rural areas.”
How will Blackbirds in Gardens help?
The BTO is conducting a survey to delve into the potential for disease transmission by Blackbirds in gardens, focusing on their congregation patterns. The organisation explained that the study will shed light on how Blackbird populations utilise various garden types and their breeding success across different urbanisation gradients, from rural to urban settings.
The BTO remarked: “Although largely harmless to humans, this is the first time in modern history that a mosquito-borne viral zoonosis (a disease which can be transmitted from animals to humans) has emerged in wild animal hosts in the UK but, with changing climates, more may occur in the future.
“Using Usutu virus and Blackbirds as a case study, this survey is part of the Vector-Borne RADAR project, a wider partnership project funded by the UKRI and Defra to understand the emergence and transmission of mosquito-borne viruses in the UK more generally which are expected to increase with climate change.
“The project will improve understanding of how these viruses emerge in new environments, enhance surveillance of diseases in wild birds in the UK and develop an early warning system for disease outbreaks.”
The survey is set to run until September 2025.
How to sign up to the survey
You can sign up for Blackbirds in Gardens online.