Mosquito-borne killer disease threatens blackbirds

The blackbird is a well-known bird in the UK, famous for its cheerful and melodic song. Recently, a new disease carried by mosquitoes has arrived in Britain, raising concerns among scientists about the health of blackbirds. This disease is called the Usutu virus, and it has been spreading rapidly across southern England. New research indicates that the Usutu virus has been linked to a decline in some blackbird populations, prompting scientists to closely monitor its spread and understand the potential risks to these beloved songbirds. Dr. Arran Folly from the Animal and Plant Health Agency (APHA) stated, 'We have observed that the virus has spread further than we initially anticipated, and it has persisted in the environment. ' The common house mosquito, known scientifically as Culex pipiens, is responsible for carrying and transmitting the Usutu virus. For decades, scientists at the APHA in Weybridge, Surrey, have been studying mosquito-borne diseases in wild birds, especially as climate change transforms Europe into a more suitable habitat for these insects. Warmer summers, increased temperatures, and heavy rainfall are creating ideal conditions for mosquitoes to thrive in areas that were previously unsuitable for them. Until 2020, all tests for the Usutu virus returned negative results. However, following the intense heatwave of that summer, the virus was detected in several blackbirds in Greater London. Dr. Folly noted, 'Blackbirds are particularly vulnerable to the virus, and since 2020, we have observed a decline of approximately 40% in blackbird populations in Greater London. ' This alarming trend suggests that other mosquito-borne viruses may emerge in the UK in the future. The Usutu virus poses a growing threat to wild birds, which are already facing numerous challenges, including habitat loss, climate change, and pesticide use. The Usutu virus was first identified over fifty years ago near the Usutu River in southern Africa. Since then, it has spread globally, reaching Europe three decades ago, and was first detected in the UK in 2020. Blackbirds are especially susceptible to this virus, which can also infect horses and, on rare occasions, humans. However, the risk to humans is generally considered low. Recent data indicates that the Usutu virus has spread further than scientists had expected. It has now been detected in wild birds across much of southern England, extending as far west as Dorset and as far north as Cambridgeshire. The extent of the risk that Usutu poses to wild birds remains uncertain. While the virus has been associated with mass die-offs of blackbirds in other parts of Europe, this does not appear to be the case in Britain. The blackbird continues to be one of the most common garden birds, with stable populations in many regions, particularly in rural areas and the north. During May, blackbirds are busy nesting and raising their young, with fledglings eventually leaving the nest. To gather more information about blackbird populations and their movements, scientists have partnered with the British Trust for Ornithology (BTO). They are calling for volunteers to help count blackbirds in their gardens throughout the summer months. At this time of year, blackbirds are actively breeding and caring for their young, often seen hopping along the ground and singing from tree branches during warm summer evenings. Lucy Love, a garden birdwatch ambassador for the BTO, has developed a fondness for the blackbirds in her garden. She remarked, 'They are beautiful birds – intelligent, friendly, and they have the most beautiful song with a lovely melodic tone. ' Lucy believes it is crucial to protect blackbirds, as they play an essential role in our ecosystem. To stay informed about the latest climate and environmental news, readers can subscribe to the Future Earth newsletter, which provides updates on significant climate stories each week.