In May, a team of dedicated scientists gathered in a German nature park near the Baltic Sea, their eyes fixed on a majestic 30-meter-tall black poplar tree. Their mission was to study white-tailed eagles and decipher the mysterious stream of viruses and pathogens that travel along Europe’s migratory bird routes. While white-tailed eagles themselves are not migratory, they feed on birds that do migrate and pass these pathogens to their young.
This endeavor coincided with the breeding season, and the scientists were eager to locate nestlings as they are easier to trap than adult eagles. With the help of a local eagle watcher, they identified a nest high in the tree, and their optimism grew as they spotted a white-tailed eagle soaring in the clear sky and fresh eagle feces staining the grass below. It was time to investigate the nest.
Veterinarian Oliver Krone, an expert in white-tailed eagles, deployed a drone to get a closer look at the nest, revealing three eaglets. A skilled tree climber then ascended to the nest, bringing down the eaglets and prey found within. These samples would undergo rigorous analysis for pathogens and antibodies, shedding light on the potential transmission of diseases from migratory prey to eagles and, ultimately, to humans.
Migratory birds, including ducks, play a critical role in transporting various microbes globally. They carry pathogens such as novel influenza strains, West Nile virus, and various bacteria, some of which harbor antimicrobial resistance genes. The research conducted by Anne Günther’s team, funded by the Versatile Emerging infectious disease Observatory (VEO), has already uncovered a devastating bird flu strain within the white-tailed eagles, highlighting the importance of understanding these disease transmission pathways.
VEO, a Europe-wide collaboration with a $30 million budget, aims to enhance early warning systems for tracking key pathogens, potentially averting pandemics. Marion Koopmans, VEO’s project coordinator, emphasizes the need to identify hot spots of human risk, recognizing that numerous factors influence the transmission of diseases, including bird behavior, pathogen characteristics, vectors, and human impact on the environment.
Climate change is introducing an additional layer of complexity to the equation. As temperatures rise and moisture patterns shift, bird migrations are being affected, altering their routes, timing, and interactions with pathogens. The VEO team is particularly concerned about birds traveling through Europe to the Arctic, a region experiencing rapid warming and hosting diverse bird species.
However, the precise implications of climate-driven changes in bird migration on disease risks remain uncertain. Koopmans stresses the need to unravel these intricate relationships and identify warning signs. It is crucial to narrow down the myriad factors contributing to disease emergence and incorporate them into a monitoring system. Once a disease starts spreading, it is often too late to contain it effectively.
To comprehend the behavior and health of specific bird species, researchers are tracking their movements and sampling them for pathogens. For instance, at the Ottenby Bird Observatory in Sweden, scientists are capturing migratory birds such as wheatears to examine the pathogens they carry. This observatory serves as a hub for many bird species during their migrations, enabling the transmission of viruses and other pathogens through global flyways.
Climate change is already affecting bird migration patterns. Long-distance migrants are arriving earlier in the spring, likely due to climate-induced shifts in insect populations that they feed on. Jonas Waldenström, an ornithologist and microbiologist, has been studying over 100 bird species at Ottenby for more than two decades, uncovering various pathogens threatening poultry and humans, including influenza, Campylobacter, Salmonella, and tick-borne encephalitis virus.
Waldenström’s team now uses transmitters to track birds more effectively, revealing migration routes and timing. However, these transmitters are expensive and bulky, limiting their use to larger bird species. Understanding the complex interplay between bird migration, climate change, and disease transmission is a formidable challenge, but it is increasingly urgent as the world faces the impacts of a changing climate.
In summary, the study of bird migrations and their role in disease transmission is a multifaceted endeavor, with climate change adding a new layer of complexity. Researchers are striving to identify potential disease hotspots and develop monitoring systems to predict and prevent disease spillovers from birds to humans. The intricate relationships between bird behavior, pathogens, and climate require continued study to protect public health in an ever-changing world.
Journal Reference
(N.d.). Retrieved from https://www.science.org/content/article/changing-bird-migrations-threaten-bring-new-infectious-diseases-humans
