A startling revelation has emerged from the avian world, as wild birds are now implicated in the devastating H5N1 outbreak across North America. This panzootic, a pandemic among animals, has wreaked havoc since 2021, affecting not only wild birds but also agriculture and mammals.
The study, led by Louise H. Moncla from the School of Veterinary Medicine, uncovers a crucial aspect of this crisis. Unlike previous outbreaks, the aggressive culling of domestic birds has failed to contain the virus. Instead, it continues to infect a diverse range of species, including wild birds and mammals previously unaffected, indicating a shift in transmission patterns.
But here's the twist: Moncla and her team discovered that wild birds are the primary culprits behind the ongoing bird flu outbreak in the United States. Their research, published in Nature, highlights the evolving nature of Highly Pathogenic Avian Influenza (HPAI) viruses.
"The situation with HPAI influenza in North America and the U.S. has dramatically changed in recent years," Moncla explains. Initially, this virus was predominantly found in Asia, Northern Africa, and domestic birds. However, Europe has witnessed increasing outbreaks linked to wild birds, and since 2022, North America has faced similar challenges.
By analyzing publicly available databases and employing genomic sequencing and migratory flyway analysis, the researchers uncovered the introduction and spread of H5N1 viruses during the initial 18 months in North America. And this is the part most people miss: the outbreak's uniqueness lies in wild migrating birds being the primary vectors.
Moncla emphasizes, "Our research specifically points to Anseriformes, which include ducks, geese, and swans, as the main carriers." Since 2020, H5N1 has evolved to better infect wild birds, enabling more efficient transmission during migration. This mirrors a similar situation in Europe, which occurred two years earlier.
Controversially, H5N1 viruses in North America are still considered foreign animal diseases, despite evidence to the contrary. Moncla argues, "Our policies assume these viruses originate elsewhere, but our study proves they are now endemic. We must adapt our strategies accordingly."
The study also reveals that agricultural outbreaks result from repeated virus introductions by wild birds. Interestingly, backyard birds, defined as populations of fewer than 1,000 domestic birds, are infected earlier than commercial poultry, potentially serving as an early warning system.
Moncla notes, "Backyard birds have distinct epidemiological characteristics. Smaller farms often have less biosecurity, and these birds are more likely to be raised outdoors, increasing their exposure to wild birds."
Previous viruses primarily affected domestic chickens and turkeys, making commercial farm transmission control effective. However, wild migrating birds present a new challenge.
So, what's the solution? Moncla suggests a multi-faceted approach: "It involves improving biosecurity, developing strategies to separate domestic and wild birds, and considering vaccination for domestic birds. Continuous surveillance of wild birds, especially waterfowl, will aid in tracking and understanding viral spread."
The team's interest in risk modeling raises an intriguing question: "Can we predict high-risk periods and locations for outbreaks?" Moncla believes that understanding viral circulation among wild birds and their role in transmission could lead to a forecasting system, allowing targeted biosecurity measures during peak risk periods.
While eradicating the disease entirely may be unrealistic, Moncla emphasizes the importance of managing its impact on agricultural animals. This research sheds light on the complex dynamics of bird flu transmission and the need for adaptive strategies to combat this evolving threat.
