Overview: Why Highly Pathogenic Avian Influenza Is a Concern for Wild Bird Managers in North America

Camille Hopkins

U.S. Geological Survey Ecosystems Mission Area, Reston, Virginia, United States

In January 2021, the Interagency Steering Committee for Avian Influenza Surveillance in Wild Migratory Birds disseminated an informational memorandum (appendix 1) regarding the increasing global highly pathogenic avian influenza (HPAI) activity in poultry and wild birds. The committee includes representatives from the U.S. Department of Agriculture, the U.S. Department of the Interior, the Association of Fish and Wildlife Agencies, the National Flyway Council, and the U.S. Agency for International Development. This overview presentation compared the historical perspective of HPAI to the paradigm shift evident during the U.S. 2014–15 HPAI outbreak. Recognizing that migratory bird flyways link global avian influenza dynamics to those in North America, the Steering Committee coordinated this 3-day webinar series to (1) enhance our situational awareness of international avian influenza dynamics, (2) reflect on lessons learned from the 2014–15 U.S. HPAI outbreak, and (3) close with discussions on HPAI challenges and opportunities.

Highly Pathogenic Avian Influenza in Wild Birds: Situational Update From Asia

Yoshihiro Sakoda

Hokkaido University, Faculty of Veterinary Medicine, OIE Reference Laboratory for Highly Pathogenic Avian Influenza and Low Pathogenic Avian Influenza, Sapporo, Japan

Global dispersion of highly pathogenic avian influenza (HPAI), especially that caused by H5 clade 2.3.4.4, has threatened poultry industries and, potentially, human health. In October 2020, an HPAI virus, A/northern pintail/Hokkaido/M13/2020 (H5N8) (NP/Hok/20) belonging to clade 2.3.4.4b, was isolated from a fecal sample collected at a lake in Hokkaido, Japan, where migratory birds rested. In the phylogenetic trees of all eight gene segments, NP/Hok/20 fell into in the cluster of European isolates in 2020 but was distinct from the isolates in eastern Asia and Europe during the winter season of 2017–18. These data imply that HPAI virus clade 2.3.4.4b would have been delivered by bird migration despite the intercontinental distance, although it was not defined whether NP/Hok/20 was transported from Europe via Siberia, where migratory birds nest in the summer season. Given the probability of perpetuation of transmission in the northern territory (set of four islands off the northeastern coast of Hokkaido, Japan), periodic updates of intensive surveys on avian influenza at the global level are essential to prepare for future outbreaks of the HPAI virus.

Control measures in the case of HPAI outbreaks in poultry include culling, surveillance, and biosecurity; wild birds in captivity may also be culled, although some rare bird species may be rescued for conservation. In this study, two anti-influenza drugs, baloxavir marboxil (BXM) and peramivir (PR), used in humans were examined in treating HPAI in birds, using chickens as a model. Chickens were infected with H5N6 HPAI virus and were treated immediately or 24 hours from challenge with 20 milligrams per kilogram (mg/kg) BXM or PR twice a day for 5 days. When treated immediately, BXM significantly reduced virus replication in organs and provided full protection to chickens compared with that induced by PR. In the 24‑hour-delayed treatment, neither drug completely inhibited virus replication nor ensured the survival of infected chickens. A single administration of 2.5 mg/kg of BXM was determined as the minimum dose required to fully protect chickens from HPAI virus; the concentration of baloxavir acid, the active form of BXM, in chicken blood at this dose was sufficient for a 48‑hour antiviral effect post-administration. Thus, these data can be a starting point for the use of BXM and PR in treating captive wild birds infected with HPAI virus.

Infectivity of Contemporary Highly Pathogenic Avian Influenza Viruses Among Waterfowl Hosts

Mary Pantin-Jackwood

U.S. Department of Agriculture, Agricultural Research Service, U.S. National Poultry Research Center, Southeast Poultry Research Laboratory, Exotic and Emerging Avian Viral Disease Research Unit, Athens, Georgia, United States

Highly pathogenic avian influenza (HPAI) viruses are a threat to poultry worldwide. The most important natural reservoir of avian influenza viruses are wild waterfowl. Avian influenza viruses, including HPAI viruses, do not usually cause disease in ducks and other wild aquatic birds, the exception being the Goose/Guangdong (Gs/GD) lineage H5 subtype HPAI viruses, some of which can cause moderate to severe disease in waterfowl species. With the continuous occurrence of HPAI outbreaks in poultry it is important to address the role of wild waterfowl in the transmission and spread of these viruses. For many years our we have conducted studies examining the pathobiology in different waterfowl species of many strains of HPAI viruses. Infectivity (dose of the virus required to infect the birds), pathogenesis (clinical signs, lesions), presence of the viruses in tissues, duration and titer of virus shed, transmission to contact birds, and seroconversion to the viruses are evaluated. We have found that the pathobiology of HPAI viruses in waterfowl is affected by the strain of the virus and the species, age, health, and immune status of the birds. For most HPAI viruses examined, ducks and geese became infected and transmitted the viruses to contact birds without showing clinical signs. Viruses were also shed for many days by both the oropharyngeal and cloacal routes, which increases the probability of virus spread and transmission. Some of the Gs/GD H5 lineage viruses, including the clade 2.3.4.4 viruses, replicated to high titers causing systemic disease and mortality in waterfowl. These results help in understanding the role of wild waterfowl in the spread of HPAI viruses around the world, since many of these species are migratory.

Migratory Birds Disperse Avian Influenza Viruses Between East Asia and North America Via Alaska

Andrew M. Ramey

U.S. Geological Survey Alaska Science Center, Anchorage, Alaska, United States

The purpose of this presentation is to convey that there is substantial evidence for the dispersal of avian influenza (AI) viruses by wild birds between East Asia and North America via Alaska and why this pathway of viral dispersal is ecologically and economically relevant. Extensive research and surveillance for AI viruses since approximately 2006 provide us with a clear understanding of common wild bird hosts in Alaska. On one hand, common wild bird hosts of AI viruses in Alaska are generally similar to those reported elsewhere. For example, dabbling ducks and gulls are common hosts of AI viruses in Alaska and across much of the globe. On the other hand, some of the specific species that are most important to viral ecology in Alaska, particularly western portions of the State, have not typically been recognized as the most important hosts of AI viruses elsewhere. Example taxa include northern pintails (Anas acuta), emperor geese (Anser canagicus), glaucous (Larus hyperboreus) and glaucous-winged gulls (Larus glaucescens), and common (Uria aalge) and thick-billed murres (Uria lomvia). Identification of the most common hosts of AI viruses in Alaska is important because some individuals of these taxa make migratory movements between East Asia and North America including northern pintails, emperor geese, and glaucous gulls. These intercontinental movements facilitate the dispersal of viruses between continents. Through the targeted sampling of wild birds for AI viruses in western Alaska, including these common viral hosts with intercontinental migratory tendencies, we have detected the bi-directional exchange of AI viruses between East Asia and North America. Collective evidence from investigations of host movements and viral ecology affirms that AI viruses are sporadically dispersed by wild birds across the Bering Strait. Thus, western Alaska represents a point of entry for foreign-origin AI viruses into North America, as well as a gateway through which viruses are dispersed to East Asia. Understanding viral dispersal between East Asia and North America is ecologically and economically relevant because it informs us on the risk of introduction of foreign-origin highly pathogenic AI (HPAI) viruses. Introductions of HPAI viruses by wild birds may lead to outbreaks of disease among domestic poultry and wild birds. For example, in 2014, wild birds introduced HPAI viruses from East Asia to North America via Alaska, the same trans-Beringian pathway we have been investigating for approximately 15 years. This introduction resulted in the largest outbreak of HPAI in U.S. history, and the only outbreak that has thus far affected wild birds in North America. This outbreak extended into the summer of 2015 in poultry with sporadic detections in wild birds continuing into the summer of 2016. This outbreak resulted in the death or destruction of approximately 50 million domestic birds in the United States and an unknown number of wild birds with economic losses estimated to total approximately $3 billion.

Lessons Learned From Research and Surveillance Directed at Highly Pathogenic Avian Influenza Viruses in Wild Birds Inhabiting North America

Thomas J. DeLiberto

U.S. Department of Agriculture, Animal and Plant Health Inspection Service, Wildlife Services, National Wildlife Research Center, Fort Collins, Colorado, United States

Following detections of HPAI viruses in wild birds inhabiting East Asia after the turn of the millennium, the intensity of sampling of wild birds for AI viruses increased throughout much of North America. The objectives for many research and surveillance efforts were directed towards detecting Eurasian-origin HPAI viruses and understanding the potential of such viruses to be maintained and dispersed by wild birds. In this review, we highlight six important lessons learned from research and surveillance directed at HPAI viruses in wild birds inhabiting North America: (1) wild birds may disperse AI viruses between North America and adjacent regions via migration, (2) HPAI viruses can be introduced to wild birds in North America, (3) HPAI viruses may cross the wild bird-domestic poultry interface in North America, (4) the probability of encountering and detecting a specific virus may be low, (5) population immunity of wild birds may influence HPAI virus outbreaks in North America, and (6) proactive disease surveillance empowers agencies, producers, and conservationists to be prepared to develop solutions that will protect humans, agriculture, and wildlife by understanding the epidemiology of specific infectious diseases and zoonotic outbreaks. We review empirical support derived from research and surveillance efforts for each lesson learned and, furthermore, identify implications for future surveillance efforts, biosecurity, and population health. We conclude our review by identifying five additional areas in which we think future mechanistic research relative to AI viruses in wild birds in North America are likely to lead to other important lessons learned in the years ahead.

2014–15 Highly Pathogenic Avian Influenza Incursion Into the United States

Hon Ip

U.S. Geological Survey National Wildlife Health Center, Madison, Wisconsin, United States

Novel Eurasian lineage avian influenza A (H5N8) virus has spread rapidly and globally since January 2014. In December 2014, H5N8 and reassortant H5N2 viruses were first detected in wild birds in Washington State, and subsequently in backyard birds in the Pacific Flyway. Wild birds had minimal role in subsequent spread into commercial poultry, especially in the Midwest, where the negative impact on the economy was particularly significant.

Canada Lessons Learned: 2014–15 Environmental Highly Pathogenic Avian Influenza Surveillance

Chelsea Himsworth

Canadian Wildlife Health Cooperative British Columbia, Abbotsford, British Columbia, Canada; Animal Health Centre, British Columbia Ministry of Agriculture, Abbotsford, British Columbia, Canada; University of British Columbia, School of Population and Public Health, Vancouver, British Columbia, Canada

Wild waterfowl are the reservoir for AI (shedding virus in their feces) and the focus of AI surveillance programs around the world. Thus far, these programs have been centered on testing of individual wild birds—an approach that has significant limitations stemming from the practical and financial impediments to collecting a representative sample of wild waterfowl. These programs were in place in the United States and Canada in 2014–15 and failed to predict outbreaks in either country. In a 2015–16 pilot study, we used targeted resequencing (a genomics technology in which a specific set of viral genes are isolated and sequenced) to identify the 2014–15 outbreak AI virus in wetland sediments. We also found that the outbreak virus was widespread in wetlands throughout the Fraser Valley and likely could have been detected in advance of the outbreak had this approach been available. We subsequently embarked on a longitudinal study to refine and validate the technology. We found that targeted resequencing of sediment was able to detect a greater diversity of AI virus sequences in wetland sediment samples compared to samples from birds. For example, 434 unique clusters of N1 sequences (that is, N1 strains) were identified, of which 85 were found in both birds and sediment, 43 were found only in birds, and 306 were found only in sediment. We also found that AI virus strains were detected in sediment up to a year prior to being detected in birds and that there was no evidence that AI viruses persist in sediment between years. Targeted resequencing of wetland sediment is current being operationalized for the 2021–22 AI virus surveillance season in British Columbia.

Persistence of Avian Influenza Viruses in the Environment

David Stallknecht

University of Georgia, Department of Population Health, Southeastern Cooperative Wildlife Disease Study, Athens, Georgia, United States

In aquatic habitats, AI viruses are transmitted within wild waterfowl populations through a fecal-oral route. These viruses can maintain infectivity through extended periods of time in water and resulting environmental transmission may be a critical component of AI virus maintenance within and between waterfowl migratory seasons. The chemical and physical characteristics of water, such as temperature, pH, and salinity, can greatly influence the duration of AI virus infectivity with ideal conditions including low temperature, neutral pH, and low salinity. These relationships have been documented in laboratory studies using distilled water models and surface water obtained from waterfowl habitats throughout the United States. Although results from these studies have demonstrated the potential persistence of AI viruses for extended periods of time (months to years), translation of these results to field conditions have been problematic owing to the biological, physical, and chemical complexity of natural aquatic habitats. More recent studies have attempted to bridge this gap using field collected samples and (or) conducting field-based experiments. These studies have demonstrated that potential AI virus persistence varies greatly between waterfowl habitats and that long-term persistence of AI viruses can occur under natural cold water conditions in the field. In these field studies, it was demonstrated that AI virus infectivity can be maintained in waterfowl habitats for periods of time extending from early migration to late spring and summer. Currently, there are still many unknowns related to environmental persistence of AI viruses which need to be understood. We do not fully understand how or if the biotic community within aquatic environments (insects, filter-feeders, aquatic vegetation, bacteria, and biofilms) affect AI virus infectivity and limited studies. Likewise, we do not know if AI virus is associated with specific fractions of the aquatic environment such as sediments or aquatic vegetation. Such associations may not only affect transmissibility in these environments but also AI virus detectability. Finally, there are questions related to how these viruses associate in these environments especially related to virus aggregation. If AI viruses exist as aggregates in aquatic habitats, this also could be an important consideration related to transmissibility and detectability as well as a factor that could enhance the maintenance of infectivity. At present, there are no proven strategies to reduce environmental transmission of AI viruses by manipulation of waterfowl habitats, but with an improved understanding of mechanisms that enhance or reduce AI virus persistence in these aquatic environments, future management options cannot be discounted.

Using Genetic Information From Wild Bird Surveillance to Understand Transmission of Avian Influenza Viruses Between Wild Birds and Poultry

Dong-Hun Lee

University of Connecticut, College of Agriculture, Health and Natural Resources, Department of Pathobiology and Veterinary Science, Storrs, Connecticut, United States

Recent advances in genome sequencing through next-generation sequencing (NGS) have been transforming how laboratories diagnose and further characterize the viruses. Full-length viral genome sequencing can provide detailed information for virus discovery, diagnosis, characterization, and genotypic classification. NGS of AI viruses can reveal the approximately 13,500 nucleotide sequences of all the gene segments, including PB2, PB1, PA, HA, NP, NA, M, and NS segments. Continuous increments in viral evolution of AI viruses require enhanced genomic surveillance to further the epidemiologic understandings and design of improved outbreak prevention strategies. Phylogenetic analyses have been widely applied to the analysis of viral genome sequence datasets (Lam and others, 2010), which has been used extensively to describe the molecular epidemiology, immunological, and transmission of the evolving epidemiology of influenza viruses (Lam and others, 2010; Faria and others, 2011). Maximum-likelihood trees are the most commonly used method to demonstrate tree topologies showing genetic distances between genome sequences based on their nucleotide substitutions. Recent Bayesian phylodynamic approaches, however, use posterior probability of the tree, which is calculated from prior probability of the phylogeny and tree likelihood by Bayesian inferences (Lam and others, 2010). Such methods allow estimation of viral diffusion histories over time in greater detail (Faria and others, 2011; Volz and others, 2013). This approach could estimate the most probable origin and transmission dynamics between host species and (or) geographic regions (Holmes and Grenfell, 2009; Lam and others, 2010). For example, this approach has been used to determine the evolution and spread patterns of the 2014–15 U.S. H5N2 viruses by performing a comparative genomic study using 268 full-length genome sequences and data from outbreak investigations (Lee and others, 2018). The analysis suggests that multiple introductions of H5N2 viruses into Midwest States occurred during March–June 2015; transmission to Midwest poultry farms from Pacific wild birds occurred about 1.7 to 2.4 months before detection. Once established in poultry, the virus rapidly spread between turkey and chicken farms in neighboring States.

Emerging Technologies: Enhancing Avian Influenza Surveillance and Risk Reduction Efforts

Daniel Walsh

U.S. Geological Survey National Wildlife Health Center, Madison, Wisconsin, United States

Recent developments in modeling techniques have led to new quantitative tools that can be leveraged to improve wildlife health. In particular, machine learning approaches are creating new opportunities to examine wildlife data to inform and enhance surveillance and risk reduction efforts. For example, surveillance for known and novel influenza A viruses involves active surveillance within wild bird populations. This information is critical for understanding viral evolution forming the basis of risk assessments and countermeasure development; however, surveillance programs are resource intensive, so there is a need to improve efficiency. We use a form of machine learning, gradient boosted trees, to estimate the probability of isolating AI viruses during wild bird surveillance using historic surveillance data for AI viruses from 2006 to 2011. The resulting model had high predictive power and included the matrix gene rRT‐PCR (real-time reverse-transcriptase polymerase chain reaction) results and the geographic location of collection for each sample as important predictors. Additionally, we estimated that there is a 16‑percent probability of isolating an AI virus from a sample declared negative (that is, ≥35 Ct‑value [cycle threshold]) under current protocols. This model can be used to help inform AI virus surveillance designs that will maximize the likelihood of collecting and testing samples that will yield an AI virus isolation, thereby conserving limited resources and laboratory capacity. An ongoing study provides a second example of leveraging machine learning approaches to help reduce the risk of transboundary transmission of AI viruses to domestic poultry. It is known that one of the most effective actions for minimizing risk of AI virus transmission at the wildlife-livestock interface is separation, which is achieved through biosecurity measures implemented by individual livestock producers; however, maintaining high levels of biosecurity to reduce AI transmission risk over long periods of time is often not economically feasible and leads to “biosecurity fatigue.” Therefore, there is a desperate need for a tool that poultry producers can use to evaluate AI virus transmission risk associated with migratory bird movements and allow them to increase their biosecurity activities and awareness above baseline levels according to real-time distribution of migratory flocks. We are developing a web visualization tool to meet this need that uses machine learning approaches to harness and integrate the information gathered by NEXRAD, the network of 143 Doppler weather radars across the continental United States operated by the National Weather Service, with citizen science bird observations contained in the eBird database, to create near real-time maps of migratory bird locations. The tool can be used to ascertain the movements of migratory birds in relation to a producer’s location. Similar to the well-known radar graphics that show weather, the most exciting aspect of our tool is the real-time nature of these maps of migratory birds that would permit the creation of “personalized” AI risk assessments that are dynamic rather than static. These assessments are intended to overcome biosecurity fatigue, and most importantly allow producers to maintain biosecurity awareness. This awareness may reduce the transboundary transmission of AI between poultry and migratory birds, improving the health of both domestic and wild populations.

Wild Bird Movements and Avian Influenza Viruses—Relationships at the Wild Bird-Domestic Poultry Interface

Diann Prosser

U.S. Geological Survey Eastern Ecological Science Center, Laurel, Maryland, United States

Southeast Asia has historically been the epicenter for the emergence of HPAI viruses, which have shown the capacity to spread around the globe and have caused major concern over a potential human pandemic and serious economic loss within the poultry industry. This region, especially southeastern China, has been identified as an area of frequent transmission between wild and domestic birds owing to overlap where rice-paddy agriculture, domestic duck farming, and wild birds convene. Such regular interaction between wild and domestic birds allows for a unique viral ecology with sustained cross species transmission and viral mixing. Conversely, whereas wild birds have been shown to play a role in the spread and persistence of avian influenza into and within the United States, our agricultural practices differ from those in Southeast Asia. This necessitates study of differences in factors that enable interaction across the wild bird-domestic poultry interface. Understanding the role wild birds play in HPAI transmission, both in Asia and the United States, is critical for planning response to HPAI spread and understanding the ecology of this threat. This presentation reviews efforts to understand the role of wild waterfowl in the transmission, persistence, and amplification of AI viruses around the globe, and highlights ongoing efforts to incorporate the numerous relevant variables into models that can identify spatiotemporal trends in transmission risk across the wild bird-domestic poultry interface.

Closed-Door Session for U.S. Fish and Wildlife Service Flyway Representatives and Flyway Council Members

Russ Mason

Michigan State University, College of Agriculture and Natural Resources, Michigan Department of Natural Resources Assistant Director for University and External Partnerships and Executive in Residence, East Lansing, Michigan, United States

On the final day of the webinar, a closed-door session was held with U.S. Fish and Wildlife Service Flyway Council personnel and key State agency members of the four Flyway Councils (Pacific, Central, Mississippi, Atlantic). The aim of this session was to increase managers’ awareness of the science indicating an emerging HPAI North American threat as well as to provide information and discussion points for presentation to annual meetings of the Flyway Councils and their technical committees in late August and early September.

Russ Mason of the Michigan Department of Natural Resources provided a brief overview of the previous sessions. Emphasis was placed on the increasing likelihood that HPAI would cross into North America and that migrating waterfowl might distribute virus across the United States via the spring and fall migrations in 2022.

Participants then discussed the feasibility and practical utility of enhanced surveillance, tabletop response exercises, strategies to enhance communications among State fish and wildlife agencies, and the ability of the respective agencies to mount direct management activities if requested. Overall, there was a willingness to assist in surveillance and management efforts if Federal resources were provided to support the work. Already, State wildlife health resources are stretched thin by extensive and costly efforts to manage chronic wasting disease (CWD), tuberculosis, and other diseases affecting fish and wildlife resources. There was consensus that establishing a national wildlife disease surveillance network was increasingly important in order to proactively mount effective, efficient, and economic responses to HPAI and other emerging diseases.

Facilitated Discussion for Session 1: Update on Global Highly Pathogenic Avian Influenza Situation

Topic: Flyway management implications (focus on biosurveillance and early detection)

Moderator: Jonathan Sleeman

Panelists: Camille Hopkins, Yoshihiro Sakoda, Josanne Verhagen, Mary Pantin-Jackwood, Andrew Ramey

Participants: Webinar attendees from State and Federal agencies within the United States, Provincial and Federal agencies of Canada, the poultry industry within North America, and academic institutions from both within the United States and from abroad

Recording available at https://www.youtube.com/watch?v=klowKJNYJvk&list=PL2_jEtoY8jij11GMnDwIvDXQGVLbT8-BF&index=1

*Note: Topics are discussed throughout the video. Timestamps are approximate of where the most discussion for a topic occurs

Discussion starts at 1:31:45

Facilitated Discussion for Session 2: Lessons Learned from North American Highly Pathogenic Avian Influenza Outbreak (2014–15)

Topic: Flyway management implications (importance of vigilance to passive surveillance, rapid response upon detection in North America, interagency coordination, communication strategies, personal protection and biosecurity implications, and characterization of outbreak events)

Moderator: Julianna Lenoch

Panelists: Thomas DeLiberto, Hon Ip, Yohannes Berhane, Chelsea Himsworth

Participants: Webinar attendees from State and Federal agencies within the United States, Provincial and Federal agencies of Canada, the poultry industry within North America, and academic institutions from both within the United States and from abroad

Recording available at https://www.youtube.com/watch?v=Nw4YLaITSfA&list=PL2_jEtoY8jij11GMnDwIvDXQGVLbT8-BF&index=2

*Note: Topics are discussed throughout the video. Timestamps are approximate of where the most discussion for a topic occurs

Discussion starts at 1:42:07

Facilitated Discussion for Session 3: Highly Pathogenic Avian Influenza Challenges and Opportunities

Topic: Flyway management implications and potential mitigation strategies

Moderator: Samantha Gibbs

Panelists: David Stallknecht, Dong-Hun Lee, Daniel Walsh, Diann Prosser

Participants: Webinar attendees from State and Federal agencies within the United States, Provincial and Federal agencies of Canada, the poultry industry within North America, and academic institutions from both within the United States and from abroad

Recording available at https://www.youtube.com/watch?v=bDw9Of_9mMU&list=PL2_jEtoY8jij11GMnDwIvDXQGVLbT8-BF&index=3

*Note: Topics are discussed throughout the video. Timestamps are approximate of where the most discussion for a topic occurs

Discussion starts at 1:30:44