Experimental challenge and pathology of highly pathogenic avian influenza virus H5N1 in dunlin (Calidris alpina), an intercontinental migrant shorebird species

Highly pathogenic avian influenza A (H5N1) in marine mammals and seabirds in Peru

Highly pathogenic avian influenza (HPAI) A/H5N1 viruses (lineage 2.3.4.4b) are rapidly invading the Americas, threatening wildlife, poultry, and potentially evolving into the next global pandemic. In November 2022 HPAI arrived in Peru, triggering massive pelican and sea lion die-offs. We report genomic characterization of HPAI/H5N1 in five species of marine mammals and seabirds (dolphins, sea lions, sanderlings, pelicans and cormorants). Peruvian viruses belong to lineage 2.3.4.4b, but they are 4:4 reassortants where 4 genomic segments (PA, HA, NA and MP) position within the Eurasian lineage that initially entered North America from Eurasia, while the other 4 genomic segments (PB2, PB1, NP and NS) position within the American lineage (clade C) that circulated in North America. These viruses are rapidly accruing mutations, including mutations of concern, that warrant further examination and highlight an urgent need for active local surveillance to manage outbreaks and limit spillover into other species, including humans.

Outside the Box: Working With Wildlife in Biocontainment

Research with captive wildlife in Animal Biosafety Level 2 (ABSL2) and 3 (ABSL3) facilities is becoming increasingly necessary as emerging and re-emerging diseases involving wildlife have increasing impacts on human, animal, and environmental health. Utilizing wildlife species in a research facility often requires outside the box thinking with specialized knowledge, practices, facilities, and equipment. The USGS National Wildlife Health Center (NWHC) houses an ABSL3 facility dedicated to understanding wildlife diseases and developing tools to mitigate their impacts on animal and human health. This review presents considerations for utilizing captive wildlife for infectious disease studies, including, husbandry, animal welfare, veterinary care, and biosafety. Examples are drawn from primary literature review and collective 40-year experience of the NWHC. Working with wildlife in ABSL2 and ABSL3 facilities differs from laboratory animals in that typical laboratory housing systems, husbandry practices, and biosafety practices are not designed for work with wildlife. This requires thoughtful adaptation of standard equipment and practices, invention of customized solutions and development of appropriate enrichment plans using the natural history of the species and the microbiological characteristics of introduced and native pathogens. Ultimately, this task requires critical risk assessment, understanding of the physical and psychological needs of diverse species, creativity, innovation, and flexibility. Finally, continual reassessment and improvement are imperative in this constantly changing specialty area of infectious disease and environmental hazard research.

Conducting Influenza Virus Pathogenesis Studies in Avian Species

Avian infection studies with influenza A are an important means of assessing host susceptibility, viral pathogenesis, host responses to infection, mechanisms of transmission, viral pathotype, and viral evolution. Complex systems and natural settings may also be explored with carefully designed infection studies. In this chapter, we explore the elements of infection studies, general guidelines for choosing a virus to use, host selection, and many aspects of study design.

Serologic Evidence of Exposure to Highly Pathogenic Avian Influenza H5 Viruses in Migratory Shorebirds, Australia

Highly pathogenic avian influenza (HPAI) H5Nx viruses of the goose/Guangdong/96 lineage continue to cause outbreaks in poultry and wild birds globally. Shorebirds, known reservoirs of avian influenza viruses, migrate from Siberia to Australia along the East-Asian-Australasian Flyway. We examined whether migrating shorebirds spending nonbreeding seasons in Australia were exposed to HPAI H5 viruses. We compared those findings with those for a resident duck species. We screened >1,500 blood samples for nucleoprotein antibodies and tested positive samples for specific antibodies against 7 HPAI H5 virus antigens and 2 low pathogenicity avian influenza H5 virus antigens. We demonstrated the presence of hemagglutinin inhibitory antibodies against HPAI H5 virus clade 2.3.4.4 in the red-necked stint (Calidris ruficolis). We did not find hemagglutinin inhibitory antibodies in resident Pacific black ducks (Anas superciliosa). Our study highlights the potential role of long-distance migratory shorebirds in intercontinental spread of HPAI H5 viruses.

Experimental infection and pathology of clade 2.2 H5N1 virus in gulls

During 2006, H5N1 HPAI caused an epizootic in wild birds, resulting in a die-off of Laridae in the Novosibirsk region at Chany Lake. In the present study, we infected common gulls (Larus canus) with a high dose of the H5N1 HPAI virus isolated from a common gull to determine if severe disease could be induced over the 28 day experimental period. Moderate clinical signs including diarrhea, conjunctivitis, respiratory distress and neurological signs were observed in virus-inoculated birds, and 50% died. The most common microscopic lesions observed were necrosis of the pancreas, mild encephalitis, mild myocarditis, liver parenchymal hemorrhages, lymphocytic hepatitis, parabronchi lumen hemorrhages and interstitial pneumonia. High viral titers were shed from the oropharyngeal route and virus was still detected in one bird at 25 days after infection. In the cloaca, the virus was detected sporadically in lower titers. The virus was transmitted to direct contact gulls. Thus, infected gulls can pose a significant risk of H5N1 HPAIV transmission to other wild migratory waterfowl and pose a risk to more susceptible poultry species. These findings have important implications regarding the mode of transmission and potential risks of H5N1 HPAI spread by gulls.

Isolation and characterization of influenza A viruses from environmental water at an overwintering site of migratory birds in Japan

The Izumi plain in Kagoshima prefecture, Japan, is an overwintering site of more than 10,000 cranes. The wet paddy areas are artificially created to provide roosting sites for the cranes every winter. Since wild ducks, known to be a natural reservoir of influenza A viruses, also overwinter in this area, the cranes' roost water likely serves as a source of influenza A virus infection. To assess this potential risk, we collected 126 water samples from the cranes' roost in the 2012/2013 winter season for virus isolation. We isolated six influenza viruses of three subtypes (H3N8, H4N6, and H4N8) from the water samples collected in the months of November and December. Genetic analysis of our isolates indicated that these viruses were genetically similar to the low-pathogenic avian influenza viruses circulating among Eurasian waterfowl. These findings suggest the possibility of the cranes becoming infected with the avian influenza viruses that are present in their roost water.

Immune responses of wild birds to emerging infectious diseases

Over the past several decades, outbreaks of emerging infectious diseases (EIDs) in wild birds have attracted worldwide media attention, either because of their extreme virulence or because of alarming spillovers into agricultural animals or humans. The pathogens involved have been found to infect a variety of bird hosts ranging from relatively few species (e.g. Trichomonas gallinae) to hundreds of species (e.g. West Nile Virus). Here we review and contrast the immune responses that wild birds are able to mount against these novel pathogens. We discuss the extent to which these responses are associated with reduced clinical symptoms, pathogen load and mortality, or conversely, how they can be linked to worsened pathology and reduced survival. We then investigate how immune responses to EIDs can evolve over time in response to pathogen-driven selection using the illustrative case study of the epizootic outbreak of Mycoplasma gallisepticum in wild North American house finches (Haemorhous mexicanus). We highlight the need for future work to take advantage of the substantial inter- and intraspecific variation in disease progression and outcome following infections with EID to elucidate the extent to which immune responses confer increased resistance through pathogen clearance or may instead heighten pathogenesis.

Intercontinental genetic structure and gene flow in Dunlin (Calidris alpina), a potential vector of avian influenza

Waterfowl (Anseriformes) and shorebirds (Charadriiformes) are the most common wild vectors of influenza A viruses. Due to their migratory behavior, some may transmit disease over long distances. Migratory connectivity studies can link breeding and nonbreeding grounds while illustrating potential interactions among populations that may spread diseases. We investigated Dunlin (Calidris alpina), a shorebird with a subspecies (C. a. arcticola) that migrates from nonbreeding areas endemic to avian influenza in eastern Asia to breeding grounds in northern Alaska. Using microsatellites and mitochondrial DNA, we illustrate genetic structure among six subspecies: C. a. arcticola,C. a. pacifica,C. a. hudsonia,C. a. sakhalina,C. a. kistchinski, and C. a. actites. We demonstrate that mitochondrial DNA can help distinguish C. a. arcticola on the Asian nonbreeding grounds with >70% accuracy depending on their relative abundance, indicating that genetics can help determine whether C. a. arcticola occurs where they may be exposed to highly pathogenic avian influenza (HPAI) during outbreaks. Our data reveal asymmetric intercontinental gene flow, with some C. a. arcticola short-stopping migration to breed with C. a. pacifica in western Alaska. Because C. a. pacifica migrates along the Pacific Coast of North America, interactions between these subspecies and other taxa provide route for transmission of HPAI into other parts of North America.

Serological evidence for non-lethal exposures of Mongolian wild birds to highly pathogenic avian influenza H5N1 virus

Surveillance for highly pathogenic avian influenza viruses (HPAIV) in wild birds is logistically demanding due to the very low rates of virus detection. Serological approaches may be more cost effective as they require smaller sample sizes to identify exposed populations. We hypothesized that antigenic differences between classical Eurasian H5 subtype viruses (which have low pathogenicity in chickens) and H5N1 viruses of the Goose/Guangdong/96 H5 lineage (which are HPAIV) may be used to differentiate populations where HPAIVs have been circulating, from those where they have not. To test this we performed hemagglutination inhibition assays to compare the reactivity of serum samples from wild birds in Mongolia (where HPAIV has been circulating, n = 1,832) and Europe (where HPAIV has been rare or absent, n = 497) to a panel of reference viruses including classical Eurasian H5 (of low pathogenicity), and five HPAIV H5N1 antigens of the Asian lineage A/Goose/Guangdong/1/96. Antibody titres were detected against at least one of the test antigens for 182 Mongolian serum samples (total seroprevalence of 0.10, n = 1,832, 95% adjusted Wald confidence limits of 0.09-0.11) and 25 of the European sera tested (total seroprevalence of 0.05, n = 497, 95% adjusted Wald confidence limits of 0.03-0.07). A bias in antibody titres to HPAIV antigens was found in the Mongolian sample set (22/182) that was absent in the European sera (0/25). Although the interpretation of serological data from wild birds is complicated by the possibility of exposure to multiple strains, and variability in the timing of exposure, these findings suggest that a proportion of the Mongolian population had survived exposure to HPAIV, and that serological assays may enhance the targeting of traditional HPAIV surveillance toward populations where isolation of HPAIV is more likely.

Potential Intercontinental Movement of Influenza A(H7N9) Virus into North America by Wild Birds: Application of a Rapid Assessment Framework

A critical question surrounding emergence of novel strains of avian influenza viruses (AIV) is the ability for wild migratory birds to translocate a complete (unreassorted whole genome) AIV intercontinentally. Virus translocation via migratory birds is suspected in outbreaks of highly pathogenic strain A(H5N1) in Asia, Africa and Europe. As a result, the potential intercontinental translocation of newly emerging AIV such as A(H7N9) from Eurasia to North America via migratory movements of birds remains a concern. An estimated 2.91 million aquatic birds move annually between Eurasia and North America with an estimated AIV prevalence as high as 32.2%. Here, we present a rapid assessment to address the likelihood of whole (unreassorted)-genome translocation of Eurasian strain AIV into North America. The scope of this assessment was limited specifically to assess the weight of evidence to support the movement of an unreassorted AIV intercontinentally by migratory aquatic birds. We developed a rapid assessment framework to assess the potential for intercontinental movement of avian influenzas by aquatic birds. This framework was iteratively reviewed by a multidisciplinary panel of scientific experts until a consensus was established. Our assessment framework identified four factors that may contribute to the potential for introduction of any AIV intercontinentally into North America by wild aquatic birds. These factors, in aggregate, provide a framework for evaluating the likelihood of new forms of AIV from Eurasia to be introduced by aquatic birds into North America. Based on our assessment, we determined that the potential for introduction of A(H7N9) into North America through aquatic migratory birds is possible, but the likelihood ranges from extremely low to low.

Birds shed RNA-viruses according to the pareto principle

A major challenge in disease ecology is to understand the role of individual variation of infection load on disease transmission dynamics and how this influences the evolution of resistance or tolerance mechanisms. Such information will improve our capacity to understand, predict, and mitigate pathogen-associated disease in all organisms. In many host-pathogen systems, particularly macroparasites and sexually transmitted diseases, it has been found that approximately 20% of the population is responsible for approximately 80% of the transmission events. Although host contact rates can account for some of this pattern, pathogen transmission dynamics also depend upon host infectiousness, an area that has received relatively little attention. Therefore, we conducted a meta-analysis of pathogen shedding rates of 24 host (avian) - pathogen (RNA-virus) studies, including 17 bird species and five important zoonotic viruses. We determined that viral count data followed the Weibull distribution, the mean Gini coefficient (an index of inequality) was 0.687 (0.036 SEM), and that 22.0% (0.90 SEM) of the birds shed 80% of the virus across all studies, suggesting an adherence of viral shedding counts to the Pareto Principle. The relative position of a bird in a distribution of viral counts was affected by factors extrinsic to the host, such as exposure to corticosterone and to a lesser extent reduced food availability, but not to intrinsic host factors including age, sex, and migratory status. These data provide a quantitative view of heterogeneous virus shedding in birds that may be used to better parameterize epidemiological models and understand transmission dynamics.

Research priorities in modeling the transmission risks of H7N9 bird flu

The epidemic of H7N9 bird flu in eastern China in early 2013 has caused much attention from researchers as well as public health workers. The issue on modeling the transmission risks is very interesting topic. In this article, this issue is debated and discussed in order to promote further researches on prediction and prevention of avian influenza viruses supported by better interdisciplinary datasets from the surveillance and response system.

Avian influenza in shorebirds: experimental infection of ruddy turnstones (Arenaria interpres) with avian influenza virus

Please cite this paper as: Hall et al. (2012) Avian influenza in shorebirds: experimental infection of ruddy turnstones (Arenaria interpres) with avian influenza virus. Influenza and Other Respiratory Viruses DOI: 10.1111/j.1750‐2659.2012.00358.x.

Background  Low pathogenic avian influenza viruses (LPAIV) have been reported in shorebirds, especially at Delaware Bay, USA, during spring migration. However, data on patterns of virus excretion, minimal infectious doses, and clinical outcome are lacking. The ruddy turnstone (Arenaria interpres) is the shorebird species with the highest prevalence of influenza virus at Delaware Bay.

Objectives  The primary objective of this study was to experimentally assess the patterns of influenza virus excretion, minimal infectious doses, and clinical outcome in ruddy turnstones.

Methods  We experimentally challenged ruddy turnstones using a common LPAIV shorebird isolate, an LPAIV waterfowl isolate, or a highly pathogenic H5N1 avian influenza virus. Cloacal and oral swabs and sera were analyzed from each bird.

Results  Most ruddy turnstones had pre‐existing antibodies to avian influenza virus, and many were infected at the time of capture. The infectious doses for each challenge virus were similar (10^3·6–10^4·16 EID₅₀), regardless of exposure history. All infected birds excreted similar amounts of virus and showed no clinical signs of disease or mortality. Influenza A‐specific antibodies remained detectable for at least 2 months after inoculation.

Conclusions  These results provide a reference for interpretation of surveillance data, modeling, and predicting the risks of avian influenza transmission and movement in these important hosts.

Highly pathogenic avian influenza virus H5N1 infection in a long-distance migrant shorebird under migratory and non-migratory states

Corticosterone regulates physiological changes preparing wild birds for migration. It also modulates the immune system and may lead to increased susceptibility to infection, with implications for the spread of pathogens, including highly pathogenic avian influenza virus (HPAIV) H5N1. The red knot (Calidris canutus islandica) displays migratory changes in captivity and was used as a model to assess the effect of high plasma concentration of corticosterone on HPAIV H5N1 infection. We inoculated knots during pre-migration (N = 6), fueling (N = 5), migration (N = 9) and post-migration periods (N = 6). Knots from all groups shed similar viral titers for up to 5 days post-inoculation (dpi), peaking at 1 to 3 dpi. Lesions of acute encephalitis, associated with virus replication in neurons, were seen in 1 to 2 knots per group, leading to neurological disease and death at 5 to 11 dpi. Therefore, the risk of HPAIV H5N1 infection in wild birds and of potential transmission between wild birds and poultry may be similar at different times of the year, irrespective of wild birds' migratory status. However, in knots inoculated during the migration period, viral shedding levels positively correlated with pre-inoculation plasma concentration of corticosterone. Of these, knots that did not become productively infected had lower plasma concentration of corticosterone. Conversely, elevated plasma concentration of corticosterone did not result in an increased probability to develop clinical disease. These results suggest that birds with elevated plasma concentration of corticosterone at the time of migration (ready to migrate) may be more susceptible to acquisition of infection and shed higher viral titers--before the onset of clinical disease--than birds with low concentration of corticosterone (not ready for take-off). Yet, they may not be more prone to the development of clinical disease. Therefore, assuming no effect of sub-clinical infection on the likelihood of migratory take-off, this may favor the spread of HPAIV H5N1 by migratory birds over long distances.