Reassortment of Influenza A Viruses in Wild Birds in Alaska before H5 Clade 2.3.4.4 Outbreaks.

Sampling of mallards in Alaska during September 2014-April 2015 identified low pathogenic avian influenza A virus (subtypes H5N2 and H1N1) that shared ancestry with highly pathogenic reassortant H5N2 and H5N1 viruses. Molecular dating indicated reassortment soon after interhemispheric movement of H5N8 clade 2.3.4.4, suggesting genetic exchange in Alaska or surrounds before outbreaks.

Interspecific killing of wolverines by one wolf pack.

Interactions between different species of predators are not uncommon, yet they are generally understudied in North America. Across their range, gray wolves (Canis lupus) and wolverines (Gulo gulo) occupy similar habitats and dietary niches. However, due to the elusiveness and relatively low density of these two species, interactions between them are not well documented. Here, we describe three instances of a single wolf pack killing a wolverine in the span of 13 months. None of the wolverines killed by wolves were consumed, suggesting that food was not the primary motivation behind the killings. Alternatively, defense of a food resource, territoriality, interspecific competitive killing, or some combination of those behaviors appear to be the cause of these actions. Documentation of these occurrences improves our understanding of wolf and wolverine ecology, interspecific predator interactions, and potential future changes to this aspect of community ecology.

Serologic Evidence for Influenza A Virus Exposure in Three Loon Species Breeding in Alaska, USA.

Limited information exists about exposure to influenza A viruses (IAVs) in many wild waterbird species, including loons. We analyzed serum samples from breeding adult Pacific (Gavia pacifica), Red-throated (Gavia stellata), and Yellow-billed (Gavia adamsii) loons sampled at three locations along the coast of Alaska, US from 2008 to 2017 to gain a better understanding of the potential role loons play in IAV ecology. We screened loon sera for IAV antibodies using three tests-blocking enzyme-linked immunosorbent assay (bELISA), agar gel immunodiffusion (AGID), and hemagglutination inhibition (HI)-and examined patterns in seroprevalence among species and sampling locations. We found evidence of IAV infection in all loon species and at all breeding locations, although concordance was imperfect among serological tests. Diagnostic tests yielded seroprevalence estimates of 24% (42/172) with bELISA, 8% (5/60) with AGID, and 6% (4/70) with HI. The IAV subtypes to which loon sera reacted using HI were consistent with those detected in waterfowl and gulls at other locations in Alaska, suggesting that loons may be exposed to IAV maintained in sympatric waterbirds. Our study provided evidence that loons inhabiting Alaska were exposed to IAV. However, given imperfect concordance among serologic tests, and relatively low seroprevalence as compared to other avian taxa exposed to IAV in Alaska, they make poor IAV surveillance targets.

SURVEY OF ARCTIC ALASKAN WILDLIFE FOR INFLUENZA A ANTIBODIES: LIMITED EVIDENCE FOR EXPOSURE OF MAMMALS.

Influenza A viruses (IAVs) are maintained in wild waterbirds and have the potential to infect a broad range of species, including wild mammals. The Arctic Coastal Plain of Alaska supports a diverse suite of species, including waterfowl that are common hosts of IAVs. Mammals co-occur with geese and other migratory waterbirds during the summer breeding season, providing a plausible mechanism for interclass transmission of IAVs. To estimate IAV seroprevalence and identify the subtypes to which geese, loons, Arctic foxes ( Vulpes lagopus), caribou ( Rangifer tarandus), and polar bears ( Ursus maritimus) are potentially exposed, we used a blocking enzyme-linked immunosorbent assay (bELISA) and a hemagglutination inhibition (HI) assay to screen for antibodies to IAVs in samples collected during spring and summer of 2012-16. Apparent IAV seroprevalence using the bELISA was 50.3% in geese (range by species: 46-52.8%), 9% in loons (range by species: 3-20%), and 0.4% in Arctic foxes. We found no evidence for exposure to IAVs in polar bears or caribou by either assay. Among geese, we estimated detection probability from replicate bELISA analyses to be 0.92 and also found good concordance (>85%) between results from bELISA and HI assays, which identified antibodies reactive to H1, H6, and H9 subtype IAVs. In contrast, the HI assay detected antibodies in only one of seven loon samples that were positive by bELISA; that sample had low titers to both H4 and H5 IAV subtypes. Our results provide evidence that a relatively high proportion of waterbirds breeding on the Arctic Coastal Plain are exposed to IAVs, although it is unknown whether such exposure occurs locally or on staging or wintering grounds. In contrast, seroprevalence of IAVs in concomitant Arctic mammals is apparently low.

Maintenance of influenza A viruses and antibody response in mallards (Anas platyrhynchos) sampled during the non-breeding season in Alaska.

Prevalence of influenza A virus (IAV) infections in northern-breeding waterfowl has previously been reported to reach an annual peak during late summer or autumn; however, little is known about IAV infection dynamics in waterfowl populations persisting at high-latitude regions such as Alaska, during winter. We captured mallards (Anas platyrhynchos) throughout the non-breeding season (August-April) of 2012-2015 in Fairbanks and Anchorage, the two largest cities in Alaska, to assess patterns of IAV infection and antibody production using molecular methods and a standard serologic assay. In addition, we used virus isolation, genetic sequencing, and a virus microneutralization assay to characterize viral subtypes and to evaluate the immune response of mallards captured on multiple occasions through time. We captured 923 mallards during three successive sampling years: Fairbanks in 2012/13 and 2013/14, and Anchorage in 2014/15. Prevalence varied by age, season, and year/site with high and relatively stable estimates throughout the non-breeding season. Infected birds were detected in all locations/seasons except early-winter in Fairbanks during 2013/14. IAVs with 17 combinations of hemagglutinin (H1-5, H7-9, H11, H12) and neuraminidase (N1-6, N8, N9) subtypes were isolated. Antibodies to IAVs were detected throughout autumn and winter for all sampling locations and years, however, seroprevalence was higher among adults and varied among years. Mallards exhibited individual heterogeneity with regard to immune response, providing instances of both seroconversion and seroreversion to detected viral subtypes. The probability that an individual transitioned from one serostatus to another varied by age, with juvenile mallards having higher rates of seroconversion and seroreversion than adults. Our study provides evidence that a diversity of IAVs circulate in populations of mallards wintering at urban locations in Alaska, and we suggest waterfowl wintering at high-latitudes may play an important role in maintenance of viruses across breeding seasons.