While HPAI H5 produces high mortality in many bird species, some varieties can carry the virus asymptomatically, while others may recover from a symptomatic infection.
Our understanding of the long-term consequences of H5N1 infection among surviving birds is quite limited, but a new preprint this week has identified a fascinating after-effect in some Northern Gannets; a change of eye color from blue to black.
While a minor impact, at least compared to the horrendous losses of the seabird colony, this unusual change may help researchers identify previously infected (and recovered) birds.Although unusual, changes in eye color have been documented in humans after infections (see here and here), but never - to my knowledge - as widespread as described in the following preprint on the post-infection consequences of H5N1 on the normally blue-eyed Northern Gannet (Morus bassanus).
While we tend to focus on the tremendous losses in the poultry industry, and the potential human health hazard from HPAI H5, the long-term (and largely unquantified) ecological impact of these viruses on both avian and mammalian wildlife cannot be ignored.
High pathogenicity avian influenza (H5N1) in Northern Gannets: Global spread, clinical signs, and demographic consequences
Jude V Lane, Jana WE Jeglinski, Stephanie Avery-Gomm, Elmar Ballstaedt, Ashley C Banyard, Tatsiana Barychka, Ian H Brown, Brigitte Brugger, Tori V Burt, Noah Careen, Johan HF Castenschiold, Signe Christensen-Dalsgaard, Shannon Clifford, Sydney M Collins, Emma Cunningham, Jóhannis Danielsen, Francis Daunt, Kyle JN d’Entremont, Parker Doiron, Steven Duffy, Matthew D English, Marco Falchieri, Jolene Giacinti, Britt Gjerset, Silje Granstad, David Grémillet, Magella Guillemette, Gunnar T Hallgrímsson, Keith C Hamer, Sjúrður Hammer, Katherine Harrison, Justin D Hart, Ciaran Hatsell, Richard Humpidge, Joe James, Audrey Jenkinson, Mark Jessopp, Megan EB Jones, Stéphane Lair, Thomas Lewis, Alexandra A Malinowska, Aly McCluskie, Gretchen McPhail, Børge Moe, William A Montevecchi, Greg Morgan, Caroline Nichol, Craig Nisbet, Bergur Olsen, Jennifer Provencher, Pascal Provost, Alex Purdie, Jean-François Rail, Greg Robertson, Yannick Seyer, Maggie Sheddan, Catherine Soos, Nia Stephens, Hallvard Strøm, Vilhjálmur Svansson, T David Tierney, Glen Tyler, Tom Wade, Sarah Wanless, Christopher RE Ward, Sabina Wilhelm, Saskia Wischnewski, Lucy J Wright, Bernie Zonfrillo, Jason Matthiopoulos, Stephen C Votier
This article is a preprint and has not been certified by peer review [what does this mean?].
During 2021-22 High Pathogenicity Avian Influenza (HPAI) killed thousands of wild birds across Europe and North America, suggesting a change in infection dynamics and a shift to new hosts, including seabirds. Northern Gannets (Morus bassanus) appeared especially severely impacted, but limited understanding of how the virus spread across the metapopulation, or the demographic consequences of mass mortality limit our understanding of its severity. Accordingly, we collate information on HPAIV outbreaks across most North Atlantic gannet colonies and for the largest colony (Bass Rock, UK), provide impacts on population size, breeding success, adult survival, and preliminary results on serology.Unusually high numbers of dead gannets were first noted in Iceland during April 2022. Outbreaks in May occurred in many Scottish colonies, followed by colonies in Canada, Germany and Norway. By the end of June, outbreaks had occurred in five Canadian colonies and in the Channel Islands. Outbreaks in 12 UK and Ireland colonies appeared to follow a clockwise pattern with the last infected colonies recorded in late August/September.
Unusually high mortality was recorded at 40 colonies (75% of global total colonies). Dead birds testing positive for HPAIV H5N1 were associated with 58% of these colonies. At Bass Rock, the number of occupied sites decreased by at least 71%, breeding success declined by ∼66% compared to the long-term UK mean and adult survival between 2021 and 2022 was 42% lower than the preceding 10-year average. Serological investigation detected antibodies specific to H5 in apparently healthy birds indicating that some gannets recover from HPAIV infection.Further, most of these recovered birds had black irises, suggestive of a phenotypic indicator of previous infection. Untangling the impacts of HPAIV infection from other key pressures faced by seabirds is key to establishing effective conservation strategies for threatened seabird populations, HPAIV being a novel and pandemic threat.