#18,579
While the threat of HPAI H5N1 in livestock - and sporadic spillovers into humans - have garnered most of our bird flu attentions this past year, there has been a massive, and underappreciated, impact on both avian and mammalian wildlife around the globe.
Numbers are impossible to quantify, but hundreds of millions of wild birds have died, and hundreds of thousands - perhaps millions - of wild mammals have succumbed to the virus.
A few past blogs on this carnage include:
Travel Med. & Inf. Dis.: Pacific and Atlantic Sea Lion Mortality Caused by HPAI A(H5N1) in South America
EID Journal: Recent Changes in Patterns of Mammal Infection with Highly Pathogenic Avian Influenza A(H5N1) Virus Worldwide
EID Journal: Mass Mortality of Sea Lions Caused by HPAI A(H5N1) Virus (Peru)
We've seen other avian flu viruses infect and kill marine mammals on a much smaller scale - including H3N8 in New England (2011), H10N8 in Germany (2014), and H5N8 in the Baltic Sea (2017) - but in early 2024 we saw a Research letter in the EID Journal stating `. . . it seems likely that pinniped-to-pinniped transmission played a role in the spread of the mammal-adapted HPAI H5N1 viruses in the region.'
But even if that never happens, the impact on our shared ecosystem - and the loss of hundreds of millions of birds and hundreds of thousands of mammals - is enormous and growing.
Last year we followed attempts to protect the endangered California Condor from HPAI H5N1, after more than 20 deaths were reported in the wild (see USFWS Update: 21 Condor Deaths Attributed To HPAI H5). As scavenger birds, Condors feed almost exclusively on carrion, which increasingly runs the risk of being infected with HPAI H5 (see USDA Mammalian HPAI Infection List).
While the knock-on effects of HPAI's damage to wild birds and mammals are difficult to predict, it isn't hard to imagine what the loss of a half billion birds might have on the mosquito population in some regions - or the loss of scavenger birds on the efficient cleanup of carrion - both of which could adversely affect human health.
Last week Nature Reviews Biodiversity published a review by Sergio A. Lambertucci, Andrea Santangeli & Pablo I. Plaza on HPAI H5's threat to global biodiversity. Both Lambertucci and Plaza have been featured in this blog several times before (see here, here, and here).
I've only reproduced a few excerpts, so follow the link to read this important review in its entirety. I'll have a brief postscript after the break.
The threat of avian influenza H5N1 looms over global biodiversitySergio A. Lambertucci, Andrea Santangeli & Pablo I. Plaza
Nature Reviews Biodiversity volume 1, pages7–9 (2025) Cite this article
The highly pathogenic avian influenza H5N1 is an emerging and unexpected threat to many wild animal species, which has implications for ecological processes, ecosystem services and conservation of threatened species. International collaboration and information-sharing is essential for surveillance, early diagnosis and the provision of financial and technical instruments to enable worldwide actions.
As many wild animal populations are already under strain from habitat loss, climate change and other global change drivers, previously neglected threats such as some emerging infectious diseases can rapidly decimate wildlife populations1. One such emerging disease in wildlife is the highly pathogenic avian influenza caused by the A H5N1 virus.
(SNIP)
An estimated half a billion domestic fowl have died of H5N1 (ref. 4), and this number is rising; mortality in wildlife is more difficult to quantify than in poultry, but the effects are substantial. By mid-2024, H5N1 infections were documented in at least 406 bird and 51 mammal wild species (according to reports on the World Animal Health Information System (WAHIS)), and available reports suggest that multiple millions of wild animal individuals may have died (Fig. 1a).
The most noteworthy mass-mortality events include more than 200,000 wild birds in coastal areas of Peru6; 24,000 sea lions in South America7; 20,500 wild birds in Scotland8; 6,500 Cape cormorants in Namibia9; and 17,400 elephant seals, including >95% of the pups in Argentina10. These figures, however, largely underestimate actual mortalities, owing to a pervasive lack of monitoring, testing and reporting — particularly in inaccessible areas and in disadvantaged countries4,7.(SNIP)Apart from the intrinsic value of the wildlife being lost and the potential for concerning changes in ecosystem function, ecosystem services could be compromised by the loss of wildlife. For example, the loss of marine birds could result in lower availability of guano, an important source of fertilizer for some communities6,9. The potential ecological changes in marine coastal ecosystems15 could modify food and other provisioning services to local fishers or seaweed collectors. The service of ecotourism could be impaired by the loss of pinnipeds and marine birds (for example, penguins) in some regions, including Antarctica. Cultural services such as recreation, relaxation, leisure and spiritual enrichment could also be affected. Potential effects of ecosystem service losses should be assessed by scientists from the social and natural sciences together with Indigenous people, local communities and other stakeholders who are affected.
Events that were nearly unthinkable two or three years ago (e.g. Repeated trans-Atlantic introduction of avian flu from Europe, the spread of HPAI H5 across the length of South America, numerous spillovers of H5 into mammalian species, and the arrival of HPAI H5 to Antarctica) have now become `the new normal'.
Admittedly, for many it is easier to turn a blind eye to what is happening, as long at it doesn't affect them directly. But $10 for a dozen eggs may not be the worst fallout we'll see from this virus,
We underestimate HPAI's threat at our own, considerable, peril.