Avian Influenza on the Move: Tracking Marine Predators to Understand the Spread of Infectious Disease

Figure 3. Tracking data compiled for black-browed albatrosses (n = 341), South American fur seals (n = 74) and Magellanic penguins (n = 45) at the Falkland Islands. Yellow points indicate all location estimates within the coastal waters of South America, while red points illustrate periods of residency (resting or nearshore rafting) on/near land. Green triangles (and associated numbers) summarise other known breeding or haul-out sites across the southern Patagonian Shelf region for these three species.

By: Dr Javed Riaz

Animal migration is an extraordinary natural phenomenon, driven by an instinct to feed, survive, and reproduce. Through these long-distance movements, migratory species act as a biological bridge between geographically distant habitats, facilitating the transfer of nutrients and genes between populations. However, animal movement and population connectivity can also enable the dispersal of pathogens and infectious diseases. In some cases, this can have huge ecological and evolutionary consequences.

Since 2021, the world has been experiencing an unprecedented “panzootic” – a large-scale pandemic in domestic and wild animals caused by a highly pathogenic avian influenza (HPAI) virus. This virus has resulted in the deaths of millions of wild animals and has devastated numerous seabird populations worldwide. In Europe for example, some estimates suggest that HPAI has caused staggering (~ 75 %) population declines in certain species, including northern gannets and great skuas.

Through animal movement and migration, HPAI is now gaining a foothold in geographically remote wildlife communities in the southern hemisphere - which have traditionally been insulated from HPAI outbreaks affecting populations in Eurasia, Africa and North America. In late 2022, the virus spread southwards from North America, resulting in mass HPAI outbreaks in seabird and seal populations in South America. The continued spread of HPAI along the Atlantic coast of South America in countries like Argentina and Uruguay poses a major threat to the broader South Atlantic and Antarctic region, which is home to globally significant wildlife populations.

One area of particular concern is the Falkland Islands – a wildlife hotspot supporting an incredible biomass of marine megafauna. For example, the Falkland Islands host approximately 75% of the world’s black-browed albatross population, over 50% of the global South American fur seals population and up to 30% of the population of numerous different penguin species (i.e. southern rockhopper, gentoo and Magellanic penguins).

Despite large-scale outbreaks in coastal South America and further south in some sub-Antarctic regions (i.e. South Georgia Island) in late 2023 - early 2024, HPAI outbreaks in the Falkland Islands have been sporadic and unpredictable, with only a handful of isolated outbreaks at seabird colonies thus far (Fig. 1). Although large-scale outbreaks have not yet occurred, the threat is very much imminent and would likely have catastrophic conservation impacts.  

To inform biological risk assessments, we must have effective disease surveillance and monitoring frameworks. However, this requires a good understanding of three things: how, where and when.

• How the virus will spread via animal movement and particular vector species
• Where the high-risk migratory corridors/spatial networks of disease spread are located
• When HPAI outbreaks may occur throughout the year

Unfortunately, there are huge question marks and uncertainties in all three departments. We simply don’t have a good understanding of these basic elements of animal movement and population connectivity in the South Atlantic.  

Figure 1. Disease is an emerging and evolving threat to wildlife populations, including at the Falkland Islands, which is home to the largest population of black-browed albatross in the world.

Fortunately, the Falkland Islands have been a mecca for animal tracking research over the past 20 years. Numerous different species of seals, penguins and flying seabirds have been the focus of concerted tracking efforts. Over 800 individual animals have been tracked in the Falkland Islands, producing one of the largest animal movement datasets in the South Atlantic (Fig. 2). With these data, we can begin to understand and predict networks of disease spread to the Falkland Islands – a place of hugely significant conservation value.

Leveraging this impressive dataset, our latest research has revealed extensive population connectivity for three regionally dominant and gregarious species; black-browed albatrosses, South American fur seals and Magellanic penguins. For each of these three species, we found individuals tagged at the Falkland Islands ventured several hundreds of kilometres away into coastal waters along the Atlantic coast of South America (Argentina and Uruguay). Here, they spent extensive periods of time at or near other breeding colonies and haul-out areas, where dense aggregations of other colonial marine predators predictably occur (Fig. 3). This includes areas like Peninsula Valdes in Argentina, where massive HPAI outbreak and seal mortality events have recently been recorded. Importantly, all three species showed evidence of rapid transit between South America and the Falklands. Individuals were capable of making the crossing in a few days – well within the estimated HPAI infectious period (~ 7 days). Albatrosses and fur seals, in particular, routinely travelled between Argentina and the Falkland Islands, conducting numerous back-and-forth trips. While the results highlight the impressive mobility and population connectivity of these three species over the Patagonian Shelf, they also demonstrate HPAI outbreaks could occur in the Falkland Islands throughout much of the year.

Figure 2. A South American fur seal tagged at the Falkland Islands – enabling insight into regional-scale movement behaviour and population connectivity during the highly pathogenic avian influenza outbreak.

The animal movement and spatial connectivity findings of our study are unprecedented and reiterate the fact that HPAI outbreaks in the Falkland Islands remain an emerging and significant threat. Our study lays the groundwork for developing evidence-based disease risk assessments in the region capable of highlighting geographic vulnerabilities and forecasting the spread of diseases in wild populations.

Plenty more research is required to develop our understanding of how animal movement and connectivity may influence HPAI spread in the region. In particular, the lack of tracking data available for highly mobile scavenging seabird species, such as southern giant petrels and brown skuas, represents a major blind spot and gap in understanding that needs addressing in future research efforts. With the increasing prevalence of HPAI cases in the region, circulation of numerous different virus strains and the virus’ long-term persistence in wild populations, dedicated and collaborative animal tracking efforts must be one of the most important components of our disease surveillance toolkit. 

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