From Overseas Hotspots to Australian Shores
It was only recently that a highly virulent avian influenza strain confirmed its presence on Australian shores. But for Deakin University's disease ecology researchers, that date was not a sudden beginning. It was the latest chapter in a long-running effort to understand how bird movements shape the risk of an outbreak. Dr. Sara Ryding, who works at the Deakin Centre for Marine Science, has spent much of that time focused on migratory shorebirds.
Ryding studies how these birds move, how their movement patterns change, and what those changes mean for disease risk. In partnership with Dr. Tobias Ross and Professor Marcel Klaassen, she recently published a paper in Scientific Reports that examines which wild bird species may be most susceptible to highly pathogenic avian influenza.
The researchers' approach reflects a larger realization in disease ecology: a virus does not spread through an even field of hosts. It travels through networks shaped by behavior, ecology, and environmental change.
From Mild Infection to Global Emergency
Avian influenza has circulated in wild bird populations for a long time. Most of those strains are classified as low pathogenicity avian influenza, or LPAI. They may produce mild illness in birds or no visible signs at all. But when those viruses encounter the conditions of modern poultry production, the evolutionary calculus changes.
Industrial-scale farming creates dense, genetically similar populations that allow viruses to mutate more quickly. Under those pressures, an LPAI strain can become a high pathogenicity avian influenza strain. The HPAI H5N1 virus now spreading across wildlife worldwide is a product of this process. It has since moved beyond poultry farms and found new hosts across the globe.
Shorebirds as Living Probes
Migratory shorebirds are important to this story because they are connectors. Each year, species travel along flyways that link breeding grounds in the Northern Hemisphere with wintering habitats in Australia and Southeast Asia. During migration they stop at wetlands and mudflats shared by hundreds of other species. These stopovers act as exchange points where viruses can move from one species to another.
Changes in movement patterns can therefore change disease dynamics. A group of shorebirds that arrives earlier, skips a stopover, or winters in different wetlands may encounter new viral strains or introduce existing ones to vulnerable hosts. By monitoring those movements, Ryding and her colleagues are trying to anticipate where and when an HPAI introduction might occur, not only whether it will cross Australia's border.
Habitats and Behaviors That Raise Risk
No species exists in isolation from HPAI H5N1 in the current landscape. But certain traits can make exposure more likely.
- Colonial nesting seabirds have little protection from their own numbers. When a highly contagious virus reaches a dense breeding colony, it can sweep through quickly.
- Pink-eared ducks and other aquatic foragers may ingest feces-contaminated water while feeding, making their exposure route almost unavoidable where the virus is present.
- Birds of prey are exposed through the animals they consume. A hawk or eagle hunting an infected duck can become a secondary host.
- Ravens and magpies are opportunistic scavengers. When they feed on dead or dying birds, they may be exposed to very high concentrations of virus.
This trait-based thinking is intended to give wildlife managers a clearer sense of where surveillance should be targeted. It also counters the assumption that a bird flu issue belongs only to poultry barns.
Impacts That Cross the Species Boundary
A recent twist in the HPAI H5N1 story has been its ability to infect marine mammals. In South America, sea lions have died in significant numbers after the virus moved through their populations. The Deakin team includes such examples because they show how one introduced pathogen can rewrite whole ecosystems.
At the same time, the research notes that many species have some capacity to produce antibodies after exposure. Those antibodies may help an individual bird resist a future encounter with the virus, even if they do not prevent illness the first time. Understanding that, Ryding says, helps decision-makers look beyond mortality counts to gauge long-term population resilience.
A Long Preparation for Australia
Australia is not geographically isolated from wild bird flyways. Nonetheless, for years, many hoped that its position at the edge of the East Asian-Australasian Flyway would delay or soften the arrival of a highly virulent strain. The recent detection on Australian shores puts an end to any assumption of natural protection.
The Deakin team has been modeling overseas outbreaks for years and making predictions for Australia. Their preparation includes mapping where wild birds feed, how they interact with waterfowl and other species, and how seasonal conditions could compress birds into smaller habitats, creating risk hotspots.
Data, Modeling, and the Value of Patience
The Scientific Reports paper offers a template for preparation that does not wait for the first infected carcass. It was produced before the Australian detection became public, which highlights the role of patience in outbreak science. Researchers have to follow birds season after season, collecting information that may not appear urgent for years.
Ryding and her colleagues hope their work will help shape surveillance programs, conservation plans, and communication strategies. The virus, after all, does not respect administrative boundaries. Following its movement requires studying the world through the wings of the animals that carry it.
This article is based on reporting by Phys.org. Read the original article.
Originally published on phys.org