Avian flu could be transmitted when seabirds steal food

Photo: David Jeffrey Ringer/Adobe Stock

A study out of the University of New South Wales (UNSW) has found that high-pathogenicity avian influenza virus (HPAIV) H5N1 can be spread through the food-stealing behavior of some seabirds, known as kleptoparasitism.^1,2 Kleptoparasitism is a feeding strategy in which one bird forces another to regurgitate its prey. Researchers say that if the targeted bird is infected, the regurgitated food item could come coated in saliva with a high viral load, which could infect the kleptoparasitic bird, before being spread to others.¹

The study, led by scientists from UNSW Sydney’s Centre for Ecosystem Science, alongside BirdLife International, Deakin University, and Monash University, examined the distribution, behavior, and movements of Fregatidae (frigatebirds) and Stercorariidae (skuas), 2 worldwide families of seabird which are commonly kleptoparasitic. With the knowledge that HPAIV can be transmitted in this way, researchers can maintain proper surveillance of kleptoparasite health, aiding in early detection and potentially proving crucial to seabird conservation efforts.

“Understanding transmission is critical to monitoring and management efforts, particularly when at-risk species or regions are involved, and it’s helpful to understand threats to other animals and people,” Simon Gorta, the study’s lead author, PhD candidate at UNSW, said in a Phys.org article.¹

The virus has killed millions of birds across the world since 2021. Marine species, including seabirds, have been among the most impacted. Richard Kingsford, PhD, professor at UNSW Sydney’s School of Biological, Earth, and Environmental Sciences, and co-author of the study, explained that seabirds are especially vulnerable to the virus because of the way they group when breeding.

“Transmission among seabirds is a real concern because of their close contact and potential contamination of communal resources on densely-packed breeding islands, as well as particular behaviors like predation and scavenging of infected individuals,” Kingsford said.¹

 Researchers now believe that kleptoparasitism, which is a common behavior in seabirds, could be a key point of transmission for the virus. They also expressed concerns regarding the spread of the virus to new populations through this pathway of transmission. The virus could be carried significant distances because of the common migration tendencies of seabirds.^1,2

“Many seabirds, including these kleptoparasitic species, cover tens of thousands of kilometers in their migrations,” Alex Berryman, red list officer for BirdLife International, said.¹ “If kleptoparasites become infected during these migrations and come into contact with other individuals in a way that can facilitate transmission soon after, the disease could spread into new, threatened, and previously unexposed populations and regions.”

The study considered all species in the families Fregatidae and Stercorariidae, 5 species of Fregatidae and 7 species of Stercorariidae. Following observation, HPAIVs were detected in 2 of the 5 species of Fregatidae and in 4 of the 7 species of Stercorariidae birds.² Also, during the study, Fregatidae and Stercorariidae birds were recorded kleptoparasiting 14 additional families of birds. The kleptoparasites were typically bigger than their targets. Of the 14 targeted families, only 4 (Anhingidae, Hydrobatidae, Oceanitidae, and Phaethontidae) did not include a species that contracted HPAIVs.²

As the threat of HPAIV H5N1 continues to increase across the world, understanding transmission pathways of the virus is key for monitoring and managing wildlife populations. Previously, the virus’s reach was limited to Eurasia and Africa, before spreading to North and South America in 2021 and late 2022, respectively.¹

References

1. University of New South Wales. ‘Food Theft’ among seabirds could be transmission point for deadly avian flu. Phys.org, Science X Network. September 17, 2024. Accessed September 17, 2024.
2. Gorta S., Berryman A., Kingsford R., Klaassen M., Clarke R. Kleptoparasites in seabirds – A potential pathway for global avian influenza virus spread. Conserv Lett. 2024. https://doi.org/10.1111/conl.13052