Two alarming studies have unveiled devastating avian flu outbreaks impacting both Argentina‘s elephant seals and terns nesting on remote islands off the coast of Washington state. The findings indicate that significant declines have occurred within these animal populations following the outbreaks, raising serious concerns for conservationists.
In the first study published today in Nature Communications, a team of researchers from UC Davis and Argentina’s National Institute of Agricultural Technology (INTA) meticulously tracked the elephant seal colony’s population one year after a catastrophic outbreak decimated more than 17,000 seals, tragically resulting in the loss of approximately 97% of seal pups.
The devastating outbreak of H5N1 in 2023 exhibited a remarkably efficient transmission among marine mammals and led to the dissemination of the virus across five countries in southern South America. This alarming turn of events signifies a new risk in the region’s biodiversity.
Once the virus made its way into the elephant seal population, it underwent evolutionary changes, giving rise to distinct avian and marine mammal clades, complicating the landscape of viral transmission.
“Our study also shows that H5 marine mammal viruses are able to jump back to birds, highlighting the need for increased surveillance and research cooperation in the region,” emphasized co-leading author Agustina Rimondi, PhD, of INTA in a press release. “This adaptability underscores the importance of monitoring these viral strains closely to prevent future outbreaks.”
New potential reservoirs in seals
Mass mortality events among seals are rare, and the authors suggest that the tragic pup fatalities were largely due to seal-to-seal transmission, likely exacerbated by multiple introductions of the virus from nearby sea lions.
With this outbreak claiming more than half of the reproductive population of elephant seals, researchers estimate it may take decades for their numbers to rebound to levels recorded in 2022. Furthermore, if seals establish themselves as a reservoir for H5N1 viruses, the risk of infecting wild bird populations looms large, threatening coastal birds with recurrent spillover infections.
“Given the increasing evidence that mammal-to-mammal transmission is linked to H5N1 HPAI outbreaks in North America’s dairy cows and fur farms in Europe, the situation with the elephant seals in Peninsula Valdes highlights a concerning potential for similar mammal-to-mammal transmission dynamics,” the authors concluded.
Outbreak killed over half of terns
The 2023 outbreak on Rat Island, Washington, resulted in a staggering 56% mortality rate within a substantial breeding colony of Caspian terns due to highly pathogenic avian influenza. In Frontiers in Veterinary Science, researchers from the Washington Department of Fish and Wildlife (WDFW) along with scientists from Washington State University meticulously documented the outbreak, noting that no successful breeding of terns has been recorded on the island since last year.
During the span of the outbreak, the virus claimed the lives of 1,101 adult terns and 520 chicks. Additionally, in a worrying trend, 15 deceased harbor seals were reported in the vicinity, which is alarmingly high given that this area typically witnesses only 1 or 2 seal fatalities.
“This Caspian tern event represented the first major outbreak of avian flu in a marine environment for Washington. It caused a significant, punctuated mortality that poses a dire threat to these terns, a species already facing decline throughout this migratory flyway,” stated lead author Katherine Haman, DVM, in a press release from Washington State University.
**Interview with Dr. Agustina Rimondi on the Alarming Avian Flu Outbreaks**
**Editor:** Welcome, Dr. Rimondi, and thank you for joining us today. Your recent study on the effects of avian flu on elephant seals has raised significant concerns. Can you summarize the key findings for our audience?
**Dr. Rimondi:** Thank you for having me. Our study highlights a catastrophic outbreak of the H5N1 avian influenza virus that significantly impacted the elephant seal population along the Argentine coast. We found that more than 17,000 seals were affected, resulting in a staggering decline of about 97% of seal pups. This mass mortality event is unprecedented and has grave implications for the future of the species.
**Editor:** That is shocking. What do you believe were the main factors contributing to this outbreak and its severity?
**Dr. Rimondi:** One primary factor was the efficiency of H5N1 transmission among marine mammals. The virus managed to spread not just among seals but also allowed for adaptations that led to distinct clades capable of infecting both seals and birds. This adaptability is particularly alarming, as it creates a dynamic situation where the virus can potentially re-emerge and infect coastal bird populations.
**Editor:** You mentioned the possibility of seals becoming reservoirs for the virus. Can you elaborate on what this could mean for wildlife and biodiversity in the region?
**Dr. Rimondi:** Certainly. If elephant seals establish a reservoir for H5N1, it introduces a continuous risk of spillover infections to wild bird populations. This could lead to recurrent outbreaks, threatening already vulnerable coastal bird species. The decline of biodiversity in these ecosystems could have cascading effects on the entire marine environment, leading to further imbalances.
**Editor:** What measures do you propose to prevent similar outbreaks in the future?
**Dr. Rimondi:** Increased surveillance is crucial. We need to monitor both marine mammal and bird populations closely. Moreover, enhancing research cooperation across countries in South America is vital for timely responses to emerging diseases. Collaborative efforts will help us understand the dynamics of these viral strains better and potentially develop preventive strategies.
**Editor:** This sounds like a challenging public health and conservation issue. How can the public contribute to conservation efforts amidst these disasters?
**Dr. Rimondi:** Public awareness is key. People can support local conservation initiatives and participate in citizen science projects around wildlife monitoring. Additionally, advocating for policies that prioritize wildlife health and environmental sustainability will be essential in tackling such complex issues.
**Editor:** Thank you, Dr. Rimondi, for sharing these insights. Your work is critical in raising awareness about the risks posed by avian flu and the importance of protecting our marine ecosystems.
**Dr. Rimondi:** Thank you for having me. It’s essential that we keep these conversations going to protect wildlife and ensure a healthier biodiversity for future generations.
