Elephant Seal Colony Declines One Year After Avian Flu Outbreak
Study Chronicles First Report of ‘Bird Flu’ Transmission Between Marine Mammals
The sounds of barking elephant seals are again in the air along the breeding grounds of Península Valdés, Argentina—but it’s quieter. Roughly a year after a massive outbreak of H5N1 highly pathogenic avian influenza killed more than 17,000 elephant seals, including about 97% of their pups, scientists estimate that only about a third of the elephant seals normally expected here returned.
Lea este comunicado de prensa en Español.
“It’s beautiful to walk the beaches now and hear elephant seals again,” said Marcela Uhart, director of the Latin America Program at the UC Davis Karen C. Drayer Wildlife Health Center within the UC Davis School of Veterinary Medicine. “At the same time, we’re walking among piles of carcasses and bones, and seeing very few elephant seal harems, so it’s still disturbing.”
A study, published today in the journal Nature Communications and co-led by UC Davis and the National Institute of Agricultural Technology (INTA) in Argentina provides evidence of mammal-to-mammal transmission during the 2023 outbreak. It found that H5N1 spread efficiently among marine mammals. The outbreak in elephant seals was a stepping stone amid the first transnational spread of the virus in these species, extending across five countries in southern South America.
The study’s genomic analysis further found that, upon entering South America, the virus evolved into separate avian and marine mammal clades, which is unprecedented.
“We’re showing the evolution of H5N1 viruses that belong to genotype B3.2 over time since their introduction in South America in late 2022,” said virologist and co-leading author Agustina Rimondi of INTA and currently also with Robert Koch Institute. “This virus is capable of adapting to marine mammal species, as we can see from the mutations that are consistently found in the viruses belonging to this clade. Very importantly, 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.”