Elephant Seal Die-off in Argentina Caused by Bird Flu

Outbreak Raises Concerns for Potential Cross-Species Transmission, Including to Humans

many dead elephant seals lie on beach Argentina, victims of bird flu outbreak
Dead elephant seals line a beach in Argentina in fall 2023. Avian influenza has caused the catastrophic die-off of thousands of elephant seals in Argentina, raising concerns for wildlife and human cross-species transmission. (Ralph Vanstreels, UC Davis)

Researchers in Argentina recently reported the first outbreak of high pathogenicity H5N1 avian influenza (HPAI) in elephant seals.

The outbreak killed 70% of elephant seal pups born in the 2023 breeding season, according to research co-led by the UC Davis School of Veterinary Medicine and published in Marine Mammal Science. The mortality rate reached at least 96% by early November 2023 in the surveyed areas at Península Valdés in Argentina.

“This outbreak is the greatest calamity to affect wildlife, particularly marine mammals, in South America in recent history,” said co-author Marcela Uhart, a veterinarian with the UC Davis Karen C. Drayer Wildlife Health Center and its Latin America Program 

The outbreak has also caused the death of thousands of South American sea lions and fewer fur seals along the Argentine Patagonia coastline and now extends into Uruguay and southern Brazil. The virus has also been found in seabirds, particularly several species of terns.

“There is not much we can do once HPAI reaches wildlife populations,” Uhart said. “We need to acknowledge and work to minimize these impacts, including controlling what we can, such as poultry farm biosecurity, to reduce the chance of a continuing cycle of disease spread.”

This investigation was done in collaboration with scientists from the Wildlife Conservation Society including Claudio Campagna, Valeria Falabella, Julieta Campagna, and Victoria Zavattieri. Funding was provided by the Wildlife Conservation Society.

This blog post was adapted from an article by Tom Hinds of the UC Davis School of Veterinary Medicine. Read the full report.


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Media Resources

  • Marcela Uhart, UC Davis School of Veterinary Medicine, muhart@ucdavis.edu. (Dr. Uhart is based in Argentina and bilingual in Spanish and English.)
  • Kat Kerlin, UC Davis News and Media Relations, 530-750-9195, kekerlin@ucdavis.edu


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