Elephant seal colony struggles after bird flu deaths
Scientists only expect a third of the usual number of elephant seals to return.
An elephant seal colony in Argentina is continuing to decline, following the devastating effects of last year’s avian influenza outbreak.
The colony, which breeds in Península Valdés, had over 17,000 elephant seals die from the highly pathogenic avian influenza in 2023. This included approximately 97 per cent of the seals’ pups.
This year, scientists only expect a third of the usual number of elephant seals to return.
A new study, conducted by the UC Davis School of Veterinary Medicine and the National Institute of Agricultural Technology in Argentina, has now explored the spread of H5N1 among marine animals such as elephant seals.
The researchers have found evidence of mammal-to-mammal transmission of H5N1, with the influenza spreading efficiently among marine mammals. They believe the outbreak among the elephant seals could be a stepping stone to the first transnational spread of the virus in the species as it reached five countries across southern South America.
In an unprecedented discovery, a genomic analysis uncovered that, once it entered South America, the virus evolved into separate avian and marine mammal clades.
Agustina Rimondi, a virologist and the study’s co-leading author, said: “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.”
The effects of the H5N1 outbreak are still being seen in the elephant seal colony, with the Wildlife Conservation Society of Argentina (WCS Argentina) saying that it has reversed decades of conservation efforts.
The group says that more than half of the colony’s reproductive population of elephant seals died during the epidemic. Its data reveals that most of the adult males and many of the most experienced and fertile females have not returned.
WCS Argentina believes it could take decades for the numbers to return to the 2022 population size.
There have been no confirmed cases of H5N1 among the elephant seals this breeding season. However, scientists are still seeking answers to the causes of last year’s outbreak.
Scientists still don’t know whether the virus was transmitted by aerosol, saliva, faeces or other means. It is also unclear whether the surviving animals have developed a resistance via protective antibodies.
The researchers believe that continued investigation and monitoring will be vital to understanding how it evolves. They state that the virus’ adaptability could see it have global consequences for human health, ecosystems, and wildlife conservation.
The full study can be found in the journal Nature Communications.
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With Strangles Awareness Week just around the corner (5-11 May), vets are being encouraged to share a survey about the disease with their horse-owning clients.
