A highly contagious strain of highly pathogenic avian influenza (HPAI) is wreaking havoc among elephant seals (Mirounga leonina) off the coast of Patagonia, Argentina. According to the Wildlife Conservation Society (WCS), approximately 96% of elephant seal calves living in three breeding sites where the H5N1 strain of HPAI has been detected have died. The WCS team estimates that 17,000 elephant seals died in those spaces in 2023.
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“It’s the first report of massive elephant seal mortality in the area from any cause in the last half century. The sight of elephant seals found dead or dying along the breeding beaches can only be described as apocalyptic,” WCS Executive Director of Health Chris Walzer said in a statement. “This 2023 die-off contrasts starkly with the 18,000 pups born and successfully weaned in 2022.”
WCS believes that elephant seals have had little to no interaction with inflamed bird populations, offering additional evidence of mammal-to-mammal transmission. According to veterinarian Marcela Uhart of the University of California, Davis, since newborn elephant seals nurse their mothers for food, they must eat swollen birds. “All of this strongly suggests some kind of mammal-to-mammalian transmission,” Uhart told New Scientist.
H5N1 was first detected in 1996 in China. The virus had been largely confined to domesticated birds for several years, but has been spreading quickly in wild populations since 2021. H5N1 infected over 150 domestic and wild bird species around the world. Over 500,000 birds in South America alone have died from the disease. H5N1 has also killed more than 2,200 Dalmatian pelicans in Greece and about 20,000 Sandwich terns in the Netherlands.
Avian influenza is transmitted through air droplets and bird droppings. According to WCS, this scenario is exacerbated by adjustments in bird migration schedules due to human-induced climate change and repeated recirculation of domestic poultry. Outbreaks of the virus have also occurred on mink farms. in France and Spain, and the USDA banned poultry imports from France in October 2023. Scientists showed that the virus was transmitted to wild mammals in May 2022 and has since been detected in dozens of mammals, adding pumas, foxes, skunks and grizzly bears. . Around 700 endangered Caspian Sea seals died from the virus in 2023. H5N1 also killed a polar bear for the first time in the fall of 2023, according to Alaska health officials.
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In response to the spread, the World Health Organization has urged public health officials to prepare for a potential spillover to humans. Initially, scientists thought that mammals could only catch the virus through contact with infected birds. While cases of humans getting infected and seriously ill from bird flu are rare, the more it spreads among mammals, the easier it will be for the virus to evolve to transmit more easily between them. For COVID-19, the number of healthy humans infected by a single sick individual–or R naught value–initially ranged from 1.7 to 7 new infections. Among birds with H5N1, around 100 birds can be infected by a single sick bird.
“It is imperative that we adopt a collaborative One Health strategy to identify emerging strains of avian influenza around the world to help advance targeted universal vaccines that can treat the infection in other people to prevent another pandemic,” Walzer said. The value of inaction is already causing great harm to wildlife. As we work to help affected populations recover, we will need to remain vigilant to the spread of this fatal pathogen before it is too late.
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