After South America, bird flu threatens Antarctica – 9/4/2023 – Science

Over the past three years, a highly lethal form of bird flu has swept the world, slaughtering birds in Europe, Africa and Asia before crossing the ocean and triggering the worst outbreak of the disease in US history.

Last fall, the virus, known as H5N1, finally reached South America. It raced down the Pacific coast, killing wild birds and marine mammals in staggering numbers.

Peru and Chile alone have reported more than 500,000 dead seabirds and 25,000 sea lions, according to a new report published last week by OFFLU, a global network of flu experts.

Now, scientists are concerned about the possibility of the virus reaching Antarctica, one of only two continents – along with Australia – that has not yet been hit by the pathogen.

“The negative impact of this virus on wildlife in Antarctica could be immense — probably worse than on wildlife in South America,” the report warns.

More than 100 million birds breed on Antarctica and nearby islands, and many marine mammals swim in the surrounding waters. Some of these species, including the emperor penguin and the Antarctic fur seal, live in large colonies.

“This could be a recipe for disaster,” said Dr. Ralph Vanstreels, a researcher in a Latin American wildlife health program at the University of California, Davis and author of the new report. “We could be looking at a very high number of deaths.”

This variant of bird flu, which emerged in 2020, has caused massive outbreaks on poultry farms, resulting in the deaths of nearly 60 million poultry in the United States alone. But unlike earlier versions of the virus, it was also spread widely by wild birds and frequently spilled over into wild mammals.

The virus emerged in South America in October 2022, spreading from Colombia to Chile in just three months. “Once it started moving south, it moved very quickly,” said Dr. Marcela Uhart, who directs the Latin American Wildlife Health Program at UC Davis and is an author of the OFFLU report.

Casualties are difficult to count because many infected animals were likely never detected, scientists said, and not all dead animals that turned up were tested for the virus. But hundreds of thousands of dead seabirds, including boobies, cormorants and gulls, were reported in South America. The losses represented 36% of the Peruvian pelican population and 13% of Chile’s Humboldt penguins, according to the report.

Thousands of South American sea lions also died, representing 9% of the species’ population in Peru and Chile. (Scientists still don’t know exactly how marine mammals contract the virus or whether it is easily spreading among them.)

The virus continued to move south. In June, it appeared on a South American sea lion in the extreme south of Chile, just 1,072 km from the Antarctic Peninsula. Some birds routinely roam between South America and Antarctica, feeding in both places. Others will head to their breeding grounds in Antarctica when spring arrives in the southern hemisphere, potentially taking the virus with them.

Antarctica has never had an outbreak of highly pathogenic avian flu before, and its residents are likely to have poor immune defenses against the virus. “Populations are completely naive,” said Dr Thijs Kuiken, a veterinary pathologist at Erasmus University Medical Center in the Netherlands and author of the new report. “The concern is that the first time it happens it has a really big impact in terms of the death rate.”

Many birds in the region, including emperor penguins and shearwaters, already face other threats, from sources including climate change, the fishing industry or other human activities. Some species are restricted to some islands. “So if there’s an outbreak on these islands, basically the whole species will collapse,” Vanstreels said.

Local marine mammals may also be at risk. Although the Antarctic fur seal can vary greatly, 95% of the population lives around just one island, making it vulnerable to an outbreak.

At this point, the virus is so widespread that it may not be possible to stop it from reaching Antarctica. “Right now, there’s nothing we can do to prevent it,” Kuiken said. “Therefore, we must be as alert as possible in the coming months.”

It will be critical to monitor wild populations to better understand how the virus is spreading, which species may be most at risk and what conservation actions may be needed to help them recover, the scientists said.

“What we’re doing is documenting this really well, trying to understand how the virus is moving to see how we can better protect the species in the future,” Uhart said.