The asymptomatic cases might seem reassuring to penguins, but scientists worry that they could also serve as “Trojan horses” for other species.
Antarctic Adélie penguins tested positive for bird flu and showed outward symptoms of illness, according to researchers who traveled to thirteen remote breeding sites aboard an icebreaker cruise ship.
Since bird flu arrived in the region this year, concerns have been raised about the possibility of the virus reaching Antarctica’s fragile penguin populations. In November of last year, researchers warned in a preprint study article that if the virus causes mass mortality in those colonies, “it could be the sign of one of the biggest ecological blunders of fashionable times. “
In December 2023 and January 2024, scientists tested 16 Adélie penguins on Beagle Island on the Antarctic Peninsula for the H5N1 virus, and seven (43%) tested positive. Satellite trackers of the penguins showed that they were alive and feeding two months later, in early March 2024. Elsewhere in Red Rock Ridge, nine Adélie penguins were tested and one tested positive.
None showed symptoms of illness, which is good news for the penguins; however, the researchers warn that they may simply act as “Trojan horses” that facilitate the spread of the virus to vulnerable species.
“These asymptomatic cases may seem reassuring to the species in question, but they have strong implications for Antarctica as a whole, which could lead to widespread and inadvertent viral transmission,” the researchers, led by Fabiola León of UC Chile, wrote in the bioRxiv paper. , which has not yet been peer-reviewed.
Their findings spark “some cautious optimism for penguin populations,” says Colin Butter, an associate professor of bioveterinary sciences at the University of Lincoln, who was not involved in the research.
While it is conceivable that some penguin populations are resilient, this cannot be known for sure, as many other penguin species have died out in South America. The widespread spread of avian flu in Antarctica would also threaten other populations, including seals and whales. “Antarctica’s ecosystem is valuable and fragile. The flu virus could cause devastating disruptions from which it would not recover,” Butter said.
Ed Hutchinson, a molecular biologist at MRC-University of Glasgow’s Centre for Virus Research, who was also not involved in the study, said the limited sampling meant this survey only provided a snapshot of what was happening.
“The fact that supposedly healthy birds have been infected by the flu virus is important, but not surprising,” he said. “We know in other parts of the world that certain types of birds are more likely than others to get very sick from this virus.
“As the spread of the coronavirus among humans has reminded us, the presence of healthy but contagious Americans can be a real challenge in controlling the spread of an epidemic. . . This underlines the importance of continuous monitoring of this situation. “
Dr. Connor Bamford, a virologist at Queen’s University Belfast, said he is wary of the results. “More studies are needed to examine these animals with respect to avian influenza in terms of illness and health. High mortalities related to highly pathogenic H5 have been documented in penguins in the past. . . However, the reasons why those penguins appear to be protected, and their implications, are hard to say.
The tests were conducted between December 2023 and January 2024 along the east and west coasts of the Antarctic Peninsula and the west coast of Antarctica and provide a snapshot of how the virus is spreading across the continent.
A total of 115 supposedly healthy birds were sampled and nine tested positive, adding 8 Adelie penguins and an Antarctic cormorant. The researchers tested 31 emperor penguins and none tested positive. It is not imaginable to say whether the virus had reached those colonies and was no longer present, or whether those birds had not been exposed to them at all.
Avian flu first appeared on the Antarctic continent in February, after several cases on the sub-Antarctic islands. The paper’s researchers stated, “The first detection of suspected cases of H5N1 influenza in penguins and cormorants on the Antarctic continent marks a significant expansion. . . on this remote continent and endangers highly vulnerable bird populations. “
The spread of H5N1 has led to the deaths of millions of wild birds around the world, and thousands of sea lions and seals have also died due to “rains” on wild mammals. After arriving in the sub-Antarctic region in October, about 10 species of seabirds and Antarctic seals died.