MarionIsland_ChrisOosthuizen (130)
A wandering albatross pair at Marion Island.
(Chris Oosthuizen)
The department of forestry, fisheries and environment has confirmed the presence of the high pathogenicity avian influenza (HPAI) H5N1 virus on South Africa’s sub-Antarctic territory of Marion Island.
Samples collected from September to December last year were shipped back to mainland South Africa on the SA Agulhas II in February this year, according to the department. In March, polymerase chain reaction testing confirmed infection in six bird species: the wandering albatross, king penguin, brown skua, southern giant petrel, northern giant petrel and the sooty albatross.
“Following an initial suspected HPAI case in a brown skua at Marion Island — a bird showing clinical signs of HPAI infection including twitching and tremors — in mid-September 2024, more similar cases were reported in early November and mortalities in multiple species have continued into March 2025, though the overall death rate slowed significantly in January,” it said.
The department noted that the reduced mortality rate is “promising”. But 31 bird species breed on Marion Island and because the bird species and age composition varies throughout the year, “it is difficult to predict how the outbreak will progress”.
The potential effects on marine mammals are also of concern but no increased mortality has been reported in any mammal species so far.
Among the wandering albatrosses, chicks were mostly affected with at least 150 of about 1 900 from the 2024 cohort having died. In other species adults have been worse affected: at least 80 adult brown skuas and about 120 adult king penguins. Much smaller numbers of affected giant petrels — at least 20 southern and four northern — and five sooty albatrosses were observed.
“The deaths of adult seabirds are of greater concern than chicks, because most species start to breed from three to 10 years of age, and most affected species raise at most one chick per year,” the department said, noting that there are also a multitude of other threats to seabirds, including fisheries bycatch, climate change, plastic pollution and predation by introduced house mice on Marion Island.
Marion Island, along with neighbouring Prince Edward Island, provides critical breeding and moulting grounds for millions of seabirds and marine mammals, including nearly half of the world’s wandering albatrosses, hundreds of thousands of penguins, and large numbers of southern elephant seals and sub-Antarctic and Antarctic fur seals.
The archipelago is located in the south western Indian Ocean, about 2 000km southeast of Cape Town and halfway between Africa and Antarctica.
Observations of and laboratory test results for HPAI (H5N1) on Marion Island can assist in inferring the potential risk to animals on Prince Edward Island because they share various ecological characteristics.
Visits to Prince Edward Island are limited to one visit every four years to preserve its pristine state. The last survey was undertaken in November 2023.
Having spread around the world since 2021, HPAI (H5N1) was detected in seabirds and marine mammals in South Georgia, southeast of South America, in October 2023.
It reached the Antarctic Peninsula in February 2024 and was detected at the French archipelagos of Crozet and Kerguelen (950km and 2300km east of Marion, respectively) in October and November 2024. The virus can be transported long distances by migrating birds, and the virus moved from South Georgia to the French islands.
“The situation on Marion Island is being closely monitored by the field personnel overwintering on the island, who have been trained to recognise possible HPAI signs in birds and seals and in the necessary monitoring and mitigation methods,” the department said.
“They will continue to take all precautions to ensure they do not spread the virus. There are few other disease mitigation tools available in this type of situation.
“The HPAI protocol that has been implemented on Marion Island was developed by the department, the management authority for the Prince Edward Islands, together with Western Cape veterinary services, marine ornithologists, marine mammal biologists, disease experts and colleagues overseas with similar experience,” the department said.
Efforts to monitor and to hopefully limit the spread of the virus on the island would continue.