Above picture: A healthy Wandering Albatross chick in the Goney Plain long-term monitoring colony, Marion Island, November 2024; photograph by Rhiannon Gill

The South African Department of Forestry, Fisheries and the Environment (DFFE) announced in November 2024 that, based on field observations, High Pathogenicity Avian Influenza (HPAI) virus was suspected to have reached Marion Island, one of South Africa’s two sub-Antarctic islands in the southern Indian Ocean.  Suspected cases had been observed by island field researchers in Brown or Subantarctic Skuas Catharacta antarctica, Wandering Albatrosses Diomedea exulans and Southern Giant Petrels Macronectes giganteus.  Because of the isolation of the island, with usually no more than one official visit by ship in April-May each year, the DFFE made special arrangements for the earlier return of samples to South Africa for analysis.  The presence of the HPAI H5N1virus on Marion, affecting at least six seabird species, has now been confirmed, as described in the latest DFFE media release (see below).

The presence of HPAI on Marion Island adds one more threat to that from the introduced House Mice that are affecting the island’s seabirds.  The Saving Marion Island’s Seabirds – The Mouse-Free Marion Project will continue to work towards the eradication of the island’s mice that have taken to attacking and killing Marion’s breeding albatrosses and petrels, including the four species now known to have been infected by the virus.

Succumbed to HPAI. Corpse of a Wandering Albatross chick in the Goney Plain long-term monitoring colony, Marion Island, November 2024; photograph by Rhiannon Gill

The DFFE media release dated 24 Match 2025 follows in its entirety:

“The presence of high pathogenicity avian influenza (HPAI) H5N1 virus on Marion Island has been confirmed.  Samples collected between September and December 2024 were all shipped back to mainland South Africa, via the S.A. Agulhas II, in February 2025.  In March, Polymerase Chain Reaction (PCR) testing confirmed infection in six bird species, comprising Wandering Albatross (Diomedea exulans), King Penguin (Aptenodytes patagonicus), Brown (Subantarctic) Skua (Stercorarius antarcticus), Southern Giant Petrel (Macronectes giganteus), Northern Giant Petrel (M. halli) and Sooty Albatross (Phoebetria fusca,

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.  The reduced mortality rate is promising, but 31 bird species [actually 30 known or thought to] breed on Marion Island and the bird species and age composition varies throughout the year, therefore 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 Wandering Albatrosses, chicks were mostly affected, with at least 150 of approximately 1900 chicks from the 2024/25 cohort having died.  However, adults have been affected worst in other species: at least 80 adult Brown Skuas, and approximately 120 adult King Penguins.  Much smaller numbers of affected giant petrels (at least 20 Southern and four Northern) and Sooty Albatrosses (five) have been observed.  The deaths of adult seabirds are of greater concern than chicks, because most species only start to breed at 3 to 10 years of age, and most affected species raise at most one chick per year.  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 Subantarctic and Antarctic Fur Seals.  The Archipelago is located in the southwestern Indian Ocean, about 2000 km 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, since they share various ecological characteristics.  Visits to Prince Edward Island are limited to one visit every four years, to limit human impacts on the island and preserve its pristine state, and the last survey was undertaken in November 2023.

Having spread around the globe 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 (950 and 2300 km 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.  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 [SANAP Protocol for the Management of Avian Influenza (20 April 2024) PDF – 960.4 KB] that has been implemented on Marion Island was developed by the Department of Forestry, Fisheries and the Environment, 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.  Efforts to monitor and hopefully limit the spread of the virus on the island will continue.”

Read a media article about the HPAI announcement here.

With thanks to Rhiannon Gill, Marion Island Field Researcher, South African Polar Research Infrastructure.

John Cooper, News Correspondent, Mouse-Free Marion Project. 28 March 2025

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At risk to HJPAI: a Wandering Albatross breeds among flowering Acaena magellanica on Marion Island by Silvia Abramant of Artists & Biologists Unite for Nature (ABUN) for the Mouse-Free Marion Project; after a photograph by Camilla Smyth

 

The Mouse-Free Marion Project is a registered non-profit company (No. 2020/922433/08) in South Africa, established to eradicate the invasive albatross-killing mice on Marion Island in the Southern Ocean.  The project was initiated by BirdLife South Africa and the South African Department of Forestry, Fisheries and the Environment.  Upon successful completion, the project will restore the critical breeding habitat of over two million seabirds, many globally threatened, and improve the island’s resilience to a warming climate.  For muimore information or to support the project please visit mousefreemarion.org.