Tests confirm avian flu on remote island, affecting six bird species: SA govt

The presence of the high pathogenicity avian influenza (HPAI) H5N1 virus on sub-Antarctic Marion Island has been confirmed.

The department of forestry, fisheries and the environment said samples collected between September and December 2024 were all shipped back to mainland SA, via the SA Agulhas II, last month.

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).

Among wandering albatrosses, chicks were mostly affected, with at least 150 of about 1,900 chicks from the 2024 cohort having died. However, adults have been affected worst in other species. At least 80 adult brown skuas and about 120 adult king penguins have been affected. 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 three to 10 years of age, and most affected species raise at most one chick per year, the department said. There are also many other threats to seabirds, including fisheries bycatch, climate change, plastic pollution and predation by introduced house mice on Marion Island.

The department said 31 bird species breed on Marion Island.

"After 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 many species have continued into March, though the overall death rate slowed significantly in January. The reduced mortality rate is promising, but as 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."

Marion Island, along with neighbouring Prince Edward Island, provides critical breeding and moulting grounds for millions of seabirds and marine mammals, including nearly half 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 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, since they share some  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 (950km and 2,300km 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."

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