Thierry Boulinier

Penguins are highly susceptible to airborne mycoses, and aspergillosis due to Aspergillus fumigatus (recently classified as a priority pathogen by WHO) is common in captivity; however, environmental fungal diversity and exposure risk in natural, non-temperate breeding habitats remain poorly described. We aimed to characterize the seasonal burden and diversity of culturable fungi in wild king penguin (Aptenodytes patagonicus) colonies and to assess A. fumigatus diversity and phenotypes. During 1 year, monthly environmental sampling was performed from four different soils of Crozet archipelago, in French Southern Territories, around three penguin colonies. Samples were cultured on malt extract agar at 35 ± 2°C. Isolates were quantified (CFU) and identified by microscopy, MALDI-TOF MS, and DNA sequencing. Aspergillus fumigatus isolates underwent genotyping and phenotyping for antifungal susceptibility, as well as for tolerance to high salinity and extreme temperatures. Overall, fungal loads in penguin environments showed marked seasonality (3–1 100 CFU/month), peaking during breeding/chick rearing summer period (∼22% positive sites). After April, fungal burden declined (mean 150 CFU/month; 8.8% positive sites). Aspergillus section Fumigati represented 21%–100% of isolates (150–950 CFU/month). Aspergillus fumigatus genotypes were diverse, with no detected antifungal resistance or extreme growth phenotypes. Fungal burden in penguin natural habitats was closely linked to bird presence and breeding activity. These findings provide new insights into fungal exposure in wild groups and emphasize the importance of a One Health approach to better understand the interactions between environment, wildlife, and infectious disease risk in fragile ecosystems.

Seabird communities represent spatially structured social networks within which potential sentinels could inform us where multi-host pathogens could be present. Pasteurella multocida, the agent of avian cholera, is responsible for recurrent massive seabird mortality events on remote Amsterdam Island, Southern Indian Ocean, but little is known about its broad spatial occurrence. To explore its distribution and whether avian scavengers and predators could be used as sentinels, we screened 18 southern seabird species from 11 islands for antibodies against P. multocida (2634 plasma samples). We detected widespread but heterogeneous exposure among host populations. High seroprevalences were found in widely roaming predators and scavengers (giant petrels (Macronectes spp), and brown skua (Stercorarius antarcticus)), which could represent efficient sentinels at broad scales. Antibodies were also detected over a series of years in a non-migratory scavenger, the lesser sheathbill (Chionis minor) and an abundant penguin species, the king penguin (Aptenodytes patagonicus), suggesting that the bacterium was circulating locally at some sites. This broad scale serological screening of whole seabird host communities provides critical information to assess disease emergence risks in the context of global change.

Countries have committed to expanding the marine protected area (MPA) network to 30% of the world's ocean by 2030, more than tripling current coverage, and focusing on areas important for biodiversity. For such expansion to translate into effective conservation of marine biodiversity, it must rely on the best available knowledge. Here, we analyze tracking data on > 13,000 individuals (44 species, eight families) to map the distribution of highly mobile seabirds in the Atlantic Ocean and adjacent seas throughout the year. We identify regions important year‐round or seasonally. The High Seas are as important as national waters for highly mobile seabirds but are even less protected. Current Atlantic MPAs hold < 14% of tracked species density, but their expansion to 30% of the ocean could protect up to two thirds. We share this new knowledge layer to support national and international efforts and policies to strategically expand the Atlantic MPA network.

The recent large-scale circulation of High Pathogenicity Avian Influenza (HP AI) viruses H5Nx of clade 2.3.4.4b has been responsible for massive die-offs in wild species, notably in long-lived seabirds, with unknown implications for the immunity of surviving individuals. In the North Atlantic, northern gannet colonies were heavily affected in 2022, with more than 40% mortality observed among breeding adults and some surviving individuals developing dark irises. Using samples collected in 2023 and 2024 on Rouzic colony (France), we report persistent individual anti-AI antibody levels and seroneutralisation titres, with most of the immune individuals showing dark irises. A modelling approach further stressed the importance of long-lasting immunity in such species by showing that the proportion of individuals which kept their immunity between years strongly limited decreases in population size in case of repeated outbreaks. Overall, our results highlight the existence and importance of long-lasting immunity in long-lived species for population persistence.

High pathogenicity avian influenza (HPAI) has spread across the sub-Antarctic, causing significant wildlife impacts. We report its first detection in an Australian external territory, Heard Island and McDonald Islands, which supports over one million breeding seabirds and seals. Drone and ground surveys (October 2025, January 2026), combined with viral genome analysis, confirmed infection with Influenza A H5N1 clade 2.3.4.4b at Heard Island. Drone surveys revealed mass mortality in southern elephant seals, with 8,573 pups (62%) recorded dead across Heard Island by the final surveys. Mortality increased at an average rate of 5.6% per day in a subset of harems, and the highest observed mortality in a harem was 97%. Based on the average (76%) mortality in the final surveys, total estimated pup mortality at Heard Island was 13,359 (from a total population of 17,364 pups), though this may be an underestimate as mortality was ongoing at this time. HPAI was detected in six of nine species tested and, we suspect, led to elevated mortality in king and gentoo penguins. Phylogenetic analysis indicates the virus was introduced from Crozet Islands, with an estimated arrival around August 2025. These data show the continued easterly spread of HPAI around the sub-Antarctic, with severe but heterogeneous impacts across taxa. Our results demonstrate the value of drones for large-scale monitoring, underscoring the need for continued and enhanced HPAI surveillance across the Southern Ocean.

Summary: High pathogenicity avian influenza virus (HPAIV) H5N1 reached the sub-Antarctic and Antarctica in 2023, subsequently spreading to remote locations within this region where it had devastating impacts on seal, penguin and albatross populations. The threat to marine wildlife over this broad area exemplifies the need to understand H5N1 long-distance dispersal and evolution. We obtained 104 novel viral genomic sequences from samples that we collected at South Georgia, Kerguelen, Crozet, Prince Edward, Falklands/Malvinas Islands and the Antarctic Peninsula in a region spanning 8,000 kilometers. Using recent phylogeographic modeling advances we show that H5N1 spread encompassed numerous transmission events between distant locations, accumulating mammalian-adaptive mutations in the process. Seals are the most affected species, but we reveal that the long-distance eastward virus dispersal better aligns with the long-distance movements of large petrels and albatrosses. The risk of H5N1 endemisation, dispersal to other locations and ongoing evolution are highly concerning.

Understanding the patterns and drivers of infectious disease dynamics at different levels of life organization is a fundamental disease ecology challenge. In this study, we performed a multi-infectious agents (IA) screening of 1,983 individuals belonging to 18 seabird species, sampled between 2017 and 2022 across five sub-Antarctic islands in the Southern Indian and Atlantic Oceans. Our aim was to identify the drivers of IA community in these seabirds by considering intrinsic and extrinsic factors on three dimensions: distance between seabird metapopulations and within-island sites, macro-community (host functional traits based on feeding and breeding features) and intra-host IA community composition. Samples were screened for 24 DNA-based IAs using a high-throughput real-time PCR method, followed by subsequent hierarchical modelling of species communities. Campylobacter lari , Escherichia coli, Pasteurella multocida, Chlamydiaceae and Mycobacterium spp. were found to be present on all islands in some, but not all, species. However, only E. coli was detected in all species. According to our modelling results, the influence of year and within-island site had limited influence on IA presence/absence, accounting respectively for an average of 1.0% and 1.8% of the variation in IA community. Including host species as a response variable produced a better model fit than including host species’ functional traits, highlighting the difficulty in simplifying systems by focusing on high-level functional categories. Model outputs show how each species influences IA distribution depending on IA traits, but no clear trend has emerged. Interestingly, burrowing species were less frequently infected with directly transmitted IAs, probably due to the low frequency of transmission events associated with their breeding features and limited social contacts. Our findings pave the way for further multi-dimension studies that would combine complementary approaches to disentangle the complex processes at play in the dynamics of hosts and IAs interactions.

Since 2021, the panzootic nature of high pathogenicity avian influenza (HPAI) represents an increasing threat to wild vertebrate populations. In this context, recent vaccines developed for poultry could provide tools for the conservation of wild endangered birds populations. The king penguin ( Aptenodytes patagonicus ), a long-lived seabird breeding in dense colonies with an extended chick-rearing period, has been identified as a possible surrogate species for a vaccination trial in a sub-Antarctic natural setting. Here we investigate the immune response of king penguin chicks to a self-amplifying mRNA vaccine against a H5 HPAI clade 2.3.4.4b protein. The cohort entails thirty vaccinated chicks (primo- and boost-injections), and 20 unvaccinated controls. Along 250 days of monitoring, the vaccinated chicks show a high and persistent immune response, granting a strong sero-neutralisation capacity against the virus, up to fledging. No adverse effects are observed. Screening for antibodies against unspecific avian influenza viruses suggests that no natural infection has occurred over the entire trial. The emergence of HPAI in the Southern Indian Ocean in October 2024 highlights the timeliness of such experimental tests. Our results thus show the vaccine could provide a potentially powerful tool for mitigation of avian flu outbreaks in the wild.

Background: The northern rockhopper penguin ( Eudyptes moseleyi ) is a threatened species, listed as Endangered globally by the IUCN owing to rapid population decreases in the past, combined with a limited distributional range. Their breeding is confined to five islands in the central South Atlantic Ocean (Gough, Nightingale, Inaccessible, Alex (= Middle), and Tristan da Cunha) and two islands in the southern Indian Ocean (Amsterdam and Saint Paul). Non-breeding birds forage widely in these oceans and vagrant individuals have been recorded in the Falkland Islands/Malvinas, South Africa, Kerguelen Archipelago, Australia, and New Zealand. The origins of these vagrant birds are largely unknown, and it remains unclear to what extent northern rockhopper penguins move between islands and oceans. Understanding connectivity between populations is essential for developing appropriate conservation strategies, especially as some populations may be at greater extinction risk than others. Results: Northern rockhopper penguins from the two oceanic basins are genetically distinct, with minimal evidence of migration between ocean basins. No substructure was detected within ocean island groups and although low, the level of migration between islands was sufficient to prevent genetic differentiation. Differential signatures of genetic diversity and inbreeding may also suggest some island populations are at higher risk of inbreeding depression. Conclusions: This study provides the first comprehensive genetic population structure analysis of the entire breeding range of the Endangered northern rockhopper penguin. This gives an unparalleled understanding of the connectivity within and between populations breeding in the Atlantic and Indian oceans, and highlights areas for further investigation. Knowledge of genetic structure and population dynamics can inform effective conservation management by predicting a species’ ability to adapt and remain resilient to local or global threats, including the increasing impacts of climate-driven changes in marine environments. Our results suggest that northern rockhopper penguins should be managed as two conservation management units to maximise the conservation of genetic diversity within the species and allow strategies to be developed that consider the different pressures affecting the populations in each ocean basin.