Stable Isotope Analysis Reveals Common Teal (Anas crecca) Molting Sites in Western Siberia: Implications for Avian Influenza Virus Spread

The wetlands of southwestern Siberia (SWS) are a crossroads of bird migration routes, bringing avian influenza (AIV) strains that were previously isolated in different regions of the continent to Siberia. It is known that Anseriformes that breed in SWS migrate for the winter to central Hindustan or further west, while their migration routes to southeast Asia (SEA) remain unconfirmed. Here, we mapped the molting sites of the migrating Common Teals (Anas crecca) via analyzing stable hydrogen isotope content in feathers of hunters' prey and supplemented the analysis with the genetic structure of viruses isolated from teals in the same region. Post-breeding molt of autumn teals most likely occurred within the study region, whereas probable pre-breeding molting grounds of spring teals were in the south of Hindustan. This link was supported by viral phylogenetic analysis, which showed a close relationship between SWS isolates and viruses from south and southeast Asia. Most viral segments have the highest genetic similarity and the closest phylogenetic relationships with viruses from teal wintering areas in southeast Asian countries, including India and Korea. We assume that the winter molt of SWS breeding teals on the Hindustan coast suggests contacts with the local avifauna, including species migrating along the coast to SEA. Perhaps this is one of the vectors of AIV transmission within Eurasia.

Impact of Season on Intestinal Bacterial Communities and Pathogenic Diversity in Two Captive Duck Species

Vertebrates and their gut bacteria interact in complex and mutually beneficial ways. The intestinal microbial composition is influenced by several external influences. In addition to food, the abiotic elements of the environment, such as temperature, humidity, and seasonal fluctuation are also important determinants. Fecal samples were collected from two captive duck species, Baikal teal (Sibirionetta formosa) and common teal (Anas crecca) across four seasons (summer, autumn, winter, and spring). These ducks were consistently fed the same diet throughout the entire experiment. High throughput sequencing (Illumina Mi-seq) was employed to analyze the V4-V5 region of the 16sRNA gene. The dominant phyla in all seasons were Proteobacteria and Firmicutes. Interestingly, the alpha diversity was higher in winter for both species. The NMDS, PCoA, and ANOSIM analysis showed the distinct clustering of bacterial composition between different seasons, while no significant differences were discovered between duck species within the same season. In addition, LefSe analysis demonstrated specific biomarkers in different seasons, with the highest number revealed in winter. The co-occurrence network analysis also showed that during winter, the network illustrated a more intricate structure with the greatest number of nodes and edges. However, this study identified ten potentially pathogenic bacterial species, which showed significantly enhanced diversity and abundance throughout the summer. Overall, our results revealed that season mainly regulated the intestinal bacterial community composition and pathogenic bacteria of captive ducks under the instant diet. This study provides an important new understanding of the seasonal variations in captive wild ducks' intestinal bacterial community structure. The information available here may be essential data for preventing and controlling infections caused by pathogenic bacteria in captive waterbirds.

Gut Fungal Communities Are Influenced by Seasonality in Captive Baikal Teal (Sibirionetta formosa) and Common Teal (Anas crecca)

Understanding the dynamics of avian gut fungal communities and potentially pathogenic species across different seasons is crucial for assessing their health and ecological interactions. In this study, high-throughput sequencing was employed to examine the changes in gut fungal communities and the presence of potential pathogens between different seasons in captive Baikal teal and common teal. Between the summer and autumn seasons, both duck species showed significant differences in fungal diversity and community composition. A higher fungal diversity in both species was exhibited in the summer than in the autumn. Ascomycota and Basidiomycota were the two most common phyla, with a greater proportion of Ascomycota than Basidiomycota in both duck species in the summer. Interestingly, our study also identified animal pathogens and plant saprotrophs in the gut fungal communities. Seasonal variation had an effect on the diversity and abundance of both animal pathogens and saprotrophs. Specifically, during the summer season, the diversity and relative abundance were higher compared to the autumn season. In addition, there were differences between duck species in terms of animal pathogens, while no significant differences were observed in saprotrophs. Overall, the communities of the gut fungi, animal pathogens, and saprotrophs were found to be influenced by seasonal changes rather than host species. Therefore, seasonal variations might dominate over host genetics in shaping the gut microbiota of captive Baikal teal and common teal. This study underscores the importance of incorporating an understanding of seasonal dynamics and potential pathogens within the gut microbiota of captive ducks. Such considerations have the potential to drive progress in the development of sustainable and economically viable farming practices.