#Ocular findings in Northern #Gannets following an #outbreak of high pathogenicity avian #influenza #H5N1

 

Abstract

During 2021-2022, high pathogenicity avian influenza (HPAI) caused mass mortality in wild birds across Europe, with Northern Gannets (Morus bassanus) among the most affected. Following the outbreak, unusual alterations in the species' characteristic pale iris were observed in some individuals. Opportunistically captured gannets on Bass Rock (n=52), selected to represent a range of iris pigmentation, were examined. Slit-lamp biomicroscopy, indirect ophthalmoscopy, rebound tonometry and photography were performed. Iris pigmentation was classified as normal, mottled or black. Eleven birds underwent avian influenza virus (AIV) serology. Histopathology was performed on two eyes. Abnormal iris pigmentation was found in 74% of adult and immature gannets, with 61% affected bilaterally. Additional signs consistent with uveitis were present in 77% of affected birds. Iris pigmentation abnormalities were positively associated with AIV H5 seropositivity (Fishers exact test, P=0.018). Histopathology from affected eyes showed increased melanin deposition and disorganisation, including loss of a distinct anterior layer of melanocytic cells and hypertrophy of melanocytes within the iris stroma. Field conditions limited uniform lighting and concurrent serology. Iris pigmentation changes were associated with prior HPAI exposure and frequently accompanied by signs of uveitis, suggesting iris alterations may indicate past infection and potential chronic sequelae.

Competing Interest Statement

The authors have declared no competing interest.

Source: 

Link: https://www.biorxiv.org/content/10.64898/2026.04.15.718625v1

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Frequent seasonal #reassortment between high and low path #viruses drives the diversification of #influenza #H5N1

 

Abstract

Since 2021, highly pathogenic (HPAI) H5N1 viruses have spread across the Americas, diversifying via reassortment into new genotypes that have spilled into humans and livestock, raising fears of a new influenza pandemic. Pandemic lineages are typically associated with reassortment, but we currently have limited understanding of where and when reassortment is expected to occur, which limits our ability to assess pandemic risks. Using a dataset of 9,052 full-genome sequences, we show that reassortment and novel genotype formation are associated with seasonal variation in low pathogenicity avian influenza (LPAI) cases and with the spatial and host distributions of viral transmission. We pinpoint ducks, geese, and the Central flyway as frequent sources of new genotypes, and show that reassortment rates vary seasonally, driven by mixing between high- and low-pathogenicity viruses. Cattle spillover genotypes (B3.13 and D1.1) evolved during periods of high reassortment, implicating reassortment as a common occurrence in lineages evolving during particular time periods. Together, these findings reframe reassortment as a predictable ecological process, with direct implications for how surveillance and pandemic risk assessment should be designed.

Competing Interest Statement

The authors have declared no competing interest.

Funder Information Declared

US Centers for Disease Control Insight Net, CDC-RFA-FT-23-0069

Source: 

Link: https://www.biorxiv.org/content/10.64898/2026.04.17.719307v1

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