Emergence of novel highly pathogenic H5N1 avian influenza in slender-billed gulls (Chroicocephalus genei) and gull-billed terns (Gelochelidon nilotica) at Dukan Lake, Iraq.

Authors

Nasih Ali, Harem Mustafa, Nadia Salih, Pavel Qader, Snur Hassan, Dashty Amin

Published in

Open veterinary journal. Volume 16. Issue 2. Pages 788-801. Epub Feb 28, 2026.

Abstract

Highly pathogenic avian influenza (HPAI) H5N1 continues to cause severe mortality among wild birds globally.
The present study aimed to investigate the mass mortality in Slender-billed Gulls (Chroicocephalus genei) and Gull-billed Terns (Gelochelidon nilotica) at Dukan Lake, Iraq, during the 2024 breeding season.
Field monitoring was conducted at breeding colonies, and dead carcasses were collected for necropsy, histopathology, and molecular analysis. Virus detection and genetic characterization were performed by reverse transcription polymerase chain reaction and sequencing. In addition, the viral lineage was inferred by phylogenetic analysis of the hemagglutinin (HA) and neuraminidase (NA) genes.
More than 3,200 gulls and terns were found dead, exhibiting severe neurological signs and systemic illness. Necropsy and histopathological investigations indicated significant multi-organ damage, with gulls showing more pronounced visceral lesions than terns, while terns exhibited greater neurological damage. Molecular characterization confirmed the virus as HPAI H5N1, and analysis of the HA and NA genes revealed that the strain from Dukan Lake falls within clade 2.3.4.4b, displaying a high genetic resemblance (>98%) with the recently identified H5N1 strain isolated from Mute swans in Kazakhstan. The virus showed multibasic cleavage sites characteristic of high pathogenicity but maintained receptor-binding specificity for avian hosts. Moreover, the results demonstrate the recent introduction of the virus via migratory flyways and the significance of gulls and terns in the disease ecology of HPAI virus (HPAIV).
This outbreak is the first recorded mass mortality of gulls and terns due to HPAI H5N1 in Iraq. The results emphasize the need for improved surveillance at migratory stopover and breeding sites to observe viral evolution, host susceptibility, and potential risks for cross-species transmission.

PMID:
42682318
Bibliographic data and abstract were imported from PubMed on 02 Sep 2026.

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