Shift in HPAI infection dynamics causes significant losses in seabird populations across Great Britain

Abstract

This focus article has been prepared by Marco Falchieri, Scott M. Reid, Craig S. Ross, Joe James, Alexander M. P. Byrne, Madalina Zamfir, Ian H. Brown and Ashley C. Banyard of the APHA; Glen Tyler and Emma Philip of NatureScot; and Will Miles of Scottish Oceans Institute, School of Biology, University of St Andrews.

Pathology of naturally acquired high pathogenicity avian influenza virus H5N1 infection in seabirds

“…The pathway of incursion in free-ranging seabirds is not understood but has been proposed to be either independent incursion or onward introductions from species movements between colonies and the movement of seabirds between mainland and islands particularly during the breeding season. 16,44 Herring gull and great skua can opportunistically predate or scavenge on other birds, 16,26,31,51 and this was observed in the outbreak in gannet colonies. Further, contact transmission between common gulls ( Larus canus ) and European herring gulls have been documented previously with experimental infection with HPAIV H5N1 clade 2.2 and H5N8 clade 2.3.4.4b.…”

“…These behaviours could facilitate dissemination of HPAIV especially if virus replication is prominent in respiratory and intestinal tracts. 16 Infections through such contact can lead to birds from other colonies becoming exposed and infected, which then themselves spread virus to new localities and susceptible avian species. Further, these seabirds are often in areas with high seal populations plus other scavenging mammals that can predate on sick or dead birds, and result in exposures of other host population types to infectious materials either directly or indirectly through the environment.…”

“…In contrast during summer 2022, infection in great skuas ( Stercorarius skua ) was detected several months earlier than seen during 2021 and was followed by extensive outbreaks in a number of shorebird species (Order Charadriiformes). 16 High mortality events in seabirds including northern gannet, great skua and several species of gull species were observed. 4,16 Seabirds from the Laridae family have been previously associated with infection with low pathogenicity avian influenza virus (LPAIV).…”

“…16 High mortality events in seabirds including northern gannet, great skua and several species of gull species were observed. 4,16 Seabirds from the Laridae family have been previously associated with infection with low pathogenicity avian influenza virus (LPAIV). 18,20,24,32,50 However, a recent experimental model has demonstrated previous exposure of the European herring gulls with LPAIV H5N1 or H13N6 only confer partial protection to subsequent HPAIV H5N8 clade 2.3.4.4b challenge.…”

“…Prior to the unusual increased in cases during summer 2022, HPAIV-associated disease in the Laridae has been sporadically reported in East Asia and Europe, often in small numbers. 1,2,12,15,34,36,37,39 More recently there has been an increased detection of HPAI positive seabirds or Charadriiformes, 16,27 and critically, mortality events in seabirds associated with HPAIV infection reported in the UK, Europe and North America. 5,6,44 Data collected through the avian influenza wild bird passive surveillance in Great Britain have shown a rise in high pathogenicity H5Nx positive birds within the Laridae family from 1.3% during the 2020-2021 season and up to 15% within the 2021-2022 season.…”