PRO/AH/EDR> Avian influenza (158): Antarctic (South Georgia) wild birds, H5N1, 1st rep


A ProMED-mail post
ProMED-mail is a program of the
International Society for Infectious Diseases

Date: Mon 23 Oct 2023
Source: British Antarctic Survey [edited]

Highly pathogenic avian influenza (HPAI) has been confirmed in brown
skua populations on Bird Island, South Georgia — the first known
cases in the Antarctic region.

Following reports of several potentially symptomatic birds and
unexplained mortality, British Antarctic Survey (BAS) staff on Bird
Island took samples for testing. The swabs were returned to the UK and
tested by the Animal and Plant Health Agency laboratories in
Weybridge, where they returned positive results for HPAI H5N1.

Natural pathways are the primary means of spread of HPAI, and it is
likely that the spread of the disease was caused by the return of
birds from their migration to South America, where there are a high
number of HPAI cases. BAS and Government of South Georgia & the South
Sandwich Islands (GSGSSI) remain vigilant for further cases, and
science and visitor programmes are currently continuing under enhanced
biosecurity measures.

BAS is working in close partnership with the GSGSSI, guided by their
tiered response plan to monitor and manage the outbreak. The most
recent version of these protocols can be found in the GSGSSI
Biosecurity Handbook

BAS operates 2 research stations on South Georgia, including one at
Bird Island where the confirmed cases were identified. As result of
the confirmed cases of HPAI, the majority of field work involving
animal handling has been suspended. Biosecurity measures continue,
including the enhanced cleaning of clothing and field equipment, and
observation of areas of high wildlife density.

Key elements of the wider science programme at Bird Island continue
under caution, including long-term monitoring of marine predators such
as wandering, black-browed and grey-headed albatrosses, northern and
southern giant petrels, macaroni penguins, and gentoo penguins. These
observations make Bird Island one of the most closely monitored
seabird colonies in the world, equipping scientists and
conservationists with indicators of change for species.

It is not possible to forecast the impacts of HPAI across South
Georgia, given that the patterns of transmission and mortality in
Europe and the Americas space [have] been highly variable. GSGSSI and
BAS will continue to work together to monitor the impact of the
wildlife at Bird Island, and the potential spread to other areas.

Avian influenza is a viral disease that primarily affects birds. Low
pathogenic avian influenza viruses are common in wild birds and often
cause no signs of disease. However, some strains of the virus
including H5 and H7 are highly pathogenic in domestic poultry and can
cause high mortality if they escape into wild bird populations. These
are known as highly pathogenic avian influenza (HPAI).

The current outbreak of H5N1 HPAI began in 2022 and has resulted in
the death of high numbers of seabirds in the Northern Hemisphere, the
south of Africa and around the Atlantic and Pacific Oceans and
throughout South America. Whilst predominantly still a virus that
affects birds, during the current outbreak some mammals have been
infected. Often this is due to predators and scavengers consuming
infected birds or carcasses, but cases have also been noted in some
marine mammals where this mode of transmission would not apply.

Although primarily a virus that is spread among birds, the World
Health Organisation (WHO) has noted that whilst the number of cases in
humans is extremely rare, the increasing number of detections of the
current H5N1 strain among mammals raises concerns that the virus might
adapt to infect humans more easily.

The primary means of spread of HPAI is through natural pathways and
the confirmed presence of the disease on the South American continent
made it highly probable that the disease would arrive in South Georgia
in the 2023/24 season. In readiness the Government of South Georgia &
the South Sandwich Islands (GSGSSI) updated its guidance on HPAI risk
and response in the Territory. These included enhanced biosecurity
procedures and mitigation measures to be put in place for different
groups/activities depending on the HPAI risk at each visitor landing
or science site.

Whilst the source of the disease on Bird Island is not certain, it is
likely that it was introduced via skuas returning from their migration
in Argentina where there are known to be a high number of cases.

The presence of HPAI could have serious implications for the
Territories abundant seabird colonies, and GSGSSI and British
Antarctic Survey are working in partnerships to monitor the ongoing

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