A Press Release from the
BRITISH ORNITHOLOGISTS’ UNION
Avian Influenza and other bird diseases
An international conference on avian diseases organised by the British Ornithologists’ Union was held in Peterborough on 20 & 21 November 2006. Presentations explored a wide range of issues relating to the epidemiology of avian diseases, their role in the dynamics of wild bird populations – including implications for bird conservation, and consequences of zoonotic infection for humans and livestock. The second day’s programme focussed specifically on Avian Influenza.
This BOU conference provided a timely opportunity to reflect on emerging issues and future priorities. This release also coincides with the Ornis Committee and the Standing Committee on the Food Chain and Animal Health (SCFCAH) in Brussels today which will review last winters Avian Influenza events.
Avian Influenza is a poultry disease
Avian Influenza of the HPAI H5N1 strain is clearly a poultry-based disease and now appears to be endemic to many parts of Asia.
Avian Influenza in wild birds
HPAI H5N1 has been found in a very small number of wild birds (miniscule when measured against the wild birds populations). The majority of outbreaks have been in wildfowl (swans, geese and ducks) and other water birds (e.g. gulls). The source of the disease in each case is unclear, but in the majority of cases investigated, the probable source was poultry farming activities or poultry-based products being used in the local area. For example, Lake Qinghai, China – a large outbreak in wild Bar-headed Geese and other species likely source was either from local poultry farming (on the lake shore and surrounding area) or, from the release of captive-bred Bar-headed Geese reared to supplement the wild population in order to maintain a high level of higher quality poultry meat for harvesting and human consumption.
Another significant feature of the disease in wild birds is that it rarely affects more than a tiny proportion of a local population; it is only in the close confines of poultry stock that massive mortalities are recorded. Similarly, it is only under these conditions that the disease has yet been spread to humans; there are no known cases of infection in the wild from wild birds.
Spread of HPAI H5N1 into Europe and Africa
The spread of H5N1 from Asia westwards into Europe does not follow natural migration routes of wild birds. The spread follows an east-west direction cutting across the north-south flyways of wild birds. The main line of spread of H5N1 closely correlates with the main east-west transportation routes, human movement and habitation.
In Africa, the isolated and highly separate cases are indicative of Man-moved poultry and not movements of wild birds. Nigerian officials were quick to announce that their confirmed cases were caused by the illegal importation (from the Far East) of poultry.
Movements of wild birds
Where the identity of the species of infected wild bird is known (many cases do not identify the infected bird to species), in most cases the species involved are not long distance migrants, but species which move relatively short distances, and mainly associated with dispersal movements (not migrations) associated with weather. For example, the short distance movements of Mute Swans dispersing from the freezing over of the Black Sea.
Where known long distance migrant species have been identified, the source of the infection remains unclear. For example, the Whooper Swan believed to be the source of the H5N1 outbreak in Ruegen, Germany, was reported to have come from the far south-east (i.e. Asia) of this species known breeding range. The bird in question was however individually marked (leg ring) and its life history known. It was ringed as a nestling in Latvia in August 2005, sighted at Ruegen with a marked sibling on 10.02.06, was found dead on 15.02.06, and its marked sibling was seen alive with the family group on 18.02.06.
Management of HPAI H5N1 outbreak in Britain
Cellardyke in Fife, Scotland remains the only confirmed outbreak of HPAI H5N1 in Britain. A single infected Whooper Swan was found on the shoreline. The contingency plan was rolled out and proved effective in managing the incident, containing the risk of spread and increasing surveillance of wild birds in region.
Investigation of HPAI H5N1 outbreaks in Europe
It is clear that all future outbreaks need to be collaboratively investigated by veterinary researchers, virologists and ornithologists in order to obtain the clearest picture of each outbreak.
Wild bird surveillance in Britain and Europe
Surveillance of wild birds in Europe was already high before HPAI H5N1. With the spread westwards if HPAI H5N1 surveillance was stepped up and have been increased again with the known occurrence of HPAI H5N1 in Europe. Britain in particular has detailed data on British wild bird populations and matching this to poultry activity in the Britain, priority surveillance areas have already been identified based on the possible association of higher risk wild bird species (wildfowl and other water birds) with poultry stocks (www.defra.gov.uk/animalh/diseases/notifiable/disease/ai/wildbirds/surveymap.htm).
Public health and risk associated with dead wild birds
The perceived public health risk of dead wild birds remains very high when in fact it is actually very low.
HPAI H5N1 remains a poultry-based disease. Unless this strain mutates into a human-infectious disease, the risk to humans remains extremely low. The known cases of humans contracting ‘bird flu’ in the Far East relate to individuals working with infected poultry. There are no known cases of infection in humans from infected wild birds.
Wild birds can however carry many other diseases, some of which are infectious to humans. Simple precautions such as thoroughly cleaning hands and any soiled clothing with soap and water after contact with any dead wild bird should be sufficient. Further information is available from Defra (www.defra.gov.uk/animalh/diseases/notifiable/disease/ai/wildbirds/index.htm#reporting).
Reporting of dead wild birds
Dead wild birds of all species should still be reported for several reasons. Dead swans, geese and ducks and other water birds, or any other species where HPAI H5N1 might be suspected, particularly those within the priority surveillance areas (see above) should be reported should follow Defra guidance (www.defra.gov.uk/animalh/diseases/notifiable/disease/ai/wildbirds/index.htm#reporting).
Across Britain, increased mortality in many garden bird species (finches, sparrows, doves, pigeons) has been occurring in recent years. This is not related to Avian Influenza. Research is being undertaken to investigate the cause and spread of garden bird deaths and further information is again available from Defra (www.defra.gov.uk/animalh/diseases/vetsurveillance/species/wildlife/gardenbirds.htm).
Members if the public experiencing garden bird deaths can contact the Garden Bird health Initiative Helpline 020 7449 6685 for advise.
Ringed birds can be reported via either of the above schemes or reported direct to the British Trust for Ornithology (www.bto.org).
Countryside access
The outbreak of Foot and Mouth Disease (FMD) in 2001 saw a closure of many countryside areas which were at little or no risk from FMD spread and infection. The Cellardyke Avian Influenza incident (above) illustrated that the countryside can remain open during such incidents which are being carefully managed and appropriate surveillance has been put in place. Residents in Fife heard and understood the message that the countryside areas around Cellardyke (including the Isle of May National Nature Reserve which was within the 20km surveillance zone) remained safe and open for access.
The BOU's Avian Influenza and other Bird Diseases conference was supportred by funding provided by Environment and Heritage Service (Northern Ireland) and Scottish Natural Heritage for supporting the conference.
ENDS
Further information available at http://newsbou.blogspot.com/ - including -
Abstracts from conference
Conference conclusions
British Ornithologists’ Union information
BOU contact: press @ bou.org.uk.
