Here is the ,Risk Assessment' used by DEFRA. More like a 'No risk assessment, to me. The statement that pigeons have shed the virus in laboratory tests is one we haven,t been aware of before. As for the possibility of mechanical transfer, that's pure guesswork.
The need for a 7 Day Isolation period for birds returning in race time is tenuous and needs to be overturned for the sake of Channel Club racing.
Avian influenza (bird flu) - Veterinary advice on methods to reduce the likelihood of the transmission of highly pathogenic avian influenza (HPAI) for the gathering and flying of pigeons
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Risk questions addressed in this document
What are the risks of spreading HPAI infection through events involving the gathering and flying of pigeons in the British Isles and from continental Europe.
What risk management options are available for reducing these risks?
Introduction
This document represents current veterinary opinion based on the disease situation and the available epidemiological evidence at the time of publication.
Transmission of avian influenza viruses between susceptible birds occurs mainly through direct close contact with infective excretions and secretions, particularly faeces.
Spatial spread of HPAI infection can occur through:
Movement of infective birds.
Movement of fomites e.g. cages, clothes and footwear contaminated with infective faeces.
Evidence suggests that live poultry, captive birds and wild birds may play a role in the spatial and temporal spread of HPAI viruses.
There is emerging evidence, albeit circumstantial, that wild birds may have the potential to act as a disease reservoir for HPAI H5N1.
The overall risk of exposure to HPAI H5N1 in Great Britain is currently low.
Objective
To reduce the risk of spread of highly pathogenic avian influenza infection by domesticated pigeons (Columba livia) gathered together for the purposes of flying.
Summary of risk factors
The risk factors that need to be taken into account are:
Susceptibility of pigeons to infection with HPAI viruses and the ability of pigeons to carry, excrete and transmit HPAI viruses.
The risk that pigeons have been infected with HPAI viruses in the few days prior to a gathering or flight and are not showing clinical signs of disease.
The risk of spread of infection between pigeons at the gathering prior to release for a flight.
The risk of spread of infection via contaminated shoes and clothes of persons attending to the pigeons prior to the flight.
The risk that HPAI infection is present in wild or domestic birds in areas where pigeons are released for flight, in areas that they may fly through, or areas that they may rest in during a flight.
The risk that pigeons have direct or indirect contact with wild birds or domestic poultry during a race and spread HPAI viruses.
The risk that infected pigeons returning from a flight may spread infection to other pigeons.
General
Pigeon racing
The pigeon racing season begins in April and finishes in early October. Most races take place during the summer months. International races are scheduled for mid summer when day length allows birds to cover greater distances in a day.
Pigeon fanciers keep their birds in ‘lofts’. Prior to a race fanciers belonging to a pigeon racing club will gather their birds at their club where the birds are given a rubber race ring, placed in release crates and transported to the liberation site for release. For larger races pigeons that have been gathered at club level will then be taken to another location and loaded on to transporters with birds from other clubs for release.
For UK races birds are usually liberated within 24 hours of being placed in the release crates and for the longer international races birds are usually released within 72 hours. However if there is a delay to the start of the race, possibly due to adverse weather, this period may be extended.
Following release, for races within GB, birds are expected to return to their loft within 24 hours. For longer international races this period may be up to 72 hours (birds returning from southern France or from Spain may rest on the northern coast of France when night falls).
There are exceptions to this; a small number of weaker or disorientated birds may return several days after the others or return to a different loft altogether. Factors such as adverse weather may delay a large number of birds from returning within the expected timeframe.
In addition to organised races pigeons are also gathered together for training flights. This may be done on an informal basis. Birds from several lofts may be gathered together and transported to a location for release. Training flights begin in advance of the racing season.
Assessment of the risk
Risk factors
Susceptibility of pigeons to infection with HPAI viruses and the ability of pigeons to carry, excrete and transmit HPAI viruses.
There is variable evidence from laboratory and surveillance activities demonstrating pigeons to be susceptible to HPAI infection and disease.
A number of laboratory studies have indicated that pigeons have a low susceptibility to HPAI infection. However, pigeons have been demonstrated to be susceptible to Asian lineage HPAI H5N1. Viral shedding has also been demonstrated in some laboratory studies.
To date, available evidence suggests that pigeons have not contributed significantly to spreading HPAI viruses.
Current expert opinion, as supported by the European Food Safety Authority (EFSA) Expert Group report, suggests that pigeons may have the potential to act as one of the potential ‘bridging’ species between waterfowl and poultry i.e. that they may transfer disease from infective waterfowl to poultry.
A preliminary analysis of findings from the European wild bird survey programme indicates that between 1st February and 31st May 2006 there were no detections of HPAI H5N1 in pigeons in EU Member States. However the number of pigeons tested was only a very small proportion of the total. This does not provide sufficient evidence to support pigeons as a ‘non risk species’ with regard to HPAI H5N1 spread.
At present, there is not a substantial evidence base to define susceptibility of pigeons to Asian lineage HPAI H5N1. There is an uncertain level of risk that infected pigeons may spread HPAI following infection.
Mechanical spread of infective faecal material over short distances is a possibility. The risk of mechanical spread decreases with distance. Therefore when HPAI viruses are circulating in wild birds or poultry, carriage of infective material (i.e. faeces from infective birds) on the feet and feathers (mechanical spread) of pigeons is a potential, but low risk.
The risk that pigeons have been infected with HPAI viruses in the few days prior to a gathering or flight and are not showing clinical signs of disease.
Avian influenza is a notifiable disease in racing pigeons. Any person suspecting avian influenza in racing pigeons has a legal obligation to notify the State Veterinary Service (SVS).
Pigeons are regularly inspected by their owners; they are also checked individually when being placed in a crate prior to release at a liberation site.
It is likely that clinical disease would be detected by the owner or race handler.
The incubation period is the time interval from initial infection until the onset of clinical disease.
Incubation periods can vary depending on factors such as species, age, general health and viral dose. The maximum incubation period for Notifiable Avian Influenza as defined by the OIE (World Organisation for Animal Health) is set at 21 days. The average incubation period is 3-5 days.
During this period, if birds are infected, they will not show clinical signs of disease; infection would remain undetected.
Asymptomatic infection is also a possibility in infected pigeons, although there is insufficient evidence to define this risk.
Therefore it is possible that pigeons that have been exposed to an infective dose of avian influenza viruses prior to a race or gathering may be infected with avian influenza but not show signs. It would be expected that most birds would show signs within 3-5 days of infection. However some birds may take significantly longer to develop clinical disease than others.
The risk of spread of infection between pigeons at the gathering prior to release for a flight.
Prior to a race pigeons from several different lofts are placed into release crates. Pigeons remain in the crates for the duration of the journey to the liberation site. For international races this period may last up to approximately 72 hours, for GB races this is unlikely to be longer than 24 hours (source RPRA). If infection is present, there is a higher risk of spread owing to the increased contact between birds. The risk increases with the length of time birds remain in the crates. Infection may also be spread by contaminated crates or utensils.
It is normal practice for individual birds to be checked for signs of disease when being placed into the crates.
If infective birds are present this period represents a higher risk for disease transmission between pigeons in release crates from different lofts.
The risk of spread of infection via contaminated shoes and clothes of persons attending to the pigeons prior to the flight.
There is a risk that infection may be spread on contaminated clothing or objects. The risk will be greater for people that have recently been in contact with poultry, other captive birds or wild birds. The risk will be greater from those that have visited higher risk areas and had contact with birds.
Contaminated litter accumulated at the gathering is also a risk for disease spread.
These risks can be mitigated by the adoption of effective biosecurity measures.
The risk of spread of infection via contaminated litter and shoes and clothes of persons attending to pigeons is low if good biosecurity practices are maintained.
The risk that HPAI infection is present in wild or domestic birds in areas where pigeons are released, in areas that they may fly through, or areas that they may rest in during a flight.
Apart from a case in Cellardyke, Scotland where HPAI H5N1 virus was isolated from a dead wild Whooper swan (sampled on 31st March ’06), there have been no confirmed isolations of HPAI viruses in wild birds in the UK during 2006 or 2007, despite enhanced surveillance.
As of 05/03/07 the outbreak of HPAI H5N1 in turkeys in Holton, Suffolk (confirmed on 03/02/07) does not appear to be associated with infected wild birds or other UK domestic poultry or captive birds.
EU Member States are required to notify detections of HPAI H5N1 in wild birds or domestic poultry to the European Commission. Information for wild birds is published on the EU Animal Disease Notification System website.
Surveillance activities in domestic poultry and wild birds in EU Member States aim to detect any HPAI infection early.
There were widespread and sporadic detections of HPAI H5N1 viruses in dead wild birds and poultry in European Member States during the spring and summer months of 2006.
Since then there have been 2 confirmed outbreaks of HPAI H5N1 Asian lineage in domestic free range geese in Hungary (most recent 30/01/07) and 1 confirmed outbreak in indoor poultry in the UK (03/02/07).
There has not been a confirmed detection of HPAI H5N1 in EU Member States in wild birds since August 3rd 2006.
The consensus of opinion amongst national and European experts, including epidemiologists and ornithologists, is that the detection of HPAI H5N1 in wild birds in Europe is more likely during the autumn migration and over wintering period of migratory water bird species. These birds normally begin arriving in mainland Europe during autumn (August/September); they remain (‘over winter’) in Europe until the spring time (March/April). This may vary on an annual basis depending on climatic conditions.
Surveillance is a useful tool for detecting avian influenza occurrence in wild birds. However it has limitations; sample sizes are small in relation to the true wild bird population and therefore unlikely to provide an accurate estimate of prevalence. Negative findings provide evidence to support absence of disease, but it cannot be assumed that an area is free from disease in wild birds when HPAI viruses have not been detected. There is a possibility that infection in wild birds may go undetected.
There is ongoing wild bird surveillance across Europe. It can be assumed that the likelihood of HPAI infections in wild birds will be greater in areas where these viruses have been detected. Areas known to receive significant numbers of wild birds (of species thought to play a role in HPAI spread) from affected regions are also at an increased risk.
The risk that HPAI infection is present in wild or domestic birds in areas where pigeons are released, in areas that they may fly through, or areas that they may rest in during a race depends on the disease situation at the time of the race.
The risk that pigeons have direct or indirect contact with wild birds or domestic poultry during a flight.
Pigeons may rest during a race if they encounter adverse weather conditions, during a long distance race or at dusk. This provides an opportunity for racing pigeons to mix with wild birds (including feral pigeons) or poultry kept outdoors, or come into contact with a contaminated environment. If avian influenza infection is prevalent in an area there is the possibility that pigeons may be infected directly by contact with infective birds or indirectly through contact with a contaminated environment*.
There is the possibility that pigeons may clash with other wild birds in flight, although this is very unlikely to result in disease spread.
*The survivability of AI viruses in the environment depends on factors such as the nature of the environment, level of contamination, ambient temperature, presence of water, pH of water and intensity of sunlight. Wetland areas harbouring large numbers of infective birds will provide a better environment for survivability of AI viruses than warmer arid areas.
Some pigeons become disorientated during a race or are weaker. These pigeons may arrive at their loft significantly later than their loft mates. The likelihood of contact with wild birds or extensively kept poultry en route will be greater.
The risk that pigeons have direct or indirect contact with wild birds during a race is variable. In optimal conditions for longer races the risk will be higher than for short races. Adverse weather causing birds to be grounded en route will lead to a greater risk of such contact.
The risk that infected pigeons returning from a flight may spread infection to other pigeons.
It is unlikely that diseased birds would complete a longer race and return to their loft.
However the average incubation period for HPAI is 3-5 days. The duration of longer international pigeon races is rarely greater than 72 hours. Therefore pigeons that become infected during a race are likely to return to their loft before showing clinical signs.
There is also the possibility of asymptomatic infection, although there is insufficient evidence to define this risk.
The level of contact between pigeons within a loft is high. This provides a good opportunity for disease spread between birds.
If pigeons were to become infected just prior to a race or during a race through contact with infective wild birds or a contaminated environment there is a risk that infection will spread through the loft when infective birds return.
Summary
Although evidence from some studies suggests that pigeons have a relatively low susceptibility to HPAI viruses, infection in pigeons has been demonstrated.
It is difficult to estimate the probability of contact between pigeons and wild birds but the likelihood of such contact will be greater during races that are longer in terms of time and distance. Delays in return due to events such as adverse weather conditions are also more likely during longer races.
Pigeon racing from outside Great Britain carries a greater risk for introduction of HPAI than racing within Great Britain.
It is recommended that pigeon races do not take place from or through areas where there are known to be or have recently been confirmed cases of HPAI in wild birds or domestic poultry, or areas that are linked to these by a likely route of disease spread. This should take into account the geographical distribution of confirmed cases and the distribution of areas at higher risk. The period after which an area is deemed to be safe for pigeon racing will depend on an individual risk assessment taking into account the topography of the area, population density of higher risk water bird species and level of surveillance in the area.
Seasonal risk should also be taken into account; based on current available evidence and expert opinion the risk of HPAI H5N1 occurrence in wild birds in mainland Europe will be greater during autumn migration and over wintering period of wild bird species thought to be more likely to play a role in the spread of HPAI H5N1.
HPAI H5N1 outbreak in turkeys in Holton (03/02/07):
As of 5th March 2007 there is no evidence to suggest that this outbreak is associated with the circulation of HPAI H5N1 in wild birds or other UK domestic poultry or captive birds. Despite enhanced wild bird and poultry surveillance in the Suffolk and Norfolk area - following the outbreak - no HPAI viruses were detected. Surveillance and epidemiological findings supporting the absence of HPAI H5N1 - in poultry, captive birds or wild birds - from this area will inform the lifting of final restrictions.
There is no evidence to suggest that wild birds in the area were infected prior to the outbreak and no evidence to suggest that the virus was circulating in wild birds after the outbreak as a result of ‘spill over’.
Since there does not appear to be involvement of infected wild birds or other UK domestic poultry or captive birds in this outbreak the overall risk posed by pigeon racing remains unchanged as a result of the outbreak.
Conclusions
There is not a substantial evidence base to accurately define the level of risk that pigeons pose to spreading Asian lineage HPAI H5N1. However pigeons have been demonstrated to be susceptible to these viruses.
It is recommended that flying of pigeons should not take place in or through areas where HPAI is circulating in poultry or wild birds. This can also be applied to areas that, on the basis of a risk assessment, are deemed to be high risk.
Pigeon racing should therefore not take place from or through areas where there have recently been confirmed cases of HPAI in wild birds or domestic poultry or areas that are known to be linked to these by likely routes of disease spread.
Keith Hamilton, Veterinary Exotic Diseases, Research and Official Controls Division, 5th March 2007.
References
Narayan, O., Lang, G. and Rouse, S.T. (1969). A new influenza A virus infection in turkeys. IV Experimental susceptibility of domestic birds to virus strain ty/Ontario/7732/1966. Archiv fur die gesamte Virusforschung, 26, 149-165.
Slemons, R.D. & Easterday, B.C. (1972). Host response differences among five avian species to an influenza virus – A/turkey/Ontario/7732/66 (Hav5N?). Bulletin WHO 47, 521-525.
Panigrahy, B., Senne, D.A., Pedersen, J.C., Shafer, A.L. & Pearson, J.E. (1996). Susceptibility of pigeons to avian influenza. Avian Diseases 40, 600-604.
Perkins, L.E.L. & Swayne, D.E. (2002) Pathogenicity of a Hong Kong-origin H5N1 highly pathogenic avian influenza virus for emus, geese, ducks and pigeons Avian Diseases 46, 53-63.
Nettles, V.F., Wood, J.M. & Webster, R.G. (1985) Wildlife surveillance associated with an outbreak of lethal H5N2 avian influenza in domestic poultry. Avian Diseases 29, 733-741.
HPAI information on the OIE website
Animal Disease Notification System
European Food Safety Authority
Page last modified: March 16, 2007
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