Although we have seen little media coverage of avian influenza (AI) of late, the Soil Association is still working hard as part of Defra's AI stakeholder group to ensure that the organic sector is fully represented. This page provides an update on the mapping and modelling work that Defra has been doing and on the position for the potential use of vaccination for AI. Mapping the risk One of the first things the Soil Association asked Defra to do last year was to provide migration maps so that poultry producers could assess whether they were in particularly high risk areas for the potential introduction of AI via migratory birds. Since then Defra have been working hard on modelling both migration of the wild species thought to be most likely to carry AI, as well as the position and size of domestic poultry units. Defra have now gathered a huge amount of information on a range of wild bird species, targeting those that are most likely to potentially carry avian influenza. The data comes from surveillance in other EU countries, results from British and Irish ringed bird surveys, and the monitoring of wild bird sites across the EU. This has allowed Defra to plot the range of individual species on a month by month basis to a level of detail that not only shows where the majority of the population is at any one time, but also the limits of any sightings for a particular month. Defra officials have then looked at the effect of weather. For example, last winter we know that the exceptionally cold weather pushed birds westward, bringing species that we would not normally expect into the country. The modelling therefore has to take account of these potential variations. In order to map domestic poultry Defra have used data from the poultry register, poultry clubs and other organisations. The map is not simply based on the numbers of birds in any one place but also the perceived risk. This therefore means that they have ranked free range and organic birds as potentially at greater risk than, say, an indoor hatchery. Other information like the position of areas of water used by migratory birds is also taken into account. The models are 'live' and are constantly updated with any new information, such as ornithologists reporting sightings, meteorological data, and positive AI tests from Europe and beyond. Defra's disease priority map When putting together the wild bird information and the domestic bird information Defra have mapped the UK down to 10km squares, with each square assigned a level of risk of incursion of H5N1 avian influenza. From these 10km squares they have now developed a county-by-county disease priority map. From the point of view of monitoring and testing dead wild birds found by the public it is likely that they will only be interested in those found in the priority areas (unless of course there is an unusual find such as lots of different species found dead together). Defra's density of domestic poultry map Another interesting Defra map is that of the density of domestic poultry. The map on page six is probably most interesting, which shows the density of farms and other premises that have poultry. These maps can indicate if you are in an area where there is potential risk of AI incursion from wild birds. Some 'hot spots', such as the Devon and Somerset border, are clearly apparent on the map. Every poultry producer should have a plan about what they could do if there was an order to enclose birds – even if your farm is not in a priority area. Defra are clear that any order to house birds would be proportionate to the risk, and they would only issue such an order if there is an incidence of AI. Even then, they would try to both restrict the area affected and minimise the length of time that birds must be enclosed. Defra will only ask producers to house birds in the event of an outbreak if it is practicable for them to do so. If you cannot house your birds you will need to have some other way of stopping your birds from interacting with wild birds. Read Defra's current advice on separating domestic birds from wild birds. Previous Soil Association guidance on enclosing birds is also still available. Limitations to modelling There is no existing UK transmission data for highly pathogenic AI which would make disease models more accurate. Although data is available from the Netherlands, their parameters in terms of the set up and density of their poultry sector is so different that Defra did not feel that using this data would give any better models. Vaccination First some good news: the Soil Association has always believed that vaccination should form part of Defra's armoury for the control of any potential AI outbreak. We were therefore pleased to see that, after our lobbying on this issue, Defra now have five million doses of vaccine in stock with a further five million on the way. The first five million doses have a shelf life of two years. For the second five million doses there is an agreement with Intervet that they will always have five million doses available for the UK and this stock will be rotated so it does not go out of date. There are still discussions about how and when this vaccine could be used. To see the Soil Association's suggested trigger points for vaccination see the 18 July 2006 statement, Soil Association Position on Vaccination to Control Bird 'Flu in Domestic Poultry and Waterfowl – Strategic not preventative. Plan for actually vaccinating birds A plan to vaccinate birds is being drawn up and has been discussed at AI stakeholder meetings. This goes through the practicalities of getting vaccine to vets and poultry keepers, as well as the monitoring process they would need to adhere to once they had vaccinated. The aim would be for poultry keepers to vaccinate their own birds with the support of their vets, as necessary. We would be very interested to hear about your views on the practicalities of doing this. For example, would you be happy to inject your birds? Could you catch them easily? Submit your views to Anna Bassett on 01822 880334 or abassett@soilassociation.org Cost of vaccination Defra have carried out some preliminary costs for use of vaccination. They looked at flocks of 50 or less and those of 10,000 or more. The figures they have come up with seem rather high and they have agreed to look at them again. For the small flocks they estimated a cost of £20/bird for one years cover. This estimate was based on the assumption that all the vaccine would be presented in 1,000 dose bottles, which had to be used within 24 hours of being opened. The cost of vaccine was therefore artificially high due to anticipated wastage of vaccine. Defra have now agreed with Intervet that some of the second batch of the vaccine that will be held for the UK will be supplied in 40 dose bottles, and this should help to reduce the cost. The rest of the cost includes delivery, syringes, labour and so on, as well as the cost of monitoring. The cost for large flocks is estimated at £2/bird. This is still a significantly higher than estimates that the Soil Association made last year, using information from one of the vaccine manufacturers. At that time the Soil Association predicted a cost of 20–30p/bird vaccinated. Having spoken to vaccine manufacturers again we still think our estimate is more accurate – at least for larger flocks. The cost of monitoring could be the key here and we are anticipating more information from Defra on how they developed their costs. Vaccine developments The new Intervet vaccine is regarded by many as an important new development: it could potentially be delivered in water or by misting it over birds so that it enters via the mucus membranes. However, the vaccine is still undergoing trials to establish its efficacy. The current available vaccines carry risks, primarily due to them not being effective enough and the problems of 'silent spread' due to vaccinated birds still shedding virus. This means that you have to increase the risk of disease quite markedly (as in our suggested trigger points for vaccination) before the balance between the risk of vaccinating and the risk of not vaccinating changes. The new vaccine would answer a lot of these questions if it proves as effective as they hope in field trials. One concern was that even if it proved effective in trials that it would take a long time to gain approval for use within the EU/UK. There is an allowance that came out of foot and mouth disease outbreak that if a product is found to be effective in trials then it can be used while it is going through the whole licensing process, rather than waiting until that is completed. Defra say that they think that if the vaccine did prove effective in trials we would be 'pushing at an open door' to get it in use as quickly as possible. The Soil Association will keep an eye on this issue and apply pressure, as necessary. Interesting developments A couple of interesting developments came up at a recent stakeholder meeting. There have been two instances in the last few months in zoos in Europe of single juvenile birds contracting the high pathogenic H5N1 but not passing it on to any other birds. There was also a case in Poland where one swan out of a group of 100 birds in a park died of high pathogenic H5N1. The remainder of the group was tested and 30 of them were found to be carrying H5N1, yet were still living, while the remainder appeared totally unaffected. We asked whether this meant that some sort of immunity was developing; the answer was that this was certainly a possibility. This is the second year that high pathogenic AI is circulating in Europe; these were adult birds and there was a possibility that some immunity was developing. This could either be from earlier exposure to high pathogenic AI or the fact that previous exposure to low path could provide some immunity to other forms of AI. We are talking about a disease that mutates and all the media predictions so far have been that any mutation will naturally lead to a potentially stronger and more dangerous virus. Aside from the build up of immunity among wild birds, we could also be witnessing a mutation to a less virulent form of the disease. Some epidemiologists did comment right at the beginning of the outbreaks of high pathogenic AI that very virulent virus mutations do not tend to last very long as they are so effective at killing their hosts that they themselves die out. This issue is that we just do not know enough at the moment to be able to gauge whether these anomalies are due to the build up of natural immunity or change in the virus – or even both. Summary The Defra modelling work mentioned above takes into account any positive cases of AI across Europe and beyond. Cases have been very limited over the last few months. From all this work, Defra have reached the following broad conclusions: Large outbreaks of long duration are unlikely (a large outbreak is defined here as being 10 or more premises) Defra's control plan, as outlined in its AI contingency plan, appears to be adequate Vaccination is not an adequate response to the current risk (this would represent a pre-outbreak use and the Soil Association would agree with this position) Vaccination could have a role to play if there was a localised outbreak Vaccination could also be used if there were large outbreaks The Soil Association is pleased that vaccination is now being taken seriously as an option. The position above – that vaccination could have a role to play in certain circumstances – matches with the Soil Association's view. Vaccination should be a tool for the control of AI but, as with any vaccine, under organic standards we should only use it when the risk of disease outweighs any downside of using the vaccine. The Soil Association's position can be summarised below: The Soil Association does not support the preventative use of vaccination ahead of an outbreak of high-pathogenic AI in UK domestic poultry or waterfowl. This is because we believe that: Present risk assessments indicate no need to vaccinate immediately Preventative vaccination runs contrary to organic principles of minimising the use of any vaccine until absolutely necessary, or required by law Current available vaccines have limitations: it takes several weeks for immunity to develop, so there is a risk of virus shedding in vaccinated birds which could mask the presence and spread of the disease The Soil Association does support the use of vaccine if certain 'key triggers' are met, as outlined below: Birds are enclosed/isolated due to AI restrictions for a considerable time, and there are further outbreaks of the disease Culling is failing to control the disease The disease has become endemic in wild birds in the UK To find out more about the Soil Association's suggested triggers for vaccination and the justifications, read the 18 July 2006 statement, Soil Association Position on Vaccination to Control Bird 'Flu in Domestic Poultry and Waterfowl – Strategic not preventative. If you have any questions or comments on this page or any other aspect of the Soil Association's position on avian influenza contact Anna Bassett on 01822 880334 or abassett@soilassociation.org » download this information as a PDF [PDF, 1.5 MB] Published: 19/10/2006 » Back to advice for organic poultry farmers