The report concludes that, at the time of writing, the outbreak is confined to the index case, which is also the first case and a secondary case as a result of transmission by vehicles, people or other things on the sites.
The report states that it is not yet possible to categorically identify the source of the outbreak and that no evidence has been found so far to indicate introduction via infected poultry or poultry products or vehicles/people transporting them, from countries that have undisclosed infection in their domestic turkey, geese and duck population.
Wild birds cannot be ruled out as a source of infection, but the report states that there is no evidence of H5N1 infection in the local wild bird population or in Great Britain as a whole. Defra hopes that continued surveillance may help clarify the infection status of the wild bird population. Further surveillance, testing and epidemiological work on the AI outbreak is ongoing.
In response to the report, Geoffrey Buchanan, operations director at Redgrave Park, said: "We continue to fully co-operate with Defra and all the relevant authorities in their investigation into the cause of the recent avian influenza outbreak.
"Defra has completed the culling of 96,600 birds at six farms, which we fully support. Avian flu was found in turkeys from one paddock at Redgrave Park farm and in a small number of turkeys at Hill Meadow farm. Defra praised the speed of the response by our staff on suspecting a notifiable disease, as this allowed the earliest possible containment of the outbreak.
"Redgrave Park is a free-range farm, where poultry was kept in field paddocks with access to housing during the day and at night. There are five paddocks for turkeys, one for geese and one for ducks. The birds did not have any access to the lake on the property, as we use electrified and permanent fencing, empty ground and a road to segregate our poultry from the lake. Similarly, our ducks, geese and turkeys were not raised or housed in the same paddocks.
"Defra stated that, on clinical inspection, the Hill Meadow flock appeared healthy, which indicates the infection was in its very early stages. We have now seen Defra's report in to the potential causes of the outbreak and agree with many of the conclusions. Redgrave Poultry purchased the affected farms at the beginning of this year and had already identified a number of these as issues that needed addressing. Due to our commitments to our customers and the lack of available organic land, it was simply not practical to make all of the planned changes for this season.
"We believe in the highest standards of organic and free-range farming for these production systems, so we have looked for lessons from the recent outbreak and have identified a number of improvements that we are implementing. We will continue to discuss and review these and other improvements with Defra."
Peter Bradnock, BPC chief executive said: "Defra has recognised the speed with which this outbreak was notified to Animal Health by Gressingham Foods and how useful that was in efficient containment and eradication; the poultry sector also recognises the hard work put in by government officials and the partnership approach we have further developed during this outbreak."
"The report highlights two areas - foremost how we handle the risk of infection to free-range and organic poultry flocks. We will be sitting down with the government and looking at further guidance on biosecurity for outdoor flocks; this will be essential, as consumers and retailers show an increasing preference for free-range poultry meat.
"This was an incident involving small, free-range flocks in one distinct section of a poultry company. They, and the wider poultry sector, will be looking at the lessons here in terms of movements between farms and the location of free-range flocks. There may be planning implications that will have to be overcome in relation to the poultry sector's ability to relocate some farms."