It didn’t take a lot ornithological nous to realise that nine Mute Swans with H5N8 bird flu virus in Dorset were quite likely to have come from Abbotsbury Swannery – as surmised in this blog on Saturday and trumpetted by the national press yesterday (Guardian, Telegraph, BBC). Defra doesn’t test additional birds from a location once the virus is confirmed so there may be many more Abbotsbury Mute Swans which have died from bird flu over and above the nine carcasses which contained the virus (and are assumed to have died because of it). About twice as many Mute Swans have died at Abbotsbury this winter (c80) compared with a normal winter. Interestingly it appears that young birds (hatched this year) make up most of the birds which have died.
There continues to be speculation on Twitter about Pheasants and bird flu. This is hardly surprising since the Pheasant is the UK’s most numerous ‘wild, but not really wild’ bird because 35 million (or 45 million, or 50+ million depending on who you believe) Pheasants are released into the countryside every year for ‘sporting’ purposes. If you have an exceptionally good memory of this blog, then you will recall that nearly three years ago I asked my then MP, Andy Sawford, to ask Defra some questions about Pheasant and Partridge imports (see here, here and here).
The second of those posts sets out the official figures on numbers of Pheasant, partridge and ‘galliform’ poults imported into the UK each year – almost 8 million. That is a lot of birds, hatched abroad, transported to the UK, kept in pens and then they become, as if by magic, wild birds when released to be shot. But from the point of view of bird flu I assume that most of these birds are imported in the summer and not at this time of year – is that right does anyone know?
Defra also wrote at that time: Pheasants are not generally considered a risk of transmission of avian influenza: these viruses are usually found in wildfowl and it is contact with wild or farmed ducks, geese etc that is high risk.
Of course you will find more bird flu in waterfowl if those nice people at Abbotsbury, WWT and RSPB send in lots of dead ducks, geese and swans for analysis and Pheasant shooters don’t, so on the face of it we shouldn’t give too much weight to the reported number of positive cases in particular species or groups of species. There may be a danger of confirmation bias here. It’s not clear that Defra records the number of negative cases by species so it may not be possible to compare the percentages of positive and negative tests by species.
I’ve asked the Defra Chief Vet, Nigel Gibbens, on Twitter (@ChiefVetUK) about whether any Pheasants have been tested for H5N8 but he hasn’t replied. This is fair enough as I am sure he has a lot on his plate. But an FoI will be heading his way once we get past this outbreak of H5N8.
It’s all very rudimentary stuff, and I fear that useful information on wild birds and H5N8 isn’t being collected. All too often in my past dealings with Defra vets it seemed that a wild bird was a wild bird was a wild bird, rather than them being different species with different ecologies and movement patterns which would affect their likelihood of transmitting avian flu viruses.
- Posted in: bird flu