This newspaper article (below the fold) proposes the $100-million question and then conveniently forgets to answer it. However, I am curious to know what you think;
[ ..] those who run intensive poultry farms are keen to point out that they protect their livestock from disease coming in from outside, by keeping them in sealed sheds, with carefully monitored ventilation.
They are also in a better position, they say, than farmers with free-range birds, to monitor their health and administer medicine if necessary.
[ .. ]
However, some farmers with free-range flocks are adamant that their poultry are healthier than intensively reared birds, and feel their exposure to the outdoors makes them stronger and less likely to succumb to disease.
To the best of my knowledge, free-range poultry are the same inbred stock as the intensively-raised birds, except they are kept outdoors. So my guess is the outdoor birds are no more healthy than the intensively-raised birds since they are more likely to be exposed to diseases carried by wild birds, whereas the indoor birds might be less likely to be exposed to the disease, however, the birds are so overcrowded and inbred that disease can rapidly spread and wipe out the entire flock once it makes an appearance.
Cited story.
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There is a difference between caged chickens and free-range chickens.
Wild chickens (from Southeast Asia) are predators, hunting for live prey -- bugs, grubs, worms, and anything small enough to kill quickly. Their domesticated descendants are predators as well. Given the chance to hunt for their food, chickens will hunt for hours, eating their catches. This gives them exercise, a diet of mostly fresh animal protein, and engages their normal defenses against diseases.
Caged birds simply feed. They are like hospital inpatients, not hunters. Their food is mostly cereal.
i realize there is a difference between free-range and "in patients" .. i am just wondering if the differences between their life styles is sufficient to overcome the other factors, such as inbreeding to the point that the birds are nearly identical, genetically.
There will be two levels to epidemic spread: the initial contact from outside, and then the spread within a farm/factory. The relative rates of the two should give a clue as to the answer.
I was at a seminar in November where some of the modelling ideas were presented: I don't know the literature that well, but it seems to have developed to the point where the models are available. You just have to understand random graphs....
Bob
i think it was the author of Omnivore's Delimma who reported, on NPR, that free range chickens are kept indoors for the first 5 weeks of their life, then a door at the end of the barn is opened so that they can go outside for the last week or two before the slaughter. The chickens don't go outside because they've never been outside, and it's scary. Granted, they aren't in cages, but they are hardly anything close to wild chicken preditors.
I think free range is a legal definition, rather like organic is a legal definition.
I found this info.from an article :Surveillance failure as bird flu hits UK farm? straw bedding that had been stacked outside and possibly infected by a passing bird?
Turkeys are so sensitive to the virus that someone needed merely to have stepped in infected bird droppings and tracked it into the barn.
There could well have been some around to step in. Wigeons, a dabbling duck, are wintering just 20 kilometres from the Suffolk farm outbreak in the Minsmere nature reserve, after spending the summer in Siberia. Flu spreads most effectively among wild birds on summer breeding grounds, with the highest percentage of birds infected by early autumn.
http://www.newscientist.com/article.ns?id=dn11109&feedId=online-news_rs…
I remain unconvinced that wild birds have much to do with these outbreaks. Even though lots of news stories on this topic contain some phrase like "infected wild birds can fly hundreds of miles", I have searched and searched to no avail to find any documentation of this assertion. Until that is proven, the facts tend to make me think that poultry practices like importing eggs (responsible for the outbreak in Nigeria a few years ago) might be a bit more of a likely suspect.
Please do recall that there is no proof that a wild bird can fly very far with this lethal virus, and even the WHO is fairly cautious about this hypothesis - "Should this new role of migratory birds be scientifically confirmed, it will mark a change in a long-standing stable relationship between the H5N1 virus and its natural wild-bird reservoir."
And the USFWS notes: "The precise roles played by migratory birds in the spread of H5N1 and its transmittal to domestic poultry and humans remain uncertain and continue to be debated by experts."
The timing of many outbreaks (in the dead of winter when migration has ceased) and the location of many outbreaks (not in the direct North/South routs of major flyways) also should contribute to a bit of skepticism about this hypothesis. See this site and this forum for some more healthy skepticism about this as-yet-unproven hypothesis.
Recently I came across an article on low pathogenic bird flu in migrating swans. I wonder if this was a case of the virus evolving away from virulence in wild population?
Recently I came across an article on low pathogenic bird flu in migrating swans. I wonder if this was a case of the virus evolving away from virulence in wild populations?
To the best of my knowledge, free-range poultry are the same inbred stock as the intensively-raised birds, except they are kept outdoors.
That very much depends on the individual farmer, at least over here in the UK. While all domestic fowl (and indeed all domestic animals) are inbred to some degree, some varieties are more inbred than others, and there are many varieties available.
Personally, I tend to think that if you were to set out to design an environment for the optimum development and transmission of novel pathogenic organisms, it would look a heck of a lot like a modern, intensive poultry farm.
i think it was the author of Omnivore's Delimma who reported, on NPR, that free range chickens are kept indoors for the first 5 weeks of their life, then a door at the end of the barn is opened so that they can go outside for the last week or two before the slaughter. The chickens don't go outside because they've never been outside, and it's scary.
Well, there's "free range" and then there's free range. Like most forms of agriculure, practices are not absolutely monolithic. But you can't necessarily rely on a "free range" label to tell you anything particularly useful about rearing conditions - it's basically a marketing tool. Personally, I always go for organic where possible, as the welfare standards are much stricter for the organic designation than for free-range - in the UK, anyway. I have a mate on a farm a few miles down the road who keeps organic chooks, and I know they're kept in very good conditions.
BREAKING NEWS & INVESTGATION: Bird flu: Hungary link probed
1:21am today
Bird flu may have arrived in the UK on "poultry product" imported from Hungary, a senior Government vet said.
The virus found at a Bernard Matthews farm in Holton, Suffolk, last week and the virus found in wild geese in Hungary last month may be "identical", said the Department for Environment, Food and Rural Affairs (Defra).
And scientists were checking food processing arrangements at a Bernard Matthews-owned plant in Hungary in an effort to trace the source of the deadly bug, added officials.
http://www.theherald.co.uk/national_news/index.var.39250.0.bird_flu_hun…?
For more detail on the developing story (surprise, surprise!) that the outbreak of H5N1 in England was due to human-assisted rather than wild-bird-assisted infection from Hungary, see this link
After all these examples of H5N1 transmission due to human transport of domestic bird products, or domestic bird workers, why are migratory birds still considered a primary source of infection?
That's a good question; why are migratory birds still considered a primary source of infection?
Here are a couple of hypotheses.
1) Wild birds don't have as much clout as industrial poultry farmers.
2) International flu experts don't know much about wild bird physiology or about their migratory routes and schedules.
3) The notion that wild birds could transmit this disease during migration gained a lot of early publicity and acceptance, based primarily on (1) and (2) above, and has caught on with both experts and the general public. So despite lots of evidence to the contrary, and a complete lack of evidence that any wild bird would get very far with tis disease, the notion is still prevalent. I have noticed that the initial page one stories about new outbreaks ALWAYS include a sentence or paragraph about the wild bird migration hypothesis. But the follow-up stories, describing a possible or likely human-assisted cause, are always on the back page. So it may take a long time to remove this (so far) unsupported hypothesis from the minds of officials and the general public.