Thursday, November 03, 2005

Avian Flu and the Home Flock

Q: We keep a small flock of chickens. Should we get rid of them?

A: No.


Keeping chickens is a sort of window to the wider world. The everyday chores of caring for poultry is something that humans have been doing in similar fashion for most of recorded time. It is also something that is done, with little variation, almost everywhere that people live.

It was hard to stop thinking about those first bird flu reports from Asia. I saw fleeting images of beautiful birds on the evening news as they told of killing all poultry in whole provinces. At first I wondered how many interesting breeds of chickens were going extinct.

Then I worried about the households that owned those birds. The Food and Agriculture Organization of the United Nations tells us that one-quarter of the world's poor keep livestock and that livestock is often the "only means of asset accumulation and risk diversification that can prevent a slide into abject poverty by rural poor in marginal areas." Poultry is traditionally the livestock of choice for women because the animals are smaller and more manageable, and they don't require a long trek to pasture. If culling chickens was impoverishing households, these were likely to be the households headed by women. It was particularly hard to imagine impoverishing more women in Thailand, which has an active prostitution industry, and where AIDS is already entrenched. I wondered if culling chickens to prevent a potential bird flu epidemic was really preferable to leaving women and children with no economic alternatives except the sex trade and the very real AIDS epidemic.

For a while, watching the avian flu news was like watching two raindrops make their way down a windowpane. The virus would eventually make its way to my neighborhood, but would it be spread by humans or birds? When the tsunami hit Southeast Asia, the chicken farmer in me started to relax. It seemed inevitable that all of those people crowded into refugee camps would be the opportunity the virus needed to start spreading through the human population.

But it didn't happen that way. Now the nightly news tells us that the virus has been found in Turkey, then Romania, then London. The matter-of-fact explanation is that the virus is spread by the migration of "wild birds".

Bird lovers are, naturally, alarmed by this talk, especially when authorities start proposing to kill wild birds and drain wetlands. Seattle Audubon published a nice page on the implications for bird watchers and policy-makers. They note that songbirds are not known carriers of the virus and that keeping feeders in one's backyard is not a health risk. (Birds can spread other diseases to each other at backyard feeders, so it is a good idea to disinfect them periodically with bleach.)

Living the Scientific Life lays the blame for SE Asia's poultry epidemic on farming methods, not wild bird:
Bird flu is typically carried in the intestines of wild birds. These avian carriers often remain healthy but shed the virus in their feces, especially when they are under stress, thus transmitting it to other birds and also becoming ill themselves. In 1997, this bird flu virus roared onto the epidemiological scene by decimating poultry markets in Hong Kong and stunning health officials around the world by killing six people in that city. However, after extensive testing, scientists realized that this supposedly new virus had actually been identified decades earlier: It is a variant of the H5N1 virus that was first isolated in 1961 from terns in South Africa.

It is not known how this particular virus managed to disperse away from South Africa, but scientists suspect that it sequestered itself inside the intestines of migratory wild birds and hitchhiked around the world, as is typical for flu viruses. But this virus did not pose an international health problem until it reached eastern Asia, where huge concentrations of domestic poultry are found. Thus, combined with the effects of widespread poverty, particularly with its resulting overcrowding, poor hygiene and inadequate nutrition, H5N1 found itself in the ideal environment to enhance its lethality and transmissibility while also being presented with numerous opportunities to jump the species barrier into humans and other animal species.
I'm frustrated by the lack of hard science in the news reports about bird flu. (You can't understand viral diseases without understanding evolution, and if we're afraid to evolutionvoultion in school, what do you think is going to happen to our understanding of diseases like influenza and West Nile virus and AIDS?) The news reports repeat the same "facts" over and over again without asking the qualifying questions that might help us make sense of the situation. The avian flu situation is a dramatic picture of how science works; data is gathered, theories are posed, the next round of data either supports or disproves the current theories. The news media wants to make this all into a neatly packaged cause-effect-cure scenario, when no such scenario exists.

A population addicted to CSI-style dramas might just appreciate the science thriller of avian flu research, except that the tools and funds that real scientists have at their disposal grossly inferior to the glamorous world of TV crime labs. A January 2005 article in Nature, Vietnam's War on Flu, details the opportunity for studying human exposure to the virus in the countryside of Vietnam:

Vietnam's economy may be growing rapidly, but the vast majority of its people are still small-scale farmers who share their living space with chickens and ducks. "The hinterland of Vietnam is, for all practical purposes, one huge free-roaming farm," says Anton Rychener, who heads the Hanoi office of the UN Food and Agriculture Organization (FAO). This, experts agree, provides the ideal breeding ground for deadly strains of flu, which are likely to emerge when viruses pass between different species of livestock and people, and exchange genetic material in the process.

Yet, the few epidemiologists working in Vietnam complained that the rest of the world is interested, not in doing public health research in Vietnam, but in collecting samples and then high-tailing it back to their first-world labs. Many people have been exposed to avian flu in Vietnam, but only a small percentage appear to have gotten sick. It would be very interesting to check both populations (human and poultry) for avian flu antibodies in an attempt to answer some very basic questions: Are only a few poultry infected, or have most poultry been exposed? Are birds that are kept in less stressful conditions more likely to resist infection? Are people simply not getting infected or are they having very mild symptoms? If they aren't getting infected, why not? Is the virus just not good at infecting humans, or have the humans gotten an immunity from somewhere?

One of the researchers in the Nature article noted that most of the people who died from avian flu were young. He wondered if the elders had acquired immunity from some previous wave of poultry flu. I read accounts of the Spanish flu epidemic that my grandparents lived through, and once again, it was the young people in the prime of life that seemed most susceptible. The theory is that the disease killed by overactivating the immune system, thus people with the most healthy immune systems were the most vulnerable. Yet, the similarities between the two situations are interesting. Humpoultry pountry have been living in close contact for so long (yes, evolving together) that it is inevitable that the two species would occasionally swap viruses. Will it turn out that contact with poultry results in a immunity (or even a partial immunity)against the next wave of flu virus?

In the last few days, President Bush has announced a new avian flu initiative. The epidemiologists at Effect Measure are glad to see avian flu getting attention and funding, but they note that the US has been systematically dismantling our public health infrastructure since the Reagan administration. The worry that, even if we can catch up from years of failing to fund basic research, we may lack the networks that will be needed to distribute vaccine or flu drugs, or even to effectively monitor the progress of an epidemic. In the end, any funding of public health initiatives is an improvement over the "less government is always better" philosophy.

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So what does this mean to those of us who keep backyard poultry? The CDC's one-syllable answer, top of this page, to the only reporter who thought to ask the question, seems comical at best. Most of the information on poultry disease is aimed at farms with large indoor flocks. I found little information appropriate to a home flock situation; APHIS Tips on Biosecurity came as close as anything. They advocate housing birds away from foot traffic, quarantining new birds, disinfecting food and water equipment.

I will never be able to keep my chickens away from all contact with wild birds, but it seems that the wild birds I really have to worry about are ducks, geese, wild turkeys, and seagulls. It makes sense to dedicate a pair of boots for working around the chickens, and then avoid wearing that footwear to the piers, beaches, or golf courses where there is likely to be wild bird poop. My dirt floor barn, although it is great for keeping birds warm in winter and protected from predators, cannot be thoroughly disinfected. I may keep a much smaller flock next summer and house them in a structure that can either be cleaned or burned. I anticipate that at some point we will no longer be able to ship live poultry though the mail, so I am thinking about how to get along with that nasty rooster of mine, and how to encourage my hens to brood eggs next spring. I am culling hens this fall, keeping a handful of Partridge Rocks and Black Australorps as they have always been sturdy and healthy breeds. I need to make my whole setup leaner and more flexible, so I can change my methods as the situation unfolds.

The situation will unfold, as real science does, as a series of observations, guesses, experiments, and then more observations and guesses. All backyard poultry farmers are hands-on scientists, watching our birds, trying new methods, discarding what flops and refining what works, but always observing. We need to extend that home-grown pragmatism and demand that our tax dollars be spent on real science, where the theories spring from the observations, instead of visa versa.

Cornell Ornithology



The image at the top of the page is from The Red Jungle Fowl, posted by HS Wong of Kuala Lumpur. The Red Jungle Fowl (gallus gallus) is the original chicken, from which all domestic chicken breeds are descended.

The next avian flu post

2 comments:

John Daly said...

I have been donating money to the International Heifer Project to pay for their supply of rabbits to poor people in developing countries. If there is to be a big problem with poultry, then perhaps another source of protein from animals might be a help.

Susan Och said...

I'm afraid rabbits can't replicate the egg laying, bug and weed eating, grub and seed scratching economies of chickens.