Wednesday, March 30, 2005

Avian Influenza and the 'War on Birds'

Millions of birds are being slaughtered throughout eastern Asia in an effort to contain the deadly “bird flu”. The avian influenza virus, which causes “bird flu”, is very contagious among birds, and often has dramatic consequences when it infects domestic ducks, chickens, geese and turkeys. Even though influenza often enters the domestic poultry population by crossing from wild to domestic ducks, domestic chickens are most acutely affected, usually hemorrhaging to death within 24 hours after infection.

But as illustrated by an editorial cartoon in the January 27 (2005) Bangkok Post that depicted migratory birds dropping “H5N1” fecal bombs from the sky onto an innocent planet Earth, wild birds have been vilified for a problem that primarily stems from human-based activities. In fact, the widely sanctioned practice of harassing and killing wild birds only makes the problem worse by distracting public attention and energy from the real problem, poultry farming methods.

“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.

To prevent the “bird flu” from becoming established in the area, panicked officials implemented a domestic poultry “depopulation” program combined with a vigorous campaign to slaughter wild and migratory birds and pet exotic birds. This extermination program has been ongoing for several years now, and has triggered increasing numbers of protests worldwide. Fortunately, after attending last month’s emergency Avian Influenza meeting in Ho Chi Minh City, Vietnam, United Nations officials finally ended their silence on this matter several days ago.

“Killing wild birds will not help to prevent or control avian influenza outbreaks,” asserted Juan Lubroth of the Food and Agriculture Organization (FAO) of the United Nations Animal Health Service. Even though wild birds do act as a reservoir for avian influenza viruses, “to date, there is no scientific evidence that wildlife is the major factor in the resurgence of the disease in the region.”

Further, avian eradication programs can have dramatic, unanticipated and tragic consequences, as illustrated by China’s Great Leap Forward Program in the late 1950s. This misguided program effectively declared war on birds by legitimizing the extensive slaughter of sparrows and crows, which led to the failure of rice crops and triggered widespread famine because these birds actually controlled crop pests.

The other main focus of this program, the unrestricted harassment of wild birds, also exacerbates the problem, according to William Karesh of the Wildlife Conservation Society, based in New York City. “Hunting wild birds, some of which are listed as endangered, or cutting down trees to destroy roosting sites, is likely to disperse wild birds into new areas, stress them further and could make them susceptible to avian influenza or other diseases.”

Instead of making war on wild birds, public health officials should instead focus their attention on designing effective programs that honestly assess and realistically deal with how poultry farming practices in the region contribute to the development of increasingly lethal avian influenzas. This would have the added benefit of improving public health in the region because other pathogenic organisms thrive in the same or similar conditions as avian influenza viruses.

First, more than 90 percent of domestic chickens and ducks in Asia are free-range birds that can intermingle with wild birds. These wild birds then potentially infect their domestic brethren with influenza viruses. These free-range domestic birds then bring the virus home to their roosts or carry it with them to market, where cramped, damp and filthy living quarters facilitate rapid transmission.

Such overcrowded living situations also provide avian influenza with many opportunities to infect other animal species. In fact, this season’s H5N1 variant is becoming progressively better at making this jump, a feat that greatly concerns health officials. By late 2004, this virus had “jumped” the “species barrier” numerous times by infecting 55 people, killing 48 of them. It also jumped into cats, another species that avian influenza had never before infected. It rapidly killed several endangered tigers and leopards after they ate infected chicken carcasses provided by zookeepers.

Second, intensive poultry farming is growing rapidly in Asia and as such, presents increasing opportunities for avian influenza to mutate. Intensive poultry farming relies upon overcrowding birds and raising them to a marketable size as quickly as possible so as to maximize profits. Because overcrowding birds stresses them and thus weakens their immune systems, they become vulnerable to infections that they normally could fight off. To avoid this problem, poultry farmers provide commercial feeds that are laced with small doses of several antibiotics. Antibiotics in feed conveniently mask latent disease problems and have the added benefit of increasing the rate of weight gain in young, growing animals, for reasons that are still not clear.

Antibiotics have no effect on viruses, but they do affect bacteria. In fact, widespread use of antibiotic-laced animal feeds by farmers around the world is one of the main contributors to the development of drug resistant bacteria, some of which cause pneumonia when inhaled by flu patients. Pneumonia, whether bacterially- or virally-caused, is the most common sequela of influenza. As if that was not bad enough, drug-resistant “super bugs” freely share their resistance genes with other species of bacteria in the environment that may have never been exposed to these antibiotics, some of which also cause disease.

Dr. Romeo Quijano, a medical doctor and toxicologist at the School of Pharmacology with the University of the Philippines, says “the massive use of antibiotics and many other toxic chemicals inherent in the capitalist food production system leads to the weakening of the natural capacity of both animals and humans to co-exist peacefully with microbes.”

Co-existence is certainly a worthy goal because, if anything, avian influenza is already established throughout the region. “This virus is not just endemic in Vietnam and Thailand,” says Dr. Guan Yi, an avian-flu expert at the University of Hong Kong. “In countries like Cambodia they don’t have a systematic surveillance program, so we don’t know yet. But I’m sure the virus is endemic in Southeast Asia.”

In 2004, H5N1 influenza was found in 10 countries and is known to be currently present in at least four; Thailand, Cambodia, Viet Nam and Indonesia. Estimates place the Asian population of domestic chickens in excess of 7 billion birds, even though more than 50 million have already been slaughtered and mass poultry killings are ongoing in Thailand, Viet Nam, Indonesia, Pakistan, China and Taiwan.

Faced with the magnitude of avian influenza’s distribution and its increasing capacity to jump into new species, the ultimate goal should be to prevent influenza infection of domestic birds, and not the killing of wild, migratory and exotic pet birds. The most immediate, realistic way to accomplish this objective is through improved biosecurity for poultry; this means (1) keeping domestic birds – particularly chickens and ducks – separate from their wild brethren using fences, (2) quarantining all poultry for at least several days before eating or selling them, and (3) thoroughly disinfecting baskets used to transport birds to market.

“We can talk about vaccine development, strength of surveillance, stocking of Tamiflu [an expensive antiviral drug], and all that, but in the end the reduction of pandemic risk will be decided by the number of chickens infected in Asia,” says Dr. Klaus Stohr who heads the World Health Organization’s Global Influenza Program.

It is short sighted, ineffective and potentially dangerous to exterminate wild, migratory and exotic pet birds when the real problem can be found in how people raise and market domestic poultry. The way to deal with this problem and to prevent a pandemic is by educating the populace about safe poultry husbandry, slaughter and meat-handling practices and also by investing money, materials and personnel into improving poultry farming methods in the region.


Sources


Avian flu: no need to kill wild birds [FAO Newsroom]

Farmers 'key to bird-flu control' [CNN].

Avian Flu: one more indictment of unsafe industrial food production [Centro Internazionale Crocevia]

Russian Scientists Join Effort to Track Avian Flu [Audio Link to All Things Considered, National Public Radio story, 28 March 2005].

My brain, which collects all sorts of information from the many (many!) papers, books and magazines that I read, from the scientists who tell me cool things, and from the superb university classes I've taken.

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More Essays about Avian Influenza;

Avian Influenza and 'The War on Birds', Part 2.

Avian Influenza and 'The War on Birds'.

Influenza: How Its Biology Affects Vaccine Production.

Public Confusion Surrounding Influenza.

Is Avian Influenza THAT deadly?

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This essay was recognized as among the "Best Medical Blog Writing" by
Medical Grand Rounds XXVIII.

The Tangled Bank

Included with "The Best of Science, Nature and Medical Blog Writing"
Issue 25.

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© 2004, 2005, 2006 by GrrlScientist

11 Peer Reviews:

Blogger Mike the Mad Biologist said...

Super post! You should have been a microbiologist...

9:25 PM  
Anonymous slimedog said...

Great run-down on bird flu, this really puts all information together in one place. I do worry about some of the experts, though:

'Dr. Romeo Quijano, a medical doctor and toxicologist ... with the University of the Philippines, says “the massive use of antibiotics and many other toxic chemicals inherent in the capitalist food production system..."' (my emphasis)

Perhaps Dr. Q. should take a look at what the communist system did to the Aral Sea before he lets loose with his economic adjectives. Intensive livestock farming is hazardous whether done by saints, sinners, cowboys, or Indians.

Of course, you weren't doing an experiment here, just an observational study, so any goofiness comes from your subjects, not your POV. Good stuff--keep it coming.

12:39 AM  
Blogger GrrlScientist said...

Thanks Mike .. I actually do have a microbiology/virology degree .. and worked in an HIV lab while an undergraduate .. it was great but I was not interested to work in a hospital (been there, did that, bzzzzt!), I instead wanted to grow up to be a "virus hunter"!

I agree with your comments about Dr. Quijano, Slimedog, and debated about including that quote. I finally included it because he does have a valid point, even if he has a wacky opinion about the source of the problem. I figured my readers are mature enough to get his point and not worry too much about his politics.

8:43 AM  
Blogger Rexroth's Daughter said...

It always seems to come down to a choice between the thoughtless brutal way: killing wild birds; or the thoughtful co-existing way: improving the practices of domestic bird handling.
The thoughtless way is fast and has the appearance of problem-solving (even when it has unintended consequences) The thoughtful way is slower and often requires people to take some personal responsibility. A choice between dead wild birds and personal responsibility? Mmmm...

9:43 AM  
Anonymous Anonymous said...

Today, mostly, I have been eating domestic chicken (not a real bird)mixed with cold cooked pasta and a me-made light salsa made from piri piri seasoning, tomatoes, balsamic vinegar and lemon juice. Helped along with a glass of Italian table wine. Earlier I had weetabix with sunflower seeds and banana with lashings of hot coffee.

1:32 PM  
Anonymous Nuthatch said...

Many thanks for this excellent post. There is so little regard for science, logic, and critical thinking these days. Ran into similar hysteria over West Nile Virus (which you inspired me to blog about today, though nowhere near as eloquently: http://nuthatch.typepad.com/ba/2005/03/bird_diseases.html)

3:43 PM  
Blogger Phila said...

Thanks a million for this post. This is something that can't be said often enough.

4:25 PM  
Blogger jojo said...

Great article! We just never learn. Much like the BSE crisis we in Canada are having with our cattle, you simply can't farm crappily and lazily.

5:21 PM  
Blogger GrrlScientist said...

Wow, such a big response .. I am pleased! I agree with your thoughts, Rexroth's Daughter, it's terribly frustrating that so few people see the folly of making birds the culprit in this whole thing when it's really due to the humongus congregation of poultry living in terrible conditions that have really created this problem! This is especially striking when one realizes that the first recorded influenza pandemic was recent; a little more than 100 years ago, actually. The reason? Influenza is a "crowd disease" that must have large numbers of vulnerable, closely-packed hosts available to keep it "alive". This is nicely provided both by large cities and by so-called modern poultry farming methods.

Thanks for reading, nuthatch, phila and Jojo, I am pleased to read that you enjoyed the story. I truly admire your blog name, too, nuthatch! Your namesakes are true avian cuties!

1:44 PM  
Blogger Donna said...

I agree with all the other comments on the excellence of this post. But one thing did occur to me as I read. We (westerners) are quick to damn the farming practices of those on other continents, but rarely reflect the same degree of scrutiny on our own practices.

I live in Vancouver, British Columbia. Last summer we had to "cull" all avians in the Fraser Valley. From farmed poultry to domestic birds, no winged animal was safe from the block. The reason, of course, was to try to slow the spread of the same avian flu that has decimated factory farmed birds in Asia.

2:26 PM  
Blogger NonToxic Chuck said...

I know quite a few people who had great anxiety over the bird flu scare. Some even stocked up food. Turns out, nothing has come of it.

10:04 PM  

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