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Forum: In Wild Birds Does the Virus Die

04 August 2006

Allan – at 11:21

Question: We know that wild birds can be asymptomatic carriers. They can have the H5N1 flu and not have visable symptoms of it. It is just an intestinal virus that they can shed in their scat (Feces).

Can they rid them selves of the virus after their body has developed immunity? I see the storks in Vietnam in a park all have it and the Vietnamese solution is to kill them all. If the birds immune system can kill the virus, why not just isolate those beautiful birds untio they test negative for the virus. They would then have immunity and could go back on display.

Where am I wrong in my thinking?

Allan – at 12:13

I’ve tried e-mailing Niman on this, but he has not responded. Probably too busy with his work. IF birds can fight off the infection, why not just isolate them until they have fought it off and have immunity. No need to kill park or zoo animals if they can rid themselves of the virus. Right?

Allan – at 13:49

This is amazing. Nobody who posts on this board knows if birds have an immune system that is capable of killing the virus? Surly, I thought that there would be somebody who posts on this board who would know the answer.

Bronco Bill – at 18:24

If the birds immune system can kill the virus, why not just isolate those beautiful birds untio they test negative for the virus.

If the birds are simply carriers of the virus, and don’t show any symptoms, then the only reasonable alternative is to cull. The virus won’t just die if it’s living in a host, but the host may not show any outward symptoms of having the virus.

Bronco Bill – at 18:25

I may be wrong, but I may be right.

Allan – at 20:26

Bill, the virus uses the birds to replicate but may not do it so well in the birds that are asymptomatic. It seems logical to me that the virus can’t live forever and must be replicating to continue its species.

If so, and it kills cells in the process of replication as is always the case, then the bird’s immune system should be trying to fight against it.

Is there a virologist in the crowd?

pfwag – at 20:46

Birds carry West Nile virus and then mosquitos pick it up from birds and pass it to other birds, animals and people.

Why not H5N1? Exactly how is it spreading among the bird population?

Bronco Bill – at 21:28

If so, and it kills cells in the process of replication as is always the case, then the bird’s immune system should be trying to fight against it.

And, those infected birds eventually die from it.

Northstar – at 21:29

pfwag, if they have found H5N1 in human victims’ blood — and they have — I would think it’s entirely reasonable that this could be a blood borne pathogen.

NJ. Preppie – at 22:08

The article - Storks in Vietnam does mention isolating the storks that do not have H5N1, and disinfecting the bird cages; so it sounds like a zoo type park. Their waterhole may have been contaminated by wild ducks or geese. It’s true that some species are hardier and can survive the virus, and don’t remain carriers past a couple of weeks. If influenza doesn’t kill you, you’ll get better and not remain infectious, which is not to be confused with other diseases that can be chronically carried.

heddiecalifornia – at 22:16

There is a variety of equine virus called Swamp Fever that is spread by mosquito. If it doesn’t kill the horse, the horse becomes a carrier, so even if it recovers it is still a danger to other horses around it, so is put down. They are having an outbreak in Ireland right now — it’s from the U.S. and some horses here have resistance to it somehow.

  I am no expert by any means, but I recall reading that somewhere. 
  Oh, by the way, the Boston Globe this morning had a report on mosquito born encephalitis in Massachusetts, at least two human deaths; they are starting to use sprays. 

05 August 2006

pfwag – at 03:43

heddie - swell, I am going to Mass next week. I’ll take double the amount of CS.

The West Nile Virus also hits horses. It killed one down the street last year. We have our horses vaccinated for it.

06 August 2006

Allan – at 09:59

Bronco Bill – at 21:28

“And, those infected birds eventually die from it.”

Bill, I don’t think that is correct in most cases. I believe that asymptomatic birds can eventually rid themselves of the virus. Just like we can rid ourselves of any of the standard Bird Flu viruses within a week to ten days. I’ve had H1N1, H2N2 and H3N2 and got rid of the virus each and every time. I have not carried those viruses with me all of my life. I believe that the birds don’t either. They get sick. They get better and then have imunity. Life goes on!

This is what I believe until proven wrong. Are there any virologists in the crowd?

Allan – at 10:06

pfwag – at 20:46

“Birds carry West Nile virus and then mosquitos pick it up from birds and pass it to other birds, animals and people. Why not H5N1? Exactly how is it spreading among the bird population?”

pfwag, In birds, H5N1 is an intestinal virus and is spread via the oral fecal route. Most bottom feeding water birds poop in the water, and then sift through bord poop with their bills and injest many many little viruses. Bottom feeders are very very unclean birds. (I’m surprized that they did not get lumped in with the unclean pigs in the Hebrew sacred writing.)

Chickens and other birds will peck through their own dropppings looking for tasty morsels and pick up the virus that another bird left behind. Birds feed on human provided bird feeders where one infected bird leaves the virus behind and thousands of others come along and pick it up by stepping in scatta and then preen themselves and thus injest the virus. There are hundreds of other ways..

Racter – at 11:36

Allan:

“‘’It seems logical to me that the virus can’t live forever and must be replicating to continue its species.

If so, and it kills cells in the process of replication as is always the case, then the bird’s immune system should be trying to fight against it.’‘“

It’s not as clear-cut as you might think. Infection of a cell by influenza does eventually lead to the death of the cell. Some viruses produce “lytic” infection, during which the cell wall is specifically targeted for destruction, which causes massive numbers of virions to be released all at once. Influenza, however, is what is termed an “enveloped” virus. Newly-formed virions are released gradually via “budding” from the host cell, at which time the final stage in their construction is accomplished: coating of the nascent virions with a layer of protective material “stolen” directly from the outer surface of the host cell itself.

Exactly what it is that does cause the death of an infected cell is a tricky question, but it makes sense that while the virus is on board, the cell and the virus are in competition for resources, and when a point is reached at which the cell is no longer able to maintain its own functions, the game is over. How soon that point is reached will depend a lot on just how efficient the virus is at comandeering cellular machinery.

There is a lot of focus on receptor binding specificities, but access to the cell isn’t the only aspect of infection worthy of attention. We might hypothetically consider two strains, equal in that regard, but one of which was better able than the other to turn cellular processes to it own ends. We might consider the implications of this in terms of overall viral load on the host over some period of time, and we might consider the implications of that for transmissibility. Calculating this might get hairy.

A less aggressively replicating virus might perk away quietly for some time, staying below the host immune system’s radar. The more efficient replicator would be getting more “speed”, but less “mileage” out of each cell it invaded. Viral loads would have higher peaks, which would tend to facilitate better transmission to new hosts (at the price of being likely to trigger an earlier and more aggressive response by the host immune system — the more heavy-handed aspects of which, by the way, cause far more cell death in the typical infection than does the exhausting of cells by viral replication, and are responsible for much of what is observed as “symptoms”).

Viral shedding stops after seroconversion, but some species of waterfowl do not develop a detectable antibody response, and continue to shed virus for long periods. In some species, the virus wipes out entire flocks within a couple of days, while in others, seroconversion is the only evidence of its presence. The only solution to that puzzle I can come up with is that in the latter case, the virus has settled into a “sweet spot” between viral loads so low as to inhibit infection of new cells, and so high as to trigger host immune response.

Allan – at 19:30

Thank you.

07 August 2006

Allan – at 09:55

Of course with that understanding, can it now be inferred that the Chinese style Bird Flu shots for poultry only give the chickens the capacity to live with the H5N1 infection and that they can pass it on to non immunized birds?

If we believe that the virus can remain in the intestinal tract and not be totally killed or eliminated by the bird’s immune system than we have to believe that all those immunized birds could be a vast resevoir of H5N1 virus that can then be transmitted to people via contact with feces or bird intestines.

I would prefer that the vaccine and the normal immunilogical system of the bird help the bird kill the virus and totally eliminate it from the body.

At any rate, then I wonder if the only two solutions are to vaccinate and accept the pptential presence of the virus forever more, Or to cull any infected birds for evermore. This is a quandry.

Racter – at 11:50

Allan:

can it now be inferred that the Chinese style Bird Flu shots for poultry only give the chickens the capacity to live with the H5N1 infection and that they can pass it on to non immunized birds?

That’s certainly a concern.

Ideally, entire flocks would be vaccinated all at once, and kept isolated even then, so the only other birds they would have the opportunity to pass the virus on to would be unvaccinated sentinel birds deliberately introduced into the flocks for the purpose of monitoring the situation. In the real world, isolating birds is a tough trick to pull off. It’s hard enough with chickens, which aren’t known for their flying abilities, but with something like storks, it could get pretty expensive.

Initially, the Chinese reported very high efficacy for the vaccine they had developed. On close examination, however, it looks a bit like fishing in a barrel. You take an isolate, develop a vaccine for it, innoculate birds with it, then expose them to the virus and see if they get sick. The problem is that H5N1 is a moving target; nothing guarantees that in the real world, the birds you want to protect will be faced with the same virus you developed a vaccine against. Now, you might decide to go ahead and jab them anyway, in the hope that the vax might provide at least some protection, and it might even work. On the other hand, just as tossing out the last half of an antibiotic script is a recipe for antibiotic-resistant bacteria, a partially effective vaccine increases selective pressure on the virus, potentially leading to strains even more difficult to develop vaccines against.

At any rate, then I wonder if the only two solutions are to vaccinate and accept the potential presence of the virus forever more, Or to cull any infected birds for evermore. This is a quandry.

It’s an economic quandry as much as anything. The virus has firmly established its presence already, and most wild bird populations will have to fight their battles against it without much aid from us — in fact, many of them will have to continue to fight both it and us, and even more so if we percieve them as reservoirs for the virus. Certain species we depend on economically, and some of us depend a LOT on them, so we are motivated to do everything we can to save them. The “Hong Kong” model looks like about the best approach we have so far: keep waterfowl out of the markets, vaccinate the rest, and keep everything clean, clean, clean. The better the vaccines are, the better this will work, but perfect solutions are not visible anywhere on the horizon.

Got any good tofu recipies? (ARE there any good tofu recipies?)

Lily – at 12:04

Tried Tofu at the vegetarian kitchen in a Budhist monestary in many shapes and flavors. The only thing I found palatable on their menu was the cooked cabbage. You have to grow up with the stuff or be a vegetarian to fully appreciate it. As far as eating chicken, until I know otherwise its on my menu.When I go to the State Fair I look at the chickens, won’t be any different if I go this year. I’ll stroll among the chickens, and talk to the kids that raise them.

Allan – at 12:06

My wife has a breat stir fry recipe for Tofu with sliced vegitables that uses a dollup of peanut butter/crushed peanuts along with soy sauce that is darn good.

Put it over rice and it is a fantastic meal.

Only problem is, that one would tire of it eventually. Still, I think I could eat it three times a week as a main meal. Now, what else to eat?

Allan – at 12:08

Breat is actually Great. I am fat fingered.

10 October 2006

Closed - Bronco Bill – at 20:36

Closed to maintain Forum speed.

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