Re: What is it with swans?

[Guest guest]

It could be that swans are particularly susceptible to H5N1. But then, where did they get infected? From their own species? From other bird species? Swans are large birds, so a dead swan carcass would not go unnoticed. ez <mamkmm2@...> wrote: Ok, a warning of a potentially dumb question ... but what is it with swans being the bird I am most often seeing reported as being found dead of H5N1?Is it just because they are a popular bird so get the press?Is it because they are so big they aren't being missed like maybe smaller dead birds would be?Are they that much more susceptible to H5N1 for some reason?Like I said, this might be a dumb question, but I am serious in asking it.Kathy in

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[Guest guest]

I don't think that it is because they are popular or that they are

the only noticed because they are big, although that probably helps

to get them noticed. But I have a feeling that dead birds do not go

unnoticed these days regardless of their size. On the other hand, I

do not know the answer and am also curious. Could it be because of

migration patterns?

>

> Ok, a warning of a potentially dumb question ... but what is it

with

> swans being the bird I am most often seeing reported as being found

> dead of H5N1?

>

> Is it just because they are a popular bird so get the press?

>

> Is it because they are so big they aren't being missed like maybe

> smaller dead birds would be?

>

> Are they that much more susceptible to H5N1 for some reason?

>

> Like I said, this might be a dumb question, but I am serious in

asking

> it.

>

> Kathy in FL

>

[Guest guest]

maybe their behaviour, their food or their long neck ?

They often clean their feathers, maybe feather mites are involved.

(freyana anserina ?) They did with their bill in dirts which could contain

feces of other birds, they often live near goose and whooper-swans

+mute swans live together

I'm just speculating here

[Guest guest]

Here is one person's opinion:

Avian influenza continued its advance across Europe: Health officials

in Poland reported evidence of the virus in a pair of dead swans. And

the Bulgarian government pledged to sanitize the area where four

infected swans had been discovered. The highly pathogenic H5N1 strain

has also turned up in dead swans in Austria, Bosnia, Croatia,

Germany, Greece, Hungary, Iran, Italy, Serbia, and Slovenia. Why do

we keep finding bird flu in swans?

They seem to be susceptible to the disease, and it's easy to notice

when they die. Scientists don't think swans are being infected at a

higher rate than other waterfowl. In fact, migratory ducks are

considered somewhat more likely than other birds to carry the

disease. But ducks are also less likely than swans to exhibit

symptoms of the flu.

Migrating birds often share space in shallow bodies of water where a

bird-flu infection can be passed around with ease. An infected duck,

for example, can shed the virus in its droppings and contaminate the

water. (The virus can survive for quite some time in a cold

environment.) Another bird—a mute swan, for example—might ingest some

of that water and develop the disease. Since epidemiologists think

the effects of the flu are more acute in swans, the swan would most

likely die first.

But the sudden rash of swan deaths might have as much to do with the

size and color of the bird as its susceptibility to the virus. Health

officials find out about possible bird flu cases only when someone

notices a dead animal. And people are more likely to notice a large,

lifeless, white swan than a little dead brown duck.

So, why did we see so many swan deaths in such a short time? (New

outbreaks were discovered in many of these countries within just a

couple of weeks.) No one knows for sure. At first ecologists thought

that a sudden blast of cold weather had flushed a population of

infected mute swans out of the Danube delta toward Western Europe.

But migrating mute swans travel only 30 miles to 60 miles a day, so

it's unlikely that they could have turned up in so many different

places in such a short time.

In fact, not all mute swans migrate—those in the Western part of

their range tend to be year-round inhabitants. Another explanation

for the deaths suggests that cold weather in Eastern Europe pushed

other waterfowl toward warmer climates, where they infected these

stationary mute swans. (The migratory mute swans from the east also

seem to have brought along the disease as they moved.)

Of course, you'll also get more reports of dead swans with each new

discovery of the virus in a dead swan. As the well-publicized cases

of the flu piled up in Europe, wetlands officials must have started

paying special attention to their already conspicuous swan

populations.

The link for this article is:

http://www.slate.com/id/2137688/

And ornithologist Feare says this:

Swans do indeed seem to be highly vulnerable and I cannot say why.

They do graze arable crops and grass, and they can forage on the

bottom of water bodies deeper than accessed by dabbling ducks. There

may also be some unknown physiological suscepribility - all

speculation at this stage. Mute swans forced to move by cold weather

may be more susceptible to AI due to stress/starvation. But cold

weather might also force them to exploit unusual food sources,

possibly bringing them closer to infected material of some sort.

We must, however, be clear about movements. The swans involved now

are most likely dispersing away from areas that are apparently

experiencing extreme cold in eastern Europe and western Asia. Mute

Swans cannot feed on frozen water bodies and so must move in search

of open water. These birds have not just arrived from Russia, but

will have spent some weeks in areas that we now know have infections

in poultry. Furthermore, they are definitely not on migration to

Africa. Migrant mute swans occasionally reach Egypt and

possibly Algeria, but uncommon (Birds of Africa). Egypt does have

some feral mute swans, as does the Eastern Cape of South Africa.

Whooper and Bewicks swans both rarely visit N Africa. The current

events, assuming they are moving away from ice, do suggest that

infected birds can travel a some hundreds of km before dying, or that

the infection is present over a wider area than we thought and they

pick it up on arrival at the new venue. The implications of this are

worrying.

> >

> > Ok, a warning of a potentially dumb question ... but what is it

> with

> > swans being the bird I am most often seeing reported as being

found

> > dead of H5N1?

> >

> > Is it just because they are a popular bird so get the press?

> >

> > Is it because they are so big they aren't being missed like maybe

> > smaller dead birds would be?

> >

> > Are they that much more susceptible to H5N1 for some reason?

> >

> > Like I said, this might be a dumb question, but I am serious in

> asking

> > it.

> >

> > Kathy in FL

> >

>

[Guest guest]

I actually think it maybe a bit deeper. It could be due to the molecular make up of swans with respect to their cell receptors and the relative concentrations and diversity. For example poultry are more susceptible to H5N1 in that they have higher mortality rates in part due to the presence of human like cell receptors in poultry these same receptors are however virtually absent in ducks. The range in pathogenicity amongst various avian species I think is a worthy investigation. It resembles the scenario with West Nile virus in the US where corvid (crows) were more susceptible to WNV infection than other bird species. Again I think this does deserve further investigation. This also brings up the question of the dynamics of H5N1 spread because more susceptible avian species will die whereas those refractory to developing the disease but susceptible to infection can serve effective carriers of

the virus. This thus underscores the necessity for such data on the markers or indicators of pathogenicity amongst different avian species. Kirksterten@... wrote: maybe their behaviour, their food or their long neck ? They often clean their feathers, maybe feather mites are involved. (freyana anserina ?) They did with their bill in dirts which could contain feces of other birds, they often live near goose and whooper-swans +mute swans live together I'm just speculating here

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