Wild Ducks- H5N1

[JABIII]

April 21, 2006
No need to cull wild birds to stop birdflu: expert

By Maggie Fox, Health and Science Correspondent
WASHINGTON (Reuters)

Ducks and other wild birds are carrying the feared H5N1 virus, but there is no need to cull or otherwise target them as part of efforts to control the virus, experts said on Thursday.

Poultry are more important carriers of the virus, and H5N1 avian influenza has probably been circulating, unseen and steadily, for years in Southeast Asian flocks, the experts in the Netherlands and Sweden said.
Ducks and other wild birds are carrying the feared H5N1 virus, but there is no need to cull or otherwise target them as part of efforts to control the virus, experts said on Thursday.

"With our current limited knowledge on highly pathogenic avian influenza in wild birds, there is no solid basis for including wild birds in control strategies beyond the physical separation of poultry from wild birds," Ron Fouchier and Albert Osterhaus of Erasmus Medical Center in Rotterdam and a team of colleagues wrote in a report published in the journal Science.

"Even in areas with significant outbreaks in poultry, virus prevalence in wild birds is low, and the role of these wild birds in spreading the disease is unclear," they wrote.

"However, there is at present no scientific basis for culling wild birds to control the outbreaks and their spread, and this is further highly undesirable from a conservationist perspective," they added.

The H5N1 bird flu virus has spread quickly in recent months, and has been reported in birds in more than 40 countries across Asia, Europe and parts of Africa.

Humans rarely catch the virus, but it has killed 110 people and infected 196 since 2003. Experts fear the virus could acquire the ability to pass easily from human to human and could kill millions of people in a pandemic.

The virus is found naturally in ducks, and usually does not make them sick. But they can spread it, especially in their droppings.

"It has been shown that influenza viruses remain infectious in lake water up to 4 days at 22 degrees C (72 degrees F) and more than 30 days at 0 degrees C (32 degrees F) (7)," the researchers wrote.

DABBLING IN DISEASE

Dabbling ducks -- those that prefer to browse in shallow waters, such as mallards -- are particularly likely to carry the virus with no ill effects.

When chickens and ducks are allowed to mingle, chickens can become infected and H5N1 kills them very quickly.

Veterinarians and other animal-health experts say quick culling of poultry is the best way to deal with this, but there has been some debate about the role of wild birds.

"It is clear that the H5N1 problem originated from outbreaks in poultry and that the outbreaks and their geographical spread probably cannot be stopped without implementation of proper control measures in the global poultry industry," Fouchier's team wrote.

"Poultry trade and mechanical movement of infected materials are likely modes for spreading highly pathogenic avian influenza in general," they added.

"It is most likely that the H5N1 virus has circulated continuously in domestic birds in Southeast Asia since 1997 and, as a consequence, has evolved substantially," they wrote.

Something must have changed, experts agree. H5N1 has been around in birds since 1959 and a 1997 outbreak in Hong Kong, in which 18 people became infected, was quickly stopped with merciless culling and disinfection of bird markets.

But it re-emerged in 2003 and has accelerated its spread.

The experts suggested that the spring migration may not spread the virus much. Water fowl seem most susceptible to infection when they are young, and they cited studies showing that the viruses are more common in birds in the autumn and less common in the spring.

[JABIII]

Flu Spread Is No Reason to Kill Wild Birds, Study Says
James Owen in London
for National Geographic News

April 20, 2006

Wild ducks and other migratory birds could be important carriers of deadly bird flu, researchers say.

Even so, the infectious-disease experts say there is no solid basis for killing wild birds to protect poultry and minimize the risk of human infection.

The European team investigating the global spread of the H5N1 strain of avian influenza says certain duck species may be infecting wild bird populations.

Geese and wading birds are also possible vectors of the virus, the team says.

The team's study, to be published tomorrow in the journal Science, was led by Björn Olsen of Umeå University in Sweden. Olsen runs Europe's largest wild-bird flu-monitoring program.

Studies have shown that influenza viruses in lake water, generally passed via bird feces, can stay infectious for up to 30 days.

The migration or feeding behavior of dabbling ducks could at least partially explain the spread of the H5N1 strain of bird flu, the researchers add.

This group of duck species includes mallards, teal, pintails, and others that feed at or near the surface, where viruses in water are most likely to be picked up.

Perhaps as a result, dabblers have the highest known rates of avian influenza infection, the study says. For instance, nearly 13 percent of mallards tested positive for bird flu. Other species tested include the American black duck (18.1 percent), blue-winged teal (11.5 percent), and northern pintail (11.2 percent).

However, bird flu viruses appear to exist in ducks in a low-pathogenic form, meaning infection doesn't usually lead to severe illness and death.

Prime Hosts

"Dabbling ducks are for sure the prime hosts for low pathogenic viruses," said study co-author Ron Fouchier, a virologist at the Erasmus Medical Center in Rotterdam, Netherlands.

"But the big question is, How much of our knowledge about these viruses can we translate to high-pathogenic viruses" such as the H5N1 strain of bird flu?

In poultry avian viruses can mutate into more virulent influenza strains, including H5N1.

If this mutated virus then finds its way back into wild populations, the birds could then spread the disease through migration.

Some scientists have argued that wild birds infected with HN51 would be too ill to migrate. Swans, for instance, appear to be particularly vulnerable to the strain.

"Swans apparently drop dead quite easily, but they are unlikely to be the vector because they are not going to fly very far if they are dead," Fouchier said.

But the study team says that some birds that have been purposely infected for the sake of research show that wild birds can survive H5N1.

"For some reason H5N1 has adapted so it no longer kills dabbling ducks," Fouchier said.

This means the ducks may be able to spread the virus over a wide area.

The study team says migratory geese may also be vectors, because they often graze in huge flocks, a practice that could encourage transmission.

Migrating ducks, the researchers add, "could provide an intercontinental bridge" for bird flu to North America, which has not yet had any known cases of H5N1. (See "Bird Flu Will Reach U.S. and Canada This Fall, Experts Predict.")

No Wild Culls Needed?

However, there is currently no reason to cull wild birds to control the spread of H5N1, the study says.

Wild birds, though, should be kept away from poultry, the researchers say.

"For all of the outbreaks that have ever been recorded for bird flu, it's clear that the poultry-production industry itself is responsible for most of the spread through poultry trade [and the] movement of people and equipment between farms," Fouchier said.

"You can prevent your chickens and turkeys from getting into contact with wild birds by simple biosecurity measures" such as keeping farm birds enclosed, he added (photo: "Ducks in Detention").

BirdLife International, a global bird-conservation group based in Cambridge, England, says culling operations may in fact spread the virus to noninfected areas by forcing diseased birds to disperse.

Last week Shafqat Kakakhel of the United Nations Environment Programme spoke at a conference on bird flu and migratory birds in Nairobi, Kenya.

"Blaming avian flu on bird migrations is misleading. And a 'quick fix' of culling migratory birds is certainly not the solution," Kakakhel said.

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"experts say there is no solid basis for killing wild birds to protect poultry and minimize the risk of human infection. "


Unload the gun JAB, I know what you were thinking. You can start back killing in October. [img]smile.gif[/img]