BBC Ducks are 'a big' bird flu threat

[Guest guest]

>BBC DAILY E-MAIL: UK EDITION

>Tuesday, 19 July, 2005, 8:00 GMT 01:00 -07:00:US/Pacific

>

>

> * Ducks are 'a big' bird flu threat *

>Domestic ducks may pose a major threat of

>spreading avian flu to animals and humans,

>scientists believe.

>Full story:

>http://news.bbc.co.uk/go/em/-/1/hi/health/4692763.stm

>

Ducks are 'a big' bird flu threat

Domestic ducks may pose a major threat of

spreading avian flu to animals and humans,

scientists believe.

 

Not only do they harbour the virus with few

signs, making it hard to spot, the virus mutates

in them, meaning they could cause a large human

outbreak.

 

The International team, including experts from

China, Indonesia, Thailand, the US and Vietnam,

tested ducks in the lab.

 

Their findings appear in Proceedings of the National Academy of Sciences.

 

Ducks may play a role in spreading further outbreaks

The study authors

 

Millions of chicken and other fowl have died or

been destroyed in bird flu outbreaks in several

East Asian nations since 2003.

 

The deadliest strain - H5N1 - has killed 38

people in Vietnam, 12 in Thailand and four in

Cambodia since late 2003.

 

Humans catch the disease through close contact with live infected birds.

 

Birds excrete the virus in their faeces, which

dries and becomes pulverised, and is then inhaled.

 

To date, the main focus has been on infected

chickens. However, more recently cases have been

reported in domestic ducks.

 

Trojan horse

 

Now Dr Robert Webster, from St Jude Children's

Research Hospital in Memphis, the US, and

colleagues believe these animals have become the

" Trojan horse " of the virus - a silent reservoir

of infection.

 

They infected two four-week-old mallard ducks

with various strains of the virus isolated in

1997-2004 from humans or poultry throughout South

Asia, including H5N1.

 

Four hours later they placed these in the same

cage as two other non-infected ducks.

 

The researchers observed what happened to the birds over the next 21 days.

 

Both of the infected ducks shed the virus,

mainly through the upper respiratory tract rather

than in their droppings.

 

Both of the other two ducks caught the virus,

and one completely cleared it by day seven.

 

The team found that viral characteristics had changed since 2002.

 

Ducks infected with H5N1 from 2003 or 2004 shed

the virus for 11-17 days, a longer transmission

time than pre-2002 strains.

 

Although the virus no longer caused disease in

healthy ducks exposed to it, it was still able to

cause disease in chickens.

 

Dr Webster and colleagues told PNAS: " Here we

show that these H5N1 viruses are reverting to

nonpathogenicity in ducks.

 

" Since this newer strain is still potentially

harmful to humans, ducks may play a role in

spreading further outbreaks. "

 

The real danger is that a mutation will arise

that will mean the virus can spread directly

between humans.

 

Species jump

 

A spokeswoman from the Health Protection Agency

said: " The research offers some interesting new

information relating to disease in ducks.

 

" However, the relationship of this work or

implications for human health or human

transmission remain speculative, but clearly work

in this area is of great interest and reported

results are welcomed.

 

" A primary concern remains the possibility of

the virus evolving so that it can transfer

readily from human to human, however this is not

an issue that this research addresses. "

 

A spokeswoman from the World Health Organization

said: " The spread of avian influenza viruses in

animals needs to be monitored, as these are

viruses that have proven their ability to jump

the species barrier. "

 

Dr Juan Lubroth, an expert in avian flu from the

Food and Agriculture Organization, said the lab

work supported what they were seeing in their

field work in Asia.

 

He said it was important to look at ways of

controlling the infection, such as vaccinating

healthy animals, culling infected ones and

encouraging better farming practices.

 

For example, ensuring farmers are financially

compensated for any animals lost to culling could

encourage them to alert authorities to cases of

infection, he said.

 

Story from BBC NEWS:

http://news.bbc.co.uk/go/pr/fr/-/1/hi/health/4692763.stm

 

Published: 2005/07/19 02:26:02 GMT

 

© BBC MMV

 

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