July 19, 2005

Ducks could be bird flu host
 

Ducks could act as medical Trojan horses, spreading the pathogenic bird flu to humans and other birds even as they themselves remain unaffected by the disease, a recent US study said.

Waterfowl such as ducks have been natural hosts of the H5N1 strain even though they themselves rarely became ill from it, according the study funded by the US Public Health Service and American Lebanese Syrian Associated Charities.

In 2002, an evolving strain killed of a large number of ducks, only to mutate into a form that is less dangerous to ducks but still remains life threatening to chickens and humans.

In the research, researchers found that after domestic ducks were infected with the H5N1 strain from the years 2003 or 2004, they were contagious for 11 to 17 days. This is a longer transmission time than for pre-2002 strains.

The researchers also found that the virus was no longer transmitted faecal matter but through the upper respiratory tract.

When flu virus from ducks that had survived the disease was administered to healthy animals, it was found that the virus no longer caused disease in ducks, but still affected chickens.

For the past two years, millions of birds died or were culled across Asia because of the H5N1 bird flu virus, which has also caused the deaths of over 40 people in Asia.