ducks h5n1 threat

Friday, November 12, 2004
Domestic ducks could pose a new Avian Influenza threat
ASIA - Domestic ducks may be acting as a silent reservoir for the H5N1 Avian Influenza virus, which is highly pathogenic for chickens, and may thus have acquired an important new role in the transmission of the virus to other poultry and, possibly, to humans as well, three international agencies warned today.


The concern is greatest in rural areas of affected countries, where traditional free-ranging ducks, chickens and wildlife mingle, frequently sharing the same source of water, according to a joint statement by FAO, the World Health Organization (WHO) and the World Organization for Animal Health (OIE).

Findings pointing to an altered role for domestic ducks join other recent evidence that the H5N1 virus circulating in parts of Asia has increased its virulence in chickens and mice (a laboratory model for mammals), and has expanded its host range to include mammals, such as certain members of the felidae family (e.g. cats and tigers), not previously considered susceptible to infection.

New study
A new laboratory study of domestic ducks infected with several H5N1 viruses isolated in 2004 shows that, when compared with infections caused by viruses from 2003, domestic ducks are shedding more virus for longer periods and as before, are doing so without showing any sign of illness.

The study found that the quantities of virus excreted by healthy-looking ducks could approach those excreted by visibly diseased chickens, the agencies said. It was of public health concern that ducks might be infected and shed virus for long periods, yet give no warning signal in the form of visible signs and symptoms that alert officials and the public to take precautions, the statement added.

WHO, FAO and OIE said affected countries should be encouraged to include possible exposure to apparently healthy domestic ducks when assessing the risk of infection to humans and to issue appropriate advice for people living in affected areas.

Such advice should cover the handling of domestic ducks, particularly at slaughter (e.g. scalding the ducks prior to plucking), and avoiding use of water that has been in contact with ducks for human consumption without being treated.