# 1305
With more twists and turns than a daytime soap opera, the H5N1 saga continues to spin more intriguing subplots. Just as soon we think we understand how something works with this pathogen, something changes, and we have to go back to the drawing board.
Understandable, I suppose, given that the virus mutates and adapts as it spreads from host to host.
One such change has been the effect the virus has had on free range ducks. Once thought to be silent carriers, they now comprise a large portion of the bird deaths reported this year in Vietnam.
HEALTH-VIETNAM: Bird Flu Fighters Have Ducks in Their Sights
By Marwaan Macan-MarkarBANGKOK, Nov 30 (IPS) - As the temperature drops and another cool season approaches, attention is turning to Vietnam’s duck population, suspected to have become vulnerable to the deadly avian influenza (AI) virus.
The deaths of large numbers of free-range ducks through November appears to confirm the view that they are no more ‘’silent carriers’’ of the H5N1 virus, as was thought to be the case after the current outbreak of AI began in the winter of 2003. In the Cao Bang province, in the northern mountains of the country, 60 ducks from a flock of 82, and 12 chickens from a flock of 17, died over a five-day period, this month.
‘’Free range ducks didn’t show signs of the virus unlike chickens, which were getting infected and dying,’’ says Jeffery Gilbert, senior technical advisor on AI for the Food and Agriculture Organisation (FAO). ‘’Free-range ducks were considered silent carriers of H5N1 up to two-and-a-half years ago.’’
But the high mortality rate among ducks during the two main AI outbreaks in the South-east Asian country this year has forced animal health experts into a rethink. ‘’Nearly three-fourths of the cases reported in Vietnam in 2007 have been free range ducks,’’ Gilbert said during a telephone interview from Ho Chi Minh City. ‘’They are difficult to vaccinate and are left to roam over a three- or four-hectare area at times.’’
The U.N. agency estimates that there are some 60 million free range ducks, many of them part of small flocks owned by farmers in the southern Mekong Delta region. The ducks are often let to roam in the rice fields where they play a useful role, particularly during the harvest season, by eating snails, pests and insects attracted to the paddy ready to be reaped.
But the ducks are also found along roads and pathways, which can contribute to the spread of the virus, since it can be borne on the tyres or parts of vehicles or by people coming into contact with the infected ducks. ‘’The ducks also mix regularly with wild birds in some areas or migratory birds,’’ added Gilbert.
