Unvaccinated water fowl allow H5N1 to duck under the radar in Vietnam
The sheer size, mobility, and lack of control over the duck population makes it virtually impossible to ensure complete vaccination, which is at the root of the problem.
By any measure, Vietnam has made huge strides in managing H5N1 HPAI (highly pathogenic avian influenza). From a perilous situation in 2005, with the disease rife in poultry and people across the country, the authorities fought back and brought the situation under control. There followed an extended period during 2006 with no outbreaks in poultry and no human cases. Countrywide vaccination of poultry played a significant part in this increasingly successful disease management.
During 2007, the disease resurged in poultry with some human cases, although the authorities have just about managed to keep a lid on the problem since. Research and surveillance shows Vietnam’s huge, mobile, and difficult-to-manage duck population is at the root of the problem, presenting difficulties in ensuring that all ducks are vaccinated on time and with a full complement of vaccine.
A report listing outbreaks since July 2008, recently released by the Vietnamese government to the World Organisation for Animal Health (OIE), indicates a concentration in ducks in southern Vietnam (where most ducks are raised) and village ducks, all of which were unvaccinated (Table 1).
The latest outbreak reported by The Earth Times, but not yet displayed by OIE, claims the H5N1 avian influenza virus was found in ducks in the central Vietnamese province of Nghe An and announced by the Vietnamese authorities on Oct. 7, 2008. Bui Quang Anh, director of Vietnam's Animal Health Department, said the outbreak had killed some 300 ducks. "The ducks had only been vaccinated once," said Anh. "They need at least three injections to become resistant to H5N1." The local health department culled the ducks and disinfected the area to guard against further outbreaks, said the report, adding that outbreaks have been detected in 26 Vietnamese provinces since Jan. 1, 2008, killing 5 people and forcing the authorities to cull more than 60,000 ducks.