Vietnam is encountering high risk of bird flu return, partly because only 40 percent of ducks and 60 percent of chickens in the country's southern Mekong Delta have immunity to the disease after being vaccinated, local media reported Wednesday.

The risk is also due to loosen control over slaughter, trade and transport of poultry and related products in some localities, including border provinces, Vietnam Agriculture newspaper quoted a report of the country's National Anti-Bird flu Steering Committee.

Vietnam has conducted bird flu vaccination among 33 million fowls in 30 cities and provinces nationwide since late February.

In 2005, bird flu hit 44 cities and provinces of Vietnam, killing and leading to the forced culling of nearly 4.8 million poultry, or over 2 percent of the country's fowl population, according to the Ministry of Agriculture and Rural Development.

The country, which now has a total poultry population of nearly 220 million, has detected no bird flu outbreaks for over four months, said the ministry.

Source: Xinhua