The virus was first detected in the Southeast Asian country a month ago at three farms in two northern provinces and has spread to 17 provinces in northern Vietnam with 239 outbreaks confirmed, the FAO said in a statement.

Pork accounts for three quarters of total meat consumption in Vietnam, a country of 95 million people where most of its 30 million farm-raised pigs are consumed domestically.

"The loss of pigs due to ASF infection and control measures leads to a heavy economic burden to many rural families," Albert T. Lieberg, the FAO representative in Vietnam, said following meetings last week with Vietnamese authorities.

Read: U.S. Seizes 1 mn Pounds of Pork from China on Swine Fever Concern

Vietnam has been implementing strict movement control of pigs and pig products and culled more than 25,000, but the FAO said small farms with low biosecurity will allow ASF's spread.

The disease, which is incurable in pigs but harmless to humans, has also spread rapidly across neighboring China. Last week, Beijing banned the import of pigs, wild boars and related products from Vietnam.

REUTERS