TOKYO, Feb. 6 (Xinhua) -- The swine flu epidemic continued to spread rampantly in central and western Japan, with local authorities struggling to contain the highly-contagious virus, while the government remained reluctant to use vaccines to eradicate the problem.

Swine flu, also known as hog cholera, was first detected on farms in Gifu Prefecture in September, but has been newly detected in pigs at farms in neighboring Aichi Prefecture, as well as at farms in Osaka, Shiga and Nagano prefectures, authorities said.

They said the number of pigs to be culled and buried at affected farms is expected to reach around 15,000.

"We are facing an extremely serious situation," farm minister Takamori Yoshikawa said at his ministry in Tokyo. He instructed officials to take necessary countermeasures and underscore efforts in Gifu Prefecture to contain the virus.

A vaccine that could counter the hog cholera epidemic here and bring it under control has been snubbed by the government, however, with Yasuhiro Ozato, senior vice farm minister, expressing concern about using the vaccine.

"We will seek to resolve this by sticking to hygiene control standards," said Ozato, who was concerned that using the vaccine would hinder Japan from regaining its World Organization for Animal Health status and being able to expand its pork exports.

Ozato was intimating that if the vaccine were to be used, then Japan would fail to regain its status as a Classic Swine Fever (CSF) free country, which would severely hamper the nation's pork industry.

Up until recently, Japan has had no infections of pig cholera recorded since the first outbreak in 1992, with the virus being declared eradicated in 2007.