Yoshiyuki Kamei, minister of agriculture, forestry and fisheries, said Thursday he has urged ministry officials to investigate a hog cholera outbreak in Kagoshima Prefecture.
Ten pigs suspected of being infected with hog cholera have been found on a pig farm in the town of Takaono in the prefecture. The ministry believes unauthorized vaccines caused the infection.
"Although the circulation of unauthorized vaccines has not been confirmed, I have instructed officials to conduct thorough investigations" into the cause of the infection, Kamei told a regular news conference.
Pigs on two farms in Kayano, Kagoshima Prefecture, were also found infected with hog cholera, in March and in July. The government had concluded that the infection was connected with the unauthorized vaccines.
The disease, which affects only pigs and wild boars, has a fatality rate of almost 100 percent if it is caused by viruses found in nature. However, viruses deriving from vaccines are less toxic and contagious, according to experts.
Hog cholera does not affect humans even if they consume pork from infected animals. The ministry has basically prohibited the use of hog cholera vaccines since 2000.
The last outbreak of hog cholera in Japan was reported in Kumamoto Prefecture in 1992.