TOKYO, Japan -- Japanese officials say they have found the country's first known case of mad cow disease.
Japan's agriculture ministry said on Monday a cow has tested positive for mad cow disease in Chiba prefecture, says CNN's Peter Hadfield, reporting from the area.
Mad cow disease, or bovine spongiform encephalopathy (BSE), has only been confirmed in Western Europe until now, and today's find could signal the first case in Asia.
BSE is a brain-wasting illness that has been linked to the fatal variant Creutzfeldt-Jakob (CJD) disease in humans, which has killed around 100 people in Britain since it broke out in the mid 1980s.
CJD kills its carrier by eating holes in brain tissue and humans can catch it by eating infected meat.
Scientists believe the disease is initially transmitted through infected bone and meat meal fed to cattle.
Earlier this year the United Nations warned that Japan was at risk because it imported large quantities of meat- based animal feed from Western Europe.
But Japan's agricultural ministry has played down the danger of an outbreak.
The European Commission's office in Tokyo said in June the Japanese government had blocked the publication of an E.U. report that said BSE could theoretically break out in Japan, Reuters news agency reported.
Mad cow disease was diagnosed in Europe in 1986 and resulted in wholesale herd slaughtering, mandatory testing and a European Union ban on British beef exports that has since been lifted.
Amid signs of spreading mad cow disease across Europe, Japan last year banned E.U. beef and food made from processed beef and bull sperm, which is used for breeding.
Japan also tried to prevent the disease from entering its borders by restricting blood donations from people who lived in Britain.
Officials began to be alarmed in early August when a cow in Shiroi, Chiba prefecture, mysteriously lost the ability to stand.
The cow was slaughtered on August 6 and it was submitted for testing at a Japanese research center on August 15.
This first test was negative but, because it revealed air pockets in the cow's brain, further testing was carried out on September 6.
The results on Monday showed that this second test had come in positive for mad cow disease.
Chiba is a main supplier of agricultural products to Tokyo, which borders the state on the west.
There are a total of about 100 cattle in Shiroi, including some 30 other cows at the same farm.
Many have been quarantined but none are thought to carry the disease, The Associated Press reported. Officials have yet to decide whether to slaughter the other cattle.
Despite the discovery Japanese officials say they believe the chances of a serious outbreak of mad cow disease remain low and that there is no problem with Japanese milk or beef.
"This suspected case does not change our position that the chances of mad cow disease occurring in Japan are very low," Takemi Nagamura, director-general of the farm ministry's livestock industry department, told a news conference.
But he said the government could be forced to review its position if the disease was confirmed by specialist facilities in Europe, Reuters reported.
The ministry said the cow's meat had not reached consumers.
However, the health ministry said it had ordered a ban on sales of meat products from the farm in Chiba where the suspected case occurred "as a precautionary step."
The ban could be extended, the health ministry said, depending on the farm ministry's research, particularly into which other farms used the same animal feed suspected of being fed to the cow in Chiba.
An official panel is to decide on Tuesday whether the cow, would be sent to specialist facilities in either Britain or Switzerland for further tests.
Using Japanese government data, E.U. scientists had given Japan a risk-rating of three on a rising scale of one to four, Reuters reported.
They have judged Australia and the United States, by contrast, to be free of any risk of BSE.
Japan started in April to check for BSE in cattle that showed abnormal symptoms before they died.
The incubation period for mad cow disease is believed to be between two and eight years after infection.