The government on Tuesday began full-fledged investigations into Japan’s eighth case of mad cow disease to determine how a 23-month old Holstein was infected with an atypical form of the brain-wasting malady.

“We’re making efforts to determine” how a 23-month-old Holstein was infected with an atypical form of the brain-wasting disease, Chief Cabinet Secretary Yasuo Fukuda, told a news conference.

The Agriculture, Forestry and Fisheries Ministry also assembled experts to discuss measures and collect data. One of the main subjects of their attention will be what kind of feed the cow had eaten, because it had an abnormal type of prions — protein particles believed to be the cause of mad cow — that has never before been reported in Japan or abroad.

The cow, born in October 2001, was younger than the seven other cattle in Japan diagnosed with mad cow disease, formally known as bovine spongiform encephalopathy. It is rare for a cow younger than 24 months to have the disease, according to farm ministry officials.

Health minister Chikara Sakaguchi told a separate news conference: “There was a common view that young cows are not infected (with the disease).

“We have to examine whether the current inspection system covering all cows can detect the new type of BSE,” Sakaguchi said.

“There is no concern that (meat of the infected cow) could reach the market,” Fukuda said.

The farm ministry had instructed farmers that when an infection is discovered, they should dispose of some of the cows that have eaten the same feed on the farm.

The disease is believed to be caused by the consumption of meat-and-bone meal contaminated with prions, which are protein particles lacking nucleic acid that have been linked to nervous system illnesses such as Creutzfeldt-Jakob disease.

Because the characteristics and the contagiousness of the abnormal prions found in the animal remain unknown, the ministry said it would like to hear opinions from the experts on appropriate measures.

The ministry said last month the source of the mad cow outbreak in Japan was probably either cows imported from Britain in the 1980s or contaminated Italian-made meat-and-bone meal imported before 1990.

Ministry officials said Monday it is possible there was a different route of infection in the latest case, given that the cow was born after Japan banned the production and sales of meat-and-bone meal.

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