The reach of mad cow disease extended around the globe on 10 September, when Japan announced the first confirmed case of bovine spongiform encephalopathy (BSE) in a cow born outside Europe.

Japanese officials say that a cow in the Chiba prefecture, east of Tokyo, has been diagnosed with the disease. All previous cases outside Europe involved cattle imported from Britain.

Researchers think that BSE originally entered Japan through infected meat and bonemeal cattle feed imported from Britain during the early 1990s. But worryingly for Japan's farmers, the disease may now have spread to domestic cattle feed.

Unconfirmed reports say that the animal that died was 5 years old. Experts say that British cattle feed was probably BSE-free by the time the cow was born, suggesting that the infection came from foodstuffs produced in Japan itself, perhaps using animal parts from cattle that had carried earlier, undetected infection from British feed.

“There could have been a new round of infection,” says Marcus Doherr, a BSE expert at the University of Bern in Switzerland. But Doherr says that Japan is unlikely to see an epidemic on the British scale, as cattle feed made from animal parts was not as widely used in Japan as in Britain.