October 2, 2003

Japan's BSE Investigation Raises Certain Doubts

Scrutiny into Japan's mad cow disease outbreak two years ago has led scientists to believe the disease came either through imported Italian cattle feed or British cows. However, its still remains ambiguous how domestic herds could have been infected, according to a government panel report.

The report, released by the Agriculture Ministry, is a summary of 11 months' worth of work by a panel of scientists on the fatal bovine disease, which showed up in Japan in September 2001.

Government screening of all cattle bred for human consumption began a month later, but the source of the outbreak still eludes scientists here which the Japanese public have voiced concerns about.

Japan's outbreak likely stemmed from 14 British cows imported between 1982 and 1987, during the peak of infections there, or about 650 metric tons (715 short tons) of meat-and-bone meal made from ground-up infected animals from Italy before 1991, the report said.

One possible explanation is that the contaminated cattle and ground-up parts, which were processed into food meant only for Japan's pigs and chickens, were unwittingly mixed with cattle feed, the report said. 

Two Japanese plants - one near Tokyo, the other on the northernmost main island of Hokkaido - may not have properly cleaned their machinery between runs, allowing prions, the abnormal proteins that can trigger the brain-wasting disease, to contaminate cattle feed, the report said.

If that was the cause, Japan would have had 30 more cases of mad cow disease, according to the panel's simulated worst-case scenario. But the panel concluded that those cows were likely safely disposed of or flagged by a national inspection system before they could end up on the market.

Ministry official Tomomi Sugizaki said the report can help design better screening methods if a repeat outbreak occurs, but that the government had no plans to change current testing standards.

Japan became the first country outside of Europe to find an infected cow. Tokyo has since banned the use of meat-and-bone meal in cattle feed. The bovine illness - known formally as bovine spongiform encephalopathy - is thought to cause the fatal human variant Creutzfeldt-Jakob disease.