The specter of mad cow disease (bovine spongiform encephalopathy) continues to haunt the nation despite official assurances of safety. On Wednesday another cow tested positive at a meat inspection center in Hokkaido, even as the source of infection in the first case, confirmed in September in Chiba Prefecture, remained unknown. Thorough investigations must be conducted to find out how the animals contracted the disease.
On Oct. 18, the Health and Labor Ministry started testing all cattle for meat processing, estimated at 1.3 million head annually. It was predicted then that perhaps a few more cases might be discovered, given the highly infectious nature of the disease. Over the past month about 90,000 head throughout the country have been tested, and all but one have tested negative.
Both cases have a few things in common. The two animals that tested positive were milch cows about 5 years old, and they were both raised in Hokkaido. BSE has an incubation period of two to eight years. So it is possible that the cattle feed used in the region contained prions, the protein agent that causes the brain-wasting malady.