A Hokkaido cow was confirmed Monday to be infected with mad cow disease, the fourth case in Japan since September, health ministry officials said.

A panel of experts appointed by the Health, Labor and Welfare Ministry made the final confirmation based on data gathered from a pathological examination, as well as from a Western Blot examination, a more elaborate screening test for the disease that is formally known as bovine spongiform encephalopathy, the officials said.

The health ministry earlier said the cow — a 6-year-old female Holstein — was born and raised at a dairy farm in Ombetsu, eastern Hokkaido.

The cow had difficulty walking Tuesday, a symptom of BSE, and was diagnosed as suffering neuroparalysis to its left foreleg. It was slaughtered Friday in Kushiro, eastern Hokkaido.

The cow tested positive for the brain-wasting illness after a preliminary test Friday and in the subsequent Western Blot examination Saturday.

The confirmation of a fourth case of BSE in Japan supports theories that the disease may be prevalent in the country.

Officials at the Agriculture, Forestry and Fisheries Ministry said they will try to find the source of the infection, noting there are similarities between the latest case and the three earlier ones.

All four were born within March and April of 1996 and the first, second and fourth cows were all born in Hokkaido; the third was born in Gunma Prefecture.

It is also suspected the fourth cow was fed the same milk substitute as that given to the three other cows.

The milk substitute consumed by the first three cows contained an animal fat produced in the Netherlands, where 21 cases of BSE have been confirmed since 1997, officials said earlier.

Since Oct. 18, Japan has screened all cows slaughtered for beef for BSE. About 650,000 cows have so far been tested.

The first case of the disease in Japan was found in Chiba Prefecture in September, and the second and third in November.

Cows are believed to contract the disease by eating meat-and-bone meal contaminated with BSE. But Japanese authorities have yet to detect the source of the domestic infections.

BSE has been linked to the deaths of more than 100 people in Europe. The disease was first found in Britain in the mid-1980s. So far, about 180,000 cows have been found with the disease there.

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