Brazilian officials said the animal that died in Parana in December 2010 did not have BSE, commonly called mad cow disease.
Japan imported 1,435 tonnes of Brazilian beef in 2011, accounting for 0.3 percent of total beef imports, Japanese Agriculture Ministry ministry data showed.
The OIE has maintained Brazil's status as a country with an insignificant risk of BSE, Brazilian officials said, adding Brazil would pursue legal action if necessary against any importer trying to exploit BSE claims to block imports of Brazilian beef.
The outbreak of mad cow disease in Europe, North America and Japan over the past decade often prompted beef importers to embargo shipments and caused temporary chaos in the industry. Brazil is the world's largest beef exporter.
Results of tests carried out in England this month by the OIE on tissue from the Brazilian cow, confirmed the presence of the protein, called a prion, Brazilian officials said on Friday.
They said the protein likely appeared after a spontaneous genetic mutation in the 13-year-old cow.
But the results suggested the animal would have been unlikely to go on to develop the disease had it not died of other causes, the Brazilian agriculture ministry said, adding the simple presence of the protein, called a prion, is considered an atypical case of BSE.
Japan imported only heat-treated beef from Brazil as it cannot bring in fresh beef from the South American nation, which has reported foot-and-mouth disease.
