* Brazil ag ministry said Friday cow did not die of BSE
* Japan imports only heat-treated beef from Brazil
TOKYO/BRASILIA, Dec 10 (Reuters) - Japan says it has halted beef imports from top exporter Brazil after the South American nation notified the World Animal Health Organization (OIE) of the discovery of the protein believed to cause bovine spongiform encephalopathy (BSE) in a cow.
Brazilian officials said last Friday the pasture-fed animal that died in Parana in December 2010 did not have BSE, commonly called mad cow disease, denying reports that were published on some local media web sites
Japan imported 1,435 tonnes of Brazilian beef in 2011, accounting for 0.3 percent of total beef imports, Japanese Agriculture Ministry data showed.
The OIE has maintained Brazil's status as a country with an insignificant risk of BSE, Brazilian officials said, adding that Brazil would pursue legal action if necessary against any importer trying to exploit BSE claims to block imports of Brazilian beef.
Brazilian agriculture ministry officials were meeting on Monday to consider their response to Japan's decision, and would make a declaration later in the day, a press official said.
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.
The official OIE report confirmed that the animal did not die of BSE and said it may have had an 'atypical' case of the disease, meaning one arising spontaneously from a genetic mutation which can arise in older cattle.
The animal was 13 years old and had been kept for breeding purposes.
The Brazilian agriculture ministry said the cow would have been unlikely to go on to develop full blown BSE had it not died of other causes. The presence of the protein, known as a prion, qualifies as an atypical case of BSE.
Japan imports only heat-treated beef from Brazil as it cannot bring in fresh beef from the South American nation, which has previously had incidents of foot-and-mouth disease.