SAO PAULO (REUTERS) - Brazil has temporarily halted beef exports to China following an atypical case of mad cow disease in leading farm state Mato Grosso, the agriculture ministry said on Monday (June 3).

China, Brazil's largest beef importer by sales, spent $1.5 billion on Brazilian beef last year, totalling 322,400 tonnes or almost 20 per cent of all shipments, according to local beef exporters association Abiec.

A representative of a leading exporter told Reuters on condition of anonymity that the ban was enforced as of Monday morning, when the government formally halted issuance of international health certificates.

A ministry spokeswoman said the move stemmed from a bilateral health protocol signed by the two countries in 2015.

Listed Brazilian meatpackers including Minerva SA fell by 4%. JBS SA and Marfrig Global Foods each had dropped by 3% by the end of the business day.

The Brazilian agriculture ministry on Friday reported the case of atypical mad cow disease in a 17-year-old cow in Mato Grosso state. The case was considered "atypical" as the animal contracted the BSE protein spontaneously, rather than through the feed supply.

The ministry spokeswoman said on Monday that Brazil expects the suspension to be lifted quickly as the country is still considered free of mad cow disease by the World Organisation for Animal Health.