Brazil has confirmed a second case of atypical mad cow disease, a year after several countries banned Brazilian beef imports when a similar case was confirmed.
The agriculture ministry said that a lab in Weybridge, England confirmed it was a spontaneous case of atypical bovine spongiform encephalopathy (BSE) with no link to contaminated feed.
The 12-year-old cow found dead in March in a slaughterhouse in Mato Grosso state was born and never left the same farm where cattle are fed by pasture grazing and mineral salts, and not feed, according to a ministry statement.
Classical cases of mad cow are caused when cattle are fed brain or spinal tissue of other ruminants, which is now forbidden in nearly all beef producing countries, including Brazil.
In atypical cases, the animal contracted the protein spontaneously, rather than through the feed supply.
The ministry said the diseased animal was incinerated and none of its parts entered the feed chain.
In late 2012 tests showed that a cow that died two years earlier in Parana state had developed the protein that causes mad cow disease, though the animal never developed the disease and died of natural causes.
The World Animal Health Organisation maintained Brazil's status as a country with an insignificant risk of BSE after it confirmed the atypical Parana case in tests carried out in England in 2012.
Even so, several countries including South Korea, China and Egypt banned some or all beef imports from Brazil, the world's top exporter.
Humans can develop what is known as variant Creutzfeldt-Jakob disease from consuming animals with mad cow, and more than 150 people have died from it. Mad cow was first discovered in Britain in 1986, but strict controls have tempered its spread.