One of the problems governments face in dealing with mad cow disease is that existing diagnostics for transmissible spongiform encephalopathies, which include bovine spongiform encephalopathy (BSE) in cows, scrapie in sheep, and new variant Creutzfeldt-Jakob disease (nvCJD) in humans, rely on samples of central nervous system tissues, which can only be gathered from animals that have already been slaughtered. Blood-based tests would be better, because they would not require the wholesale slaughter of herds after one contaminated animal was found.

Last week, researchers from the Roslin Institute (Midlothian, U.K.) reported in Nature Medicine that they have found a surrogate marker for TSE infection that could do the trick.