An investigation? Why? This is not the first time this has happened. Screening tests for mad cow–tests that have a fairly high SENSITIVITY (so as not to miss cows that ARE infected) but a low SPECIFICITY (meaning a fairly high rate of false positives)–are used in the field, presently on sick-appearing cows only in The US as I understand it. When a cow tests positive, a confirmatory test with a higher specificity is done, but that takes a while (about a week I think–during which the meat is quarantined). This whole scenario went according to plan, and it will happen again.