Aguzzi warns of CWD danger

The US Department of Agriculture last month confirmed that two sheep taken from a farm in Vermont were infected with a form of transmissible spongiform encephalopathy (TSE). Further tests are being carried out to determine whether the disease is bovine spongiform encephalopathy (BSE) or scrapie. The sheep were imported from the Netherlands (Nature Med. 6, 1301; 2000). Analysis will take at least two years, and if the prion is that which causes BSE, this would be the first case of disease in the US.

The TSE family of diseases also includes chronic wasting disease (CWD) in deer, a condition that has spread in the US in recent years (Nature 416, 569; 2002). Speaking at the Days of Molecular Medicine conference in La Jolla in March, prion expert Adriano Aguzzi issued a strong warning against underestimating this form of TSE. "For more than a decade, the US has by-and-large considered mad cows to be an exquisitely European problem. The perceived need to protect US citizens from this alien threat has even prompted the deferral of blood donors from Europe," he said. "Yet the threat-from-within posed by CWD needs careful consideration, since the evidence that CWD is less dangerous to humans than BSE is less-than-complete.

Aguzzi went on to point out that CWD is arguably the most mysterious of all prion diseases. "Its horizontal spread among the wild population is exceedingly efficient, and appears to have reached a prevalence unprecedented even by BSE in the UK at its peak. The pathogenesis of CWD, therefore, deserves a vigorous research effort. Europeans also need to think about this problem, and it would be timely and appropriate to increase CWD surveillance in Europe too." Aguzzi has secured funding from the National Institutes of Health to investigate CWD, and the effort will be lead by Christina Sigurdson in his department at the University of Zurich.