Ovine Scrapie disease: Do we have to live with it?

Scrapie has persisted in sheep for centuries, and most sheep-producing countries worldwide, with few exceptions, are, or may be, affected by the disease. Why is it that the Scrapie status in many countries is not known with certainty, why has the disease appeared "in waves" from time to time in others, and why has it been so difficult to combat and eradicate ovine Scrapie disease? In this article, bits of old and new knowledge are put together, in an effort to answer some of these questions and explain why it probably will be impossible, at least in the nearest future, to eradicate all variants of prion disease in sheep. The question is also: "how can we live with the disease, reduce losses in sheep due to a lethal disease, and at the same time ensure safe food or food free of prions transferable to man?" The significance of continuing research, as well as prevailing focus on diagnosis and surveillance is vital in the foreseeable future. Artificial selection based on PrP genotyping and various strategies for eliminating the VRQ allele, which is associated with a higher risk of classical Scrapie than any other allele, can be seen as accelerating a natural process, and there is a possibility that classical Scrapie may eventually disappear from the sheep population. (c) 2008 Elsevier B.V. All rights reserved.