Laboratory diagnosis of bovine viral diarrhea virus infections

Diagnosis is defined by Webster's New Collegiate Dictionary [1] as the art or act of identifying a disease from its signs and symptoms. Use of the word "art" rather than science in this definition is not unintentional. Indeed, diagnosis, far from being a science, is an art that involves two mental processes. The first process is accumulation of data (laboratory test results). The second is reasoning from the data, to determine what they mean (interpretation) [2]. In 1976, it was predicted, "the future progress of medicine would depend largely on the development of more accurate laboratory tests based on the discoveries of medical science" [3]. This prediction has come true in veterinary medicine in general as witnessed by the "ELISA revolution" of the early 1980s and the on-going "polymerase chain reaction (PCR) revolution." However, in the case of bovine viral diarrhea virus (BVDV), the availability of "more accurate laboratory tests" has not necessarily correlated with "progress" in solving the multiple production problems posed by this virus. This state of affairs has largely resulted from a lack of rational use of the available diagnostic techniques. It is essential for the clinician to have a clear rationale for requesting BVDV testing, and to communicate this rationale to the laboratory diagnostician. In this article, two aspects will be highlighted. First, an outline of existing techniques will be presented. Second, the application of the various diagnostic methods will be discussed.