Identifying and Defining a Disease

Abstract

There are many reasons for investigating disease in wildlife but, in simplest terms, these usually resolve to some combination of: is disease present?, what is causing it?, and what effect is it having? In some cases, there may be a marked urgency to the study, as when it is necessary to determine the cause of a major outbreak of disease so that control measures can be instituted. In other instances, one can take a more leisurely approach, as when there is a need to assess if some disease factor is associated with an observed change in a population or to assess the significance of some potential risk factor, such as an agricultural pesticide. Regardless of the reason for the study, an early step in any investigation is to define the problem to be investigated as precisely as possible. Objectives in defining the disease are to identify those features that distinguish the particular disease from all others, to clearly delimit current knowledge about the disease, to identify questions about the disease that need to be answered, and to determine those methods that will be most likely to yield pertinent answers. Definition of a disease must be looked upon as a dynamic process that is modified continually as new information is obtained. In the early stages of an investigation, the definition will often be very general, but it should become increasingly precise as the investigation proceeds.

“an epidemiologist is one who thinks in an epidemiological manner, rather than one trained in one specific discipline. He must be a master of ‘lateral thinking’, trying to see connections between what are probably isolated observations of completely different natural phenomena” (Halpin, 1975).