The ecology of infectious and neoplastic disease: a conceptual unification.

The ecology of disease is framed in conceptual terms as the study of the relationships of entities and events in the natural history of disease, a definition allowing it to embrace both the infectious and neoplastic (i.e. chronic, non-infectious) diseases. Those relationships of most conceptual interest and operational relevance are the causal relationships, and thus the ecology of disease properly embraces both epidemiologic and pathologic theory. The classic epidemiologic triad of 'agent-host-environment' is integrated into hierarchical, natural historical frameworks embracing both disease causation and course. Within these ecologic frameworks and based upon discipline-related concepts of causation, it is possible to derive conceptual/operational criteria of causality applicable to both infectious and neoplastic diseases. As approaches to the comprehension of infectious and neoplastic disease share considerable conceptual common ground, it follows that approaches to their control share considerable operational common ground. Indeed, insofar as actions follow ideas, the ecology of disease provides the basis for medical ecology and the planning, conduct and evaluation of overall operational approaches to the control of disease, to include both preventive and therapeutic interventions. From these perspectives, contemporary approaches to the control of neoplastic diseases seem to be derived largely from clinical-pathologic viewpoints of effectual disease process and emphasize non-specific (agent-unrelated) therapeutic interventions. Those general approaches most successful in controlling infectious diseases (i.e. preventive interventions and agent/defect-specific therapeutic interventions) need greater emphasis and application in approaches to controlling neoplastic diseases.