Environmental Epidemiology and Sanitation

by David J. Bradley,
Richard G. Feachem,



Document Type: Proceeding Paper

Part of: Appropriate Technology in Water Supply and Waste Disposal

Abstract:

This paper reviews the key variables determining the transmission of excreta-related diseases, sets out an environmental rather than biological classification of these infections, and relates this to the efficacy of different technologies for excreta disposal in improving health. Excreta-related diseases comprise the excreted pathogens and also those infections whose vectors breed in relation to excreta. Spread of excreted infections depends on the excreted load of organisms and the infective dose for man, and upon three characteristics of the pathogen: latency of infection, persistence of the organism in the environment, and any multiplication that occurs there. Human host responses and the existence of animal reservoirs of infection are also relevant. We recognize six categories: immediately infective pathogens with large and small minimal infective doses, and four others. Three have latent periods with development in the soil, domestic stock, or aquatic invertebrates respectively, and the last category is for excreta-related insect vectors. Each has a difference response to excreta disposal methods.

Subject Headings: Diseases | Pathogens | Vector analysis | Organisms | Reservoirs | Power transmission | Load factors

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