Academic journal article Bulletin of the World Health Organization

New Geographic Approaches to Control of Some Parasitic Zoonoses

Academic journal article Bulletin of the World Health Organization

New Geographic Approaches to Control of Some Parasitic Zoonoses

Article excerpt

The advent of new technology for geographical representation and spatial analysis of databases from different sectors offers a new approach to planning and managing the control of tropical diseases. This article reviews the geographical and intersectoral aspects of the epidemiology and control of African trypanosomiasis, cutaneous and visceral leishmaniasis, Chagas disease, schistosomiasis, and foodborne trematode infections. The focal nature of their transmission, increasing recognition of the importance of animal reservoirs, and the need to understand environmental factors influencing their distribution are common to all these diseases. Geographical information systems (GIS) open a completely new perspective for intersectoral collaboration in adapting new technology to promote control of these diseases.

Introduction

Geographical approaches, particularly geographical information systems (GIS), provide common ground for dialogue between zoologists, veterinarians and medical public health workers. As a result, there is now increasing awareness of the role of animals in the epidemiology of human "emerging" infections (5), and the control of tropical diseases is gradually involving other sectors besides traditional public health services.

GIS is a computer-based technology for input, storage, analysis and display of spatial data (19). It permits cross-sectional display and analysis of multiple databases using real geographical coordinates to a specific scale, i.e., rainfall, soil type, soil humidity, health services infrastructure, disease vectors, and infection or disease in animals and people. This relatively new analytical tool in the field of epidemiology facilitates the collaboration of different sectors and can be flexibly adapted to the needs of the endemic countries. The effective integration of new technology such as GIS is done methodically in a step-by-step fashion. For control of tropical diseases all applications begin at the periphery. If the data generated at the periphery have not been reliably collected and checked, no amount of sophisticated technology at the central level can improve them. Furthermore, GIS analyses to determine causal relations are estimates or approximations to support or refute hypotheses, and their conclusions should be confirmed by field epidemiological studies.

Appropriate use of new geographical approaches will depend on (1) proven benefit from older geographical approaches in control, (2) a clear priority for the sequence of introduction of databases, and (3) scientifically sound hypotheses. If these three criteria are not fulfilled, the new geographical approaches may become junkyards or graveyards of databases.

This review describes the evolution of geographical approaches and methodology as applied to understanding the epidemiology of parasitic diseases with animal intermediate hosts. It does not include the use of remote sensing and satellite image data in relation to vector-borne diseases, which other authors have recently described (13)(16)(25) and which require sophisticated technologies (both hardware and software) to analyse the data input. Moreover, remote sensing data are managed and analysed as one of the databases in a GIS.

Geographical approaches

This article does not cover the history of geographical approaches for controlling tropical diseases. Their origins have been variously interpreted, e.g., maps of the drainage operations of the Pontine swamps in ancient Rome to eliminate malaria--long before the link between the parasite and the mosquito could be imagined, or the map of cholera cases in London in 1833--34 which pinpointed the Broad Street public pump as a point source of infection.

In all operational tropical disease programmes the necessity of maintaining a geographical approach is recognized. In the field, simple maps bring out information which can easily be interpreted and used in management of control activities. …

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