Geographic information systems: their application in animal disease control

An Introductory Framework for Choosing Spatiotemporal Analytical Tools in Population-Level Eco-Epidemiological Research

Spatiotemporal visualization and analytical tools (SATs) are increasingly being applied to risk-based surveillance/monitoring of adverse health events affecting humans, animals, and ecosystems. Different disciplines use diverse SATs to address similar research questions. The juxtaposition of these diverse techniques provides a list of options for researchers who are new to population-level spatial eco-epidemiology. Here, we are conducting a narrative review to provide an overview of the multiple available SATs, and introducing a framework for choosing among them when addressing common research questions across disciplines. The framework is comprised of three stages: (a) pre-hypothesis testing stage, in which hypotheses regarding the spatial dependence of events are generated; (b) primary hypothesis testing stage, in which the existence of spatial dependence and patterns are tested; and (c) secondary-hypothesis testing and spatial modeling stage, in which predictions and inferences were made based on the identified spatial dependences and associated covariates. In this step-wise process, six key research questions are formulated, and the answers to those questions should lead researchers to select one or more methods from four broad categories of SATs: (T1) visualization and descriptive analysis; (T2) spatial/spatiotemporal dependence and pattern recognition; (T3) spatial smoothing and interpolation; and (T4) geographic correlation studies (i.e., spatial modeling and regression). The SATs described here include both those used for decades and also other relatively new tools. Through this framework review, we intend to facilitate the choice among available SATs and promote their interdisciplinary use to support improving human, animal, and ecosystem health.

Reanalysis of the start of the UK 1967 to 1968 foot-and-mouth disease epidemic to calculate airborne transmission probabilities

The aims of this study were to statistically reassess the likelihood that windborne spread of foot-and-mouth disease (FMD) virus (FMDV) occurred at the start of the UK 1967 to 1968 FMD epidemic at Oswestry, Shropshire, and to derive dose-response probability of infection curves for farms exposed to airborne FMDV. To enable this, data on all farms present in 1967 in the parishes near Oswestry were assembled. Cases were infected premises whose date of appearance of first clinical signs was within 14 days of the depopulation of the index farm. Logistic regression was used to evaluate the association between infection status and distance and direction from the index farm. The UK Met Office's NAME atmospheric dispersion model (ADM) was used to generate plumes for each day that FMDV was excreted from the index farm based on actual historical weather records from October 1967. Daily airborne FMDV exposure rates for all farms in the study area were calculated using a geographical information system. Probit analyses were used to calculate dose-response probability of infection curves to FMDV, using relative exposure rates on case and control farms. Both the logistic regression and probit analyses gave strong statistical support to the hypothesis that airborne spread occurred. There was some evidence that incubation period was inversely proportional to the exposure rate.

Does language matter? A case study of epidemiological and public health journals, databases and professional education in French, German and Italian

Epidemiology and public health are usually context-specific. Journals published in different languages and countries play a role both as sources of data and as channels through which evidence is incorporated into local public health practice. Databases in these languages facilitate access to relevant journals, and professional education in these languages facilitates the growth of native expertise in epidemiology and public health. However, as English has become the lingua franca of scientific communication in the era of globalisation, many journals published in non-English languages face the difficult dilemma of either switching to English and competing internationally, or sticking to the native tongue and having a restricted circulation among a local readership. This paper discusses the historical development of epidemiology and the current scene of epidemiological and public health journals, databases and professional education in three Western European languages: French, German and Italian, and examines the dynamics and struggles they have today.

GIS and multiple-criteria evaluation for the optimisation of tsetse fly eradication programmes

Tsetse flies are the vectors of trypanosomes, the causal agent of trypanosomiasis, a widespread disease of livestock and people in Africa. Control of tsetse may open vast areas of land to livestock-keeping, with the associated benefits of developing mixed crop-livestock production systems. However, as well as possible positive impacts there are also risks: bush clearing would accelerate and cattle numbers would rise, leading to a reduction of vegetation cover, and an increase in runoff and erosion; there may also be increased pressure on conserved areas and reductions in biodiversity. The objective of this study is to show how remotely sensed and other environmental data can be combined in a decision support system to help inform tsetse control programmes in a manner that could be used to limit possible detrimental effects of tsetse control. For Zambia, a methodology is developed that combines a tree-based decision-support approach with the use of Multiple-Criteria Evaluation (MCE), within a Geographical Information System (GIS), in order to target areas for tsetse control. The results show clear differentiation of priority areas under a series of hypothetical scenarios, and some areas (e.g. northwest of Petauke in the Eastern Province of Zambia) are consistently flagged as high priority for control. It is also demonstrated that priority areas do not comprise isolated tsetse populations, meaning that disease control using an integrated approach is likely to be more economically viable than local eradication.

Spatial risk assessment of herd sero-status of Aujeszky's disease in a county in Hungary

A Geographic Information System (VetEpiGIS) was used to analyze the ADV (Aujeszky's disease virus) sero-status in large-scale pig units regarding certain geographical features in a county of southern Hungary. The ADV sero-statuses were collected from all swine units in Csongrád county in 1998-2000. The units' coordinates were combined with a vector graphical digital map of the county, with a resolution of 1:100,000. Logistic regression tested the associations between sero-status of large-scale units and presence of topographical features, other units and villages in the neighborhood. "Neighborhood" was defined by circular zones with radius 1-10km around the unit (in 1km increments; one logistic regression for each radius). The following topographical features showed significant positive association with the ADV seropositivity: lake (3km OR: 5.7; 5km OR: 7.5; 6km OR: 6.1; 10km OR: 5.4) and highway (5km OR: 4.2; 6km OR: 5.3). Other features had negative association with ADV seropositivity: forest (3km OR: 0.13; 4km OR: 0.15; 5km OR: 0.15; 6km OR: 0.10; 7km OR: 0.10; 8km OR: 0.23) and uninfected large-scale unit (4km OR: 0.07; 5km OR: 0.27; 6km OR: 0.32; 7km OR: 0.31).

Measuring health and disease: progress in analytical approaches

In this paper, Dr. Martin reviews the progress in analytical approaches used in veterinary medicine between the 1970s and today. The newer applications are used in such activities as monitoring/surveillance, analysis of observational study data, evaluation of tests in the absence of gold standards, the analysis of clustered data (including geographically clustered data) and modeling disease in populations. Future work will be more complex but will demand an increased emphasis on ways to enhance our biological understanding of the results of data analysis and modeling.

Potential uses for geographic information system-based planning and decision support technology in intensive food animal production

Although geographic information systems (GIS) have been used in many disciplines, the available technology in planning and decision support has only recently begun to be used in intensive animal production, in areas such as confined animal feeding operations. GIS-based planning and decision support systems have the potential to enhance many aspects of intensive animal production, such as disease monitoring and prevention, emergency management and nutrient waste disposal. Current uses of GIS in animal production are reviewed. Potential uses are illustrated using the example of the poultry industry on the Delmarva Peninsula, USA.

Spatial statistics and geographical information systems in epidemiology and public health

This chapter surveys the principles behind spatial statistics and geographic information systems (GIS), and their application to epidemiology and public health. Like the other introductory chapters, it is aimed mainly to facilitate understanding in the chapters specific to certain diseases that follow, and to provide a short introduction to the field. A brief overview of spatial statistics and GIS is provided in the introduction. The sections that follow explore the ways in which we can map the distribution of disease, ways in which we can look for spatial patterns in the distribution of disease, and ways in which we can apply spatial statistics and GIS to the problem of identifying the causal factors of observed patterns. In the last section I discuss some of the ways in which these techniques have been applied to assist decision making for disease intervention, and conclude by discussing future developments in the field, and some of the issues surrounding the integration of spatial statistics and GIS.

Communicable disease surveillance with limited resources: the scope to link human and veterinary programmes

Zoonoses are an important cause of human disease in much of Africa, but limitations in current diagnosis and surveillance strategies restrict the effectiveness of control and prevention programmes. Outbreaks of disease, ranging from Ebola virus infection to Rift Valley Fever, that have occurred recently in Africa have demonstrated the need for improved disease surveillance and monitoring. Strategies are suggested for co-ordinating human and animal disease surveillance programmes, at the district and regional level, to make more effective use of limited resources.

Techniques for analysis of disease clustering in space and in time in veterinary epidemiology

Techniques to describe and investigate clustering of disease in space - the nearest-neighbour test, autocorrelation, Cuzick-and-Edwards' test and the spatial scan statistic - and in time - the Ederer-Myers-Mantel test and the temporal scan statistic - are reviewed. The application of these techniques in veterinary epidemiology is demonstrated by the analysis of a data set describing the occurrence of blowfly strike - both body strike and breech strike - between August 1998 and May 1999 in 33 commercial sheep flocks located within two local government areas of southeastern Queensland, Australia. By applying a combination of these methods, the occurrence of blowfly strike in the study area is well-characterised in both space and time. Guidelines for investigating disease clusters in veterinary epidemiology are discussed.

Geographic Information Systems and the Selection of Priority Areas for Control of Tsetse-transmitted Trypanosomiasis in Africa

In this paper, Tim Robinson describes the use of geographic information systems (GIS) to prioritize areas for tsetse and trypanosomiasis control in Zambia. Digital maps of land tenure, percentage agriculture, stocking rates and relative arable potential are combined within a GIS to identify areas where trypanosomiasis is a direct constraint to agricultural development and where the presence of tsetse prevents access to areas adjacent to those under high pressure from livestock and agriculture. The techniques described in this paper could be applied to a range of livestock diseases in many parts of the world.