Abstract
BackgroundAfrican swine fever (ASF) is endemic in several countries of Africa and may pose a risk to all pig producing areas on the continent. Official ASF reporting is often rare and there remains limited awareness of the continent-wide distribution of the disease.In the absence of accurate ASF outbreak data and few quantitative studies on the epidemiology of the disease in Africa, we used spatial multi-criteria decision analysis (MCDA) to derive predictions of the continental distribution of suitability for ASF persistence in domestic pig populations as part of sylvatic or domestic transmission cycles. In order to incorporate the uncertainty in the relative importance of different criteria in defining suitability, we modelled decisions within the MCDA framework using a stochastic approach. The predictive performance of suitability estimates was assessed via a partial ROC analysis using ASF outbreak data reported to the OIE since 2005.ResultsOutputs from the spatial MCDA indicate that large areas of sub-Saharan Africa may be suitable for ASF persistence as part of either domestic or sylvatic transmission cycles. Areas with high suitability for pig to pig transmission (‘domestic cycles’) were estimated to occur throughout sub-Saharan Africa, whilst areas with high suitability for introduction from wildlife reservoirs (‘sylvatic cycles’) were found predominantly in East, Central and Southern Africa. Based on average AUC ratios from the partial ROC analysis, the predictive ability of suitability estimates for domestic cycles alone was considerably higher than suitability estimates for sylvatic cycles alone, or domestic and sylvatic cycles in combination.ConclusionsThis study provides the first standardised estimates of the distribution of suitability for ASF transmission associated with domestic and sylvatic cycles in Africa. We provide further evidence for the utility of knowledge-driven risk mapping in animal health, particularly in data-sparse environments.
Highlights
African swine fever (ASF) is endemic in several countries of Africa and may pose a risk to all pig producing areas on the continent
Multi-criteria decision analysis (MCDA) The multi-criteria decision analysis (MCDA) procedure used in this study involved the following general steps: 1. Assessment of the suitability structure: identifying risk factors for ASF transmission and determining their importance in relation to the objective(s)
The combined suitability estimates derived from the MCDA procedure reveal a good degree of agreement with the distribution of cases reported to the OIE between 2005 and 2012, the number of officially reported ASF cases are likely to represent only a small proportion of those that occur across Africa, in areas in which the disease is endemic
Summary
African swine fever (ASF) is endemic in several countries of Africa and may pose a risk to all pig producing areas on the continent. In the absence of accurate ASF outbreak data and few quantitative studies on the epidemiology of the disease in Africa, we used spatial multi-criteria decision analysis (MCDA) to derive predictions of the continental distribution of suitability for ASF persistence in domestic pig populations as part of sylvatic or domestic transmission cycles. In parts of eastern and southern Africa, for example, cycles involving wild suids, such as warthogs (Phacochoerus africanus) and soft tick vectors of the Ornithodoros moubata complex provide a reservoir of ASFV for domestic pigs [5]. Such ‘sylvatic’ cycles may allow the disease to persist in pig populations, even in areas with low pig population density. In parts of de Glanville et al BMC Veterinary Research 2014, 10:9 http://www.biomedcentral.com/1746-6148/10/9
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