Spatial Multi-criteria Decision Analysis to Predict Suitability for African Swine Fever Endemicity in Africa29 January 2014
Although the potential for spill-over from wildlife reservoirs should not be ignored, an international group of researchers has developed a model that suggests it is mainly domestic transmission of African Swine Fever (ASF) that accounts for the persistence of the disease in sub-Saharan Africa.
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, according to William de Glanville of the Royal Veterinary College in the UK and co-authors in a paper in BMC Veterinary Research.
In the absence of accurate ASF outbreak data and few quantitative studies on the epidemiology of the disease in Africa, the researchers 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, they 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.
They found that outputs from the spatial MCDA indicate 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.
This study provides the first standardised estimates of the distribution of suitability for ASF transmission associated with domestic and sylvatic cycles in Africa, concluded de Glanville and co-authors.
They also provide further evidence for the utility of knowledge-driven risk mapping in animal health, particularly in data-sparse environments.
De Glanville W.A., L. Vial, S. Costard, B. Wieland and D.U. Pfeiffer. 2014. Spatial multi-criteria decision analysis to predict suitability for African swine fever endemicity in Africa. BMC Veterinary Research. 10:9 doi:10.1186/1746-6148-10-9