Ecological drivers of African swine fever virus persistence in wild boar populations: Insight for control

• Published in: Ecology and evolution Vol. 10; no. 6; pp. 2846 - 2859
• Main Authors: Pepin, Kim M., Golnar, Andrew J., Abdo, Zaid, Podgórski, Tomasz
• Format: Journal Article
• Language: English
• Published: England John Wiley & Sons, Inc 01-03-2020; John Wiley and Sons Inc; Wiley
• Subjects: African swine fever; Age; approximate Bayesian computation; Asfarviridae; Bayesian analysis; carcass; Carcasses; Density; Disease transmission; Ecological conditions; Environmental impact; environmental transmission; Epidemics; Epidemiology; Fever; Hogs; Infections; Laboratories; Livestock; Original Research; Parameter estimation; Pathogens; persistence; Population; Populations; Sensitivity analysis; spatial model; Sus scrofa; Swine; transmission; Viruses; wild boar; Poland; Belarus; carcass; environmental transmission; transmission; African swine fever; wild boar; persistence; spatial model; approximate Bayesian computation
• ISSN: 2045-7758; 2045-7758
• DOI: 10.1002/ece3.6100

Environmental sources of infection can play a primary role in shaping epidemiological dynamics; however, the relative impact of environmental transmission on host‐pathogen systems is rarely estimated. We developed and fit a spatially explicit model of African swine fever virus (ASFV) in wild boar to estimate what proportion of carcass‐based transmission is contributing to the low‐level persistence of ASFV in Eastern European wild boar. Our model was developed based on ecological insight and data from field studies of ASFV and wild boar in Eastern Poland. We predicted that carcass‐based transmission would play a substantial role in persistence, especially in low‐density host populations where contact rates are low. By fitting the model to outbreak data using approximate Bayesian computation, we inferred that between 53% and 66% of transmission events were carcass‐based that is, transmitted through contact of a live host with a contaminated carcass. Model fitting and sensitivity analyses showed that the frequency of carcass‐based transmission increased with decreasing host density, suggesting that management policies should emphasize the removal of carcasses and consider how reductions in host densities may drive carcass‐based transmission. Sensitivity analyses also demonstrated that carcass‐based transmission is necessary for the autonomous persistence of ASFV under realistic parameters. Autonomous persistence through direct transmission alone required high host densities; otherwise re‐introduction of virus periodically was required for persistence when direct transmission probabilities were moderately high. We quantify the relative role of different persistence mechanisms for a low‐prevalence disease using readily collected ecological data and viral surveillance data. Understanding how the frequency of different transmission mechanisms vary across host densities can help identify optimal management strategies across changing ecological conditions.
African swine fever (ASF) is a highly virulent disease of swine with devastating socio‐economic consequences with persistence mechanisms that remain unknown in Eastern Europe. In this manuscript, we developed and fit a spatially explicit mechanistic epidemiological model to spatio‐temporal disease surveillance data using approximate Bayesian computation (ABC) to estimate the relative role of carcass‐based transmission in ASF virus persistence and spatial spread. We inferred that 53%‐66% of ASF virus transmission events occurred through the contact of susceptible hosts with dead carcasses and we found that the relative importance of transmission mechanisms depended critically on host density.