Epsilon Archive for Student Projects

Abstract

African swine fever (ASF) is a contagious, often mortal viral disease affecting domestic pigs and wild boar. In September 2023, Sweden reported its first ASF outbreak in wild boar. Through extensive control measures, Sweden was declared free from ASF one year later, one of few
successful eradication campaigns in Europe. The purpose of this study was to improve the understanding of the 2023 outbreak in Sweden by developing a stochastic diffusion model describing the spatial and temporal spread of ASF among wild boar. The model, adapted from Lentz et al.
(2023) and implemented in R, used field data from the Swedish outbreak to estimate diffusion coefficients, spread radius, and wave front velocity.
Results indicate that the spatial spread of ASF in Sweden was slower than the estimated spread in Germany, with a median diffusion coefficient of 27 702 (IQR: 25 729-29 903) m²/day compared to 220 000 ± 10 000 (IQR) m²/day, and a mean wave front velocity of 14 m/day (at day 136 in the
Swedish study) compared to 40 m/day (at day 150 in the German study). These differences likely reflect the outbreak-specific factors such as wild boar density and local environment factors as well as data handling and model differences. The model slightly underestimated the simulated
outbreak radius by approximately 13%, suggesting that refinement is possible.
Improved data handling including biological parameters such as incubation time could improve the model’s output. This work illustrates how diffusion modelling can be applied to explore ASF spread dynamics and evaluate potential control strategies.