Velocity of ASF spread in wild boar in the European Union (2014–2017)

Purpose: The continued advance of African Swine Fever (ASF) through Eastern European countries represents a threat for the European pig industry. ASF is often described as a highly contagious infectious disease of swine. In the current affected countries in the European Union (EU), the spatio-temporal dynamics of ASF spread in wild boar appear to be different; i.e. in Estonia, the whole country has been affected since its introduction in 2014, while in Poland, ASF remained within the limits of a single county for a long period. Here we quantify the velocity of spread of ASF in wild boar in the EU to elucidate whether it is constant or increasing, which can help to understand if further cases are expected in other areas as well as the rate of occurrence. Methods & Materials: We apply a spatio-temporal kriging model to interpolate the date of a total of 7112 ASF notifications in wild boar from 2014 to 2017 taking into account the spatial variance in the study area (rasterized in 50 × 50 km cells). ASF was notified by the EU Member States to the ADNS (Animal Disease Notification System) quarterly, which constitute the input data (using as variable the indicatrix 0-1 by cell: ASF reported not-yes respectively). The velocity of progression of the wave-front of ASF in wild boar is expressed, by month, in km/time, through a derivative function of the surface in the wave-front (value = zero), and is compared between countries. Results: The universal kriging surface had high velocity values on the wave-front of the first years, which is consistent with the input values. The velocity ranged between 0.6 and 54 km/month (mean = 11.28 km/month, SD = 10.48). There are variations in velocity among countries and trimesters. The spatial continuity in the direction E-W is strong. Conclusion: These findings have important implications for ASF control. Assuming equal efforts to combat ASF based on the EU regulation, the differences observed in the velocity of spread between countries could be explained by the different quality of available habitats for wild boar, the knowledge of which is fundamental to tailor disease management strategies in wild boar. Funded by AT 2015-002 (INIA-CISA research-project) and RTA2015-00033-C02-01.