African swine fever virus (ASFV) in wild boar – modus operandi

Dr Tomasz Podgórski

Czech University of Life Sciences, Prague, Czech Republic & Mammal Research Institute, Polish Academy of Sciences, Białoweża, Poland

Date: Wednesday, 14.11.2018, 13:00, Cent Lecture Theatre 0142                                         How to get there: Lecture theatre 0142 is c. ~15 meters to the right after entering CeNT

Abstract. African Swine Fever (ASF) is a devastating viral disease of wild and domestic suids. It results in high lethality and has severe socio-economic consequences. The disease has been spreading among wild boar – host of the ASF virus in the wild – in eastern Europe for a decade now, following its first occurrence in Georgia in 2007. However, the role of wild boar ecology and behaviour in the epidemiology of ASF is poorly understood and remains largely speculative. I will present the most recent findings on the factors underlying ASF dynamics in Poland and discuss their relevance for disease control and wild boar management. First, host mobility is often expected to enhance spread of infectious diseases. In contrast to these expectations, wild boar movements were found to be poor predictors of ASF dynamics in space and time. Severity of the disease, which quickly hampers extensive movements and restricts disease transmission to only the most immediate individuals, appears to limit the influence of host movements on ASF spread. Wild boar social structure, the short duration of low-level virus shedding, and high virus-induced lethality most likely shape the gradual spread of ASF in space, estimated at 1 – 2 km/month within the wild boar population. Second, host abundance and landscape structure often interact to shape spatial patterns of many wildlife diseases. Occurrence of ASF was positively related to wild boar densities and this effect was stronger at locations near previous ASF incidents. ASF was also more likely to occur in forested areas and this pattern was consistent at low and high wild boar densities. Third, indirect transmission of ASFV, i.e. through infectious carcass, can play a primary role in the epidemiology of ASF in wild boar but its importance relative to direct transmission in this host-pathogen system is unknown. Using simulation models and epidemiological field data, we found that carcass-based indirect transmission is more prevalent than direct route and the role of indirect transmission becomes more important with decreasing host densities. These findings suggest that disease control efforts should target high-density populations and suitable habitats (large forested areas), emphasize removal of carcasses and consider how reductions in host densities may drive carcass-based transmission. The intensity of control measures should decrease with distance from the infected area to match the observed spatial pattern of ASF occurrence probability.