PhD Thesis defense by Carolina Muñoz Peréz at the VISAVET Centre of the Complutense University of Madrid

March 21^st, 2024

African swine fever (ASF) is a devastating infectious disease of swine, which is listed as notifiable to the World Organisation for Animal Health (WOAH). In the last few years, the disease has spread worldwide. Nowadays, this pandemic spread poses the greatest threat to the global swine industry. In view of this situation, this doctoral thesis entitled: “Strategies for African swine fever prevention”, aims to develop epidemiological knowledge regarding the most important risk factors for ASF entry into an ASF-free area, in particular, the natural movement of wild boar populations and the international trade of pigs and pork and pork products.

Wild boar populations are playing an essential role in ASF spread and persistence in Europe. Based on this, the first objective of this doctoral thesis is to define the main epidemiological ecoregions in Europe for wild boar. A multivariate clustering method was applied to obtain nine ecoregions in the Western Palearctic realm according to variables related to ecological and sanitary aspects of ASF distribution in wild boar. Subsequently, an analysis was conducted in terms of the extent of the ecoregions and ASF notifications. Several ecoregions stand out for harbouring the greatest of number ASF cases and for being in the vicinity of affected areas, suggesting a relevant role in ASF epidemiology. This cartographic tool could be useful to understand patterns in the distribution and spread of ASF in wild boar in the European scenario. Moreover, it could serve to improve prevention and control strategies, not only in ASF but also in other diseases affecting wild boar.

The second and third objectives of this doctoral thesis are to analyse the other most important risk factors for ASF introduction, in particular, the importation of live swine and the importation of pork and swine products. These studies are specifically focused on Spain. Based on this, quantitative risk assessments were developed following WOAH guidelines to estimate the risk of ASF entry by both of these pathways.

The results revealed an annual probability of ASF introduction by legal import of live swine into Spain of 1.07 × 10−4. On the other hand, the annual probability of ASF introduction into Spain by legal import of swine products was quantified as 1.74 × 10−4. Both analyses showed that the highest risk originated in importations from countries, such as Belgium, Germany, Hungary, Luxembourg, the Netherlands, Poland, and Portugal. Finally, a sensitivity analysis was performed to estimate the parameters with a greater influence on both models. Subacute forms of ASF, swill-feeding practices, and wild boar access to food waste are identified as critical risk factors that require further attention. The studies presented herein could be used to develop and improve prevention strategies that, ultimately, would help reduce the risk of ASF introduction into Spain.

All objectives are specifically focused on the European scenario. The methodology is fully described and can also be used as a model applicable to other regions worldwide. The tools and epidemiological knowledge presented in this doctoral thesis represent a step toward the ultimate objective of this thesis, the prevention of ASF entry into ASF-free areas.