African swine fever outbreaks in German pig holdings - experiences, epidemiological considerations and genome sequences.

Abstract

Until December 2025, 18 African swine fever outbreaks have occurred in domestic pig holdings in Germany. However, nine of them emerged in western Germany in 2024, representing a separate spatial and temporal cluster. Thus, the current study is limited to the remaining nine outbreaks. We aimed to illustrate the epidemiological background of each of the nine outbreaks. The assessments included the results of the outbreak investigations and of the genome sequencing. This is the first study to provide a detailed overview of these outbreaks and, in particular, to publish the genome sequences involved. In several outbreaks, a connection to the neighboring affected wild boar population was considered likely. The hypotheses were supported by genome sequencing; thus, the study has underscored the benefit of including results of genome sequencing in the evaluation of disease epidemiology. However, outbreaks also occurred on farms without reported cases in wild boar in the vicinity. Similarly, outbreaks were observed in farms with low biosecurity standards but also in farms with very high biosecurity, emphasizing the difficulty to identify a pattern in the outbreaks. Still, it has to be acknowledged that a consistent and sustained compliance with biosecurity measures represents the most important factor in preventing virus introduction.