Re-Emergence and Spread of Haemorrhagic Septicaemia in Germany: The Wolf as a Vector?

Since 2010, outbreaks of haemorrhagic septicaemia (HS) caused by (.) capsular type B (B) emerged in Germany. In 2017, we noticed a close spatiotemporal relationship between HS outbreak sites and wolf () territories. Thus, the main objectives of our study were to investigate the molecular epidemiology of German B-HS-isolates and to assess the role of wolves as putative vectors of this pathogen. We collected 83 B isolates from HS outbreaks that occurred between 2010 and 2019 and sampled 150 wolves, which were found dead in the years 2017 to 2019, revealing another three B isolates. A maximum-likelihood-based phylogeny of the core genomes of 65 B-HS-isolates and the three B-wolf-isolates showed high relatedness. Furthermore, all belonged to capsular:LPS:MLST genotype B:L2:ST122 and showed highly similar virulence gene profiles, but clustered separately from 35 global ST122 strains. Our data revealed that German HS outbreaks were caused by a distinct genomic lineage of B-ST122 strains, hinting towards an independent, ongoing epidemiologic event. We demonstrated for the first time, that carnivores, i.e., wolves, might harbour B as a part of their oropharyngeal microbiota. Furthermore, the results of our study imply that wolves can carry the pathogen over long distances, indicating a major role of that animal species in the ongoing epidemiological event of HS in Germany.