Cattle mass grave from the Roman villa of Vilauba reveals a Clostridium strain harbouring virulence genes

In the ancient Roman world, cattle played an integral role in daily agricultural tasks, providing the means necessary to plough fields, mill grains, and transport goods. The research presented here deals with the remains of 14 cattle discovered in a mass grave at the Roman villa of Vilauba in Catalonia, Spain. According to the archaeological record, it can be ruled out that the animals were slaughtered for consumption, banqueting, or sacrificial purposes. The abnormal circumstances surrounding this mass grave are therefore highly suggestive of a disease outbreak among the herd. By investigating the metagenomic sequences generated from the bovine remains, we identified in multiple individuals a pathogenic Clostridium strain possessing several virulence genes linked to cell adhesion, hemolysis, and degradation of extracellular matrix components. Moreover, we discovered a Mycolicibacterium species phylogenetically related to known opportunistic pathogens. Taken together, these results infer that some of the cattle suffered from a form of soft tissue gangrene, which likely prompted the villa's inhabitants to slaughter the herd.