Ancient animal reservoirs of zoonotic diseases

Since the COVID-19 pandemic, diseases caused by pathogens that spread from animals to humans have become a phenomenon widely recognised by a broad public. It is less well known that such processes date back a very long time, and yet most of today's infectious diseases in humans are so-called zoonoses. Different lines of evidence suggest that the Eurasian Bronze Age in the 4^th and 3^rd millennium BCE was a pivotal period when many zoonoses emerged that still exist today.

“The Bronze Age period was characterized by major human migrations and, importantly, the widespread adoption of pastoralism – a type of subsistence based on domesticated animals. While it is hypothesized that this may have paved the way for the emergence of zoonoses, ancient pathogen DNA investigations of animal remains are so far largely lacking.” explains Anne Kathrine W. Runge, lead author of a new study now published in Nature Communications, in which the Eurasia Department and the Archaeozoological Research Group at the DAI headquarters played a key role.

Animal Bones as a Research Source
The reconstruction of ancient pathogen genomes from animal remains faces additional challenges compared to the more established ancient pathogen genome reconstruction from human remains. Felix M. Key, research group leader at the Max Planck Institute for Infection Biology, Berlin explains this with the fact that animal food remains were often affected by cooking, the pathogen DNA identification is even more challenging. However, this research is also a unique opportunity to trace and identify reservoirs of prehistoric zoonotic diseases, the geographic spread, and the genetic mechanisms facilitating spillover into the human population.

Sites and Collaborations
For this study, the DAI was able to draw on expertise in archaeozoology (R. Gillis, N. Benecke) and provide a comprehensive set of samples from the relevant period, e.g. from the excavation sites at Pietrele (S. Hansen) and Petreni (S. Hansen, R. Uhl) in South-Eastern Europe, and from North Caucasian sites resulting from long-term bioarchaeological research in the region (S. Hansen, S. Reinhold) or the Tilla Bulak site in Uzbekistan. Working alongside specialists in palaeogenetics and palaeopathology, suitable individuals were thus selected.

Initial Findings and Outlook
In addition to numerous genomes of diseases that could not be precisely identified down to the pathogen, two pathogens were detected – Streptococcus lutetiensis and Erysipelothrix rhusiopathiae – which cause inflammation of the mammary glands (mastitis) and skin infections respectively. The study thus provides an initial approach to a new field of research, for which animal bone remains from archaeological sites form the basis. They can contribute to a better undestanding of the origins of modern zoonotic diseases, clarifying their history and age.