Leptospirosis is considered the world’s most widespread bacterial zoonosis and is responsible for 1.03 million illness cases and 60,000 deaths annually. While several comparative genomic studies have revealed insights into the epidemiology, evolution, and genetic contents of Leptospira sp., no study has traced a deep-time co-evolution between these pathogens and their putative hosts. With the advent of ancient DNA, we now have the opportunity to detect microbes that co-occurred at an individual’s time of demise and therefore acquire a better understanding of the emergence and evolutionary history of these pathogens across time. To our knowledge, cases of ancient leptospirosis have been reported in a few humans but not in rodents, although rodents are key candidates to act as host reservoirs for leptospirosis. To address this gap, our project aims to investigate the long-term host-pathogen dynamics by analyzing an extensive dataset of water voles (Arvicola), which are known to harbor high levels of leptospirosis in modern populations. Our dataset spans much of their geographic range across Eurasia and covers various timescales, from 500 thousand years ago (ka) to the present. This way we aim to first detect occurrences of ancient Leptospira strains in ancient and current Arvicola populations. This will allow us to calibrate the leptospirosis phylogeny and have a better understanding of the evolution of the pathogen with regards to the evolution of its host through time and space. Therefore the main objective of this project aims to investigate the coevolution of water voles and Leptospira sp. through metagenomic analyses of modern and ancient DNA. This project has already been granted and will begin in the beginning of January 2025. To conduct this project properly we will need a small compute project to analyze the following generated data.