The historical prevalence of infection with Ascaris spp. and Trichuris trichiura in Europe was influenced by a combination of population density and climate

Abstract Infections with soil-transmitted helminths, Ascaris spp. and Trichuris trichiura , were commonplace across Europe prior to the Industrial era. The eggs of these nematodes are environmentally resilient and can be recovered from the pelvic/sacral region of millennia-old skeletal samples, allowing an estimation of the frequency of infection among sets of remains at a given location, representing a proxy for the prevalence of infection at the time of death. Here, we assemble a dataset of the observed frequency of Ascaris spp. and T. trichiura in human remains from published studies covering 54 European archaeological sites. We present a geospatial analysis of Prehistoric to pre-Industrial sites within this dataset and demonstrate a relationship between historical population density and observed parasite frequency. Higher historical population densities were associated with a greater probability of being infected, but the minimum population density required for a high frequency of T. trichiura was greater than that required for Ascaris spp. The range of temperatures associated with higher frequencies of T. trichiura was also smaller than that for Ascaris spp. We propose that whilst the transmission of both parasites is affected by the interactions between population density and environmental conditions, T. trichiura is more fastidious than Ascaris spp., which may explain the discrepancies between the observed frequencies of these parasites in the archaeoparasitological record. These data provide insight into factors that affect nematode prevalence in the absence of modern anthelminthics and could prove useful in setting baselines for studies aimed at reducing infection in modern endemic communities.