Universiteit Leiden

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Research project

Mapping Medieval Malaria

A multidisciplinary analysis of the distribution and impact of malaria in the Netherlands.

2019 - 2023
Rachel Schats
NWO Veni NWO Veni
Elise Mathilde Fonds Elise Mathilde Fonds
Leiden University Fund Leiden University Fund
EASI-Genomics EASI-Genomics


This project studies the distribution and impact of a previously neglected, yet potentially influential medieval disease in the Netherlands: malaria. Malaria is known to have had—and still has—a massive impact on health. The disease is associated with debilitating symptoms such as fevers, muscle pains, and severe anaemia, incapacitating entire populations. Although currently absent in the Netherlands, written records indicate that the disease was endemic here from the 17th to the mid-20th century, mainly in the coastal regions. Considering the environmental circumstances, particularly along the coast, it is very likely that malaria was present in the medieval period as well. The paucity of historical information concerning disease in this period means that malaria is only rarely included in discussions on medieval health, hampering our interpretations of past societies. Gaining a better understanding of malaria in the medieval period is therefore essential.

Cribra orbitalia

While the paucity of historic documentation has thus far limited the possibilities to study past malaria, recent developments in osteoarchaeology allow for an assessment of the disease in skeletal remains. Several palaeopathological studies suggest that a skeletal indicator of anaemia, termed cribra orbitalia (see figure) can be used as a marker for the disease in the archaeological record. Although cribra orbitalia is commonly described as the result of general physiological stress, since anaemia can be the result of many illnesses, there appears to be a strong correlation between this orbital pathology and malaria. A pilot study by Schats demonstrated a similar correlation between the orbital pathology and potential malaria endemic areas for the medieval period in the Netherlands.

Building on these new insights, this project investigates cribra orbitalia prevalence in human skeletal remains from several medieval archaeological sites in order to identify potential malaria regions. These data will be supported by biomolecular data demonstrating the presence of the disease in bone. Subsequently, by combining these results with contextual biological and archaeological data, the socioeconomic consequences of malaria on medieval society will be studied.

The two main objectives of this project are to assess (a) the distribution and (b) the socioeconomic implications of malaria in the medieval Netherlands to better understand its influence on individuals, communities, and society as a whole.

To meet these objectives, this research project is divided into three phases with separate materials and methods. Phases 1 (mapping cribra orbitalia) and 2 (biomolecular identification of malaria) will assess the distribution of malaria (a). The impact of malaria (b) will be studied in phase 3 (malaria in its social context).

Phase 1

The first phase of this research will create a malaria prediction model by investigating the medieval prevalence and distribution of cribra orbitalia using concepts from spatial epidemiology. This will result in a map indicating cribra orbitalia hotspots (i.e., areas where the orbital pathology is highly prevalent), which will serve as a proxy for the presence of malaria and as such will determine biomolecular sample selection in phase 2. To do this, human crania from 29 medieval sites spread across the Netherlands will be analysed for the presence or absence of cribra orbitalia.

Phase 2

In the second phase, the findings from phase 1 will be supported by the identification of malaria in the bones themselves. this project will apply a new method pioneered and validated by Dr. J. Inwood (Yale University) that targets the polymer hemozoin, a disposal product formed from the digestion of blood by the malaria parasite. A sample 200 individuals from areas where malaria is expected and 50 individuals from areas with low malaria expectancy (based on results in phase 1), as a negative control, will be subjected to biomolecular testing.

Phase 3

Phase 3 moves beyond the distribution patterns produced in earlier phases of this investigation by looking at malaria in a multiscalar fashion illuminating what the disease meant to individuals, communities and society as a whole. To do so, this third phase combines the data collected in phase 1 and 2 with contextual biological information of the individuals, such as data on sex and age-at-death, and archaeological and historical information (i.e., living environments (rural/urban), house types, activities, and population densities). By integrating local narratives with current clinical data on the physical and social effects of malaria on human health, an assessment of the impact of malaria on individuals and communities can be made.

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