Developing an archaeology of malaria. A critical review of current approaches and a discussion on ways forward

Embracing complexity. Porous cranial lesions and their paleopathological significance in two population samples from Neolithic Northern Germany

OBJECTIVE

To assess phenotypic variation of porous cranial lesions and their co-occurrence with infections of the upper respiratory apparatus and endocranial lesions, to infer disease burden in two different Neolithic socio-economic groups.

MATERIALS

Human skulls of at least 111 individuals from a collective grave at Sorsum (farmers) and 30 individual biurials at Ostorf (aquatic foragers) from northern Germany (c. 3300-2900 BCE).

METHODS

A new data recording protocol for scoring porous cranial lesion phenotypic variation and the assessment of inter- and intra-site frequencies and anatomical distribution. Statistical analysis of lesion frequencies and co-occurrences.

RESULTS

High odds of porous cranial lesions and upper respiratory apparatus lesions co-occurrence, and of subperiosteal new bone formation of the vault (a porous cranial lesion phenotype) and endocranial lesions, are noted for both sites. Site-specific phenotypic profiles and distribution patterns differ. For Sorsum, juvenile individuals show greater porous cranial lesion frequencies and active lesions.

CONCLUSIONS

Considering disease interplay is key for understanding porous cranial lesion phenotypic variation. Disease profiles can be associated with subsistence strategies. The results rule out dichotomic models (e.g. "civilization stress") and support more nuanced reconstructions of the Neolithic social-economic transformations.

SIGNIFICANCE

This study emphasizes the need to adopt data recording protocols that include a wider range of porous cranial lesions to understand overlapping pathophysiological pathways.

LIMITATIONS

Considerable preservation bias of the population samples. Inter-observer error is to be tested. Radiographic analyses are needed to corroborate the results.

SUGGESTIONS FOR FURTHER RESEARCH

Further studies on larger assemblages from different geographical and chronological contexts are needed.

Distinct Physical Properties of β-Hematin in Two Synthetic Media: Compelling Evidence

It is now widely accepted that detailed knowledge of the physicochemical characteristics of the β-hematin crystals, i.e., the synthetic versions of the natural hemozoin crystals, is important for understanding their formation, the design of antimalarial medicines, and malarial diagnosis. We report that the overall physical properties exhibited by β-hematins greatly depend on the synthetic media. Here, we synthesize β-hematin from hemin in aqueous-acetate and in aqueous-oily media and characterize their properties by several techniques. Infrared spectra clearly demonstrate the formation of β-hematin in both media. The β-hematin crystals prepared in aqueous-acetate are composed by needle-like particles with average lengths around 760-770 nm; their lattice parameters and unit cell volumes are larger than those reported in the literature. They are paramagnetic at 300 K and antiferromagnetic at very low temperatures. Their Mössbauer spectra at 298 K, 77 K, and 10 K are consistent with the presence of high-spin Fe (III) and are less asymmetric as a result of the occurrence of fast spin-spin relaxation time, and their surface composition is complex, showing the presence of a multiplicity of iron oxidation and spin states (although with a majority of high-spin Fe3+ ions). In comparison, the β-hematin crystals prepared in aqueous-oily medium have significantly smaller lengths (ca. 560 nm) and slightly larger unit cell volume in comparison to the previous sample. The magnetic measurements show that they are affected by superparamagnetism and paramagnetism at 298 K and the coexistence of weakly ferromagnetic or possibly ferrimagnetic and paramagnetic phases at 80 K. Their Mössbauer spectra at 298 K, 77 K, and 10 K, also consistent with the presence of high-spin Fe (III), show longer spin-spin relaxation times, and their surface composition is also complex containing less surface OH- groups and higher amounts of Fe (II) ions in low- and high-spin states. The observed differences are discussed in relation to the specific formation conditions present in the synthesis medium. The results reported here are of outmost importance for understanding how the physicochemical properties of β-hematins depend on the synthesis conditions.

Intra-individual variability in ancient plasmodium DNA recovery highlights need for enhanced sampling

Malaria has been a leading cause of death in human populations for centuries and remains a major public health challenge in African countries, especially affecting children. Among the five Plasmodium species infecting humans, Plasmodium falciparum is the most lethal. Ancient DNA research has provided key insights into the origins, evolution, and virulence of pathogens that affect humans. However, extensive screening of ancient skeletal remains for Plasmodium DNA has shown that such genomic material is rare, with no studies so far addressing potential intra-individual variability. Consequently, the pool of ancient mitochondrial DNA (mtDNA) or genomic sequences for P. falciparum is extremely limited, with fewer than 20 ancient sequences available for genetic analysis, and no complete P. falciparum mtDNA from Classical antiquity published to date. To investigate intra-individual diversity and genetic origins of P. falciparum from the Roman period, we generated 39 sequencing libraries from multiple teeth and two from the femur of a Roman malaria-infected individual. The results revealed considerable variability in P. falciparum recovery across different dental samples within the individual, while the femur samples showed no preservation of Plasmodium DNA. The reconstructed 43-fold P. falciparum mtDNA genome supports the hypothesis of an Indian origin for European P. falciparum and suggests mtDNA continuity in Europe over the past 2000 years.

Ancient Plasmodium genomes shed light on the history of human malaria

Malaria-causing protozoa of the genus Plasmodium have exerted one of the strongest selective pressures on the human genome, and resistance alleles provide biomolecular footprints that outline the historical reach of these species1. Nevertheless, debate persists over when and how malaria parasites emerged as human pathogens and spread around the globe1,2. To address these questions, we generated high-coverage ancient mitochondrial and nuclear genome-wide data from P. falciparum, P. vivax and P. malariae from 16 countries spanning around 5,500 years of human history. We identified P. vivax and P. falciparum across geographically disparate regions of Eurasia from as early as the fourth and first millennia BCE, respectively; for P. vivax, this evidence pre-dates textual references by several millennia3. Genomic analysis supports distinct disease histories for P. falciparum and P. vivax in the Americas: similarities between now-eliminated European and peri-contact South American strains indicate that European colonizers were the source of American P. vivax, whereas the trans-Atlantic slave trade probably introduced P. falciparum into the Americas. Our data underscore the role of cross-cultural contacts in the dissemination of malaria, laying the biomolecular foundation for future palaeo-epidemiological research into the impact of Plasmodium parasites on human history. Finally, our unexpected discovery of P. falciparum in the high-altitude Himalayas provides a rare case study in which individual mobility can be inferred from infection status, adding to our knowledge of cross-cultural connectivity in the region nearly three millennia ago.

Pathogen prospecting of museums: Reconstructing malaria epidemiology

Malaria is a disease of global significance. Ongoing changes to the earth's climate, antimalarial resistance, insecticide resistance, and socioeconomic decline test the resilience of malaria prevention programs. Museum insect specimens present an untapped resource for studying vector-borne pathogens, spurring the question: Do historical mosquito collections contain Plasmodium DNA, and, if so, can museum specimens be used to reconstruct the historical epidemiology of malaria? In this Perspective, we explore molecular techniques practical to pathogen prospecting, which, more broadly, we define as the science of screening entomological museum specimens for human, animal, or plant pathogens. Historical DNA and pathogen prospecting provide a means of describing the coevolution of human, vector, and parasite, informing the development of insecticides, diagnostics, therapeutics, and vaccines.

Perspectives on anemia: Factors confounding understanding of past occurrence

OBJECTIVE

This paper reviews factors confounding the understanding of the past occurrence of anemia. Using the evidence gathered, a framework is presented of ways forward to enable greater confidence in diagnosing acquired anemia in paleopathology, facilitating insights into longer-term perspectives on this globally relevant condition.

RESULTS

To date, porotic lesions have been central to paleopathological investigations of anemia. The fact that porotic bone lesions are omnipresent and have multiple causes but are likely to have a relatively low, age-related frequency in individuals with anemia, a condition that will have been common in past communities, is confounding.

METHODS

Establishing frameworks that move away from porotic lesions is proposed to facilitate higher levels of more accurate anemia diagnoses in paleopathology.

SIGNIFICANCE

Acceptance of the fundamental principle that anemia may be better considered as a condition requiring metric evaluation of bone structures, supplemented by careful consideration of lesions, will advance understanding of acquired anemia in past communities. Such an approach would provide a clear basis for further consideration of congenital conditions causing anemia, such as sickle-cell disease and thalassemia.

LIMITATIONS

This paper simply opens the conversation on the better diagnosis of anemia in paleopathology; it starts the iterative process of achieving some consensus and progress on diagnosing anemia in paleopathology.

SUGGESTIONS FOR FURTHER RESEARCH

Engagement with ideas presented, sharing data and development of metric parameters will assist in identifying the effects of marrow hyperplasia on bone, enabling more robust work on the important topic of anemia.

The millennial dynamics of malaria in the mediterranean basin: documenting Plasmodium spp. on the medieval island of Corsica

Introduction

The lack of well-preserved material upon which to base the paleo-microbiological detection of Plasmodium parasites has prevented extensive documentation of past outbreaks of malaria in Europe. By trapping intact erythrocytes at the time of death, dental pulp has been shown to be a suitable tissue for documenting ancient intraerythrocytic pathogens such as Plasmodium parasites.

Methods

Total DNA and proteins extracted from 23 dental pulp specimens collected from individuals exhumed from the 9th to 13th century archaeological site in Mariana, Corsica, were analyzed using open-mind paleo-auto-immunohistochemistry and direct metagenomics, Plasmodium-targeting immunochromatography assays. All experiments incorporated appropriate negative controls.

Results

Paleo-auto-immunohistochemistry revealed the presence of parasites Plasmodium spp. in the dental pulp of nine teeth. A further immunochromatography assay identified the presence of at least one Plasmodium antigen in nine individuals. The nine teeth, for which the PfHRP-2 antigen specific of P. falciparum was detected, were also positive using paleo-autoimmunohistochemistry and metagenomics.

Conclusion

Dental pulp erythrocytes proved to be suitable for the direct paleomicrobiology documentation of malaria in nine individuals buried in medieval Corsica, in agreement with historical data. This provides additional information on the millennial dynamics of Plasmodium spp. in the Mediterranean basin.