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.