Abstract
The plague of 1630–1632 was one of the deadliest plague epidemics to ever hit Northern Italy, and for many of the affected regions, it was also the last. While accounts on plague during the early 1630s in Florence and Milan are frequent, much less is known about the city of Imola. We analyzed the full skeletal assemblage of four mass graves (n = 133 individuals) at the Lazaretto dell’Osservanza, which date back to the outbreak of 1630–1632 in Imola and evaluated our results by integrating new archival sources. The skeletons showed little evidence of physical trauma and were covered by multiple layers of lime, which is characteristic for epidemic mass mortality sites. We screened 15 teeth for Yersinia pestis aDNA and were able to confirm the presence of plague in Imola via metagenomic analysis. Additionally, we studied a contemporaneous register, in which a friar recorded patient outcomes at the lazaretto during the last year of the epidemic. Our multidisciplinary approach combining historical, osteological and genomic data provided a unique opportunity to reconstruct an in-depth picture of the last plague of Imola through the city's main lazaretto.
Highlights
Imola is a city located in the Italian province of Bologna and the region Emilia-Romagna
We apply a multidisciplinary approach to study the plague outbreaks in Imola between 1630 and 1632 by analysing the remains discovered in four mass graves excavated at the Lazaretto dell’Osservanza and by integrating data from an unpublished register detailing the outcomes of patients, which were treated at the lazaretto at the time of the outbreak
The results of this study identify the causative pathogen of the epidemic, which affected Imola between 1630 and 1632, as Yersinia pestis
Summary
Contrary to Kraken[2], M etaphlan[218] yielded no Y. pestis hits for all shotgun datasets (Table 2 and Fig. S2) This is not surprising considering the low number of observed hits using Kraken[2]. Shotgun reads for all three samples were mapped against the Y. pestis CO92 reference sequence (Table 3 and Fig. S5). The reads mapping to the human mitochondrion showcased clear signs of deamination (Fig. S4), which combined with the small insert sizes (mean 48.59–69 bp) observed across all samples, is consistent with aDNA. Unique reads mapping to the Y. pestis CO92 reference genome (MQ > 30) were extracted and taxonomically classified using both Kraken[2] and Metaphlan[2] (Table 2, Fig. S2). While low when considering that multiple enriched libraries were used for this assembly, the coverage across plasmids seems to increase with copy number and we could confirm the presence of the Y. pestis specific plasmids pPCP1 and p MT19
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