The fur trade could have spread the scourge in Europe

A new, old DNA study shows that plague outbreaks of the fourteenth century could result from repeated introductions of Yersinia pestis into Europe. Trade routes, including the fur trade routes, would have contributed to the rapid spread of plague throughout Europe during the Middle Ages.

Yersinia pestisis is the causative agent of bubonic and pulmonary plague in humans. The plague is primarily a wildlife disease and is maintained in reservoirs, which are present today on every continent except for Australia and Western Europe. .

Undoubtedly, the Black Death, which marks the arrival of Y. pestisinto in Europe in 1347, represents one of the most significant events that marked the beginning of the second plague pandemic during the medieval period. In fact, from 1347 to 1353, the plague spread throughout Europe as a wildfire, resulting in a 30% decline in the European population. After this dramatic period and for more than 350 years, Europe has experienced a series of recurring devastating epidemics. pestis.

In recent decades, various studies have attempted to understand the origin of these epidemics. Two hypotheses emerged from these studies. According to the first hypothesis, after a first introduction during the Black Death, one or more reservoirs of Y. Pestis have been established in Western Europe – which explains these recurring epidemics.
"The other hypothesis suggests that the plague was introduced several times in western Europe from a reservoir located in eastern Europe / central Asia and that it spread through the trade routes and by human movement, "says Professor Nils Chr. Stenseth. He has headed the University of Oslo's Center for Ecological and Evolutionary Synthesis (CEES) for more than 10 years and is now a strategic advisor to the UiO's Faculty of Mathematics and Natural Sciences.

In a new article of the CEES, published in PNAS, these two scenarios are studied with the aid of five recently presented ancient genomes (ADNa) of Y. pestis, isolated from skeletons distributed in archaeological sites of the South (Abbadia San Salvatore). , Italy and St. Lawrence). Cabrerisse, France) in northern Europe (Bergen-op-Zoom in the Netherlands and Oslo, Norway). The ancient genomes of Abbadia San Salvatore and Oslo are the earliest ancient DNA sequences reported from Italy and Norway.

Unlike previous studies, the authors constructed an integrative approach to interpret all the ancient genomes of the second plague pandemic with respect to their historical context. A total number of strains of 126 Y. pestis and 15 old genomes were analyzed in this study. Five of the eleven old DNA samples from the second plague pandemic were part of the first wave of introduction of Y. pestis into Europe during the Black Death.

These old DNA samples were isolated in the cities of Abbadia San Salvatore (Italy), Saint-Laurent-de-la-Cabrairisse (France), Barcelona (Spain), London (United Kingdom). Kingdom) and Oslo (Norway). Curiously, all these ancient genomes were identical except for the isolated one of Abbadia San Salvatore, for which the authors discovered two additional point mutations.

Historical data on contacts and bed wills conducted by the authors revealed the high percentage of people killed by the plague in the four months that followed late June-early September 1348 in Abbadia San Salvatore. CEES researcher, Amine Namouchi, and her colleagues argue in their article that these two additional point mutations were acquired via a large chain of transmission in Italy, rather than in a newly created local wildlife reservoir. Regarding the DNA found in Oslo, the authors found that it was probably dated to 1348. This corresponds to the historical, archaeological and radiocarbon dating data described in their paper.

A new hypothesis
While the origin of the Black Death remains unclear, the authors advance, in their article on the PNAS, a new hypothesis that links the onset of the Black Death to the arrival of a wide variety of furs in the ports of the Black Sea to 1340 departing from trade routes. from Sarai.

In fact, during the same period, a new continental route linking Sarai, Tana and Caffa had been established with the support of the Golden Horde, observes Amine Namouchi and his colleagues. The Golden Horde was originally a Mongolian then Turkic khanate established in the 13th century and hailing from the northwestern sector of the Mongol empire. The Crimean khanate and the Kazakh khanate, the last vestiges of the Golden Horde, survived until 1783 and 1847 respectively.

Just after the period of the Black Death, the authors confirm the so-called "pestis secundat" that occurred from 1357 to 1366.
"The DNA group belonging to The Pestis Secundain includes samples from London, Bolgar-City (Russia) and the two recently introduced new Bergen-op-Zoom DNAs. Four-point mutations separate the DNAa group from the black plague from the group belonging to thepestis secunda. Corroborated by the historical data, we affirm that the pestis is also the result of the introduction of Y. pestisalong the fur trade routes established between Novgorod (Russia) and Western Europe through the Hanseatic League ", Namouchi adds.

Overall, in this new article published in PNAS, describing all of the previously described and newly described YDNAs. Namouchi and his colleagues provided further evidence that recurrent plague outbreaks during the second plague pandemic were the result of multiple waves of introduction of Y. pestis from a reservoir in Eastern Europe / Central Asia.

This result is in line with previous studies based on ecological evidence. Trade routes, including the fur trade route, as well as human movements would have contributed to the rapid spread of plague throughout Europe during the Middle Ages.

The investigation at the origin of the new scientific paper was carried out as part of the MedPlag research project, led by the paleogeneticist and CEES researcher, Barbara Bramanti. In 2013, she received an advanced grant from the European Research Council (ERC). The grant is used to study, with the help of DNA technology, the plague and other potential human diseases caused by the microbes of the Middle Ages.

Reference: Amine Namouchi, Meriam Guellil, Oliver Kersten, Stephanie Hänsch, Claudio Ottoni, Boris V. Schmid, Elsa Pacciani, Luisa Quaglia, Marco Vermunt, Egil L. Bauer, Michael Derrick and Anne Ø. Jensen, Sacha Kacki, Samuel Cohn Jr., Nils C. Stenseth and Barbara Bramanti: Integrative approach using the genomes of Yersinia pestis to revisit the historical landscape of the plague during the medieval period. PNAS, November 26, 2018.

Source: University of Oslo