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Plague persisted in Europe for 3 centuries, DNA analysis shows
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Plague caused by the bacterium Yersinia pestis may have persisted in Europe for 300 years, including the period commonly known as the “Black Death,” according to a recent DNA analysis of human remains in Germany.
The second plague pandemic, which peaked between 1346 and 1353, wiped out almost one-third of the entire human population, researchers said. There has been some debate about whether the disease was continuously reintroduced to Europe from Central Asia via major trade routes like the Silk Road, for example, or if the causative agent of plague persisted in Europe in an unknown host for a longer period than previously assumed. The answer to that question may lie in the similarities or differences in genotypes of Y. Pestis strains present in plague victims.
Figure 1. Original photograph of the triple-inhumation of three male soldiers in Brandenburg, Germany, which is dated to the Thirty Years' War (1618-1648).
Source: Seifert L, et al.
Holger C. Scholz, PhD, from the Bundeswehr Institute of Microbiology in Munich, and colleagues analyzed ancient DNA recovered from 30 victims of the second plague pandemic who were buried at two separate sites in Germany — one in Bavaria and another located in Brandenburg — over the span of roughly 3 centuries. They also compared their findings with data from other European countries.
According to the researchers, eight of the 30 skeletons were positive for Y. pestis-specific nucleic acid. Although some of the victims were buried up to 500 kilometers and 300 years apart, a single genotype of Y. pestis was identified. That same genotype was found in the remains of individuals buried in the East Smithfield cemetery in London between 1348 and 1350, and was “highly similar” to genotypes of Y. pestis strains identified elsewhere in Europe, the researchers said.
Rather than being a product of continuous reintroduction from Central Asia over the course of 300 years or a single pathogen that persisted long-term in an unknown reservoir in Europe, the researchers said the second plague pandemic may have resulted from combination of both scenarios.
“The results of the present study clearly indicate that at least one genotype, which was introduced to Europe at the beginning of the Black Death from Asia, persisted in Europe from the 14th century until the Thirty Years’ War (1618-1648),” Scholz and colleagues wrote. “We therefore suggest a model in which Y. pestis was introduced to Europe from Asia in several waves combined with a long-time persistence of the pathogen in not yet identified reservoirs.”
Some scientists have questioned the role of Y. pestis in the first and second plague pandemics, even suggesting a virus could have been the cause. However, recent studies have confirmed that the bacterium was responsible for both outbreaks.
In a genomic analysis published in 2014, researchers concluded that the first plague pandemic between A.D. 541 and 543 — or “Plague of Justinian” — was caused by a different Y. pestis strain than the one responsible for the Black Death approximately 800 years later. However, both major outbreaks appear to have been transmitted zoonotically from rodents, according to researchers.
“The epidemiological pattern that we propose suggests that several Y. pestis lineages, which are currently ecologically established in rodent foci worldwide, remain capable of emerging and igniting epidemics of plague in human beings, as they have repeatedly in the past,” they wrote. – by John Schoen
Reference:
Wagner DM, et al. Lancet Infect Dis. 2014;doi:10.1016/S1473-3099(13)70323-2.
Disclosure: The researchers report no relevant financial disclosures.
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