deadly Archives - New Historian

New Insight into the Deadly Reach of Sixth Century Plague

Yersinia pestis, the bacterium behind the Black Death, could also have been behind the sixth century plague epidemic. Michal Feldman, Johannes Krause and Michaela Harbeck, scientists based in Germany who are among the authors of the study, have recovered the bacterial culprit from sixth century skeletons found in Altenerding, an ancient southern German burial site near Munich. The genome found at Altenerding dates back to the beginnings of the outbreak of the plague, and confirms Yersinia pestis was the bacteria behind the outbreak. The new sequence reveals new insights into the molecular evolution of Yersinia pestis since the Byzantine period. It has also revealed new features that couldn’t be detected in a previous ‘draft genome’ of the bacterium, including 30 newly identified mutations and structural rearrangements unique to the Justinianic strain. “The fact that the archeological skeletons which gave these exciting insights were excavated over 50 years ago underscores the importance of maintaining well curated anthropological collections,” said Harbeck. “We were very fortunate to find another plague victim with very good DNA preservation in a graveyard just a few kilometers from where the individual analyzed in Wagner et al. [a recent study describing a draft genome] was found. It provided us with the great opportunity to reconstruct the first high quality genome in addition to the previously published draft genome.” Harbeck and colleagues’ results suggest that the strain of Yersinia pestis behind the Justinian Plague was more genetically diverse than previously thought. They are still unable to determine how and why the lethal pathogen reached Germany, however. Beyond simply analysing the development of a sixth century disease, the study could have far reaching applications. The authors have used the results to develop new guidelines that may improve the quality and authenticity of genetic data recovered from ancient pathogens. In addition, with plague re-emerging in certain regions of the world, the study provides a historical resource for the evolutionary changes, adaptation and human impact of the disease. “Our research confirms that the Justinianic plague reached far beyond the historically documented affected region and provides new insights into the evolutionary history of Yersinia pestis, illustrating the potential of ancient genomic reconstructions to broaden our understanding of pathogen evolution and of historical events,” said Feldman. “Our reanalysis of previous datasets stresses the importance of following strict criteria to avoid errors in the reconstruction of ancient pathogen genomes.” Image courtesy of State Collection of Anthropology and Palaeoanatomy Munich]]>

Deadly Pesticides Banned in the 1970s Still Increasing Autism Risk

Environmental Health Perspectives. Organochlorine chemicals, used in pesticides and insulating material, were banned in 1977. The dangerous compounds were thought to have been confined to history; but the recently published study suggests that they might still be haunting us in the form of a link between higher levels of exposure to the chemicals during pregnancy and an increased risk of autism spectrum disorder in children. The results suggest that children born after being exposed to the highest levels of certain compounds of the chemicals during their mother’s pregnancy were 80% more likely to be diagnosed with autism compared to those who had only been exposed to the very lowest levels of these chemicals. Despite the 1977 US ban on organochlorine chemicals, such as DDT, the compounds remain in the envrionment. Human exposure to the chemicals comes when they are absorbed into animals whose meat make up part of our diet. “There’s a fair amount of research examining exposure to these chemicals during pregnancy in association with other outcomes, like birth weight — but little research on autism, specifically,” said Kristen Lyall, ScD, assistant professor in Drexel University’s A.J. Drexel Autism Institute and the lead author of the study; in a Drexel University press release. “To examine the role of environmental exposures in risk of autism, it is important that samples are collected during time frames with evidence for susceptibility for autism — termed ‘critical windows’ in neurodevelopment. Fetal development is one of those critical windows.” Two different classes of organochlorine chemicals formed the basis of the study: olychlorinated biphenyls (PCBs, which were used as lubricants, coolants and insulators in consumer and electrical products) and organochlorine pesticides (OCPs, which include chemicals like DDT). Rachel Carson’s 1962 book, Silent Spring, documented the detrimental effects pesticides such as DDT had on the environment. It was a watershed moment in the history of environmentalism in the USA, challenging the disinformation propagated by chemical companies and ultimately leading to the ban on DDT and other organochlorines. Lyall and colleagues’ work however, has shown the long term impact of the historical use of these chemicals. “Exposure to PCBs and OCPs is ubiquitous,” said Lyall. “Work from the National Health and Nutrition Examination Survey, which includes pregnant women, shows that people in the U.S. generally still have measurable levels of these chemicals in their bodies.” For the test, participants from a population sample of 1,144 children born in Southern California between 2000 and 2003, were divided into three groups: 545 who were diagnosed with autism spectrum disorder, 181 with intellectual disabilities but no autism diagnosis, and 418 with a diagnosis of neither. Blood tests taken from the second trimester of the mother’s pregnancy were then used to determine the level of exposure to PCBs and OCPs. Lyall stressed that the level of exposure was key in determining risk. “Adverse effects are related to levels of exposure, not just presence or absence of detectable levels,” she said. “In our Southern California study population, we found evidence for modestly increased risk for individuals in the highest 25th percentile of exposure to some of these chemicals.” The consequences of the chemicals were not restricted to autism; the highest exposure to PCBs seemed to double the risk of a child being diagnosed with intellectual disabilities when compared with the cases of the lowest exposure. “The results suggest that prenatal exposure to these chemicals above a certain level may influence neurodevelopment in adverse ways,” Lyall said. The team plan to continue their work, to gain more of an understanding of how chemicals banned decades ago continue to haunt us in the present. “We are definitely doing more research to build on this — including work examining genetics, as well as mixtures of chemicals,” Lyall said. “This investigation draws from a rich dataset and we need more studies like this in autism research.” The full study is available here ]]>