What’s true of all the evils in the world is true of the plague as well. It helps men to rise above themselves. All the same, when you see the misery it brings, you’d need to be a madman, or a coward, or stone blind, to give in tamely to the plague. The Plague, Part 2. Albert Camus.
Black Gold refers to the 99% reconstructed genome of the bacterium Yersinia pestis (Y. pestis) from victim remains of Black Death, also known as plague,dating from 1348 to 1350 in London, England. The DNA sequence is golden because the reconstruction represents the first draft of a genomic sequence from an ancient pathogen of documented origin, allowing scientists to track the organism’s evolution and to determine its relationship to current and emerging circulating strains.The international research team, whose findings were published in the 12 October 2011 issue of Nature, determined that nearly all modern Y. pestis strains are descendants of the medieval variant. Moreover, factors other than changes in the genomic structure of the pathogen, such as environment and host genetics influenced the spread and severity of plague and continue to do so.
Plague has been the designated cause of three pandemics, which altogether killed approximately 200 million people.The first occurred in AD 541, named the “Justinianic Plague”, spreading from central Africa to Asia Minor; “Black Death” was the second pandemic from 1347 to 1665, arising in central Asia and overtaking Europe with the decimation of one-third of the European population; and the third “Modern” pandemic from about 1894 to 1901, spreading from China to Hong Kong to Gulf Coast ports in the United States. Plague is still among us and is a quarantinable disease under international health regulations.
Transmitted to humans generally from infected rodents directly or by flea vectors, Y.pestis infection can take three forms: Bubonic plague, the most common form, involves the body’s lymph nodes; Septicemic plague via the bloodstream, leading to internal bleeding and shock; and Pneumonic plague following inhalation of contaminated droplets and transferable from human to human by coughing or sneezing. Pneumonic plague is highly infectious and rapidly fatal although it can be treated successfully with antibiotics, if diagnosed early. Because Y. pestis bacteria are viable in the air for up to an hour, and thus aerosolizable, they are potential agents of biological warfare; no vaccine for pneumonic plague is currently available in the U.S. Both a live-attenuated vaccine and a formalin-inactivated vaccine have been developed and used, but discontinued due to safety and efficacy concerns. Studies to make a plague vaccine are ongoing.
Y. pestis, one of three yersiniae pathogenic to humans, arose from one of them in short evolutionary time, Yersinia pseudotuberculosis, a soil-dwelling and gastrointestinal pathogen. In the course of its evolution, Y. pestis acquired two additional circular DNA units (plasmids), which replicate independent of the chromosomal DNA within a bacterial cell and account in part for the Y. pestis jump from enteric to flea-transmitted pathogen.
Reconstructing the genome of this ancient pathogen was a tour de force as the scientists retrieved and sorted plague DNA fragments isolated from the teeth of Black Death victims recovered in the 1980s from the East Smithfield cemetery in London; the teeth are among the burial ground artifacts in a museum collection. No modern Y. pestis strain has the same genetic profile as the medieval strain, but the data indicate that few molecular differences separate the time distant pathogens in known virulence-associated genes. The scientific team suggests that genetic changes in pathogens constitute only one factor among many contributing to disease distribution and severity. Further genomic analysis will provide another measure to better understand epidemiology and historical pandemics.
References and Read-More-About-It
1. Bos KI, Schuenemann VJ, Golding GB et al. A draft genome of Yersinia pestis from victims of the Black Death. Nature. 2011 Oct 12. doi: 10.1038/nature10549. [Epub ahead of print].
2. Human Diseases and Conditions. Bioterrorism. http://www.humanillnesses.com/General-Information-and-Infectious-Diseases-A-Co/Bioterrorism.htmlAccessed 10/26/2011.
3. Wren BW. The yersiniae: a model genus to study the rapid evolution of bacterial pathogens. Nat Rev Microbiol. 2003 Oct;1(1):55-64.
4. Huang XZ, Nikolich MP, and Lindler LE. Current trends in plague research: from genomics to virulence. Clin Med Res. 2006 Sep;4(3):189-99.
5. Manbir online. Diseases and conditions. History of plague. http://manbir-online.com/diseases/plagur-history.htm Accessed 10/26/2011.