The+Purple+People+Eater

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Yersinia Pestis: The Real Purple People Eater

Abstract Plague was once one of the most feared diseases by humankind. Throughout history, 200 million people have fallen victim to the disease. Plague is a nasty and efficient murderer, capable of killing its host within a few days. At the root of it all is a tiny bacterium known as //Yersinia pestis//. This bacterium has had a massive impact on society, having created three deadly pandemics. The most famous of which, commonly referred to as the Black Death, greatly effected European civilization. The plague is incredibly contagious as it contains several ways of spreading. The most common patterns of transmission are flea bites and inhalation of infected airborne droplets. The disease is able to manifest itself in three forms: bubonic, pneumonic and septicemic plague. If victims are unable to receive medical treatment, they have a 60% chance of succumbing to bubonic plague. Death is almost guaranteed in its other two forms. Recent advancements in medicine have significantly reduced the mortality rate of infected people. Antibiotics such as streptomycin, have reduced the mortality rate of infected victims all the way down to 14.3 % in the United States.

Introduction //Yersinia pestis// is quite interesting in that fact that it had an incredible impact on human history. While it has spawned three waves of pandemics, it is most noted for creating the infamous Black Plague, a horribly bleak time for human history. This outbreak ranks as one of the deadliest pandemics to have ever hit civilization, killing an estimated one third of Europe’s population. Another fascinating characteristic of //Yersinia pestis// is the gruesome and deadly nature of its infection in humans. While I obviously can’t condone its effectiveness in its killing capacity, I find it intriguing how it can kill within such a short time frame. Then there is also the unimaginably, appalling development of buboes that I find amusing in a twisted, horror story sort of way.

It is quite important to note just how huge of an impact the plague during the mid 14th century had on society. As a result of its colossal death toll on the poor population, a surplus of goods were available to the general public and labor demand shot through the roof. These impacts made by the Black Plague are widely believed to have forced the creation of the middle class in Europe (Haddock, 2002). Additionally, the pandemic helped spur the onset of the Renaissance as many people lost faith in the Roman Catholic Church and sought out alternative ways of enlightenment (Gottfried, 1987). Furthermore, the plague helped develop many sanitation and preventive measures of disease in Europe (Blaser, 2007). It is also alarming to learn just how effective of a killer this bacterium really is. With three variations of manifestation, //Yersinia pestis// has been recorded to have killed 200 million people throughout history (Perry and Fetherston, 1997). Untreated bubonic plague has a fatality rate of 60% while its other two forms are almost always fatal (CDC, 2005). All forms of plague are capable of killing a person in under a week (Ibid.).

History This deadly bacterium has its origins rooted in North America and Eurasia (Gage, 2004). It is heavily believed to have spread by route of the Silk Road as merchants traveled between East and West Asia. The first plague pandemic is known as the Plague of Justinian which took place from the mid 6th century to the mid 7th century (Perry and Fetherston, 1997). In its wake it, the plague killed about half of Europe’s population (Ibid.). The death toll for this first wave has been estimated up to as high as 100 million people (Ibid.). The second pandemic of the plague is the Black Plague that struck Europe in 1348 and had several reoccurrences up until the 17th century. Much like its first massive outbreak, this incident claimed 100 million lives (Ibid.). The last major pandemic of the plague was the most widespread but least deadly. The last outbreak originated in China in the mid 19th century and eventually spread to every continent in the globe. Before ending in 1950 //Y. pestis// was able to claim 12.5 million lives in just China and India (Ibid.) However, there was a minor outbreak back in 1994 where 600,000 people were infected in Surat, India (Ibid.).

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Characteristics Yersinia pestis belongs to the Enterobacteria family, meaning that it is a gram-negative, rod shaped bacteria classified as a facultative anaerobe (Tortora, 2010). //Y. pestis// undergoes asexual reproduction by way of fission, with a generation time of 1.25 hours (Perry and Fetherston, 1997). It is quite capable of infecting humans as well as many animals. Mammals, especially rodents, maintain the long-term survival for //Y. pestis// (Ibid.). Indirect physical contact in the form of flea bites is the most common causative case of spreading the disease, but it can also be passed by direct physical contact or airborne transmission (Ibid.). Bactermia, the existence of bacteria in the blood, at 30% is needed to complete the transmission back to fleas (Ibid.).

Infection //Yersinia pestis// is capable of three different manifestations in humans: bubonic, pneumonic, and septicemic (CDC, 2005). The difference between these forms is the location of infection inside of the body. Its most common form, the bubonic plague, is almost always transmitted by flea bites. In this case it is vital for transmission that //Yersinia pestis// is able to form a blocking mass in the proventriculus of the flea (Perry and Fetherston, 1997). This blockage stops ingested blood from entering the stomach. As blood clogs up in the proventriculus, the flea is forced to regurgitate the now contaminated blood back into its host. An estimated 11, 000 to 24, 000 bacilli are regurgitated back into the host’s bloodstream (Ibid.). Following this event, //Y. pestis// bacilli enter the lymphatic system and are killed by the phagocytes via phagocytosis. However, surviving bacteria cells are taken up by the phagocytes, which provides them with an environment that shelters them from further harm. This allows //Y. pestis// to develop virulence factors, like endotoxins and capsules, and reproduce inside the phagocyte, eventually killing it (Ibid.). The bacteria are then released into the extracellular environment where it quickly spreads to the lymph node. Bubonic plague causes large swellings of the lymph nodes which then begin to bleed and become necrotic, forming its defining symptom, buboes (Ibid.). If left untreated the disease can develop into its deadliest forms, septicemic and pneumonic plague (Ibid.).

Pneumonic plague is primarily acquired through inhalation of airborne //Y. pestis// cells (CDC, 2005). The most telltale sign of pneumonic plague is severe coughing that result in hemoptysis, the coughing up of blood (CDC, 2005). Septicemic plague can develop as a secondary infection from the above two formations or it can occur by direct contact through broken skin. In this manifestation, endotoxins secreted by //Y. pestis//, start coagulation cascades in the surrounding area, which causes disseminated intravascular coagulation (Perry and Fetherston, 1997). As clots begin to form blood circulation is cut off to various tissues causing ischaemic necrosis (Levi, 2009). Eventually, the bodies’ ability to clot is exhausted and bleeding becomes uncontrollable. This results in the bleeding into other tissues and organs, creating a red rash to appear on the skin (Ibid.).The most common ways of testing for plague are hemagglutination tests and PCR assays (CDC, 2005). Unfortunately it takes 72 hours for confirmation of plague (Ibid.).

Current Status While //Y. pestis// causes an incredibly deadly disease, developments in medicine and communication have drastically reduced the devastating effects of the bacterium. Due to their ability to inhibit protein synthesis, streptomycin and tetracycline are the two most commonly used antibiotics to fight plague (Perry and Fetherston, 1997). Moreover, there are currently two different vaccines that can be used to prevent infection from //Y. pestis//. Unfortunately, there is much doubt as the whether they can prevent pneumonic plague (Ibid.). Development of survey and alert programs has also helped curb the incidence of plague (Ibid.). These advancements have been so efficient that currently, plague only kills 1,000 to 3,000 people around the world every year (CDC, 2005).Current treatments have been able to reduce the mortality rate to 14.3% of properly cared for victims in the United States (Perry and Fetherston, 1997).

Works Cited

Perry, Robert D., and Jacqueline Fetherston. "Yersinia Pestis--etiologic Agent of Plague -- Perry and Fetherston 10 (1): 35." //Clinical Microbiology Reviews//. American Society for Microbiology, Jan. 1997. Web. 20 Nov. 2010. <[]>.

Cornelius, Guy R., and Anne Boland. "The Virulence Plasmid of Yersinia, an Antihost Genome -- Cornelis Et Al. 62 (4): 1315." //Microbiology and Molecular Biology Reviews//. Dec. 1998. Web. 02 Dec. 2010. <[]>.

"Plague Fact Sheet." //Centers for Disease Control and Prevention//. 7 Jan. 2005. Web. 01 Dec. 2010. <[]>.

Levi, Marcel M. "Disseminated Intravascular Coagulation: EMedicine Hematology." //EMedicine - Medical Reference//. Medscape, 4 Oct. 2009. Web. 03 Dec. 2010. <[]>.

Gage, Kenneth L., and Michael Y. Kosoy. "NATURAL HISTORY OF PLAGUE: Perspectives from More than a Century of Research*." //Annual Review of Entomology// 50.1 (2005): 505-28. //Annual Reviews//. Annual Reviews, 7 Oct. 2004. Web. 10 Nov. 2010. <[]>.

Haddock, David D. "The Black Death and Property Rights." //IDEAS: Economics and Finance Research//. University of Chicago Press, June 2002. Web. 23 Nov. 2010. <[]>.

J, Blaser M. "Passover and Plague." //PubMed//. National Institutes of Health, Winter 1998. Web. 07 Nov. 2010. <[]>.

Gottfried, Robert S. "European Plagues." //Dictionary of the Middle Ages//. Vol. 9. New York: Simon & Schuster Macmillan, 1987. 672-83. Print.

Tortora, Gerard J., Berdell R. Funke, and Christine L. Case. "Normal Microbiota." //Microbiology: An Introduction//. 10th ed. San Francisco, CA: Pearson Benjamin Cummings, 2010. 400-04. Print.