The Plague paper - The Plague The Plague, often thought of...

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The Plague The Plague, often thought of as just one disease, is actually a term that refers to several systemic diseases caused by the bacteria Yersinia Pestis. Yersinia pestis is a bacterium that is primarily seen in rodent populations, and more specifically in rats. It is a member of the Enterobacteriaceae family of bacteria, and is Gram negative when looked at under a microscope. 1 Some other examples of Enterobacteriaceae include salmonella and shigella. Plague is exemplified by periodic outbreaks of disease in the rodent populations. During these outbreaks, infected fleas that have been deprived of their normal hosts search for other sources of blood. This increases the risk to humans and other animals frequenting the area because they are the next source of blood sought out by the fleas. 2 When humans are infected with the bacteria, the resulting disease is known as the Bubonic plague, named for the “buboes” or swollen glands that it causes. There are also two other manifestations of the plague named the septicemic plague and the pneumonic plague. Epidemics of plague in humans usually involve house rats and the fleas that live on them. These epidemics continue to occur in some developing countries, particularly in rural areas where house rats are more common. 3 Transmission between humans can also occur with the pneumonic plague because it can be spread in air droplets produced from the human body, usually through a cough or sneeze that sprays the droplets into the air. There are various signs and symptoms that indicate an infection with the bubonic, pneumonic, or septicemic plagues. If the vector is a flea, the bacterium lingers in its esophagus, preventing food intake, which causes the flea to desperately seek food. When it bites the human, it regurgitates bacterium laden fluid beneath the skin, where it begins to invade the surrounding cells, marking the beginning of an infection. 4 The infection attacks nearby lymphoid tissue, producing the namesake bubo, an inflamed, virulent, and hemorrhagic lymph node. 5 The infection can potentially spread to every organ, including the lungs, kidneys, liver, spleen and rarely even the brain. The more virulent pneumonic plague is spread by direct contact and inhalation of the bacteria, or when the bubonic plague spreads into the airways and lungs. The septicemic plague occurs when the infection proceeds directly to the bloodstream as opposed to passing through the lymphatic system first. Because of this, the bubo does not occur in septicemic plague. The range of symptoms for the plague is wide, and differs depending on the manifestation of the infection in the body. 6 All three manifestations of plague are acute, meaning that the symptoms appear suddenly after the bacteria invades the body, making accurate diagnosis and quick treatment vital to the survival of the 1 "Plague Information." Division of Vector-Borne Infectious Diseases . 30 Mar 2005. Centers for Disease Control. 9 Dec 2007 <http://www.cdc.gov/ncidod/dvbid/plague/info.htm>.
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This note was uploaded on 04/15/2008 for the course BIOLOGY 10100 taught by Professor Huie during the Spring '06 term at Ithaca College.

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The Plague paper - The Plague The Plague, often thought of...

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