Plague To Humans And Rodents Ships example essay topic

web Bubonic plague has had a major impact on the history of the world. Caused by the bacterium, Yersinia pestis, and transmitted by fleas often found on rats, bubonic plague has killed over 50 million people over the centuries. Burrowing rodent populations across the world keep the disease present in the world today. Outbreaks, though often small, still occur in many places.

The use of antibiotics and increased scientific knowledge first gained in the 1890's have reduced the destruction of plague outbreaks. In Medieval times, with the unknowing help of humans, bubonic plague exploded into a pandemic. Known as the ^3 Black Death^2, it decimated Europe in 1350, killing 1/3 of the population. It disrupted government, trade, and commerce.

It reshaped people^1's perspectives on life and Christianity, and found expression in many works of art. Bubonic plague^1's influence and effects have shaped events of the past and part of our world today. What is the name of the disease? Bubonic plague came by its name because of the symptoms of the disease. Bubonic plague causes very painful, swollen lymph nodes, called buboes. These swollen lymph nodes are often first found in the groin area, which is 'bourbon' in Latin.

This disease became associated with the term 'plague' because of its widespread fatality throughout history. Bubonic plague was also known as the 'Black Death' in Medieval times. This is because the dried blood under the skin turns black. What is / are the causative agent (s)?

Bubonic plague is caused by the bacterium, Yersinia pestis. It is also known as Pasteurella pestis. Other Pasteurella bacillus cause diseases such as tuberculosis. How is the disease transmitted?

Plague is caused by an infection with Yersin pestis, which is a bacterium carried by rodents and transmitted by fleas found in parts of Asia, Africa, and North and South America. The Oriental Rat flea (Xenopsylla cheops) is the most efficient carrier of plague, but other species of fleas (ex. Nosopsyllus, Xenopsylla, Pulex) can also pass the disease on to humans. Overall, 100 species of fleas are known to be infected by the plague bacillus. Plague is transmitted to humans in two ways: -Mostly by being bitten by an infected flea-Sometimes from exposure to plague infected tissue Plague is normally enzootic, (present in an animal community but occurring in only a small number of cases), among rodents.

However, with certain environmental conditions plague reaches an epizootic scale (affecting many animals in any region at the same time). It is after a significant amount of the rodent (usually rats) population dies out, that hungry, infected fleas seek other sources of blood, increasing the risk to humans and other animals. the incubation period of bubonic plague is 2 to 6 days after exposure. Between disease outbreaks, the plague bacterium exists among certain burrowing rodent populations without causing much illness. These animals act as long-term reservoirs of infection.

What happens (biologically) to people who get the disease and why? Once the bacterium, Yersinia pestis, enters the bloodstream, it travels to the liver, spleen, kidneys, lungs, and brain. The incubation period is commonly 2 to 6 days after exposure. Early symptoms include: -shivering-vomiting-headache-giddiness-intolerance to light-pain in the back and limbs-white coating on tongue Eventually, pain occurs in the groin, armpit, and neck (all the areas that contain lymph nodes).

Later, there is painful swelling of the lymph nodes called 'b oboes', hard lumps that begin to appear on the inner thigh, neck, and armpit. Blood vessels then break, causing internal bleeding. Soon, dried blood under the skin begins to turn black. Yersinia pestis, in autopsies, has been found in the periodical sac, spleen, liver, lymph nodes, and bone marrow.

If untreated, plague mortality is very high (up to 75%). Once a person is infected and recovers they become immune. What are the methods available for disease prevention? Fourteenth century physicians didn't know what caused the plague, but they knew it was contagious.

As a result they wore an early kind of bio protective suit which included a large beaked head piece. The beak of the head piece, which made them look like large birds, was filled with vinegar, sweet oils and other strong smelling compounds to counteract the stench of the dead and dying plague victims. Bubonic plague has a vaccine. It lasts for about 6 months. Currently, plague vaccine is not available in the United States.

A new vaccine is being worked on and could be licensed later this year. Travelers to plague infested areas should take prophylaxis antibiotics. The preferred antibiotic for prophylaxis is tetracycline or, and for children 8 or less, sulfonamides. Bubonic plague is easily treated if caught early. Streptomycin is the preferred drug, but, , and chloramphenicol also are effective. Penicillin is useless on plague.

Treatment shortly after exposure can reduce overall plague mortality from 60%-100% to 10%-15%. The most effective way to prevent plague is better sanitary conditions and precautions. These conditions and precautions include: -rat populations should be controlled using rodenticide-effective insecticides should be used to control the flea population that transmits plague to humans and rodents-ships should be fumigated with hydrocyanic gas before arriving in port-conditions around human dwellings should be made more sanitary, diminishing the food and shelter for rodents-separate facilities should be used for livestock-bubonic plague patients should be isolated as soon as diagnosed The improvement of bubonic plague prevention has evolved over the centuries. The people of the 14th century were uneducated and susceptible to superstitions. Some early treatments included: -bathing in human urine-wearing of excrement-placing dead animals in homes-use of leeches-drinking molten gold and powdered emeralds As plague epidemics occurred regularly after 1350, preventive measures emerged. Bubonic plague patients were placed in pesthouses, isolated from the general population.

Ships coming from plague infested areas were forced to stay out of port for forty days. This stopped plague infested individuals from coming ashore, and if plague was present on a ship it would die out during the 40 day quarantine. Doctors wore protective gear to prevent infection. The amazing thing is that until 1890's no one knew what exactly caused plague and spread it. After all, Redi's concept of spontaneous generation, in which living organisms arose from dead matter, wasn't disproved until the 17th century. (For more on the scientific history of bubonic plague, see that section on this web page).

Where does this disease occur, and why? Bubonic plague occurs primarily in areas where there are large communities of burrowing rodents. This is because the rodents act as long term reservoirs of the disease. The virulence of Yersinia pestis is diminished in extremely cold and hot locations.

Major areas of bubonic plague reservoirs are in China, eastern and southern Africa, the Western United States, and parts of Bolivia, Peru, Ecuador, and Brazil. Human infection usually occurs in areas of unsanitary living conditions where humans come into close contact with rats. Rural areas outside of cities, where conditions are poor and access to antibiotics is scare, usually are the focus of plague outbreaks. However, plague cab occur in areas of increased urbanization that bring human beings into large rodent habitats. What has been the historical and social impact of this disease? There have been three major outbreaks of bubonic plague in history.

The first outbreak is known as the Plague of Justinian (542-543). It killed 70,000 in the city of Constaniople in two years. At its peak, 10, 00 people a week died. The plague followed trade routes to France and Italy. Smaller outbreaks occurred for an additional 52 years. Before this time, bubonic plague had been unknown in the Mediterranean.

The Byzantine emperor Justinian (ruled, 527-565) was attempting to reestablish the Roman Empire and was close to completing his dream. The outbreak of plague destroyed his dream. The consequences of the Plague of Justinian are far-reaching. Justinian^1's efforts to reunify imperial Rome failed in a large part to the decrease in imperial resources caused by plague. The failure of Roman and Persian forces to resist Moslem armies in 634 happened because of the diminution of the population in the Mediterranean coastlines from 542 onward. Also, the shift of the center of European culture from the Mediterranean to Northern Europe occurred because of the long series of outbreaks that ravaged the territories within easy reach of Mediterranean ports.

Smaller outbreaks occurred up until 1340. The second major outbreak of bubonic plague, and the most devastating, occurred in Europe in 1346-50. Known as the ^3 Black Death^2, bubonic plague spread across Asia and Europe. It began with the siege of Kaffa, a cathedral town on the Crimean coast.

The Tartars, lead by Jani berg Khan carried the disease from Asia to Kaffa when they laid siege to it. The residents of Kaffa who fled on ships carried the plague with them to Europe. By the end of 1348, plague covered all of Italy and most of France. It crossed over the Alps, and it spread to Switzerland. England was reached in August, and it spread to Scotland, Ireland, Denmark, and most of Germany.

By 1351, the Black Death reached Russia. The Black Death killed about 1/3 of the population of Europe, or 25 million people. In four years it resulted in more deaths than the Plague of Justinian did in fifty. Government, trade, and commerce in Europe almost came to a halt. The Black Death caused the depopulation of about 1,000 villages in England.

There was a drastic reduction of the amount of land under cultivation due to the death of many laborers. This ruined many landowners. The shortage of labor compelled landowners too substitute wages and money rents instead of labor services in order to keep tenets. The Black Death created a preoccupation with death and the afterlife. The Roman Catholic church lost some of its influence as people moved to mysticism and other spiritual expressions. Jews were blamed for the plague and were massacred.

Also, public health institutions came into being because of efforts to stop the spread of the plague. There were recurrences of the plague in 1361-63, 1369-71, 1390, and 1400. Another big outbreak was the Great Plague of London in 1665 which killed 17,440 out of the total population of 93,000. A fire that burned most of the city ended the outbreak.

The third major outbreak of bubonic plague in history began in Manchuria in 1890, reaching San Francisco in 1900. By the time the plague had begun to die out, it killed 12,597,789 people primarily in India and Asia. What is the scientific history of the disease? Major players in modern plague research. The scientific history of bubonic plague begins with Procopius of Caesarea in 541 AD. Procopius is credited with the first detailed description of bubonic plague.

Ideas about what caused the plague were clouded by superstitions and false beliefs up until the late 1800's. Alexandre Yersin and Kita sato Shibasabaroo discovered almost simultaneously the bacillus Pasteurella pestis, the infectious agent of bubonic plague in 1894. Shortly after this, Professor M. Ogata, of the Hygiene Institute in Tokyo, proved that fleas taken from infected rats contain plague bacilli. A.W. Bacot then suggested that fleas might be the carriers of the disease and infected animals while attempting to draw blood. In 1897, P.L. Simond proved that fleas transmitted plague.

The clue that led to this discovery were the bites on the legs of victims. They appeared as small grayish spots and the presence of these bites always brought about the bubonic swelling in the affected region of the body. W.M.W. Haffkine created a vaccine made of killed broth cultures of the plague bacillus. What is in store for the future? Bubonic plague will continue to inflict humans for a long time to come because of plague^1's presence in so many burrowing rodents. Sporadic human cases associated with wild rodents occur annually in the western United States. In 1992 human plague cases were reported in Brazil, China, Madagascar, Mongolia, Myanmar, Peru, the United States, Vietnam, and Zaire.

Major outbreaks in India have occurred as late as 1994. As long as plague infested rodents can come into close contact with human habitats, outbreaks of bubonic plague will continue to appear across the world.