Infection Of Plague example essay topic

Since the reign of Emperor Justinian in 542 A.D., man has one unwelcome organism along for the ride, Yersinia pestis. This is the bacterium more commonly know as the Black Death, the plague. Plague is divided into three biotypes, each associated with one of three major pandemics occurring in history. Each of these biotypes are then divided into three distinct types, classified by method of infection. The most widely know is bubonic, an infection of plague that resides in the lymph nodes, causing them to swell. The Black Death of the 14th century was mainly of this type.

Bubonic plague is commonly spread through fleas that have made a meal from an infected Rattus rattus. The most dangerous type of plague is pneumonic. It can be spread through aerosol droplets released through coughs, sneezes, or through fluid contact. It may also become a secondary result of a case of untreated bubonic or septicemic plague. Although not as common as the bubonic strain, it is more deadly. It has an untreated mortality rate on nearly 100%, as compared to 50% untreated mortality for bubonic plague.

It attacks the respiratory track, furthering the cycle. The third type of plague is septemic. It is spread by direct bodily fluid contact. It may also develop as a secondary result of untreated bubonic or pneumonic plague.

A LITTLE HISTORY As mentioned before, the most known incidence of bubonic plague was in 14th century Europe. In 1346 reports of a terrible pestilence in China, spreading through Mesopotamia and Asia Minor had reached Europe, but caused no concern until two years later. In January of 1348 the plague had reached Marseille in France and Tunis in Africa. By the end of the next year the plague had reached as far as Norway, Scotland, Prussia, Iceland and Italy. In 1351 the infection had spread to include Russia. The plague was an equal opportunity killer.

In Avignon nine bishops were killed, King Alfonso XI of Castile succumbed, and peasants died wherever they lay. Though the plague had, for the most part, ceased less than ten years after it started, it killed nearly one third of the European population. In many towns the dead outnumbered the living. Bodies piled in the streets faster than nuns, monks, and relatives could bury them. Many bodies were interred in mass graves, overflowing with dead, or dumped into nearby rivers. Domesticated cats and dogs, along with wolves, dug dead out of shallow graves, and sometimes attacked those still living.

Many animals did either from plague or lack of care. Henry Knighton noted more than 5,000 dead sheep in one field alone. The death of a very large portion of the work force aided those that were still living. The sheer scarcity of workers enabled the remainder to make demands of higher wages and better conditions.

Farms located on poor soil were abandoned because the demand for grain had decreased, enabling fewer farms, located on the better tracts of land to feed the population. There have been a few encounters with bubonic plague in modern times. In the American and Canadian west, from Texas and Oklahoma in the east to the Pacific Ocean in the west, it is most often transmitted from species of squirrels. The last occurrence of transmissions from rats to people, or people to people in the United States occurred in 1924 in Los Angeles. In that epidemic there were 32 cases of pneumonic plague with 31 fatalities.

Since then there have been around 16 cases a year in the United States, most connected with rock squirrels and its common flea Oropsylla montana. In the years of World War II the Japaneese army formed a special biological warfare division. This unit worked on developing a method to deliver the plague bacteria to the civilian population of China. They tested the effectiveness of the plague as a weapon of war first on prisoners of war, then on unsuspecting civilians.

In their first tests they confined a small group of prisoners in a room with thousands of plague infested fleas. The morality rate in these experiments were somewhere in the neighborhood of 50-60 percent. The next step was to release the plague on the general population of Manchuria. This was accomplished by planes flying over cities and villages and releasing huge amounts of plague infested fleas over the town.

When this proved to be an inaccurate way of spreading the disease, and would periodically result in the infection of the air crew, another method was devised. The infected fleas were packed into the shell of a conventional bomb and dropped, exploding just over the targeted towns. While exact figures are not know, it is known that these attacks killed many people and caused wide-spread terror in the towns. How is the disease transmitted Plague is caused by an infection with Yer sian 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 fascia tus, Xenopsylla brasiliensis, Pulex irri taus) 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.

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