Animal - Book Report/Review Example

First time, it was identified in 1894 by a French bacteriologist and the pathogen was named after him. At this juncture, it will be most appropriate to understand the nature and the life cycle of Yersinia pestis – plague-causing bacteria. The bacillus lives in the blood of rats and moves in rat community via rat fleas known as Xenopsylla cheopis that essentially functions as a carrier to bacillus. The flea while biting an infected rat takes in Yersinia pestis along with the blood. That is how bacillus reaches to the flea's digestive tract, multiply there forming a solid mass to block the flea's digestion tract.

Because of obstruction in its digestive tract, the flea begins suffering from starvation. Due to pangs of hunger, the fleas moves with more frantic speed to other rats and keep on biting them; however, due to blockage in the digestive tract, the flea fails to swallow the blood and vomit it back to the rat's bloodstream. In this process, some of the Yersinia pestis reaches to the blood stream of an uninfected rat. Further development depends upon the immune system of the rat. If it is quick to respond then infection can be suppressed and bacillus may live in the rat's blood stream as a non-harming parasite.

When some other flea comes into contact of this rat, it gets infected and spreads the infection to other rats. Thus, rats and fleas, being two hosts for this plague-causing bacillus become a reason for its spread (Man and Disease: The Black Death). It is pertinent to note that though the Xenopsylla cheopis prefers to feed on rats, but for some reason when the populations of rats decline, the fleas need to feed on some other rodents or mammals, the risk of spreading Yersinia pestis becomes imminent in other mammals too including humans.

Most of the humans did not have enough resistance to plague bacillus during the medieval period when plague spread at a sporadic rate. Human survival is possible depending upon how quickly immune system responds to the infection. It is also true that immune system remembers the bacillus after their first attack and can thwart any future assault. That is why hardly any person contracts plague twice (Man and Disease: The Black Death). The other form of plague called Pneumonic Plague has been considered more virulent because it spreads from humans to humans without involving fleas as carriers.

When an infected human exhales, the person near to the victim gets infected. Human lungs are so designed that it can ingest air-borne material into the bloodstream quickly and that is why pneumonic plague was found to be more fatal. Usually, it took hours for an infected person to collapse. There was no remedy to the disease until 20th century when modern medical science could invent antibiotics to cure and thwart this deadly disease. Since plague attacked on humans with great speed wiping out families and towns in only a few weeks, its impact on people was horrific.

Merely uttering of the word the 'Black Death', in those days, was enough to cause mental distress and agony across the population. It is terrific to note that during the period plague finished almost over a quarter of the population of Europe and during the period, morale of the entire population reached to its lowest (Man and Disease: The Black Death). Effects of the Black Death across the Europe were unprecedented. The population of E