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.
It is then posed to humans by fleas that feed on the blood of rats and then bite humans, in which the bacterium is passed into the human bloodstream (Aberth, 2000). It takes between four and six days for a person infected with the Bubonic Plague to exhibit symptoms (Truitt, 2001). The most common symptom is swellings known as buboes (hence bubonic) that appear in the lymph glands near the initial flea bite (Douglass, 1996). The buboes are red at first, but later turn a dark purple or black they eventually bust open oozing blood and pus (Douglass, 1996). Other symptoms may include a high fever, often causing delirium, violent headaches, subcutaneous bleeding, and damage to the nervous system caused from the bleeding, which leads to uncontrollable twitching and jerking (Aberth, 2000).
The disease was spread through an infectious fever caused by the Yersinia pestis, passed on by the rat flea. The infection spread to anyone that had contact with the diseased. The infected found themselves pierced by a pain throughout their whole body. Soon after they developed on their thighs or the upper arms a lump the size of a walnut which some people called them “burn boils.” This then pierced them until the patient violently began vomiting blood. The vomiting of blood persisted without stopping for three days, which didn’t give the victims any time to heal their wounds.
The plague was carried into Europe in 1347 by flea-bearing black rats infesting the commercial vessels that brought goods to Mediterranean ports. The Black Death is estimated to have killed 30% to 60% of Europe’s population. The Black Death is endemic to rodents and transmitted to humans by common flea. In humans the disease invades the blood the glands under the arms and goin that would swell, sometimes to the size of an apple or an egg, and dark blotches would also appear on the skin. These blotches had the same meaning for everyone, on whom they appeared.
When a rat is infected, the flea bites the rat then the flea gets infected. The disease fills the stomach of the flea making it so the flea can't digest any more blood. The flea then becomes so hungry that it bites the human. Now the human is infected. The first symptoms are headaches, nausea, vomiting and aching joints.
The word plague means a dangerous disease that quickly spreads and causes death. Alexander Yersin identified the cause of the bubonic plague. He discovered that the disease was being caused by a deadly bacterium which he named after himself, Yersinia pestis. Yersin worked with a scientist named Pasteur in France to develop a treatment to fight the plague. Yersin was the first to suggest that rats and fleas were the main cause for the spreading of the plague.
A flea that is feeding on a rodent that is infected also becomes infected. The bacterium then multiplies inside the flea's gut. The flea's gut then becomes clogged with the bacterium and when the flea tries to bite a human the bacterium is regurgitated into the open wound. The human is then infected with the bubonic plague. Once the human is infected, many biological effects begin to take place.
These ships carried a cargo of flea infested rats, which had guts full of the bacillus Yersinia pestis (the bacteria which causes the plague). Inspectors attempted to quarantine the fleet, but it was too late. Realizing what a deadly disaster had come to them, the people quickly drove the Italians from their city. But the disease remained, and soon death was everywhere. (The Black Death) One eyewitness account said this “"The mortality in Siena began in May.
From Italy, the disease spread all over Europe, traveling along the major trade routes. The rats were responsible for carrying the disease, which was transmitted by fleas from infected rats. The fleas drank the rats' blood that carried the bacteria. The bacteria multiplied in the flea's gut. While the fleas gut was clogged with bacteria, the flea bit the human and regurgitated blood into the wound.
The fleas would then bite into their victims, releasing the disease inside them. The disease, known as the Black Death, is caused by the bacterium, Yersinia pestis (“The Plague”). Once the disease got inside of the victim, symptoms such as the formation of buboes, which is swollen lymph nodes, start to appear under the arm, on the neck, or in the groin area. Normally followed by fever, chills, and muscle aches (“The Plague”). Other symptoms include, extremely foul odor of all body fluids, and gangrene of the finger, toes, and the nose.