Introduction
Bubonic plague is one of the three forms of plague that are transmitted by the bacterium Yersinia pestis. After infection, the microorganism undergoes an incubation period of seven days and then presents flu-like symptoms, including headaches, fever, and vomiting. The areas closest to the bacterium’s point of entry develop swollen lymph nodes that could break open. It is transmitted to human beings through bites of infected fleas, inhalation, or by physical contact with infected animals. The plague was cited as the cause of the Black Death that killed approximately 50 million people in Europe during the 14th century (1). Historically, the plague has appeared in three separate pandemics. The first affected the Sassanian Empire and the Eastern Roman Empire, second affected Europe during the Late Middle Ages (the Black Death), and the third appeared during the mid-19th century in eastern Asia. Today, the plague is treated through the administration of antibiotics and the implementation of preventive measures.
History
As mentioned earlier, their main pandemics have been recorded in history in different parts of the world. The first pandemic was recorded in the Sassanian and the Byzantine empires (2). Emperor Justinian was infected, but his doctors saved him through the use of a wide array of treatment modalities. It was named the Plague of Justinian to honor the emperor. During the 6th century, about 25 million people succumbed to pestilence (1). The second pandemic appeared during the Late Middle Ages in Europe, and it is commonly referred to as the Black Death. The plague broke out in 1347 and led to the elimination of a third of the European human population (2). Several theories have been presented to explain the adverse effects of mass mortality. A section of historians has argued that the pandemic led to an increase in warfare and crime. The third pandemic emerged in the mid-19th century in Eastern Asia. The initial cases of the plague were reported towards the end of the 18th century, and it remained localized in Southwest China for a prolonged period before spreading to other areas. More than 80,000 people died during the first six months of the year 1894 (2). The plague began spreading to other parts of the world in the later years of the 19th century.
The Black Death
The Black Death was a disastrous plague that spread across the world between 1346 and 1353, killing more than 50 million people in Europe, Eurasia, and North Africa (1). China was cited as the source of the epidemic. However, recent research has shown that it originated in the steppe region in 1346 and spread to other regions (2). It began during an attack launched on Italians by the Mongols. When they fled, they carried the plague with them and introduced it to various parts of Europe.
Causes
Two theories have been put forward to explain the source of the plague: the early theory and the modern theory. According to the early theory, pestilence was caused by the heavens. Muslim scholars argued that the plague was God’s way of reassuring the people that they had a place reserved for them in heaven (2). They further stated that it was a punishment for the nonbelievers. Some scholars went as far as cautioning people against trying to treat a God-sent disease. However, a section of people who believed in science ignored the warnings and applied the preventive and treatment measures that Europeans were using to fight the plague.
The modern theory attributed the emergence of the disease to climatic changes in Asia that led to the mass migration of rodents from one area to another, thus spreading the plague. The fleas that transmit bubonic plague are found in rodents, common in areas like Central Asia, North India, and Western Asia. The bacterium responsible for the plague’s transmission was discovered in 1894 by Alexandre Yersin after the eruption of an epidemic (1). He discovered the causative agent Y. pestis and found out that it was harbored by rodents, with the rat as the major means of transmission (5). Further studies by Paul-Louis Simond in 1898 revealed that the bacterium was transmitted through bites of fleas that had harbored the microorganism throughout its incubation period (1). He stated that the blockage of the host’s midgut after the bacterium’s replication changes the feeding habits of the host. The flea eats excessively and tries to decongest the gut through regurgitation, leading to the expulsion and the deposition of plague bacteria at the feeding site, thus causing infection.
Transmission Within and Outside Asia
Researchers have maintained that the bacteria that caused the three bubonic plague waves originated from either in or near China. Extensive analysis revealed that the spread of the disease depended primarily on the transmission caused by fleas (3). Historians have identified Nestorian graves dating back to the 1330s that contain evidence of the plague (2). Epidemiologists suggest that the plague could have spread to China and India from Issyk-Kul in Kyrgyzstan. The modern theory argues that the transmission of the plague to other parts of the world was done through rat fleas on ships (2). The rodents would often die inside the ships due to the infection, however, the fleas would survive and find new hosts in the places where the ships docked (1). Rat fleas live within their hosts and move with them to new geographical locations. This gives the plague a distinctive pattern of dissemination and development. For example, a winter epidemic of plague was not observed in Norway.
Signs and Symptoms
Painful, enlarged, and swollen lymph nodes are the major symptom that is used in the diagnosis of bubonic plague. The enlarged nodes are referred to as buboes and could break up as the disease progresses in the body (3). After an infected flea bites a person, the bacterium becomes localized in the lymph nodes where they commence the process of replication (4). The bacteria reproduce and colonize lymph nodes in other areas of the body, including the armpits, neck region, the groin, and the upper femoral (4). The symptoms appear a few days after infection because the microorganism has a short incubation period. Other disease indications include organ failure, bleeding, vomiting, open sores, and fever (3). Septicemic plague results from late diagnosis and treatment. In cases where the bacterium infects the lungs, pneumonia is the main outcome (5). The World Health Organization (WHO) has stated that more than 60 percent of infected persons can succumb to the disease if they do not receive treatment.
Diagnosis and Treatment
Bubonic plague is diagnosed through a laboratory test that aims to isolate and identify Y. pestis in a blood sample collected from a patient. Serum collected from the early and late stages of infection is examined and the results are used to confirm the presence of the disease (3). Researchers have developed dipstick tests that are effective in screening for the bacterium’s antigens in samples (4). Lymph node, blood, and lung samples are collected for tests. In septicemic and pneumonic plague cases, signs of the disease are absent. Diagnosis is conducted by taking samples from individuals and testing them in the laboratory.
Bubonic plague is a serious disease that could cause death if left untreated. However, it can be fully eradicated using antibiotics. The success of recovery depends on the early diagnosis and treatment of the disease (5). Commonly used antibiotics include gentamicin, levofloxacin, chloramphenicol, ciprofloxacin, doxycycline, and moxifloxacin (3). These medications are largely effective because the mortality rate associated with treated cases of the disease is between 1 and 15 percent. In untreated cases, the mortality can be as high as 60 percent. Physicians recommend the administration of antibiotics within 24 hours after infection takes place to prevent the progression of the plague in the body (4). Other forms of treatment include respiratory support and the administration of intravenous fluids.
Epidemiology
The disease still exists, though in a less serious form because of the availability of medications. Between 2010 and 2015, approximately 3240 cases and 580 deaths were reported around the world. Incidence is greatest in Peru, China, India, Algeria, Madagascar, and the Democratic Republic of Congo. Between 2012 and 2017, prevalence increased in Madagascar owing to poor hygiene and political instability. The United States records an average of 9 cases annually, and incidence rates are higher in the states of Nevada, Colorado, Oregon, California, Arizona, and New Mexico (3). In 2020, cases of bubonic plague were reported in Mongolia. A couple died while hunting marmots, which serve as the bacterium’s host that conducts transmission.
Conclusion
Bubonic plague is a serious infectious disease that can be transmitted from animals to human beings. It is caused by the bacterium Yersinia pestis and transmitted by fleas that are hosted by rodents. The disease is responsible for massive deaths in the 14th century, and it is also referred to as the Black Death. Millions of people died in the three recorded bubonic plague epidemics. Signs and symptoms include swollen and painful lymph nodes, vomiting, bleeding, and fever. Diagnosis is conducted through laboratory tests that identify the bacterium’s antigens in serum samples of patients. The main treatment modality is the use of antibiotics.
Works Cited
Cartwright, Mark. “Black Death.” Ancient History Encyclopedia, 2020, Web.
Krasner, Barbara. Bubonic Plague: How the Black Death Changed History. Capstone, 2019.
“Plague”. Mayo Clinic, 2019, Web.
Roberts, Michelle. What is bubonic Plague? BBC News, 2020, Web.
Ryan, Kenneth J, and Ray C George, editors. Sherris Medical Microbiology. 4th ed., McGraw Hill, 2004.