In this lesson, we will examine plague, more widely known as Black Death, including the three major types of plague, the most common symptoms, diagnosis, and treatment.
Two Days Until Death
The life of a high school senior can be hectic, stressful, and exciting. There are so many choices and changes on the horizon during the transition to adulthood.
Every kid deserves a little break now and then to blow off some steam. That was what B.T. (the name has been changed to protect confidentiality) thought with his final exams and wrestling championships fast approaching.
What better way to relax than a nice nature hike through the beautiful scenery of central Arizona? He might even get to feed the prairie dogs again.Two days after his hike, B.T. suffered a groin injury while wrestling. His leg was swollen and very painful, and he was starting to develop a fever. His doctor advised at-home rest and observation. The next morning, B.
T. was found dead on his bathroom floor. The doctors racked their brains trying to find a cause. On a whim, the public health department decided to retrace B.T.’s hiking trail.
There, they found a colony of prairie dogs. But the rodents were not acting normal. Many were sick. Others had already died. Could the disease affecting the prairie dog colony be related to B.T.
‘s death?The health department managed to trap a sick prairie dog for testing. It turns out the prairie dogs were dying of plague – you know, Black Death, Middle Ages plague! Who gets plague these days – and in the United States, no less? A quick test confirmed that B.T. also died of plague. A healthy individual in a relatively protected, developed country died of one of the most notorious diseases in human history. And it only took 2 days. So let’s look a little closer at the plague.
Maybe if B.T. had been more informed, his death could have been prevented.
Plague and its Symptoms
Plague is a deadly, infectious disease caused by the bacterium Yersinia pestis. There are three main types of plague – bubonic, pneumonic and septicemic – each with its own unique characteristics. Let’s take a quick look at all three, beginning with the most infamous: bubonic plague.Bubonic plague is the classic form of plague transmitted through the bite of an infected flea. When an infected flea bites a human, it injects Yersinia cells into the human host.
It can take as few as 3 cells to start an active, life-threatening infection. Once bitten, the bacteria travel to the lymph node closest to the bite site, where they are filtered out of the lymph fluid. The bacteria encapsulate, making a compartment within the lymph node where they can grow and divide.
This causes inflammation and cell death of the node. The lymph node rapidly begins to swell and becomes painful. The swelling of the node is called a bubo – hence the name ‘bubonic plague.’ In addition, bubonic plague victims suffer from a sudden onset of fever, headache, chills, and muscle weakness.
Bubonic plague has a mortality rate of around 15%, even with treatment.Pneumonic plague is a highly contagious form of plague usually transmitted person-to-person through inhaled aerosolized respiratory droplets. Yersinia cells inhaled will encapsulate and cause inflammation in the lungs, resulting in the rapid onset of pneumonia. The patient will have shortness of breath, chest pain, coughing, and bloody mucous. In addition, the normal immune response to a bacterial infection will cause fever, headache, and general weakness. This is the most serious form of plague and the only form that can be passed from person to person. But that is not the only way to develop pneumonic plague.
If a case of bubonic or septicemic plague is allowed to progress without treatment, Yersinia cells will eventually invade the lungs, leading to pneumonic plague. Without treatment, nearly 100% of patients will die within 6 days from respiratory failure and shock. Even with treatment, prognosis is grave. As a result of the grave prognosis and ability to aerosolize, plague is a very serious bioterrorism threat.
Septicemic plague is a form of plague in which the bacteria have invaded the host’s blood stream. This form of plague can develop directly from a flea bite, through bacterial contamination of broken skin, or as a later stage of both bubonic and pneumonic plague. Symptoms include fever, chills, extreme weakness, abdominal pain, and bleeding under the skin or in the organs.
Eventually, shock and death result from the body-wide infection. It is septicemic plague that started the name ‘Black Death.’ As bleeding under the skin increases, large purple-to-black patches of blood and dying tissue develop. By the time these patches develop, about 50% of patients undergoing treatment will die.
In untreated patients, the disease is 100% fatal.
As we learned in the introduction, diagnosis of plague can be difficult simply from an awareness standpoint. No one considers plague a legitimate health threat in the United States anymore, leading to misdiagnosis. Since the disease kills so rapidly, any delay in treatment can be deadly. Diagnosis is based on the rapid onset of symptoms and a recent exposure to rodents that could harbor the fleas that carry the bacteria. Treatment usually begins with this information alone.
A more positive diagnosis involves growing the bacteria for microscopic examination. Technicians can perform a simple Gram stain on cultured bacteria or tissue removed from a patient’s lymph nodes to identify the bacteria. Yersinia pestis has a unique appearance when stained. The bacteria stain very heavily on the ends, with the center of the cells taking up very little stain. This gives Yersinia a classic ‘safety pin’ appearance.
If caught early, all forms of plague are very straightforward to treat. Currently, the antibiotics streptomycin or gentamicin are the treatments of choice. The earlier the antibiotics are given, the better the chance the patient has of making a full recovery. Treatment does not guarantee a cure, however. Even with treatment, many patients will still die of the disease.
Patients that test positive for plague should be quarantined during treatment to avoid infecting others. Anyone working in close proximity to a plague patient should also be monitored and possibly given a prophylactic dose of antibiotics, just in case.
It’s time to review.Plague is a deadly, infectious disease caused by the bacterium Yersinia pestis. There are three main forms of plague. Bubonic plague is the classic form of plague transmitted through the bite of an infected flea.
Bubonic plague victims can expect swollen and painful lymph nodes and the sudden onset of fever, headache, chills, and muscle weakness. Pneumonic plague is a highly contagious form of plague usually transmitted person-to-person through inhaled aerosolized respiratory droplets. Pneumonic plague is the most serious form of plague and patients can expect shortness of breath, chest pain, coughing, bloody mucous, fever, headache, and general weakness. Septicemic plague is a form of plague in which the bacteria have invaded the host’s blood stream. Victims can expect fever, chills, extreme weakness, abdominal pain, and bleeding under the skin or in the organs.
This bleeding causes black, dying patches of skin, leading to the common name Black Death.All types of plague are serious and potentially deadly. Diagnosis must be made rapidly and is usually limited to the rapid onset of symptoms and a recent exposure to rodents that could carry the fleas that transmit the bacteria.
Treatment begun as early as possible yields the most success and includes the antibiotics streptomycin or gentamicin.
After watching this lesson, you should be able to:
- Identify the three types of plague
- Discuss symptoms, diagnosis, and treatment options for plague