Author: Volker Schuck, medical author
March 16, 2020
The plague has caused several pandemics in the past. The bacterium Yersinia pestis, as the "black death" is called in technical terms, no longer falls victim to as many people as it did in earlier times. Even so, infection is still a threat. Everything about causes, prevention and treatment.
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The plague is no longer the "hostage of humanity" than it occurred, for example, in the 14th century. At that time, about a quarter to a third of all inhabitants in Europe died of the "black death". Better hygienic conditions and modern medicines have helped to fade the memories of earlier devastating diseases in this country.
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Nevertheless, the plague caused by the bacterium Yersinia pestis is still a very serious infectious disease, which kills many infected people if they are treated too late. The plague is characterized by various clinical pictures, which are mostly due to the type of transmission.
Symptoms of infection with the pest pathogen Yersinia pestis
The first symptoms of an infection with the plague do not differ significantly from those of other infectious diseases.
An infection with Yersinia pestis begins with a high fever with chills, headache and body aches and fatigue. With bubonic plague, painful swelling occurs in a lymph node group near the puncture site within a day or two; In the case of pulmonary plague, there is usually a painful cough on the second day, possibly with bloody expectoration, difficulty breathing and chest pain. The lips can turn blue-black. The gastrointestinal area can also be affected with abdominal pain, vomiting and diarrhea.
If the disease spreads throughout the body (blood poisoning from dying pathogens, pestsepsis), this leads to a racing pulse (tachycardia), lethargy, confusion, enlargement of the spleen and liver as well as bleeding, sometimes visible under the skin (petechiae).
In rare cases, the pest pathogens can also cause meningitis (plague meningitis), which is accompanied by headaches, neck stiffness, nausea, hypersensitivity to light and loud noises as well as confusion or reduced consciousness. If the pathogen is taken in through the mouth (orally), inflammation of the throat can develop (plague pharyngitis), with symptoms such as a dry throat, swelling of the lymph nodes in the throat area and headache.
Fleas are often the source of the plague
The pathogen Yersinia pestis, which is responsible for the plague, can be transmitted in different ways and – depending on the mode of transmission – also cause different clinical pictures.
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The most common type of transmission of the plague occurs through fleas, which as intermediate hosts have taken up the pathogen with the blood of infected organisms (for example rats) and release it into the bloodstream again with the next bite. This can even work from person to person, but only in rare but then violent cases. However, like the real flu (influenza), the plague can also be spread by a droplet infection. However, this rarely happens.
In many areas of the world, the plague occurs not only in rats but also in squirrels, marmots and mice. In such cases, however, the risk is lower because there is no intermediate host, such as the rat flea, which is dangerous for humans. However, there are also cases where infected pets such as cats have transmitted the plague to their owners. Plague cases have been sporadic in recent years from North America (especially the southwest of the USA), from Central and South America, Asia (e.g. Russia, Kazakhstan, China, India and Vietnam) and from Africa (including Uganda, Congo, Madagascar) and Tanzania).
If the plague pathogen is transmitted through a flea bite, it reaches the nearest lymph node via the lymphatic system, which swells like a bulge due to the following inflammation (bubonic or bubonic plague; bubo = bulge). As a result, the pathogen can spread throughout the body and also affect organs such as the lungs (secondary lung plague). It comes from the toxins that release dying Yersinia bacteria, into blood poisoning, blood vessels burst or the blood stops in the bloodstream (disseminated intravascular coagulation), which makes the skin appear dark colored (hence the term "black death").
However, if the pathogen comes into the lungs through the airways via coughed up infected blood or saliva from sick people, this usually triggers the primary lung plague.
Because of the high risk of infection, the pathogen Yersinia pestis is also feared as a possible biological weapon.
Risk of confusion when diagnosing the plague
Since the symptoms of the plague can also indicate various other diseases, the pathogen must be detected by examining the blood, lymph fluid or coughing up (sputum).
For the diagnosis of the plague, a dye is added that makes the Yersinia pestis rods visible under the microscope (fluorescence microscopy). Another important investigation is the PCR detection, in which genetic material from the body fluids is specifically increased in order to be able to better detect pathogens, for example. Antibodies to the pathogen can also be detected using a rapid test.
It is important that a plague infection should not be confused with other clinical pictures: for example, pneumonia resembles other severe pneumonia caused by bacteria. The plague sepsis could also be mistaken for meningococcal infection, malaria or typhoid. The lymph swelling associated with bubonic plague should also be confused with other lymphatic diseases at the beginning.
Treatment of the plague with antibiotics
Antibiotics should be used as quickly as possible to treat the plague (streptomycin, gentamicin, tetracycline, fluoroquinolone). The duration of treatment is at least ten days. In the case of plague meningitis, chloramphenicol is used for treatment; if there is a risk of infection, potential contact persons are generally given doxycycline and ciprofloxacin.
Vaccination against bubonic plague for people at risk
There is an obligation to report for infection with Yersinia pestis; the sick are put in quarantine immediately, contact persons must be found and treated if necessary.
It is also important to identify the source of the plague and, in the event of a flea transmission, to take appropriate measures to combat it. This also includes the search for the animals that carry the pathogen.
Vaccination against the bubonic plague exists, which is recommended for those groups at higher risk. This vaccine is not freely available to others. According to the Tropical Institute, the risk of infection is reduced by avoiding contact with living or dead rodents.
The main vaccinations