Pathogens

Yersinia pestis – infection, transmission and diseases

Yersinia pestis

The bacterium Yersinia pestis (also called Pasteurelle pestis ) is the causative agent of the dangerous infectious disease plague . There are several forms of plague, bubonic plague, pneumonic plague, plague-sepsis, skin plague, abortive plague and plague-meningitis. Except for skin plague, all are very dangerous and often fatal if left untreated. Even today, between 10 and 15 percent of the patients treated still die from the disease.

What is Yersinia pestis?

The plague bacterium Yersinia pestis belongs to the Enterobacteriaceae family . It got its name from the Swiss doctor and explorer Alexandre Yersin, who researched the plague and discovered the pathogen in 1894. It was he who first recognized that Yersina pestis is primarily transmitted by rats and mice, or by rat fleas and insects.

The plague is not easy to diagnose at first. Frequently, the first symptoms are mistaken for malaria , spotted fever and typhoid before the plague bubo becomes visible.

The plague bacterium is isolated from the patient’s blood , pus or sputum and either stained and viewed under a microscope or cultivated in a culture. A test with special antigens is also used.

Occurrence, Distribution & Properties

The history of the plague is a horror story. Plague epidemics have been reported since ancient times. The first recorded wave of plague occurred in the 6th century. Its outbreak probably began in Egypt, spread from there across North Africa and the entire Mediterranean region, hitting the Byzantine Empire in particular. It is not known how many people fell victim to it, but it must have been almost half of all people living in the region at the time. Whole family groups were wiped out, hardly anyone dared to leave the house anymore, the fields remained uncultivated, famine broke out.The second great plague wave then shook the same region again in the 8th century. In the 14th century, the “Black Death” found its way throughout Europe. This time he probably came with traders from Asia, especially China. This plague epidemic also decimated the population very badly and probably claimed millions of lives.

Up until the 18th century and on the fringes of Europe even into the 20th century, the plague reappeared again and again. The last major plague outbreak occurred in Central Asia in the late 19th and early 20th centuries, where it killed an estimated 12 million people.

One of the reasons why the plague bacterium is so dangerous is that it can be transmitted in various ways. In most cases, infection begins when a rat flea bites a plague-infected rat and then infects other rats. This is how a great rat die-off begins and the fleas, which can no longer find any host animals, also spread to mice, squirrels, other rodents and their hunters, but also to humans.

Not only rat fleas spread the plague, human fleas and many insects such as mosquitoes, lice, ants and spiders can also transmit it. In addition, the infection occurs through direct contact with infected tissue , with objects or through droplet infection from person to person.

The incubation period for bubonic plague is about 7 days, for pneumonic plague only a few hours to 2 days. The illness then breaks out with high fever , chills , headaches and body aches , nausea , diarrhea and vomiting . Only 24 hours later do the first pus-filled bumps appear due to the swelling of the lymph nodes . Pneumonic plague causes severe shortness of breath , coughing and black bloody sputum. In the case of plague sepsis or plague meningitis, patients often die before the first visible symptoms appear.

Diseases & Ailments

But even today there are still cases of plague, especially in Asia, but also in Africa and North America. According to the WHO, between 1000 and 2000 cases of illness are registered every year and the number of unreported cases is high. However, improved hygienic conditions, effective quarantine measures and effective treatment methods have prevented major epidemics.The plague pathogen is still dangerous and in the slums and shantytowns of the world illnesses occur again and again. There are now vaccines against the plague, but they are comparatively poorly effective due to extreme genetic changes in the pathogens and have severe side effects . For this reason they are only used in exceptional cases. However, there is the possibility of chemoprophylaxis for all people who have to travel to plague areas.

The plague pathogen also poses a great danger as a possible biological weapon. The WHO counts the bacterium yersinia pestis, just like the pathogens of Ebola , anthrax , cholera and smallpox among the “dirty weapons” used by terrorist groups or in wars could be used.

Today, the plague is treated with effective antibiotics . The drugs of first choice are streptomycin , tetracyclines and quinolones . In addition, the severe symptoms of the disease are alleviated and, if possible, the fever is reduced. The patients are strictly isolated to minimize the risk of infection. If the patient survives the plague, there is lifelong immunity against this specific pathogen.

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Hello! I am Lisa Newlon, and I am a medical writer and researcher with over 10 years of experience in the healthcare industry. I have a Master’s degree in Medicine, and my deep understanding of medical terminology, practices, and procedures has made me a trusted source of information in the medical world.