What is the Plague?
Plague is an acute, especially dangerous zoonotic vector-borne infection with severe intoxication and serous-hemorrhagic inflammation in the lymph nodes, lungs and other organs, as well as the possible development of sepsis.
In the history of mankind, there is no other such infectious disease that would lead to such enormous devastation and mortality among the population as the plague. From ancient times, information about the plague disease that has occurred in humans in the form of epidemics with a large number of deaths has been preserved. It was noted that plague epidemics developed as a result of contact with sick animals. At times, the spread of the disease was pandemic. Three pandemic plagues are known. The first, known as the “Justinian Plague,” raged in Egypt and the East Roman Empire in 527-565. The second, called the “great” or “black” death, in 1345-1350. covered Crimea, the Mediterranean and Western Europe; this most devastating pandemic claimed about 60 million lives. The third pandemic began in 1895 in Hong Kong, then spread to India, where over 12 million people died. At the very beginning, important discoveries were made (the causative agent was isolated, the role of rats in the epidemiology of plague was proved), which made it possible to organize prevention on a scientific basis. The causative agent of the plague was discovered by G.N. Minh (1878) and independently A. Yersen and S. Kitazato (1894). Since the XIV century, the plague has repeatedly visited Russia in the form of epidemics. Working on outbreaks to prevent the spread of the disease and treat patients, a great contribution to the study of plague was made by Russian scientists D.K. Zabolotny, N.N. Klodnitsky, I.I. Mechnikov, N.F. Gamaleya et al. In the 20th century, N.N. Zhukov-Verezhnikov, E.I. Korobkovoy and G.P. Rudnev developed the principles of the pathogenesis, diagnosis and treatment of patients with plague, and also created a plague vaccine.
Causes of the Plague
The causative agent is a gram-negative immobile facultative anaerobic bacterium Y. pestis of the genus Yersinia of the Enterobacteriaceae family. According to many morphological and biochemical characteristics, plague bacillus is similar to pathogens of pseudotuberculosis, yersiniosis, tularemia and pasteurellosis, which cause serious diseases in both rodents and humans. It is distinguished by pronounced polymorphism, the most typical are ovoid bacilli, stained bipolar, There are several subspecies of the pathogen, different in virulence. It grows on ordinary nutrient media with the addition of hemolyzed blood or sodium sulfite to stimulate growth. Contains more than 30 antigens, exo and endotoxins. Capsules protect bacteria from absorption by polymorphonuclear leukocytes, and V- and W-antigens protect them from lysis in the cytoplasm of phagocytes, which ensures their intracellular reproduction. The causative agent of the plague is well preserved in the excreta of patients and environmental objects (it lasts 20-30 days in the pus of bubo, up to 60 days in the bodies of people, camels, rodents), but is highly sensitive to sunlight, atmospheric oxygen, elevated temperature, and environmental reactions (especially acidic), chemicals (including disinfectants). Under the influence of mercuric chloride in a dilution of 1: 1000 dies in 1-2 minutes. It tolerates low temperatures, freezing.