2023 Author: Philip Bishop | [email protected]. Last modified: 2023-08-25 07:54
Plague causes, symptoms and treatment
What is plague?
Plague is an extremely dangerous, acute zoonotic vector-borne infection that causes severe intoxication, as well as serous-hemorrhagic inflammation in the lungs, lymph nodes and other organs, and it is often accompanied by the development of sepsis.
Brief historical information
In the entire history of mankind, there has not been such a ruthless infectious disease as the plague. She devastated cities, causing record deaths. Information has reached our time that in antiquity, plague epidemics claimed a huge number of human lives. As a rule, epidemics began after contact of people with infected animals. Often, the spread of this disease turned into pandemics, three such cases are known.
The first pandemic, dubbed the "Justinian plague", was recorded in Egypt and the Eastern Roman Empire from 527 to 565. The second was called the "great" and "black" death, for 5 years, starting in 1345, it raged in the Mediterranean, Western Europe and Crimea, taking with it about 60 million human lives. The third pandemic began in Hong Kong in 1895 and later spread to India, where more than 12 million people died.
During the last pandemic, important discoveries were made, thanks to which it became possible to carry out prevention of the disease, guided by data on the identified causative agent of the plague. Rats have also been shown to help spread the infection. In 1878, Professor GN Minkh discovered the causative agent of the plague, and in 1894 scientists Sh. Kitazato and A. Yersen worked on this issue.
There were plague epidemics in Russia as well - since the XIV century, this terrible disease periodically declared itself. Many Russian scientists have made a great contribution to the study of this disease. Such scientists as I. I. Mechnikov, D. K. Zabolotny, N. F. Gamaleya, N. N. Klodnitsky prevented the spread of the epidemic and dealt with the treatment of patients. And in the XX century G. P. Rudnev, N. N. Zhukov-Verezhnikov and E. I. Korobkova developed the principles of diagnosis and pathogenesis of plague, and also a vaccine against this infection was created and methods of treating the disease were determined.
What provokes the plague?
The causative agent of the infection is the immobile gram-negative facultative anaerobic bacterium Y. pestis, which belongs to the genus Yersinia and the family Enterobacteriaceae. In terms of its biochemical and morphological characteristics, the plague bacillus resembles the causative agents of diseases such as pseudotuberculosis, pasteurellosis, yersiniosis and tularemia - humans and rodents are susceptible to them. The causative agent is characterized by polymorphism, it has the form of an ovoid rod, which is bipolarly colored. There are several subspecies of this pathogen, which differ in virulence.
The growth of the pathogen occurs in a nutrient medium; to stimulate growth, it needs sodium sulfite or hemolyzed blood. The composition contains more than 30 antigens, as well as exo- and endotoxins. The absorption of bacteria by polymorphonuclear leukocytes is prevented by capsules, and V- and W-antigens are protected from lysis in the cytoplasm of phagocytes, which is why they multiply inside the cells.
The causative agent of plague is able to persist not only in the excreta, infected, but also various objects of the external environment contain it. For example, in pus bubo can persist for 30 days, and in the corpses of rodents, camels and people - about two months. The sensitivity of the pathogen to the sun's rays, oxygen, high temperatures, reactions of an acidic environment, as well as some chemicals, disinfectants is noticed. A solution of mercuric chloride (1: 1000) is able to destroy the pathogen in 2 minutes. But the pathogen tolerates low temperatures and freezing well.
The main source of plague, as well as its reservoir, are wild rodents, of which there are about 300 species, and they are ubiquitous. But not all animals are capable of retaining the pathogen. Each natural focus has the main species that store and transmit infection. The main natural sources are ground squirrels, marmots, voles, gerbils, pikas and others. For anthropurgic centers of plague - cities, ports, synanthropic rats are the main threat. Among them, one can distinguish a gray rat, which is also called a pasyuk. She usually lives in the sewage system of large cities. And also a black - Egyptian or Alexandrian rat, living in houses or on ships.
Dogs are resistant to the plague pathogen, but fleas can be infected from them. More and more cases of infection in cats, which can transmit the infection to humans. A person can also pick up an infection from a camel. The plague infection persists through the transmission of the pathogen of infected animals to healthy ones, in this a special role is played by fleas that parasitize on rodents.
If an acute form of the disease develops in rodents, then the animals quickly die, and the spread of the infection (epizootic) stops. But some rodents, for example, marmots, ground squirrels, tarbagans, hibernating, carry the disease in a latent form, and in the spring they become sources of plague, which is why a natural focus of infection appears in their habitat.
Infected people also become sources of the plague. For example, if a person has a disease such as pneumonic plague, and also if there is contact with the pus of a bubo, or if fleas from a patient with plague septicemia become infected. Corpses of plague patients are often the cause of the spread of infection. Of all these cases, people infected with pneumonic plague are considered especially dangerous.
There are quite a few ways of transmission of infection, but the main one is vector-borne, but in the pulmonary form of the disease, infection can occur by airborne droplets. The vectors are not only fleas (there are about 100 species of them), but also ticks, which support the epizootic process in nature, transmitting the infection to rodents, cats, dogs and camels, and they, in turn, transfer these parasites into human housing.
The infection is transmitted to a person from fleas not so much through a bite, but because after that feces or regurgitated masses of an insect are rubbed into the skin. In the intestines of an infected flea, bacteria multiply that produce coagulase. This substance forms a kind of cork or plague block, and it blocks the flow of blood into her body. As a result, the parasite, trying to get enough, regurgitates infected masses on the skin at the site of the bite. These insects, feeling hungry, try to get enough through animals. Usually fleas remain infectious for about 7 weeks, but there is evidence that some individuals can be carriers for up to a year.
You can also get infected by contact, for example, through the mucous membrane or damage to the skin. This can happen when cutting and processing the carcasses of infected animals (hares, foxes, saigas, and others), as well as in the case of eating this meat.
People are highly susceptible to infection, regardless of the mode of infection and the age group to which the person belongs. If a person has suffered a plague, he has some kind of immunity to this disease, but the possibility of re-infection is not excluded. Moreover, a second infection with the plague is not a rare case, and the disease passes in an equally severe form.
The main epidemiological signs of plague
Plague foci in nature can occupy about 7% of the land, and have been recorded on almost all continents (the only exceptions are Australia and Antarctica). Several hundred people around the world are infected with the plague every year. On the territory of the CIS, 43 natural foci were identified, the area of which is at least 216 million hectares. The outbreaks are located on the plains - desert, steppe, and in the highlands.
Natural foci are divided into two types: "wild" and rat plague. Under natural conditions, plague has the form of an epizootic of rodents and lagomorphs. Rodents sleeping in winter carry the disease in warm weather (spring), and animals that do not hibernate contribute to the formation of two seasonal peaks of plague, which occur during their active reproduction. As a rule, men are more likely to become infected with the plague - this is due to the fact that they are forced to stay in the natural focus of the plague more often (activities related to hunting, animal husbandry). In urban conditions, the role of carriers is taken by rats - gray and black.
If we compare the epidemiology of two types of plague - bubonic and pneumonic, significant differences can be noted. First of all, bubonic plague develops rather slowly, and the pulmonary form can spread very widely in the shortest possible time - this is due to the easy transmission of bacteria. People with bubonic plague are almost non-infectious and slightly contagious. There are no pathogens in their secretions, and there are quite a few of them in the pus.
If the disease has turned into a septic form or bubonic plague has complications with secondary pneumonia, which allows the pathogen to be transmitted by airborne droplets, an epidemic of pneumonic plague of the primary type begins, which is characterized by a high degree of contagiousness. Most often, pneumonic plague appears after bubonic plague, then spreads with it and very quickly turns into the leading epidemiological and clinical form.
There is an opinion that the causative agent of the infection is able to stay in the soil, being in an uncultivated state for a long time. At the same time, rodents that dig holes in contaminated soils receive primary infection. Scientists confirm this hypothesis by experimental studies, as well as by the search for the causative agent of plague among rodents during interepizootic periods, the futility of which allows us to draw some conclusions.
It is known that the incubation period of plague is from 3 to 6 days, but in an epidemic or in a septic form it can be reduced to 1 day. The maximum incubation period that has been recorded is 9 days.
The disease begins acutely, accompanied by a rapid increase in body temperature, severe chills and signs of intoxication. Patients often complain of pain in muscles and joints, pain in the sacrum and head. The person vomits (sometimes - with blood), is tormented by thirst. In the first hours of the disease, psychomotor agitation is observed. The patient becomes restless and too active, the urge to run appears (this is where the saying "runs like crazy" takes roots), then hallucinations and delirium appear. A person can no longer speak clearly and walk straight. Sometimes, on the contrary, they notice apathy and lethargy, and due to weakness, the patient is not able to get out of bed.
Of the external signs, puffiness of the face, flushing, and injection of the sclera can be noted. The expression on his face takes on a suffering look, it bears the stamp of horror, or, as they say, “the mask of the plague”. In severe cases, a hemorrhagic rash appears on the skin. The tongue increases in size, becomes covered with a white coating, reminiscent of chalk. Also noted are cardiac arrhythmias, tachycardia, blood pressure gradually decreases. Even local forms of the disease are characterized by the development of anuria, oliguria, tachypnea. These symptoms are more pronounced at the initial stage of the disease, but they accompany all forms of plague.
In 1970, G. P. Rudnev proposed the following clinical classification of plague:
- local forms (bubonic, cutaneous and skin-bubonic);
- generalized (primary and secondary septic);
- externally disseminated (primary and secondary pulmonary, as well as intestinal).
This form of the disease is characterized by the appearance of a carbuncle in the place where the pathogen entered. First, a pustule forms on the skin (the appearance is accompanied by a sharp pain) with a dark red content. It is located on the subcutaneous edematous tissue, around it there is a zone of hyperemia and infiltration. If the pustule is opened, an ulcer that grows in size with a yellowish bottom appears in its place. Then this bottom is covered with a black scab, which is torn away, leaving behind scars.
This is the most common form of the disease. Bubonic plague affects the lymph nodes that are closest to the site of introduction of the pathogen. Usually these are inguinal nodes, sometimes axillary, and less often cervical. Most often, buboes are single, but they can be multiple. At the site of the next bubo formed, pains occur, this is accompanied by intoxication.
It is possible to palpate the lymph nodes in 1-2 days after their appearance, the firm consistency gradually changes to a softer one. The nodes combine into a sedentary conglomerate, which can fluctuate on palpation due to the presence of periadenitis in it. The disease develops for about 7 days, followed by a period of convalescence. Enlarged nodes can dissolve, ulcerate or scleroze, this is facilitated by necrosis and serous-hemorrhagic inflammation.
This form is a change in lymph nodes and skin lesions. Local forms of the disease can develop into secondary pneumonia and secondary plague sepsis. The clinical characteristics of these forms do not differ from the primary forms of the same diseases.
The primary septic form appears for a short (1-2 days) incubation period and is accompanied by the rapid onset of intoxication, as well as hemorrhagic manifestations - gastrointestinal or renal bleeding, hemorrhages in the mucous membranes and skin. In the shortest possible time, infectious-toxic shock develops. If the disease is not treated, then death is inevitable.
The primary pulmonary form appears after aerogenic infection. It has a short incubation period - it can be several hours, maximum - two days. The disease develops sharply, first there is an intoxication syndrome. On the second or third day, there is a cough and pain in the chest area, shortness of breath. When coughing, vitreous (at first), and then liquid foamy sputum with blood is released.
The obtained physical data of the lungs are extremely scarce, signs of lobar or focal pneumonia are visible on the roentgenogram. Cardiovascular insufficiency increases, which is expressed in tachycardia and a gradual decrease in blood pressure, cyanosis develops. At the terminal stage, patients enter a soporotic state, which is accompanied by shortness of breath, hemorrhagic manifestations (extensive hemorrhages), after which the person falls into a coma.
With the intestinal form, patients experience severe intoxication, and at the same time a sharp abdominal pain, constant vomiting and diarrhea, accompanied by tenesmus. Mucous and bloody discharge are visible in the stool. For other forms of plague, similar manifestations are also characteristic (probably, this is associated with enteral infection), therefore the question of the existence of the intestinal form of this disease as an independent one remains controversial.
Various forms of plague - bubonic, cutaneous, and also bubonic cutaneous - must be distinguished from diseases such as tularemia, lymphadenopathy, and carbuncles. And septic and pulmonary forms can have symptoms that resemble lung disease, sepsis, and meningococcal etiology.
All forms of plague are characterized by severe intoxication, the progressive signs of which appear at the very beginning of the disease. A person's temperature rises, chills appear, he vomits, is tormented by thirst. Psychomotor agitation, anxiety, hallucinations and delusions are also alarming. On examination, slurred speech, an uncertain gait are revealed, the face becomes puffy, an expression of suffering and horror appears on it, the tongue is white. Cardiovascular failure, oliguria, tachypnea develop.
Cutaneous and bubonic forms of plague can be detected by sharp pain in the affected areas, it is easy to determine the stages of development of the carbuncle (first a pustule, then an ulcer, then a black scab and a scar), during the formation of bubo, periadenitis is observed.
Pulmonary and septic forms are accompanied by the extremely rapid development of intoxication, as well as manifestations of hemorrhagic syndrome and infectious-toxic shock. Lung damage is accompanied by a sharp pain in the chest and a violent cough with vitreous, and after foamy sputum with blood. Physical findings often do not correspond to the apparent serious condition of the patient.
This type of diagnosis is based on the use of biological and microbiological, immunoserological and genetic methods. The hemogram shows leukocytosis and neutrophilia with a shift to the left, as well as an increase in ESR. The causative agent is isolated in specialized specialized laboratories, created specifically to work with causative agents of the most dangerous infections. Studies are being conducted to confirm clinically significant cases of plague, and are examining people who are in the focus of infection, and their body temperature is above normal. Material taken from plague patients or those who died from this disease is subjected to bacteriological analysis. Punctates are taken from carbuncles and buboes, and the departments of ulcers, phlegm, mucus and blood are also examined. Experiments are carried out with laboratory animals, which after infection with plague can live for about 7 days.
As for serological methods, they use RNAH, RNGA, RNAT, RTPGA, ELISA. If the PCR gives a positive result, then 6 hours after the test, we can talk about the presence of DNA from the plague microbe and confirm the preliminary diagnosis. In order to finally confirm the presence of the etiology of plague, a pure culture of the pathogen is isolated and identified.
Patients can be treated exclusively in a hospital setting. Drugs for etiotropic therapy, their doses, and treatment regimens are determined depending on the form of the disease. Typically, the course of therapy is 7 to 10 days, regardless of the form of the disease. In this case, the following drugs are used:
- cutaneous form - cotrimoxazole (4 tablets per day);
- the bubonic form is chloramphenicol (dose: 80 mg / kg per day) and streptomycin is simultaneously used (dose: 50 mg / kg per day). The drugs are administered intravenously. The effectiveness of tetracycline was noted;
- pulmonary and septic forms - a combination of chloramphenicol with streptomycin + doxycycline (dose: 0.3 grams per day) or tetracycline (4-6 g / day), taken orally.
Along with this, massive detoxification therapy is carried out: albumin, fresh frozen plasma, rheopolyglucin, intravenous crystalloid solutions, hemodesis, methods of extracorporeal detoxification. Prescribed drugs that improve microcirculation: picamilon, trental in combination with solcoseryl. Forcing diuresis, cardiac glycosides, as well as respiratory and vascular analeptics, symptomatic and antipyretic drugs.
As a rule, the success of the treatment carried out depends on how timely the therapy was carried out. Etiotropic drugs are usually prescribed at the first suspicion of plague, based on clinical and epidemiological data.
The forecast of the epidemic and epizootic situation in individual natural foci determines the nature, direction and volume of measures to prevent the disease. This takes into account the data obtained from tracking the increase in the number of people infected with plague worldwide. All countries should inform WHO of cases of plague, movement of infection, epizootics among animals, as well as measures taken to combat the disease. Typically, a country is developing a system of certification that records natural foci of plague and allows for regionalization of the territory in accordance with the scale of the epidemic.
The leading role in the complex of preventive measures is played by measures preventing the import of infection from other countries, as well as preventing the development of plague in enzootic foci. In order to prevent the import of infection, international sanitary rules have been created. And in enzootic foci, the number and species composition of rodents is monitored, animal studies are carried out to detect infection. If an epizootic was detected, then deratization and various disinfestation measures are carried out. Synanthropic rodents are exterminated without identifying infected individuals, if more than 15% of those caught in the traps are infected. Rodents and ectoparasites on the plains and near human settlements destroy special anti-plague, and in the settlements themselves - departments of the Center for Sanitary and Epidemiological Surveillance.
If an epizootic of plague is noticed in rodents or cases of disease among domestic animals are detected, as well as if the importation of infection by an infected person is likely, prophylactic immunization of the population is carried out. Vaccination can be carried out individually or selectively - to individuals who have connections with those territories where epizootics exist (hunters, agronomists, geologists, archaeologists). All medical institutions should have a stock of medicines, as well as protective and preventive means, and it is necessary to develop a scheme for transferring information and alerting personnel. Preventive measures in enzootic regions, as well as for persons who are in contact with pathogens of dangerous infections, are carried out by various anti-plague and many other health institutions.
Activities in the epidemic focus
If a case of plague has been identified, or there is a suspicion that a person is a carrier of this infection, urgent measures must be taken to localize and eliminate the focus. Based on the epidemiological or epizootic situation, they determine the size of the territory in which it is necessary to introduce restrictive measures - quarantine. They also take into account the possible operating factors through which the infection can be transmitted, sanitary and hygienic conditions, the number of migrants and transport links with nearby territories.
The Emergency Anti-Epidemic Commission is in charge of activities in the area of the focus of infection. The anti-epidemic regime must be strictly observed, the staff of the commission must use protective suits. An extraordinary commission makes a decision on the introduction of quarantine throughout the outbreak.
Specialized hospitals are being set up for plague patients and those with suspicious symptoms. Infected people are transported in a strictly defined manner, in accordance with the current sanitary rules for biological safety. Those infected with bubonic plague can be accommodated in several people in one room, and patients with pulmonary form must be distributed to separate rooms. It is allowed to write out a person who has suffered bubonic plague at least 4 weeks after the moment of clinical recovery (the presence of negative results of bacteriological tests). With pneumonic plague, a person must be in the hospital after recovery for at least 6 weeks. After the patient leaves the hospital, he is monitored for 3 months.
The focus of infection is subject to thorough disinfection (current and final). Those persons who came into contact with infected people, their things, corpses, as well as participants in the slaughter of sick animals are isolated for 6 days and are subject to medical supervision. In the case of pneumonic plague, individual isolation for 6 days is necessary for all persons who may have become infected, and to provide them with prophylactic antibiotics (rifampicin, streptomycin, and the like).
Author of the article: Danilova Tatyana Vyacheslavovna | Infectionist
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