Plague is a highly contagious bacterial infection with multiple transmission routes and epidemic spread, occurring with fever–intoxication syndrome, lymph node, lung and skin lesions. The clinical course of various forms of plague is characterized by high fever, severe intoxication, agitation, excruciating thirst, vomiting, regional lymphadenitis, hemorrhagic rash, DIC syndrome, as well as its own specific symptoms (necrotic ulcers, plague bubons, hemoptysis). Diagnosis of plague is carried out by laboratory methods (ELISA, RPH, PCR). Treatment is carried out in strict isolation: tetracycline antibiotics, detoxification, pathogenetic and symptomatic therapy are indicated.
Plague is an acute infectious disease transmitted mainly by a transmissible mechanism, manifested by inflammation of lymph nodes, lungs, and other organs having a serous-hemorrhagic character, or occurring in septic form. The plague belongs to a group of particularly dangerous infections.
The plague belongs to a group of particularly dangerous infections. In the past, pandemics of the “black death”, as the plague was called, claimed millions of human lives. Three global outbreaks of plague are described in history: in the VI century. in the Eastern Roman Empire (“Justinian’s plague”); in the XIV century. in the Crimea, the Mediterranean and Western Europe; in the late XIX century. in Hong Kong. Currently, thanks to the development of effective anti-epidemic measures and an anti-plague vaccine, only sporadic cases of infection in natural foci are registered.
Characteristics of the pathogen
Yersinia pestis is a stationary facultative anaerobic gram-negative rod-shaped bacterium from the genus of Enterobacteria. The plague bacillus can remain viable for a long time in the separable of sick people, corpses (in bubonic pus, yersinia live up to 20-30 days, in the corpses of people and fallen animals – up to 60 days), tolerates freezing. Environmental factors (sunlight, atmospheric oxygen, heating, changes in the acidity of the environment, disinfection) this bacterium is quite sensitive.
Ways of infection
The reservoir and the source of the plague are wild rodents (marmots, voles, gerbils, squeakers). In various natural foci, different types of rodents can serve as a reservoir, in urban conditions – mainly rats. Dogs resistant to human plague can serve as a source of pathogen for fleas. In rare cases (with the pulmonary form of plague, or with direct contact with bubonic pus), a person can become the source of infection, fleas can also receive the pathogen from patients with septic plague. Infection often occurs directly from plague corpses.
The plague is transmitted through a variety of mechanisms, the leading place among which is occupied by the transmissible. The carriers of the causative agent of the plague are fleas and ticks of some species. Fleas infect animals that carry the pathogen with migration, spreading fleas as well. People get infected by rubbing flea excrement into the skin when combing. Insects remain contagious for about 7 weeks (there is evidence of flea contagiousness throughout the year).
Plague infection can also occur by contact (through damaged skin when interacting with dead animals, cutting carcasses, harvesting skins, etc.), alimentary (when eating meat of sick animals for food).
People have an absolute natural susceptibility to infection, the disease develops when infected in any way and at any age. Post-infectious immunity is relative, it does not protect against re-infection, but repeated cases of plague usually occur in a milder form.
Plague is classified according to clinical forms depending on the predominant symptoms. There are local, generalized and externally differentiated forms:
- Local plague is divided into cutaneous, bubonic and skin-bubonic.
- Generalized plague can be primary and secondary septic.
- The externally disseminated form is divided into primary and secondary- pulmonary, as well as intestinal.
The incubation period of the plague on average takes about 3-6 days (up to a maximum of 9 days). In case of mass epidemics or in the case of generalized forms, the incubation period may be shortened to one or two days. The onset of the disease is acute, characterized by rapid development of fever, accompanied by tremendous chills, pronounced intoxication syndrome.
Patients may complain of pain in the muscles, joints, and sacral region. Vomiting appears (often with blood), thirst (excruciating). From the very first hours, patients are in an excited state, there may be perceptual disorders (delusions, hallucinations). Coordination is disrupted, speech intelligibility is lost. Lethargy and apathy occur much less frequently, patients weaken to the point of being unable to get out of bed.
The patients’ face is puffy, hyperemic, the sclera are injected. In severe cases, hemorrhagic rashes are noted. A characteristic feature of the plague is a “chalky tongue” – dry, thickened, densely covered with a bright white coating. Physical examination shows pronounced tachycardia, progressive arterial hypotension, shortness of breath and oliguria (up to anuria). In the initial period of the plague, this symptomatic picture is noted in all clinical forms of the plague.
It manifests itself in the form of a carbuncle in the area of the introduction of the pathogen. The carbuncle progresses, going through the following stages sequentially: first, a pustule forms on the hyperemic, edematous skin (pronounced painful, filled with hemorrhagic contents), which after opening leaves an ulcer with raised edges and a yellowish bottom. The ulcer tends to increase. Soon, a necrotic black scab forms in its center, quickly filling the entire bottom of the ulcer. After rejection of the scab, the carbuncle heals, leaving a rough scar.
It is the most common form of plague. Bubons are called specifically altered lymph nodes. Thus, with this form of infection, the predominant clinical manifestation is regional purulent lymphadenitis in relation to the area of introduction of the pathogen. Bubones, as a rule, are single, in some cases they can be multiple. Initially, soreness is noted in the area of the lymph node, after 1-2 days, enlarged painful lymph nodes are found on palpation, at first dense, softening to a dough-like consistency with the progression of the process, merging into a single conglomerate soldered to the surrounding tissues. The further course of the bubo can lead both to its independent resorption, and to the formation of an ulcer, sclerosing area or necrosis. The height of the disease lasts for a week, then comes a period of convalescence, and the clinical symptoms gradually subside.
It is characterized by a combination of skin manifestations with lymphadenopathy. Local forms of plague can progress into a secondary septic and secondary pulmonary form. The clinical course of these forms does not differ from their primary counterparts.
Primary septic form
It develops at lightning speed, after a shortened incubation (1-2 days), is characterized by a rapid increase in severe intoxication, severe hemorrhagic syndrome (numerous hemorrhages in the skin, mucous membranes, conjunctiva, intestinal and renal bleeding), rapid development of infectious and toxic shock. The septic form of the plague without proper timely medical care ends in death.
Primary pulmonary form
Occurs in the case of an aerogenic pathway of infection, the incubation period is also shortened, can be several hours or last about two days. The onset is acute, characteristic of all forms of plague – increasing intoxication, fever. Pulmonary symptoms manifest by the second or third day of the disease: there is a strong debilitating cough, first with transparent vitreous, later with foamy bloody sputum, chest pain, difficulty breathing. Progressive intoxication contributes to the development of acute cardiovascular insufficiency. The outcome of this condition may be sopor and subsequent coma.
It is characterized by intense sharp abdominal pain with severe general intoxication and fever, frequent vomiting, diarrhea soon joins. The stool is abundant, with impurities of mucus and blood. Often – tenesmus (painful urge to defecate). Given the wide spread of other intestinal infections, the question has not been resolved at present: is intestinal plague an independent form of the disease that developed as a result of microorganisms entering the intestine, or is it associated with the activation of intestinal flora.
Due to the special danger of infection and extremely high susceptibility to the microorganism, the pathogen is isolated in specially equipped laboratories. The material is taken from bubons, carbuncles, ulcers, sputum and mucus from the oropharynx. It is possible to isolate the pathogen from the blood. Specific bacteriological diagnostics are performed to confirm the clinical diagnosis, or, with prolonged intense fever in patients, in an epidemiological focus.
Serological diagnosis of plague can be performed using RPH, ELISA, NAb, AAR and HI. It is possible to isolate the DNA of plague bacillus using PCR. Non-specific diagnostic methods – blood and urine analysis (there is a picture of acute bacterial lesion), with a pulmonary form – lung radiography (signs of pneumonia are noted).
Treatment is carried out in specialized infectious departments of the hospital, in strict isolation. Etiotropic therapy is performed with antibacterial agents in accordance with the clinical form of the disease. The duration of the course takes 7-10 days.
- Specific therapy. In the cutaneous form, co-trimoxazole is prescribed, in bubonic form, chloramphenicol with streptomycin is intravenously administered. Tetracycline antibiotics can also be used. Tetracycline or doxycycline is supplemented with a complex of chloramphenicol with streptomycin for plague pneumonia and sepsis.
- Non-specific therapy. It includes a complex of detoxification measures (intravenous infusion of salt solutions, dextran, albumin, plasma) in combination with forcing diuresis, agents that improve microcirculation (pentoxifylline). If necessary, cardiovascular, bronchodilators, antipyretic drugs are prescribed.
Currently, in modern hospitals, when using antibacterial agents, the mortality rate from plague is quite low – no more than 5-10%. Early medical care, prevention of generalization contribute to recovery without pronounced consequences. In rare cases, transient plague sepsis develops (a lightning-fast form of the plague), which is difficult to diagnose and treat, often ending in an early fatal outcome.
Currently, there is practically no infection in developed countries, so the main preventive measures are aimed at excluding the import of the pathogen from epidemiologically dangerous regions and sanitation of natural foci. Specific prevention consists in vaccination with a live plague vaccine, produced to the population in areas with an unfavorable epidemiological situation (the prevalence of plague among rodents, cases of infection of domestic animals) and to persons traveling to regions with an increased risk of infection.
Identification of a plague patient is an indication to take urgent measures to isolate him. In case of forced contacts with patients, means of individual prevention are used – anti-plague suits. Contact persons are observed for 6 days, in case of contact with a patient with a pulmonary form of plague, preventive antibiotic therapy is performed. Patients are discharged from the hospital no earlier than 4 weeks after clinical recovery and negative tests for bacterial excretion (in case of pulmonary form – after 6 weeks).