Epidemiology and spread risk
Despite medical advances, plague remains an extremely relevant infection. According to WHO data, up to 2.5 thousand cases are recorded worldwide annually. The natural reservoirs of the plague bacterium are rodents (such as rats), and transmission to humans frequently occurs vector-borne, via bites from infected fleas.
In Russia, there are active natural foci of our own (Astrakhan Oblast, Kabardino-Balkaria, Chechnya, Ingushetia); however, the threat is also associated with the importation of the infection from neighboring states (Mongolia, China, Kazakhstan) and Southeast Asian countries.
Why does a high risk of importation into the Russian Federation persist?
- Long incubation period, allowing an infected person to travel between countries.
- Multiple transmission mechanisms (including the most dangerous airborne droplet route).
- Universal population susceptibility against the background of a lack of reliable specific prophylaxis.
- Importation of the specific vector—the flea Xenopsylla cheopis—into the country's territory.
Pathogenesis and clinical presentation
From the perspective of pathogenesis, the disease goes through several stages. After the microbe invades at the site of entry, a primary affect is formed. Lymphogenic spread then occurs: the pathogen reaches the regional lymph nodes, causing their acute inflammation. In an unfavorable course, generalization of the process ensues—bacteremia and septicemia—leading to parenchymal diffusion, infectious-toxic shock (ITS), and secondary pneumonia.
According to G.N. Rudnev's classification, cutaneous, bubonic, septic, pulmonary, and intestinal forms are distinguished.
Clinical manifestations using the bubonic form as an example:
- Intoxication syndrome: hyperacute onset, shaking chills, hyperthermia (up to 38–39°C and higher). The patient develops neurotoxicosis—they are restless, inadequate, and their speech is disjointed.
- Lymphoid tissue involvement: a bubo forms—a sharply painful, enlarged lymph node (e.g., submandibular) with indistinct contours. Periadenitis develops: the skin over the node is pasty and hyperemic.
- Local changes: erosive-hemorrhagic lesions of the oropharynx, petechial enanthema on the palate, serous-hemorrhagic discharge on the tonsils.
- Hemodynamic disorders: pronounced arterial hypotension, tachycardia, and tachypnea.
«First-contact» physician's tactics
The variety of clinical forms of plague and the lack of clinical suspicion among physicians complicate diagnostics. However, upon suspicion of any especially dangerous infection (EDI), a physician is obliged to act according to a strict algorithm:
- Strict isolation. Under no circumstances should the physician let the patient go or leave themselves. They are obliged to stay with the patient in the room, isolating them from others.
- Notification. It is necessary to immediately report the suspicion to the head of their medical institution via phone, without leaving the office.
- Organization of care. The head transmits the information to the Center for State Sanitary and Epidemiological Surveillance (EDI department) and organizes the delivery of personal protective equipment and emergency medications to the physician.
- Waiting and hospitalization. The physician waits for the arrival of the specialized consultative team. The patient is hospitalized strictly into a box unit of an infectious diseases hospital.
Briefly: answers to topical questions
With which infectious and non-infectious diseases is it necessary to differentiate the bubonic form of plague?
The bubonic form of plague should be differentiated from similar diseases accompanied by intoxication syndrome and the formation of regional lymphadenitis. The provided sources indicate the following for differential diagnosis:
- tularemia;
- bacterial tonsillitis of other etiologies;
- other forms of plague.
Non-infectious diseases for the differential diagnosis of the bubonic form of plague are not specified in the sources.
What morphological and tinctorial properties are characteristic of the plague pathogen (Yersinia pestis)?
The plague pathogen (Yersinia pestis) is characterized by the properties of gram-negative short ovoid bacteria.
- Morphological properties — short ovoid rods of medium size (0.5 x 1.75 µm). The bacterium is immobile (lacks flagella) and does not form spores, but is capable of forming a glycoprotein capsule in the body of warm-blooded animals.
- Tinctorial properties — gram-negative, characterized by intense bipolar staining with aniline dyes (Gram stain or Loeffler's methylene blue).
Which antibacterial drugs are the drugs of choice for the etiotropic therapy of plague?
The drug of choice for antibacterial etiotropic therapy of plague is streptomycin.
- Streptomycin: administered intravenously, then intramuscularly at 1.0 g twice a day; course duration is at least 10 days.
- The sources also indicate the subsequent use of a combination of streptomycin and doxycycline.
Which vaccines are used for the specific prophylaxis of plague according to epidemiological indications?
For the specific prophylaxis of plague, the sources indicate:
- live plague vaccine;
- chemical plague vaccine;
- oral vaccine developed by A.A. Vorobyov and E.M. Zemskov;
- aerosol vaccine developed by V.A. Lebedinsky's group.
For anti-plague vaccination, the administration routes are indicated: percutaneous — for children, the elderly, pregnant women; subcutaneous — for individuals aged 14 to 60 years. Revaccination is carried out routinely after 1 year, and after 6 months in an unfavorable epidemiological situation.
Class and exam questions
What epidemiological history data indicate the likelihood of plague?
The patient's stay in endemic regions (e.g., Southeast Asia or the southern republics of the Russian Federation) within the last 5–10 days, contact with rodents, or flea bites.
What is a bubo and what does it look like on examination?
A bubo is a specifically inflamed regional lymph node. It is sharply painful, the size of a plum or larger, with indistinct contours due to periadenitis, and the skin over it is hyperemic and pasty.
What diseases should plague be differentiated from in the first place?
Depending on the form, differential diagnosis is carried out with tularemia, as well as with severe bacterial tonsillitis of other etiologies accompanied by lymphadenitis.
What else to study on this topic
- Classification of clinical forms of plague according to G.N. Rudnev
- Pathogen genetics: chromosomal and plasmid pathogenicity factors
- Rapid diagnostic methods, bacteriological and immunological studies
- Etiotropic therapy: choice of antibiotics and course duration
- Rules for emergency prophylaxis and quarantine measures in natural foci
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