Anthrax
The causative agent is the Gram-positive bacterium Bacillus anthracis. Its spores can survive in the environment for decades (in water up to 10 years, in soil up to 30 years).
Routes of transmission:
- Airborne (droplet): leads to the pulmonary form.
- Alimentary: leads to the intestinal form.
- Contact: infection through skin lesions.
- Vector-borne: via blood-sucking insects in the summer.
Pathogenesis is associated with capsule and toxin production, causing endothelial damage and necrosis. The most frequent form is cutaneous (95% of cases), characterized by the formation of an anthrax carbuncle.
Tularemia
An acute infectious disease caused by Gram-negative coccobacilli Francisella tularensis.
Sources and routes of infection: Reservoirs include rodents (mice, rats, hares). Human infection occurs via contact, arthropod bites, as well as alimentary and inhalation routes.
The disease manifests with intoxication, fever, and lymph node involvement with the formation of primary tularemia buboes (necrosis and granulomatous reaction). The bubonic, generalized, and pulmonary forms are distinguished.
Epidemic relapsing fever
Caused by the spirochete Borrelia recurrentis. The vectors are lice. Infection occurs not through a bite, but when the insect is crushed and spirochetes enter wounds during scratching.
It is characterized by alternating bouts of fever and remissions. Spirochetes multiply in the RES, then break into the bloodstream. When they die, endotoxins are released, which triggers the attack.
Brucellosis
The causative agent is bacteria of the genus Brucella (intracellular parasites of the RES).
Epidemiology: The reservoir is cattle and pigs. Infection often occurs alimentarily (through dairy and meat products), as well as by contact and airborne routes.
Characterized by the absence of a clear primary affect, generalization of the infection with the pathogen spreading to RES organs, and a wave-like course.
Briefly: answers to topical questions
What stages of development does the skin rash undergo in smallpox?
The skin rash in smallpox undergoes six sequential stages of development. The dynamics of the elements include:
- Spots — primary rash.
- Papules — pea-sized nodules.
- Vesicles — the stage of blister formation.
- Pustules — transformation into pus-filled lesions.
- Crusts — the stage of element drying.
- Scars — remain after crusts fall off (especially pronounced on the face).
What specific intracellular inclusions are found in the epidermis in smallpox?
Specific viral inclusions are found in cells in smallpox. These include:
- Paschen bodies — clusters of virus visible under a light microscope with special staining.
- Guarnieri bodies — intracellular clusters of the virus in epithelial cells, appearing as small granules (formed in the cytoplasm).
Which clinical and morphological forms of smallpox are distinguished depending on the severity of the course?
Depending on the severity of the course, three main clinical and morphological forms of smallpox are distinguished.
- Mild forms — varioloid (rash development stops at the vesicle stage), smallpox without rash, and smallpox without fever.
- Moderate forms — pustular (disseminated) smallpox with typical signs, usually not causing hemorrhages.
- Severe forms — pustular-hemorrhagic ("black smallpox") and confluent smallpox, distinguished by an extremely severe course and 100% mortality.
What macroscopic and microscopic changes are characteristic of an anthrax carbuncle?
An anthrax carbuncle is characterized by the development of serous-hemorrhagic inflammation and deep necrosis.
- Macroscopic changes — formation of a pitch-black scab with a hard ("scorched") crust. The scab is surrounded by an infiltrate in the form of a purple ridge, accompanied by extensive gelatinous edema.
- Microscopic changes — the exudate is poor in cellular elements. The necrosis zone extends into the thickness of all layers of the dermis and subcutaneous adipose tissue.
What pathomorphological changes develop in the lymph nodes during the formation of a primary tularemia bubo?
During the formation of a primary tularemia bubo, the lymph nodes enlarge and fuse together. The following pathomorphological changes develop in them:
- Necrosis and suppuration — primary foci of alteration arise.
- Granulomatous reaction — formation of specific tularemia granulomas prone to suppuration.
- Cellular infiltration — in the center of the granuloma is a focus of necrosis surrounded by neutrophils, eosinophils, and epithelioid cells, while lymphocytes, plasma cells, and Langhans giant cells accumulate at the periphery.
Which specific organs of the reticuloendothelial system are affected in generalized brucellosis?
During the hematogenous phase of brucellosis, bacteremia and dissemination of brucellae into the organs of the macrophage system occur. The source lists the following organs:
- Lymph nodes.
- Liver.
- Spleen.
- Kidneys.
- Lungs.
- Bone marrow.
Class and exam questions
Why is there no information about smallpox in the article?
Smallpox is not mentioned in the source materials used to write the article. Anthrax, tularemia, relapsing fever, and brucellosis are described.
Which form of anthrax is the most common?
The cutaneous form develops in 95% of patients and is characterized by the formation of an anthrax carbuncle.
What else to study on this topic
- Morphological characteristics of the anthrax carbuncle
- Complications of the cutaneous form of anthrax
- Clinical and morphological forms of tularemia
- Mechanism of relapse development in relapsing fever
- Brucella species and their pathogenicity
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