Clinical picture and diagnostic triad
The disease begins acutely with high fever, sweating, severe headaches, and muscle/joint pain (myalgia and arthralgia). The pathogenesis is based on the development of systemic vasculitis. In endemic foci, the diagnosis can be made clinically without waiting for laboratory confirmation if the patient presents with the classic triad:
- Primary affect: the site of the infection's entry portal ("black spot").
- Regional lymphadenitis: enlargement of the lymph nodes draining the bite area.
- Exanthem: a profuse, polymorphic, maculopapular rash spreading across the entire body. Important feature: marked pigmentation persists for a long time after the rash fades.
Internal organs show moderate hepatosplenomegaly (the spleen enlarges more frequently than the liver). During the first week, a decrease in daily urine output, febrile albuminuria, and the appearance of red and white blood cells in the urine are characteristic.
Severity forms and complications
The prognosis is generally favorable. The drop in temperature is accompanied by the normalization of hemodynamics and clearing of the coated tongue. However, the severity of the course can vary:
- Mild form: lasts no more than a week, low-grade fever, sparse rash (predominantly roseolous). The patient's condition is satisfactory.
- Severe course (3–5% of cases): risk groups include elderly individuals and patients with a burdened premorbid background. Severe intoxication with hyperpyrexia. The rash acquires a hemorrhagic character. Severe damage to the cardiovascular system (arterial hypotension, tachycardia, muffled heart sounds) and CNS (delirium, general tremor, prostration — typhoid state) develops. Mortality in this form can reach 5–6%.
- Atypical course: the rash may be absent, or the primary affect fails to form (often in children). Asymptomatic (inapparent) or abortive courses are possible.
Complications develop extremely rarely. Specific complications include endocarditis, pericarditis, and myocardial ischemia. Secondary complications (due to superimposed flora) include pneumonia and thrombophlebitis.
Laboratory diagnostics
The hemogram in the first week reveals decreased hemoglobin, thrombocytopenia, leukopenia (normocytosis is rare), anethesinophilia (aneosinophilia), neutropenia, and relative lymphomonocytosis. These are indirect signs.
Specific serology is used to confirm the diagnosis (it is important to record rising titers in paired sera):
- CFT (complement fixation test): antibodies to R. conorii antigens appear by days 5–10 (diagnostic titer 1:40–1:160). They may persist at low titers for years, which is useful for retrospective diagnosis.
- IHA and IFA (HAI and IFA): diagnostic titers are 1:200 and 1:32–1:64, respectively.
- Specialized laboratories use PCR (DNA detection) and ELISA.
Astrakhan spotted fever
This is a regional form of tick-borne spotted fevers. The causative agent is R. conorii subsp. caspiensis. The main vector is the tick Rhipicephalus pumilo, and the universal reservoir host maintaining the natural focus is the long-eared hedgehog (Hemiechinus auritus).
Incidence is sporadic with pronounced seasonality (May–September). The natural focus has transformed into an anthropurgic one: people frequently become infected through contact with dogs.
Features of the clinical presentation of ASF:
- An aerogenic route of infection frequently occurs (when crushing ticks removed from dogs and getting their hemolymph onto mucous membranes).
- Because of this, the primary affect is rare (less than 30%), but 70% of patients exhibit oropharyngeal hyperemia with enanthem on the soft palate.
- A characteristic feature is the "monkey gait" — walking on semi-flexed legs due to severe pain in the calf muscles and joints.
- A typhoid state does not develop, and the prognosis is always favorable.
Differential diagnosis and management
The disease is differentiated from epidemic typhus, typhoid fever, Crimean-Congo hemorrhagic fever, leptospirosis, measles, rubella, secondary syphilis, and meningococcemia.
Hospitalization is indicated for moderate and severe cases. Management is comprehensive (targeted, detoxifying, and symptomatic therapy). The patient is discharged on days 8–10 of sustained body temperature normalization and after the complete resolution of clinical symptoms.
Briefly: answers to topical questions
Which drugs are used for the targeted therapy of Mediterranean spotted fever?
For the targeted therapy of tick-borne spotted fevers, which include Mediterranean spotted fever, tetracycline antibiotics are used. Treatment is carried out in accordance with the general provisions of the "Tick-borne spotted fevers" topic.
What is the detailed pathogenesis of vascular and internal organ lesions in Mediterranean spotted fever?
The pathogenetic basis of Mediterranean spotted fever is the development of acute universal vasculitis. Rickettsiae penetrate and multiply within the endothelial cells of blood and lymphatic vessels at the site of entry and in regional lymph nodes. In the initial period, proliferative-desquamative vasculitis develops. The involvement of small vessels is predominantly functional and proliferative in nature, without pronounced destructive changes. Morphological signs of vasculitis include:
- swelling and proliferation of endothelial cells;
- edema of the surrounding perivascular tissue;
- focal accumulations of leukocyte-series cells.
In the area of the entry site, the pathological process is caused by the development of vasculitis. In the 1st week, functional renal disorders are possible: clinically—decreased daily diuresis; laboratory-wise—febrile albuminuria, microscopically—elevated leukocyte and erythrocyte counts, isolated hyaline and granular casts. Hepatosplenomegaly is inconsistent and moderately expressed; spleen enlargement is observed more frequently than liver enlargement. In the final stages of pathogenesis, the development of hypoxemia, hypoxia, metabolic acidosis, and hemostasis alterations has been described.
The PLE triad: Primary affect, Lymphadenitis, Exanthem.
Class and exam questions
On what basis can a diagnosis be made in the first days?
In endemic foci, the diagnosis is established clinically based on acute intoxication and the classical triad (primary affect, regional lymphadenitis, polymorphic rash).
Why is a primary affect rare in Astrakhan spotted fever?
This is due to the predominance of the airborne route of transmission, when a person inhales an aerosol of hemolymph or feces from crushing ticks removed from animals.
What is "simian gait"?
This is a specific sign of Astrakhan spotted fever: the patient walks with semi-flexed legs due to pronounced myalgia (in the calf muscles) and arthralgia.
When do antibodies appear in the complement fixation test (CFT)?
Complement-fixing antibodies appear from days 5–10 of the illness, while they may circulate in the blood at low titers for years after recovery.
What else to study on this topic
- Criteria for differential diagnosis with measles and secondary syphilis
- Principles of targeted therapy for tick-borne rickettsioses
- Pathogenesis of typhoid state development in severe forms
- Algorithm for collecting paired sera for retrospective diagnostics
- Epidemiological significance of the long-eared hedgehog in maintaining the ASPF focus
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