Clinical Presentation and Syndromes
The diseases manifest acutely with a rapid onset of fever. The clinical picture consists of several leading syndromes that require careful differential diagnosis from rickettsioses and certain viral infections.
Key manifestations include:
- Toxic syndrome. Patients report marked chills, severe fatigue, intense headache, and muscle pain (myalgia).
- Dyspeptic symptoms. Accompanying the systemic toxicity, anorexia (loss of appetite) frequently occurs, sometimes accompanied by nausea and vomiting.
A crucial dermatological and differential diagnostic feature is the complete absence of a primary eschar at the site of pathogen inoculation across all clinical forms. Skin rashes (exanthem) may be erythematous or petechial, but are absent in many patients. For instance, in Sennetsu fever, a rash appears rarely, whereas in granulocytic anaplasmosis and monocytic ehrlichiosis, an exanthem is documented in 10–30% of cases.
Timeline and Clinical Forms
The incubation period from the moment of infection to the first clinical signs averages 7 to 14 days. The subsequent progression and duration of the febrile period directly depend on the specific clinical form of the disease.
Three main forms feature distinct fever durations:
- Human granulocytic anaplasmosis (HGA) — fever typically persists for 7–10 days.
- Sennetsu fever — the febrile period lasts no longer than two weeks.
- Human monocytic ehrlichiosis (HME) — characterized by the longest course, with fever lasting up to 3 weeks.
Microbiological Diagnostics
Establishing a definitive diagnosis requires specific laboratory methods because the clinical presentation is not absolutely pathognomonic. Modern practice relies on a multimodal approach.
- Serological testing. The primary strategy involves examining paired sera (acute-phase and convalescent-phase samples). Indirect immunofluorescence assays (IFA) or enzyme-linked immunosorbent assays (ELISA) utilize specific antigens.
- Molecular testing. Polymerase chain reaction (PCR) detects pathogen DNA in clinical samples.
- Microscopy. Blood smears are stained using Giemsa stain. The laboratory technician looks for specific structures — morulae (dense clusters of Ehrlichia or Anaplasma). Depending on the infection form, these inclusions reside inside the cytoplasm of monocytes or neutrophils.
Management and Prevention
The cornerstone of therapy for ehrlichioses and anaplasmosis is prompt etiotropic treatment. The drugs of choice are tetracycline-class antibiotics, primarily doxycycline. In cases of hypersensitivity or contraindications, chloramphenicol serves as an alternative backup agent (though rarely required).
Prevention strategies:
- Specific prophylaxis. No human vaccine is currently available.
- Post-exposure prophylaxis. Consists of a preventive course of doxycycline administered immediately following a confirmed tick bite.
- Nonspecific prevention. Includes standard tick-precaution measures: using repellents, wearing protective clothing, and conducting regular tick checks after visiting endemic natural areas.