Symptoms of Ehrlichiosis
Ehrlichiosis typically presents with fever, headache, malaise, and myalgia, with rash occurring in only about one-third of patients—making it easy to miss if you're expecting a classic tick-borne rash presentation. 1
Core Clinical Presentation by Species
Ehrlichia chaffeensis (Most Common)
The classic symptom constellation includes: 1
- Fever (96% of cases) appearing median 9 days after tick bite (range 5-14 days)
- Headache (72%)
- Malaise (77%)
- Myalgia (68%)
- Gastrointestinal symptoms are prominent and often misleading:
- Nausea (57%)
- Vomiting (47%)
- Diarrhea (25%)
- Abdominal pain (more common in children) 1
Critical pitfall: The prominent GI symptoms frequently lead clinicians down the wrong diagnostic path, delaying appropriate treatment. 1
Rash Characteristics (Important Distinctions)
- Rash occurs in only ~33% of E. chaffeensis cases 1
- Much more common in children than adults 1
- Appears median 5 days after illness onset 1
- Variable patterns: petechial, maculopapular, or diffuse erythema 1
- Can involve extremities, trunk, palms, soles, or face 1
This is fundamentally different from Rocky Mountain spotted fever where rash is expected—don't rule out ehrlichiosis just because there's no rash. 1
Neurologic Manifestations
- Central nervous system involvement occurs in ~20% of E. chaffeensis cases 1
- Presents as meningitis or meningoencephalitis 1
- CSF typically shows lymphocytic pleocytosis (though neutrophilic pleocytosis can occur) 1
Respiratory Symptoms
- Cough or respiratory symptoms in ~28% of patients 1
- More common in adults than children 1
- Can progress to ARDS in severe cases 1
Ehrlichia ewingii Presentation
E. ewingii causes similar symptoms to E. chaffeensis but with key differences: 1
- Fever, headache, malaise, myalgia present
- Gastrointestinal symptoms LESS common 1
- Rash is RARE 1
- Generally fewer severe manifestations than E. chaffeensis 1
- No deaths reported to date 1
Ehrlichia muris-Like (EML) Agent
Symptom frequencies: 1
- Fever (87%)
- Malaise (76%)
- Headache (67%)
- Myalgia (60%)
- Rash (only 12% of cases) 1
- No fatal cases reported 1
High-Risk Populations and Severity Markers
Increased severity strongly associated with: 1
- Age ≥60 years
- Immunosuppression (HIV, organ transplant, immunosuppressive therapy, splenectomy)
- Children <10 years paradoxically have highest case-fatality rate despite often having milder symptoms 1
- Sulfonamide antimicrobial use may predispose to severe illness 1
Case-fatality rate for E. chaffeensis is approximately 3% 1
Characteristic Laboratory Abnormalities (Part of Clinical Picture)
These lab findings are so consistent they should raise suspicion even before confirmatory testing: 1
- Leukopenia (nadir 1,300-4,000 cells/μL)
- Thrombocytopenia (nadir 50,000-140,000 platelets/μL, occasionally <20,000)
- Elevated hepatic transaminases (mild to moderate)
- Anemia (occurs later, in 50% of patients) 1
- Mild-to-moderate hyponatremia 1
- Relative and absolute lymphocytosis during recovery period 1
For E. muris-like agent specifically: 1
- Thrombocytopenia (67%)
- Lymphopenia (53%)
- Leukopenia (39%)
- Elevated hepatic transaminases (78%)
- Anemia (36%)
Severe Manifestations to Recognize
Life-threatening complications include: 1, 2
- ARDS
- Toxic shock-like or septic shock-like syndromes
- Renal failure
- Hepatic failure
- Coagulopathies and hemorrhagic manifestations
- Opportunistic infections (in immunosuppressed patients)
The key to preventing mortality is early empirical treatment—don't wait for confirmatory testing if clinical suspicion is high based on tick exposure, fever, and characteristic cytopenias. 2, 3