Organism: Rickettsia conorii, a Gram-negative obligate intracellular bacterium (spotted fever group).
Disease: Causes Mediterranean Spotted Fever (Boutonneuse fever), a tick-borne rickettsiosis.

🧬 Characteristics

Size & Staining: Tiny Gram-negative bacillus, poorly visualised on routine Gram stain.
Intracellular lifestyle: Energy parasite → requires host ATP; grows only in tissue culture or living cells.

🌍 Source & Distribution

Geography: Endemic in the Mediterranean basin, Africa, Middle East, India.
Vector: Brown dog tick (Rhipicephalus sanguineus).
Transmission: Tick bite → inoculation of rickettsiae into bloodstream.

🩺 Clinical Features

Incubation: 5–7 days post-tick bite.
Symptoms: Fever, severe headache, malaise, myalgia.
Rash: Maculopapular, appears ~day 3, may involve palms/soles ✋🦶.
Eschar: Single necrotic lesion (“tache noire”) at bite site, often hidden (scalp, ear, genital region).
Severity: More severe than African Tick Bite Fever; can be fatal if untreated.

⚠️ Complications

Neurological: encephalitis, confusion, coma.
Pulmonary: pneumonia, pulmonary embolism (from DVT).
Multi-organ: bleeding, gangrene, hepatorenal failure, myocarditis.
Mortality: Up to 2–5% in untreated/elderly/immunocompromised.

🧾 Differential Diagnosis

Meningococcal septicaemia.
Other Gram-negative septicaemias.
Viral haemorrhagic fevers (e.g. Crimean-Congo HF).
Other rickettsioses (esp. R. africae → milder, multiple eschars).

🔍 Investigations

Bloods: Neutrophilia, thrombocytopenia, ↑ AST/ALT.
Serology: IFA/ELISA for anti-rickettsial antibodies (often retrospective).
PCR: Can confirm diagnosis from blood/eschar swab.

💊 Management

First-line: Doxycycline (100 mg PO BD for 7–10 days). 🚑 Start empirically if suspected.
Alternatives: Ciprofloxacin or chloramphenicol if doxycycline contraindicated.
Supportive: Antipyretics, fluid balance, manage complications.

💡 Clinical Pearl

Classic triad = fever + rash (palms/soles) + eschar. Single eschar → think R. conorii. Multiple eschars + milder course → think R. africae.

✅ Conclusion

Rickettsia conorii causes Mediterranean Spotted Fever, a potentially severe tick-borne illness. It presents after 5–7 days with fever, rash (often involving palms/soles), and an eschar at the bite site. Lab findings show neutrophilia, thrombocytopenia, and raised LFTs. Prompt doxycycline treatment is essential to prevent severe multi-organ complications and mortality.

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Rickettsia conorii (Mediterranean Spotted Fever)

📖 About Rickettsia conorii