Comparative table of tick-borne zoonotic infections (TBE, KFD, rickettsioses)
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Comparative Table of Tick-Borne Zoonotic Infections: TBE, KFD, and Rickettsioses
| Feature | Tick-Borne Encephalitis (TBE) | Kyasanur Forest Disease (KFD) | Tick-Borne Rickettsioses |
|---|---|---|---|
| Causative Agent | TBE virus (Flavivirus; 3 subtypes: European, Siberian, Far Eastern) | KFD virus (Flavivirus; closely related to Omsk HF virus) | Rickettsia spp. (gram-negative intracellular bacteria); e.g., R. rickettsii (RMSF), R. conorii (MSF), R. africae, R. sibirica, others |
| Classification | RNA virus, Flaviviridae | RNA virus, Flaviviridae | Alphaproteobacteria, Rickettsiaceae |
| Primary Vector | Ixodes ricinus (Europe), I. persulcatus (Asia) | Haemaphysalis spinigera and other Haemaphysalis spp. | Dermacentor, Amblyomma, Ixodes, Rhipicephalus spp. (varies by species) |
| Reservoir / Amplifying Host | Small rodents, deer; birds (long-range spread); also transmission via unpasteurized milk | Monkeys (Presbytis and Macaca spp.) as amplifying hosts; small rodents as reservoir | Ticks (transovarial transmission); small mammals |
| Geographic Distribution | Europe to Japan (endemic belt); from France eastward across Russia to northern Japan | Karnataka state, India (Kyasanur Forest region); expanding | Worldwide (species-specific): RMSF — Americas; Mediterranean SF — Mediterranean, Africa, India; African tick typhus — sub-Saharan Africa; Siberian tick typhus — Asia |
| Incubation Period | 7–14 days (range 2–28 days) | 3–8 days | 2–14 days |
| Clinical Course | Biphasic: Phase 1 — flu-like (fever, headache, myalgia, 2–7 days); Phase 2 (in ~30%) — meningoencephalitis, myelitis, radiculitis | Phase 1 — abrupt fever, headache, myalgia, hemorrhagic manifestations (bleeding from gums, nose, GI); Phase 2 (after ~3-week remission) — meningoencephalitic symptoms in some | Acute febrile illness; usually no biphasic pattern |
| Key Clinical Features | Encephalitis, meningitis, spinal cord involvement; cognitive/motor sequelae possible; hemorrhage absent | Hemorrhagic fever + late neurological involvement; thrombocytopenia; leukopenia | High fever, severe headache, characteristic rash (macular → petechial/purpuric); eschar (tache noire) in many non-RMSF species; regional lymphadenopathy in some |
| Rash | Absent | Absent (hemorrhagic manifestations instead) | Present in most; macular initially, may become petechial/purpuric; centripetal spread (wrists/ankles → trunk in RMSF); eschar at bite site (especially MSF, SENLAT, African tick typhus) |
| Hemorrhagic Features | Absent | Prominent (gingival bleeding, melena, hematemesis, epistaxis) | Rare; petechiae possible in severe RMSF |
| CNS Involvement | Central feature (encephalitis, meningitis, myelitis, radiculitis) | Late neurological phase: tremors, delirium, neck rigidity, coma | Possible in severe RMSF (delirium, coma); uncommon in milder spotted fevers |
| Eschar | Absent | Absent | Present in MSF, Siberian tick typhus, African tick typhus, Japanese SF, SENLAT; absent or rare in RMSF |
| Case Fatality Rate | European subtype ~1–2%; Siberian ~6–8%; Far Eastern ~20–40% | 3–5% (up to 10% in some outbreaks) | RMSF: 5–25% (untreated); MSF: ~3%; African tick typhus: <1%; varies widely by species and treatment |
| Pathology | Neurotropic; viral encephalitis (perivascular inflammation, neuronal necrosis, gliosis in thalamus, brainstem, cerebellum) | Endothelial damage → capillary leak and hemorrhage; hepatic/renal necrosis | Vasculitis of small vessels; endothelial cell invasion; bacteria multiply in cytoplasm and escape phagosomes; target cells are vascular endothelial cells (and monocytes in typhus group) |
| Key Lab Findings | Leukocytosis → leukopenia; CSF: lymphocytic pleocytosis; serology (IgM/IgG); PCR during viremia | Thrombocytopenia, leukopenia, elevated liver enzymes; PCR (viremic phase); serology (ELISA, PRNT) | Thrombocytopenia; elevated transaminases; hyponatremia; diagnosis: serology (IFA — gold standard), PCR, immunohistochemistry of biopsy/eschar swab |
| Gold-Standard Diagnosis | ELISA for specific IgM/IgG in serum or CSF | RT-PCR (acute phase); PRNT serology | Indirect immunofluorescence assay (IFA); PCR of blood/eschar; empiric treatment should not await confirmation |
| Treatment | Supportive only; no specific antiviral | Supportive only; ribavirin has been used but no proven efficacy; convalescent plasma trialed | Doxycycline (drug of choice, all ages); chloramphenicol as alternative; fluoroquinolones (variable efficacy); prompt treatment is critical |
| Prophylaxis / Vaccine | Effective inactivated vaccine available (FSME-Immun®, Encepur®, others); widely used in endemic Europe | Formalin-inactivated vaccine (used in India in at-risk populations); limited availability | No licensed vaccine; tick avoidance, personal protective measures, prompt tick removal |
| Transmission Route | Tick bite (primary); ingestion of unpasteurized dairy products (secondary) | Tick bite; also via infected monkey blood contact | Tick bite; attachment ≥20 hours typically required for transmission |
| Risk Groups | Outdoor workers, hikers, farmers, children in endemic areas; travelers | Forest workers, villagers at forest margins in Karnataka | Outdoor workers, hikers, campers; children <10 years (RMSF); travelers to endemic regions |
| Notifiable / Reportable | Yes (in most endemic countries) | Yes (India) | Yes (in most countries) |
Key Distinguishing Points at a Glance
| Discriminator | TBE | KFD | Rickettsioses |
|---|---|---|---|
| Biphasic course | Yes (classic) | Yes (with remission) | No |
| Hemorrhage | No | Yes (major feature) | Petechiae only (severe cases) |
| Rash | No | No | Yes (hallmark) |
| Eschar | No | No | Yes (many species) |
| Neurological | Central feature | Late-phase only | Severe cases only |
| Treatment | Supportive | Supportive | Doxycycline (curative) |
| Vaccine | Yes (effective) | Yes (limited) | No |
Sources
- Goldman-Cecil Medicine, International Edition — Rickettsioses, pp. 3286–3372 (Table 302-2; Chapters 302–303)
- Harrison's Principles of Internal Medicine 22E (2025) — Viral Hemorrhagic Fevers (Chapter on KFD/TBE)
- Goldman-Cecil Medicine — Tick-Borne Encephalitis and Viral Hemorrhagic Fevers, pp. corresponding blocks
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