Comparative table of tick-borne zoonotic infections (TBE, KFD, rickettsioses)
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I now have enough information from the textbooks to build a comprehensive comparative table. Let me synthesize it.
Comparative Table of Major Tick-Borne Zoonotic Infections
TBE | KFD | Rickettsioses
| Feature | Tick-Borne Encephalitis (TBE) | Kyasanur Forest Disease (KFD) | Spotted Fever Rickettsioses (e.g., RMSF, MSF) | Typhus Group Rickettsioses (e.g., Murine typhus) |
|---|---|---|---|---|
| Pathogen | Tick-borne encephalitis virus (Flavivirus; 3 subtypes: European, Far-Eastern, Siberian) | Kyasanur Forest disease virus (Flavivirus) | Rickettsia rickettsii, R. conorii, R. africae, R. japonica, etc. (obligate intracellular bacteria) | Rickettsia typhi (murine/endemic typhus); R. prowazekii (epidemic typhus) |
| Principal Vector | Ixodes ricinus (Europe); I. persulcatus (Asia/Russia) | Haemaphysalis spinigera and other Haemaphysalis spp. | Dermacentor, Rhipicephalus, Amblyomma, Ixodes spp. (species-specific) | Fleas (Xenopsylla cheopis, Ctenocephalides felis) — tick-borne for other species |
| Reservoir | Small rodents, birds; transovarial/transstadial tick transmission | Rodents, monkeys (monkeys serve as sentinels); hard ticks | Deer, rodents, dogs, small mammals | Rats, opossums, cats |
| Geographic Distribution | Eastern Europe to Far East Russia; ~10,000–12,000 cases/year | Karnataka state, India; Yunnan Province, China; Saudi Arabia (Alkhurma variant); ~500 cases/year | Worldwide (species-dependent): Americas, Africa, Europe, Asia, Australia | Worldwide (tropical/subtropical); common in SE Asia, China, North Africa |
| Transmission Route | Tick bite; also ingestion of unpasteurized milk/cheese from infected goats/cows | Tick bite; contact with infected animals; laboratory exposure | Tick bite (salivary inoculation during feeding) | Flea bite + autoinoculation of flea feces; rarely tick bite |
| Incubation Period | 1–2 weeks | 3–8 days | 2–14 days | 8–16 days |
| Pathogenesis | Neurotropic flavivirus; lymphohematogenous spread → CNS inflammation | Hemorrhagic fever virus; capillary leak, hemorrhage, thrombocytopenia; late neurologic phase | Endothelial cell infection → widespread vasculitis; rickettsia-induced endothelial damage → petechial hemorrhage | Endothelial/mononuclear cell infection; similar vascular injury mechanism |
| Target Cells | Mononuclear cells, macrophages → CNS neurons | Endothelial cells, monocytes; viscerotropic and neurotropic | Endothelium (primary target) → vasculitis | Endothelium, monocytes |
| Clinical Phases | Biphasic (in ~30%): Phase 1 – flu-like (fever, myalgia, fatigue); Phase 2 – meningitis/meningoencephalitis | Biphasic: Phase 1 – abrupt fever, hemorrhagic manifestations (1–2 wks); Phase 2 – neurologic (tremors, encephalitis) in subset | Monophasic febrile illness with vasculitic rash | Monophasic; fever + rash (40–50%) |
| Key Clinical Features | Encephalitis, bulbar paralysis, seizures, altered consciousness; neurologic sequelae possible | High fever, severe hemorrhage (mucosal, GI), thrombocytopenia, leukopenia, hepatosplenomegaly; CNS signs (tremors, confusion) in late/severe disease | Petechial/maculopapular rash beginning peripherally (wrists/ankles → trunk ± palms/soles); eschar at bite site (MSF/other); possible multiorgan failure if untreated | Maculopapular rash (trunk, not palms/soles); cough, pneumonia in ~1/3; neurologic symptoms in severe disease |
| Eschar (Tache Noire) | Absent | Absent | Present in Mediterranean SF, Siberian tick typhus, African tick-bite fever, others; absent in RMSF | Absent |
| Hemorrhagic Features | Rare/absent | Prominent — a hemorrhagic fever virus | Petechiae/purpura in severe RMSF | Purpura in severe cases |
| Lymphadenopathy | Absent | Regional lymphadenopathy possible | Regional lymphadenopathy in some SFG species (e.g., R. slovaca) | Uncommon |
| Lab Findings | Leukopenia, CSF pleocytosis in neurologic phase | Thrombocytopenia, leukopenia, elevated liver enzymes, proteinuria | Thrombocytopenia, leukopenia → leukocytosis, elevated transaminases, hyponatremia | Thrombocytopenia, leukopenia → leukocytosis; elevated transaminases |
| Diagnosis | RT-PCR (phase 1); serology (phase 2 — IgM/IgG) | RT-PCR; serology (ELISA, neutralization) | Serology (IFA — gold standard); PCR of blood/biopsy; skin biopsy immunohistochemistry | IFA serology; PCR; clinical |
| Treatment | Supportive only — no specific antiviral | Supportive — no specific antiviral (ribavirin studied) | Doxycycline 100 mg BID (first-line; drug of choice for all ages); chloramphenicol alternative | Doxycycline 100 mg BID (5–7 days); rifampin in pregnancy |
| Prophylaxis/Vaccine | Inactivated vaccine available (European + Far-Eastern strains); used routinely in Austria, E. Europe, Russia | Inactivated vaccine available in India | No vaccine; tick avoidance, repellents | No vaccine |
| Mortality (untreated/treated) | 1–2% (European subtype); ~20% (Far-Eastern subtype in Russia) | ~2–10% (case fatality in outbreaks) | RMSF: up to 20–25% untreated; <5% with early doxycycline; MSF: 1.5–2.5% hospitalized | ~1–4% with treatment; higher in G6PD deficiency |
| Person-to-Person Transmission | Not reported | Not reported (laboratory infections documented) | Not reported | Not reported |
Key Distinguishing Points
| TBE | KFD | Spotted Fever Rickettsia | Typhus Rickettsia | |
|---|---|---|---|---|
| Viral vs Bacterial | Viral | Viral | Bacterial | Bacterial |
| Biphasic course | Yes (30%) | Yes | No | No |
| Hemorrhage prominent | No | Yes | Petechiae/purpura late | Petechiae in severe cases |
| Encephalitis | Central feature | Late/severe disease | Rare | Rare |
| Eschar | No | No | Often yes (species-dependent) | No |
| Specific therapy | Supportive only | Supportive only | Doxycycline | Doxycycline |
| Vaccine | Yes | Yes (India) | No | No |
Sources:
- Goldman-Cecil Medicine International Edition, pp. 3286–3372 (Rickettsial Diseases table, rickettsioses, Q fever, ehrlichioses)
- Goldman-Cecil Medicine International Edition, pp. 3644 (KFD/viral hemorrhagic fevers table)
- Goldman-Cecil Medicine International Edition, pp. 3651–3653 (TBE — definition, pathobiology, clinical features, treatment)
- Harrison's Principles of Internal Medicine 22E (KFD, TBE vaccine)
- Jawetz, Melnick & Adelberg's Medical Microbiology 28E, p. 571 (TBE epidemiology and subtypes)
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