Siberian Tick Typhus

🏷

Classifications

Harrison's Part

⚙

Pathophysiology

7

Dermacentor-Borne Rickettsia sibirica Inoculation

Feeding Dermacentor ticks inoculate R. sibirica subsp. sibirica into the dermis, initiating local infection at the arthropod attachment site.

Downstream

Dermal Mononuclear Phagocyte Rickettsia sibirica Infection Tick inoculation exposes dermal phagocytes to R. sibirica.

Show evidence (1 reference)

PMID:22493192 SUPPORT Other

"Rickettsia sibirica sibirica is the causative agent of Siberian or North Asian tick typhus, a tick-borne rickettsiosis known to exist in Siberia and eastern China. Here we present the draft genome of Rickettsia sibirica sibirica strain BJ-90 isolated from Dermacentor sinicus ticks collected in..."

The abstract identifies Siberian tick typhus as tick-borne and documents R. sibirica subsp. sibirica recovery from Dermacentor ticks.

Dermal Mononuclear Phagocyte Rickettsia sibirica Infection

After tick inoculation, rickettsiae enter dermal macrophages and dendritic cells, creating the inoculation-site lesion that seeds lymphatic and hematogenous dissemination.

macrophage CL:0000235 dendritic cell CL:0000451

symbiont entry into host cell GO:0046718

Downstream

Rickettsial Lymphatic Dissemination Rickettsiae disseminate from skin phagocytes into lymphatics.

Eschar Local inoculation-site infection produces a necrotic eschar.

Show evidence (1 reference)

PMID:30148688 SUPPORT REVIEW SYNTHESIS Other

"The pathogenic sequence of events that occur in rickettsial infection begins with the entry of organisms inoculated by the feeding tick or mite or scratched into the skin from infected louse or flea feces deposited on the skin. The initial target cells of infection are CD68+ cells (macrophages..."

The rickettsial pathogenesis review places macrophages or dendritic cells at the start of vector-inoculated skin infection.

Rickettsial Lymphatic Dissemination

Rickettsiae spread from the skin inoculation site through lymphatic vessels to regional lymph nodes before hematogenous seeding of systemic endothelial targets.

biological process involved in interaction with host GO:0051701

Downstream

Endothelial Cell Rickettsia sibirica Infection Lymphatic spread precedes hematogenous endothelial seeding.

Regional Lymphadenopathy Drainage from the inoculation site enlarges regional lymph nodes.

Show evidence (1 reference)

PMID:30148688 SUPPORT REVIEW SYNTHESIS Other

"The rickettsiae then spread via lymphatic vessels to the regional lymph nodes as has been observed vividly in the lymphangitis associated with R. sibirica mongolitimoniae infection"

The review uses lymphangitis in sibling R. sibirica subsp. mongolitimonae infection as the vivid example of lymphatic spread after the vector-inoculated skin lesion.

Endothelial Cell Rickettsia sibirica Infection

Hematogenously disseminated R. sibirica, like other pathogenic Rickettsia species, mainly infects systemic endothelial cells.

endothelial cell of vascular tree CL:0002139

biological process involved in interaction with host GO:0051701

Downstream

Rickettsial Vasculitis Endothelial infection activates vascular inflammation.

Show evidence (1 reference)

PMID:30148688 SUPPORT REVIEW SYNTHESIS Other

"Rickettsiae then spread hematogenously throughout the body and infect mainly endothelial cells"

The conserved rickettsial dissemination sequence identifies endothelial cells as the main hematogenous infection target.

Rickettsial Vasculitis

Rickettsial endothelial infection and activation produce a microvascular vasculitis with inflammatory cell infiltration and increased vascular permeability.

endothelial cell of vascular tree CL:0002139

inflammatory response GO:0006954 positive regulation of vascular permeability GO:0043117 ↑ INCREASED

Downstream

Fever Systemic endothelial infection and inflammation produce fever.

Maculopapular Rash Cutaneous rickettsial vasculitis produces the maculopapular rash.

Show evidence (2 references)

PMID:30148688 SUPPORT REVIEW SYNTHESIS Other

"The fundamental lesion of rickettsial diseases is vasculitis"

The review names vasculitis as the core lesion produced after endothelial rickettsial infection.

PMID:30148688 SUPPORT REVIEW SYNTHESIS Other

"The pathophysiologic events can be attributed principally to rickettsia infection-associated increased vascular permeability leading to edema, hypovolemia, hypotension, reduced perfusion of organs, acute respiratory distress syndrome, and CNS abnormalities."

The review links rickettsial endothelial infection to increased vascular permeability and downstream edema in systemic rickettsioses.

Rickettsial Ribosomal Translation

R. sibirica, like other bacteria, depends on ribosomal translation of its mRNA, making the bacterial ribosome the conserved antibiotic target for tetracycline therapy.

Translation GO:0006412

Show evidence (1 reference)

PMID:24336183 SUPPORT REVIEW SYNTHESIS Other

"The ribosome is one of the main antibiotic targets in the bacterial cell."

Review evidence for the bacterial ribosome as the conserved antibiotic target class for tetracyclines such as doxycycline.

Intracytosolic Rickettsia sibirica Niche

Rickettsia species reside free in the host-cell cytosol and exploit host metabolites, so effective Siberian tick typhus therapy must reach the intracellular bacterial compartment.

biological process involved in interaction with host GO:0051701

Show evidence (1 reference)

PMID:30148688 SUPPORT REVIEW SYNTHESIS Other

"Residing free in the cytosol of the host cell, they acquire many necessary components via transport mechanisms instead of maintaining genes for synthesizing sugars, lipids, nucleotides, and amino acids."

The review supports the free cytosolic niche for pathogenic Rickettsia species, including R. sibirica.

⬡

Pathograph

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Phenotypes

4

Cardiovascular 1

Regional Lymphadenopathy HP:0002716

Show evidence (1 reference)

PMID:27172113 SUPPORT REVIEW SYNTHESIS Human Clinical

"Siberian tick typhus (also known as North Asian tick typhus) North Asia Rickettsia sibirica Fever, eschar, regional lymphadenopathy, and rash (maculopapular); typically mild illness"

The CDC table lists regional lymphadenopathy among the clinical manifestations of Siberian tick typhus.

Immune 1

Maculopapular Rash Maculopapular exanthema HP:0040186

Show evidence (1 reference)

PMID:27172113 SUPPORT REVIEW SYNTHESIS Human Clinical

"Siberian tick typhus (also known as North Asian tick typhus) North Asia Rickettsia sibirica Fever, eschar, regional lymphadenopathy, and rash (maculopapular); typically mild illness"

The CDC table lists maculopapular rash among the clinical manifestations of Siberian tick typhus.

Integument 1

Eschar HP:6000793

Show evidence (1 reference)

PMID:27172113 SUPPORT REVIEW SYNTHESIS Human Clinical

"Siberian tick typhus (also known as North Asian tick typhus) North Asia Rickettsia sibirica Fever, eschar, regional lymphadenopathy, and rash (maculopapular); typically mild illness"

The CDC table lists eschar among the clinical manifestations of Siberian tick typhus.

Metabolism 1

Fever HP:0001945

Show evidence (1 reference)

PMID:27172113 SUPPORT REVIEW SYNTHESIS Human Clinical

"Siberian tick typhus (also known as North Asian tick typhus) North Asia Rickettsia sibirica Fever, eschar, regional lymphadenopathy, and rash (maculopapular); typically mild illness"

The CDC table lists fever among the clinical manifestations of Siberian tick typhus.

💊

Medical Actions

2

Empiric doxycycline

Action: Pharmacotherapy NCIT:C15986

Agent: doxycycline CHEBI:50845

Platform: Small molecule

Doxycycline is first-line empiric therapy for suspected tick-borne rickettsial disease, including Siberian tick typhus, because it inhibits rickettsial ribosomal translation and reaches the host-cell cytosol where R. sibirica resides.

Mechanism Target:

INHIBITS Rickettsial Ribosomal Translation — Doxycycline blocks rickettsial protein synthesis at the ribosome.

BYPASSES Intracytosolic Rickettsia sibirica Niche — Doxycycline can reach the cytosolic rickettsial compartment.

Show evidence (1 reference)

PMID:27172113 SUPPORT REVIEW SYNTHESIS Human Clinical

"Doxycycline is the drug of choice for treatment of all tickborne rickettsial diseases in patients of all ages, including children aged <8 years, and should be initiated immediately in persons with signs and symptoms suggestive of rickettsial disease"

Siberian tick typhus is a tick-borne rickettsial disease, so this CDC first-line treatment recommendation covers empiric therapy for suspected Siberian tick typhus.

Personal protection against tick bites

Platform: Behavioral / lifestyle

Repellent-based personal protection can reduce the risk of infectious Dermacentor bites in Siberian tick typhus foci.

Show evidence (1 reference)

PMID:27172113 SUPPORT REVIEW SYNTHESIS Human Clinical

"Repellents can reduce the risk for tick bites from numerous tick species"

The CDC prevention guidance supports repellents as personal protection against the tick bites that transmit Siberian tick typhus.

🔬

Diagnosis

2

Rickettsial PCR on eschar specimens

PCR on an unroofed eschar swab or biopsy can detect spotted-fever-group rickettsial DNA during early eschar-associated illness.

polymerase chain reaction NCIT:C17003

Results: A positive PCR from an eschar swab or biopsy supports early molecular confirmation of spotted-fever-group rickettsiosis.

Show evidence (1 reference)

PMID:27172113 SUPPORT REVIEW SYNTHESIS Human Clinical

"Eschar Swab of unroofed eschar SFG rickettsiae PCR Swab is less invasive than skin biopsy. Assessment of swab might be less sensitive than evaluation of eschar biopsy and does not allow for culture or IHC."

The CDC diagnostic table identifies unroofed eschar swabs as a specimen type for spotted-fever-group rickettsial PCR.

Indirect immunofluorescence assay serology

Paired acute and convalescent indirect immunofluorescence serology is the reference standard for retrospective confirmation, although acute sera can be negative and genus-level cross-reactivity prevents species assignment.

indirect immunofluorescence serology NCIT:C217458

Results: A fourfold or greater rise in IgG antibody titer between acute and convalescent specimens confirms acute tick-borne rickettsial infection.

Show evidence (1 reference)

PMID:27172113 SUPPORT REVIEW SYNTHESIS Human Clinical

"IFA Antibodies are often absent during the first week of illness. Antibodies are usually specific to the genus rather than the species of pathogen. Confirmation requires a fourfold or greater increase in titer between acute and convalescent serum specimens"

The CDC diagnostic table describes the timing and fourfold-titer-rise interpretation of IFA serology for tick-borne rickettsial disease.

📈

Progression

1

Mild acute illness

Siberian tick typhus is typically a mild spotted-fever-group illness with fever, eschar, regional lymphadenopathy, and a maculopapular rash.

Show evidence (1 reference)

PMID:27172113 SUPPORT REVIEW SYNTHESIS Human Clinical

"Siberian tick typhus (also known as North Asian tick typhus) North Asia Rickettsia sibirica Fever, eschar, regional lymphadenopathy, and rash (maculopapular); typically mild illness"

The CDC table summarizes the characteristic Siberian tick typhus syndrome as a typically mild illness.

🌍

Epidemiology

1

North Asian Dermacentor exposure

Siberian tick typhus occurs in northern Asian Dermacentor habitats, including Siberian foci and eastern China, with humans exposed as incidental hosts during tick activity.

North Asian tick exposure Dermacentor tick exposure

Show evidence (2 references)

PMID:22493192 SUPPORT Other

"Rickettsia sibirica sibirica is the causative agent of Siberian or North Asian tick typhus, a tick-borne rickettsiosis known to exist in Siberia and eastern China."

The source places Siberian or North Asian tick typhus in Siberia and eastern China.

PMID:27172113 SUPPORT REVIEW SYNTHESIS Human Clinical

"Siberian tick typhus (also known as North Asian tick typhus) North Asia Rickettsia sibirica Fever, eschar, regional lymphadenopathy, and rash (maculopapular); typically mild illness"

The CDC tick-borne rickettsial disease table identifies the disease as a North Asian R. sibirica rickettsiosis.

🦠

Infectious Agent

1

Rickettsia sibirica subsp. sibirica

Obligate intracellular spotted-fever-group rickettsial subspecies that causes Siberian or North Asian tick typhus.

Rickettsia sibirica subsp. sibirica NCBITaxon:1144281

Show evidence (1 reference)

PMID:22493192 SUPPORT Other

"Rickettsia sibirica sibirica is the causative agent of Siberian or North Asian tick typhus, a tick-borne rickettsiosis known to exist in Siberia and eastern China."

The source identifies R. sibirica subsp. sibirica as the etiologic rickettsial agent of the disease.

↔️

Transmission

1

Dermacentor tick bite inoculation

R. sibirica subsp. sibirica is acquired when infected Dermacentor ticks feed and inoculate spotted-fever-group rickettsiae into the bite site.

Show evidence (2 references)

PMID:22493192 SUPPORT Other

"Rickettsia sibirica sibirica is the causative agent of Siberian or North Asian tick typhus, a tick-borne rickettsiosis known to exist in Siberia and eastern China. Here we present the draft genome of Rickettsia sibirica sibirica strain BJ-90 isolated from Dermacentor sinicus ticks collected in..."

The genome announcement identifies Siberian tick typhus as tick-borne and documents R. sibirica subsp. sibirica recovery from Dermacentor ticks.

PMID:35934699 SUPPORT Other

"The tick species Dermacentor nuttalli is considered the main vector carrying SFGR in Inner Mongolia."

The tick surveillance study identifies D. nuttalli as the main local Dermacentor vector carrying spotted-fever-group Rickettsia in an endemic region where R. sibirica was detected.

{ }

Source YAML

click to show

name: Siberian Tick Typhus
creation_date: "2026-09-25T12:57:17Z"
updated_date: "2026-09-25T12:57:17Z"
category: Infectious Disease
description: >-
  Siberian tick typhus, also called North Asian tick typhus, is an acute
  tick-borne spotted-fever-group rickettsiosis caused by Rickettsia sibirica
  subsp. sibirica in northern Asia. Dermacentor ticks maintain the organism in
  enzootic foci and inoculate rickettsiae into skin, where early infection of
  mononuclear phagocytes creates an eschar and regional lymphadenopathy before
  hematogenous spread reaches the microvascular endothelium. The resulting
  rickettsial vasculitis accounts for the fever and maculopapular rash that
  characterize this usually mild spotted-fever-group disease.
disease_term:
  preferred_term: Siberian tick typhus
  term:
    id: MONDO:0001154
    label: Siberian tick typhus
parents:
- Spotted fever rickettsiosis
synonyms:
- North Asian tick typhus
- Rickettsia sibirica sibirica infection
references:
- reference: PMID:22493192
  title: Sequence and annotation of Rickettsia sibirica sibirica genome.
  found_in:
  - Siberian_Tick_Typhus-deep-research-openscientist.md
  findings:
  - statement: >-
      Rickettsia sibirica subsp. sibirica causes Siberian or North Asian tick
      typhus, a tick-borne rickettsiosis reported from Siberia and eastern
      China.
    supporting_text: >-
      Rickettsia sibirica sibirica is the causative agent of Siberian or North
      Asian tick typhus, a tick-borne rickettsiosis known to exist in Siberia
      and eastern China.
- reference: PMID:35934699
  title: >-
    Identification and genetic diversity analysis of Rickettsia in Dermacentor
    nuttalli within inner Mongolia, China.
  found_in:
  - Siberian_Tick_Typhus-deep-research-openscientist.md
  findings:
  - statement: >-
      Dermacentor nuttalli ticks in Inner Mongolia carry spotted-fever-group
      rickettsiae, including R. sibirica, in molecular surveillance.
    supporting_text: >-
      The tick species Dermacentor nuttalli is considered the main vector
      carrying SFGR in Inner Mongolia.
classifications:
  harrisons_chapter:
  - classification_value: INFECTIOUS_DISEASES
    evidence:
    - reference: PMID:22493192
      reference_title: Sequence and annotation of Rickettsia sibirica sibirica genome.
      supports: SUPPORT
      evidence_source: OTHER
      snippet: >-
        Rickettsia sibirica sibirica is the causative agent of Siberian or North
        Asian tick typhus, a tick-borne rickettsiosis known to exist in Siberia and
        eastern China.
      explanation: >-
        The genome announcement names Siberian tick typhus as a bacterial
        tick-borne rickettsiosis, placing it in Harrison's Infectious Diseases Part.

infectious_agent:
- name: Rickettsia sibirica subsp. sibirica
  infectious_agent_term:
    preferred_term: Rickettsia sibirica subsp. sibirica
    term:
      id: NCBITaxon:1144281
      label: Rickettsia sibirica subsp. sibirica
  description: >-
    Obligate intracellular spotted-fever-group rickettsial subspecies that
    causes Siberian or North Asian tick typhus.
  evidence:
  - reference: PMID:22493192
    reference_title: Sequence and annotation of Rickettsia sibirica sibirica genome.
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      Rickettsia sibirica sibirica is the causative agent of Siberian or North
      Asian tick typhus, a tick-borne rickettsiosis known to exist in Siberia and
      eastern China.
    explanation: >-
      The source identifies R. sibirica subsp. sibirica as the etiologic
      rickettsial agent of the disease.

transmission:
- name: Dermacentor tick bite inoculation
  description: >-
    R. sibirica subsp. sibirica is acquired when infected Dermacentor ticks feed
    and inoculate spotted-fever-group rickettsiae into the bite site.
  evidence:
  - reference: PMID:22493192
    reference_title: Sequence and annotation of Rickettsia sibirica sibirica genome.
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      Rickettsia sibirica sibirica is the causative agent of Siberian or North
      Asian tick typhus, a tick-borne rickettsiosis known to exist in Siberia and
      eastern China. Here we present the draft genome of Rickettsia sibirica
      sibirica strain BJ-90 isolated from Dermacentor sinicus ticks collected in
      Beijing, China.
    explanation: >-
      The genome announcement identifies Siberian tick typhus as tick-borne and
      documents R. sibirica subsp. sibirica recovery from Dermacentor ticks.
  - reference: PMID:35934699
    reference_title: >-
      Identification and genetic diversity analysis of Rickettsia in Dermacentor
      nuttalli within inner Mongolia, China.
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      The tick species Dermacentor nuttalli is considered the main vector
      carrying SFGR in Inner Mongolia.
    explanation: >-
      The tick surveillance study identifies D. nuttalli as the main local
      Dermacentor vector carrying spotted-fever-group Rickettsia in an endemic
      region where R. sibirica was detected.

epidemiology:
- name: North Asian Dermacentor exposure
  description: >-
    Siberian tick typhus occurs in northern Asian Dermacentor habitats, including
    Siberian foci and eastern China, with humans exposed as incidental hosts
    during tick activity.
  factors:
  - North Asian tick exposure
  - Dermacentor tick exposure
  evidence:
  - reference: PMID:22493192
    reference_title: Sequence and annotation of Rickettsia sibirica sibirica genome.
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      Rickettsia sibirica sibirica is the causative agent of Siberian or North
      Asian tick typhus, a tick-borne rickettsiosis known to exist in Siberia and
      eastern China.
    explanation: >-
      The source places Siberian or North Asian tick typhus in Siberia and
      eastern China.
  - reference: PMID:27172113
    reference_title: >-
      Diagnosis and Management of Tickborne Rickettsial Diseases: Rocky Mountain
      Spotted Fever and Other Spotted Fever Group Rickettsioses, Ehrlichioses,
      and Anaplasmosis - United States.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: REVIEW_SYNTHESIS
    snippet: >-
      Siberian tick typhus (also known as North Asian tick typhus) North Asia
      Rickettsia sibirica Fever, eschar, regional lymphadenopathy, and rash
      (maculopapular); typically mild illness
    explanation: >-
      The CDC tick-borne rickettsial disease table identifies the disease as a
      North Asian R. sibirica rickettsiosis.

pathophysiology:
- name: Dermacentor-Borne Rickettsia sibirica Inoculation
  role: trigger
  description: >-
    Feeding Dermacentor ticks inoculate R. sibirica subsp. sibirica into the
    dermis, initiating local infection at the arthropod attachment site.
  evidence:
  - reference: PMID:22493192
    reference_title: Sequence and annotation of Rickettsia sibirica sibirica genome.
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      Rickettsia sibirica sibirica is the causative agent of Siberian or North
      Asian tick typhus, a tick-borne rickettsiosis known to exist in Siberia and
      eastern China. Here we present the draft genome of Rickettsia sibirica
      sibirica strain BJ-90 isolated from Dermacentor sinicus ticks collected in
      Beijing, China.
    explanation: >-
      The abstract identifies Siberian tick typhus as tick-borne and documents
      R. sibirica subsp. sibirica recovery from Dermacentor ticks.
  downstream:
  - target: Dermal Mononuclear Phagocyte Rickettsia sibirica Infection
    causal_link_type: DIRECT
    description: Tick inoculation exposes dermal phagocytes to R. sibirica.

- name: Dermal Mononuclear Phagocyte Rickettsia sibirica Infection
  role: primary_infection
  description: >-
    After tick inoculation, rickettsiae enter dermal macrophages and dendritic
    cells, creating the inoculation-site lesion that seeds lymphatic and
    hematogenous dissemination.
  cell_types:
  - preferred_term: macrophage
    term:
      id: CL:0000235
      label: macrophage
  - preferred_term: dendritic cell
    term:
      id: CL:0000451
      label: dendritic cell
  biological_processes:
  - preferred_term: symbiont entry into host cell
    term:
      id: GO:0046718
      label: symbiont entry into host cell
  evidence:
  - reference: PMID:30148688
    reference_title: "Pathogenesis of Rickettsial Diseases: Pathogenic and Immune Mechanisms of an Endotheliotropic Infection."
    supports: SUPPORT
    evidence_source: OTHER
    quote_role: REVIEW_SYNTHESIS
    snippet: >-
      The pathogenic sequence of events that occur in rickettsial infection
      begins with the entry of organisms inoculated by the feeding tick or mite
      or scratched into the skin from infected louse or flea feces deposited on
      the skin. The initial target cells of infection are CD68+ cells
      (macrophages and/or dendritic cells)
    explanation: >-
      The rickettsial pathogenesis review places macrophages or dendritic cells
      at the start of vector-inoculated skin infection.
  downstream:
  - target: Rickettsial Lymphatic Dissemination
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    description: Rickettsiae disseminate from skin phagocytes into lymphatics.
  - target: Eschar
    causal_link_type: DIRECT
    description: Local inoculation-site infection produces a necrotic eschar.

- name: Rickettsial Lymphatic Dissemination
  role: effector
  description: >-
    Rickettsiae spread from the skin inoculation site through lymphatic vessels
    to regional lymph nodes before hematogenous seeding of systemic endothelial
    targets.
  biological_processes:
  - preferred_term: biological process involved in interaction with host
    term:
      id: GO:0051701
      label: biological process involved in interaction with host
  evidence:
  - reference: PMID:30148688
    reference_title: "Pathogenesis of Rickettsial Diseases: Pathogenic and Immune Mechanisms of an Endotheliotropic Infection."
    supports: SUPPORT
    evidence_source: OTHER
    quote_role: REVIEW_SYNTHESIS
    snippet: >-
      The rickettsiae then spread via lymphatic vessels to the regional lymph
      nodes as has been observed vividly in the lymphangitis associated with R.
      sibirica mongolitimoniae infection
    explanation: >-
      The review uses lymphangitis in sibling R. sibirica subsp. mongolitimonae
      infection as the vivid example of lymphatic spread after the
      vector-inoculated skin lesion.
  downstream:
  - target: Endothelial Cell Rickettsia sibirica Infection
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    description: Lymphatic spread precedes hematogenous endothelial seeding.
  - target: Regional Lymphadenopathy
    causal_link_type: DIRECT
    description: Drainage from the inoculation site enlarges regional lymph nodes.

- name: Endothelial Cell Rickettsia sibirica Infection
  role: effector
  description: >-
    Hematogenously disseminated R. sibirica, like other pathogenic Rickettsia
    species, mainly infects systemic endothelial cells.
  cell_types:
  - preferred_term: endothelial cell of vascular tree
    term:
      id: CL:0002139
      label: endothelial cell of vascular tree
  biological_processes:
  - preferred_term: biological process involved in interaction with host
    term:
      id: GO:0051701
      label: biological process involved in interaction with host
  evidence:
  - reference: PMID:30148688
    reference_title: "Pathogenesis of Rickettsial Diseases: Pathogenic and Immune Mechanisms of an Endotheliotropic Infection."
    supports: SUPPORT
    evidence_source: OTHER
    quote_role: REVIEW_SYNTHESIS
    snippet: >-
      Rickettsiae then spread hematogenously throughout the body and infect
      mainly endothelial cells
    explanation: >-
      The conserved rickettsial dissemination sequence identifies endothelial
      cells as the main hematogenous infection target.
  downstream:
  - target: Rickettsial Vasculitis
    causal_link_type: DIRECT
    description: Endothelial infection activates vascular inflammation.

- name: Rickettsial Vasculitis
  role: vascular_response
  description: >-
    Rickettsial endothelial infection and activation produce a microvascular
    vasculitis with inflammatory cell infiltration and increased vascular
    permeability.
  cell_types:
  - preferred_term: endothelial cell of vascular tree
    term:
      id: CL:0002139
      label: endothelial cell of vascular tree
  biological_processes:
  - preferred_term: inflammatory response
    term:
      id: GO:0006954
      label: inflammatory response
  - preferred_term: positive regulation of vascular permeability
    modifier: INCREASED
    term:
      id: GO:0043117
      label: positive regulation of vascular permeability
  evidence:
  - reference: PMID:30148688
    reference_title: "Pathogenesis of Rickettsial Diseases: Pathogenic and Immune Mechanisms of an Endotheliotropic Infection."
    supports: SUPPORT
    evidence_source: OTHER
    quote_role: REVIEW_SYNTHESIS
    snippet: The fundamental lesion of rickettsial diseases is vasculitis
    explanation: >-
      The review names vasculitis as the core lesion produced after
      endothelial rickettsial infection.
  - reference: PMID:30148688
    reference_title: "Pathogenesis of Rickettsial Diseases: Pathogenic and Immune Mechanisms of an Endotheliotropic Infection."
    supports: SUPPORT
    evidence_source: OTHER
    quote_role: REVIEW_SYNTHESIS
    snippet: >-
      The pathophysiologic events can be attributed principally to rickettsia
      infection-associated increased vascular permeability leading to edema,
      hypovolemia, hypotension, reduced perfusion of organs, acute respiratory
      distress syndrome, and CNS abnormalities.
    explanation: >-
      The review links rickettsial endothelial infection to increased vascular
      permeability and downstream edema in systemic rickettsioses.
  downstream:
  - target: Fever
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    description: Systemic endothelial infection and inflammation produce fever.
  - target: Maculopapular Rash
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    description: Cutaneous rickettsial vasculitis produces the maculopapular rash.

- name: Rickettsial Ribosomal Translation
  role: therapeutic_vulnerability
  conforms_to: "bacterial_protein_synthesis_inhibition#Bacterial mRNA Translation by the Ribosome"
  description: >-
    R. sibirica, like other bacteria, depends on ribosomal translation of its
    mRNA, making the bacterial ribosome the conserved antibiotic target for
    tetracycline therapy.
  biological_processes:
  - preferred_term: Translation
    term:
      id: GO:0006412
      label: translation
  evidence:
  - reference: PMID:24336183
    reference_title: "Ribosome-targeting antibiotics and mechanisms of bacterial resistance."
    supports: SUPPORT
    evidence_source: OTHER
    quote_role: REVIEW_SYNTHESIS
    snippet: The ribosome is one of the main antibiotic targets in the bacterial cell.
    explanation: >-
      Review evidence for the bacterial ribosome as the conserved antibiotic
      target class for tetracyclines such as doxycycline.

- name: Intracytosolic Rickettsia sibirica Niche
  role: intrinsic_resistance
  conforms_to: "intracellular_pathogen_persistence#Intracellular Niche and Beta-Lactam Exclusion"
  description: >-
    Rickettsia species reside free in the host-cell cytosol and exploit host
    metabolites, so effective Siberian tick typhus therapy must reach the
    intracellular bacterial compartment.
  biological_processes:
  - preferred_term: biological process involved in interaction with host
    term:
      id: GO:0051701
      label: biological process involved in interaction with host
  evidence:
  - reference: PMID:30148688
    reference_title: "Pathogenesis of Rickettsial Diseases: Pathogenic and Immune Mechanisms of an Endotheliotropic Infection."
    supports: SUPPORT
    evidence_source: OTHER
    quote_role: REVIEW_SYNTHESIS
    snippet: >-
      Residing free in the cytosol of the host cell, they acquire many necessary
      components via transport mechanisms instead of maintaining genes for
      synthesizing sugars, lipids, nucleotides, and amino acids.
    explanation: >-
      The review supports the free cytosolic niche for pathogenic Rickettsia
      species, including R. sibirica.

phenotypes:
- name: Eschar
  category: Dermatologic
  description: >-
    Siberian tick typhus produces a necrotic eschar at the tick-inoculation
    site.
  phenotype_term:
    preferred_term: Eschar
    term:
      id: HP:6000793
      label: Eschar
  evidence:
  - reference: PMID:27172113
    reference_title: >-
      Diagnosis and Management of Tickborne Rickettsial Diseases: Rocky Mountain
      Spotted Fever and Other Spotted Fever Group Rickettsioses, Ehrlichioses,
      and Anaplasmosis - United States.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: REVIEW_SYNTHESIS
    snippet: >-
      Siberian tick typhus (also known as North Asian tick typhus) North Asia
      Rickettsia sibirica Fever, eschar, regional lymphadenopathy, and rash
      (maculopapular); typically mild illness
    explanation: >-
      The CDC table lists eschar among the clinical manifestations of Siberian
      tick typhus.

- name: Regional Lymphadenopathy
  category: Immune
  description: >-
    Draining lymph-node enlargement accompanies the inoculation-site lesion in
    Siberian tick typhus.
  phenotype_term:
    preferred_term: Regional lymphadenopathy
    term:
      id: HP:0002716
      label: Lymphadenopathy
  evidence:
  - reference: PMID:27172113
    reference_title: >-
      Diagnosis and Management of Tickborne Rickettsial Diseases: Rocky Mountain
      Spotted Fever and Other Spotted Fever Group Rickettsioses, Ehrlichioses,
      and Anaplasmosis - United States.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: REVIEW_SYNTHESIS
    snippet: >-
      Siberian tick typhus (also known as North Asian tick typhus) North Asia
      Rickettsia sibirica Fever, eschar, regional lymphadenopathy, and rash
      (maculopapular); typically mild illness
    explanation: >-
      The CDC table lists regional lymphadenopathy among the clinical
      manifestations of Siberian tick typhus.

- name: Fever
  category: Constitutional
  description: Fever is part of the acute systemic rickettsial syndrome.
  phenotype_term:
    preferred_term: Fever
    term:
      id: HP:0001945
      label: Fever
  evidence:
  - reference: PMID:27172113
    reference_title: >-
      Diagnosis and Management of Tickborne Rickettsial Diseases: Rocky Mountain
      Spotted Fever and Other Spotted Fever Group Rickettsioses, Ehrlichioses,
      and Anaplasmosis - United States.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: REVIEW_SYNTHESIS
    snippet: >-
      Siberian tick typhus (also known as North Asian tick typhus) North Asia
      Rickettsia sibirica Fever, eschar, regional lymphadenopathy, and rash
      (maculopapular); typically mild illness
    explanation: >-
      The CDC table lists fever among the clinical manifestations of Siberian
      tick typhus.

- name: Maculopapular Rash
  category: Dermatologic
  description: >-
    Siberian tick typhus produces a maculopapular rash as part of the
    spotted-fever-group vasculitic eruption.
  phenotype_term:
    preferred_term: Maculopapular exanthema
    term:
      id: HP:0040186
      label: Maculopapular exanthema
  evidence:
  - reference: PMID:27172113
    reference_title: >-
      Diagnosis and Management of Tickborne Rickettsial Diseases: Rocky Mountain
      Spotted Fever and Other Spotted Fever Group Rickettsioses, Ehrlichioses,
      and Anaplasmosis - United States.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: REVIEW_SYNTHESIS
    snippet: >-
      Siberian tick typhus (also known as North Asian tick typhus) North Asia
      Rickettsia sibirica Fever, eschar, regional lymphadenopathy, and rash
      (maculopapular); typically mild illness
    explanation: >-
      The CDC table lists maculopapular rash among the clinical manifestations
      of Siberian tick typhus.

diagnosis:
- name: Rickettsial PCR on eschar specimens
  description: >-
    PCR on an unroofed eschar swab or biopsy can detect spotted-fever-group
    rickettsial DNA during early eschar-associated illness.
  diagnosis_term:
    preferred_term: polymerase chain reaction
    term:
      id: NCIT:C17003
      label: Polymerase Chain Reaction
  results: >-
    A positive PCR from an eschar swab or biopsy supports early molecular
    confirmation of spotted-fever-group rickettsiosis.
  evidence:
  - reference: PMID:27172113
    reference_title: >-
      Diagnosis and Management of Tickborne Rickettsial Diseases: Rocky Mountain
      Spotted Fever and Other Spotted Fever Group Rickettsioses, Ehrlichioses,
      and Anaplasmosis - United States.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: REVIEW_SYNTHESIS
    snippet: >-
      Eschar Swab of unroofed eschar SFG rickettsiae PCR Swab is less invasive
      than skin biopsy. Assessment of swab might be less sensitive than
      evaluation of eschar biopsy and does not allow for culture or IHC.
    explanation: >-
      The CDC diagnostic table identifies unroofed eschar swabs as a specimen
      type for spotted-fever-group rickettsial PCR.

- name: Indirect immunofluorescence assay serology
  description: >-
    Paired acute and convalescent indirect immunofluorescence serology is the
    reference standard for retrospective confirmation, although acute sera can
    be negative and genus-level cross-reactivity prevents species assignment.
  diagnosis_term:
    preferred_term: indirect immunofluorescence serology
    term:
      id: NCIT:C217458
      label: Diagnostic Serology Testing
  results: >-
    A fourfold or greater rise in IgG antibody titer between acute and
    convalescent specimens confirms acute tick-borne rickettsial infection.
  evidence:
  - reference: PMID:27172113
    reference_title: >-
      Diagnosis and Management of Tickborne Rickettsial Diseases: Rocky Mountain
      Spotted Fever and Other Spotted Fever Group Rickettsioses, Ehrlichioses,
      and Anaplasmosis - United States.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: REVIEW_SYNTHESIS
    snippet: >-
      IFA Antibodies are often absent during the first week of illness.
      Antibodies are usually specific to the genus rather than the species of
      pathogen. Confirmation requires a fourfold or greater increase in titer
      between acute and convalescent serum specimens
    explanation: >-
      The CDC diagnostic table describes the timing and fourfold-titer-rise
      interpretation of IFA serology for tick-borne rickettsial disease.

progression:
- phase: Mild acute illness
  notes: >-
    Siberian tick typhus is typically a mild spotted-fever-group illness with
    fever, eschar, regional lymphadenopathy, and a maculopapular rash.
  evidence:
  - reference: PMID:27172113
    reference_title: >-
      Diagnosis and Management of Tickborne Rickettsial Diseases: Rocky Mountain
      Spotted Fever and Other Spotted Fever Group Rickettsioses, Ehrlichioses,
      and Anaplasmosis - United States.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: REVIEW_SYNTHESIS
    snippet: >-
      Siberian tick typhus (also known as North Asian tick typhus) North Asia
      Rickettsia sibirica Fever, eschar, regional lymphadenopathy, and rash
      (maculopapular); typically mild illness
    explanation: >-
      The CDC table summarizes the characteristic Siberian tick typhus syndrome
      as a typically mild illness.

treatments:
- name: Empiric doxycycline
  description: >-
    Doxycycline is first-line empiric therapy for suspected tick-borne
    rickettsial disease, including Siberian tick typhus, because it inhibits
    rickettsial ribosomal translation and reaches the host-cell cytosol where R.
    sibirica resides.
  therapeutic_modality: SMALL_MOLECULE
  treatment_term:
    preferred_term: Pharmacotherapy
    term:
      id: NCIT:C15986
      label: Pharmacotherapy
    therapeutic_agent:
    - preferred_term: doxycycline
      term:
        id: CHEBI:50845
        label: doxycycline
  target_mechanisms:
  - target: Rickettsial Ribosomal Translation
    treatment_effect: INHIBITS
    description: Doxycycline blocks rickettsial protein synthesis at the ribosome.
  - target: Intracytosolic Rickettsia sibirica Niche
    treatment_effect: BYPASSES
    description: Doxycycline can reach the cytosolic rickettsial compartment.
  evidence:
  - reference: PMID:27172113
    reference_title: >-
      Diagnosis and Management of Tickborne Rickettsial Diseases: Rocky Mountain
      Spotted Fever and Other Spotted Fever Group Rickettsioses, Ehrlichioses,
      and Anaplasmosis - United States.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: REVIEW_SYNTHESIS
    snippet: >-
      Doxycycline is the drug of choice for treatment of all tickborne
      rickettsial diseases in patients of all ages, including children aged <8
      years, and should be initiated immediately in persons with signs and
      symptoms suggestive of rickettsial disease
    explanation: >-
      Siberian tick typhus is a tick-borne rickettsial disease, so this CDC
      first-line treatment recommendation covers empiric therapy for suspected
      Siberian tick typhus.

- name: Personal protection against tick bites
  description: >-
    Repellent-based personal protection can reduce the risk of infectious
    Dermacentor bites in Siberian tick typhus foci.
  therapeutic_modality: BEHAVIORAL
  treatment_term:
    preferred_term: personal tick-bite protection
  evidence:
  - reference: PMID:27172113
    reference_title: >-
      Diagnosis and Management of Tickborne Rickettsial Diseases: Rocky Mountain
      Spotted Fever and Other Spotted Fever Group Rickettsioses, Ehrlichioses,
      and Anaplasmosis - United States.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: REVIEW_SYNTHESIS
    snippet: Repellents can reduce the risk for tick bites from numerous tick species
    explanation: >-
      The CDC prevention guidance supports repellents as personal protection
      against the tick bites that transmit Siberian tick typhus.

📚

References & Deep Research

References

2

PMID:22493192

Sequence and annotation of Rickettsia sibirica sibirica genome.

1 finding

Rickettsia sibirica subsp. sibirica causes Siberian or North Asian tick typhus, a tick-borne rickettsiosis reported from Siberia and eastern China.

"Rickettsia sibirica sibirica is the causative agent of Siberian or North Asian tick typhus, a tick-borne rickettsiosis known to exist in Siberia and eastern China."

PMID:35934699

Identification and genetic diversity analysis of Rickettsia in Dermacentor nuttalli within inner Mongolia, China.

1 finding

Dermacentor nuttalli ticks in Inner Mongolia carry spotted-fever-group rickettsiae, including R. sibirica, in molecular surveillance.

"The tick species Dermacentor nuttalli is considered the main vector carrying SFGR in Inner Mongolia."

Deep Research

1

Deep research results are used as seeds for research; they do not undergo the same validation as the main records and may contain errors. How we use deep research.

Evaluations and curation notes (1)

Create: Siberian Tick Typhus · 2026-09-25T13:15:50Z · View source

Created a standalone Siberian Tick Typhus entry for MONDO:0001154 after an ignored-file-inclusive local search found the MONDO ID and major synonyms only in the Spotted_Fever_Rickettsiosis subtype row, generated Boomer/pages output, rare-disease mapping worklists, and existing rickettsial reference caches. The all-state PR search for "Siberian tick typhus" found only the merged spotted-fever root PR (#8899), and all-state GitHub issue searches for both `Siberian tick typhus` and `MONDO:0001154` returned no matches. PROMOTION. Promoted the North Asian/Siberian tick typhus subtype out of the deliberately thin Spotted_Fever_Rickettsiosis root while leaving that parent intact, and changed the subtype description there from "No standalone dismech entry yet" to `Curated in full in Siberian_Tick_Typhus.yaml`. DEEP RESEARCH. Seeded the entry with its MONDO term, Rickettsia sibirica subsp. sibirica infectious-agent binding, and a cached R. sibirica genome announcement (PMID:22493192), then ran `just research-disorder openscientist Siberian_Tick_Typhus`. The OpenScientist run completed normally and wrote `research/Siberian_Tick_Typhus-deep-research-openscientist.md`, its citation sidecar, and HTML/PDF artifacts. The report resolved all 18 references and marked 8 as on-topic. NEC. `just preflight-dr research/Siberian_Tick_Typhus-deep-research-openscientist.md MONDO:0001154` returned SKIP because MONDO records no RO:0004003 causal gene for this acquired infection. Manual identity review found one real Named Entity Confusion hazard: the report broadened the agent from R. sibirica subsp. sibirica to the R. sibirica parent species and included sibling R. sibirica subsp. mongolitimonae / lymphangitis-associated rickettsiosis evidence. The final entry keeps only NCBITaxon:1144281 as infectious agent and does not curate the mongolitimonae/LAR leads. TERM REVIEW. The report's term validation resolved 28/29 suggested CURIEs and flagged one obsolete GO term, `GO:0030260`, which is replaced by `GO:0044409`. The curated entry did not use the obsolete term. CONTENT. Curated R. sibirica subsp. sibirica as the etiologic agent, Dermacentor tick transmission, North Asian/Siberian/eastern Chinese epidemiology, Dermacentor inoculation, early dermal macrophage/dendritic-cell infection, the conserved rickettsial endothelial vasculitis mechanism, the shared bacterial ribosomal doxycycline target, and the shared intracytosolic Rickettsia niche. Added four directly supported phenotypes from the CDC tick-borne rickettsial disease table and wired all four to causal parents: eschar, regional lymphadenopathy, fever, and maculopapular rash. Added eschar PCR, indirect immunofluorescence serology, and empiric doxycycline treatment targeting both the ribosomal translation node and the intracellular niche. VALIDATION. `just validate kb/disorders/Siberian_Tick_Typhus.yaml` passed with 19 snippets checked, no skipped or unavailable snippets, and 21 titles checked. `just count-verified-snippets kb/disorders/Siberian_Tick_Typhus.yaml` reported 19/19 snippets verified against cached references. `just list-disconnected-phenotypes kb/disorders/Siberian_Tick_Typhus.yaml` reported 4/4 phenotype nodes causally connected. `just validate kb/disorders/Spotted_Fever_Rickettsiosis.yaml` passed after the parent row pointer edit.

OpenScientist ▸

Key Findings

openscientist-autonomous 17 citations 2026-09-25T06:12:20.571696

Key Findings

Finding 1 — Etiology and vector (F001)

Siberian tick typhus is a spotted-fever-group rickettsiosis caused by Rickettsia sibirica, an obligate intracellular bacterium transmitted by ixodid ticks of the genus Dermacentor. Molecular surveillance in Inner Mongolia, China (2019; 408 ticks screened) detected R. sibirica in Dermacentor nuttalli ticks, with gltA haplotypes (G8/G10) and ompA haplotypes (O16/O19) clustering phylogenetically with R. sibirica PMID: 35934699. The comprehensive geographic review by Parola et al. classifies R. sibirica among the tick-borne SFG Rickettsia zoonoses PMID: 24092850, which states: "Tick-borne rickettsioses are caused by obligate intracellular bacteria belonging to the spotted fever group of the genus Rickettsia." The Inner Mongolia study identifies the principal regional vector: "The tick species Dermacentor nuttalli is considered the main vector carrying SFGR in Inner Mongolia."

This establishes the disease as infectious, not genetic: the sole necessary cause is inoculation of R. sibirica via a tick bite. Ontology anchors: causative organism — Rickettsia sibirica (NCBITaxon:35793); vector — Dermacentor nuttalli.

Finding 2 — Clinical triad, LAR subspecies, and benign course (F002)

STT produces the classic SFG clinical triad — inoculation eschar (tache noire), fever, and maculopapular rash — often with regional lymphadenopathy following a tick bite. A clinically important variant is caused by R. sibirica subsp. mongolitimonae, which produces lymphangitis-associated rickettsiosis (LAR). The defining review states: "This bacterium induces the lymphangitis-associated rickettsiosis, a still unfamiliar rickettsiosis that is mainly characterized by fever with a rope-like lymphangitis and/or lymphadenopathy and skin eschar occurring after tick bites" and "Sequellae are very rare and treatment with doxycycline is recommended" PMID: 24034636. The frequency of the lymphangitis feature is quantified in a second source: "Approximately, one-third of the patients with this infection experience lymphangitis from the inoculation eschar to the draining lymph nodes, and, in that case, the infection is named 'lymphangitis-associated rickettsiosis' (LAR)" PMID: 33969876.

Suggested HPO phenotype terms: Fever (HP:0001945), Skin rash (HP:0000988) / Maculopapular exanthema, Lymphadenopathy (HP:0002716), Skin ulcer/eschar (HP:0200042), Headache (HP:0002315), Myalgia (HP:0003326).

Finding 3 — Pathophysiology: endothelial infection, vasculitis, and procoagulant activation (F003)

The core pathophysiology of STT, shared across SFG rickettsioses, is a diffuse vasculitis with endothelial injury. R. sibirica infects vascular endothelial cells, producing a disseminated small-vessel vasculitis. Supporting evidence from the closely related SFG agent R. conorii (Mediterranean spotted fever, MSF) states: "The physiopathology of Mediterranean spotted fever includes diffuse vasculitis with endothelial injury" PMID: 20797742. In vivo studies of MSF patients demonstrate the downstream procoagulant cascade: "Our results provide biochemical evidence for the occurrence of TXA2-dependent platelet activation and thrombin generation in vivo, together with endothelial dysfunction" PMID: 8584998 — reflecting thromboxane-A2-dependent platelet activation, thrombin generation, and elevated endothelin-1.

Suggested GO terms: response to bacterium (GO:0009617), inflammatory response (GO:0006954), blood coagulation (GO:0007596), platelet activation (GO:0030168). Suggested CL/UBERON terms: endothelial cell (CL:0000115), blood vessel endothelium (UBERON:0004638), skin (UBERON:0002097).

Finding 4 — Diagnosis by IFA serology and ompA/gltA PCR (F004)

Diagnosis relies on indirect immunofluorescence assay (IFA) serology (seroconversion or ≥4-fold titer rise), plus PCR targeting the ompA and gltA genes with DNA sequencing, ideally performed on an eschar biopsy or swab. The standard molecular protocol is described as "a standard PCR reaction using primers suitable for hybridisation within the conserved region of genes coding for outer membrane protein A (ompA) and citrate synthase (gltA) and DNA sequencing were performed" PMID: 23168048. Non-invasive eschar sampling is now validated: "New approaches, such as swabbing of eschars to obtain material to be tested by PCR, have emerged in recent years and have played a role in describing emerging tick-borne rickettsioses" PMID: 24092850. In MSF biopsy series, PCR positivity reached 72.6% of samples, and IFA identifies the majority of serologically confirmed cases.

Finding 5 — Protective immunity is cell-mediated (NK cells + CD8+ T cells + IFN-γ) (F005)

Protective immunity to endothelium-targeting SFG rickettsiae is cell-mediated, not primarily antibody-driven. In murine models, resistant animals show higher frequencies of IFN-γ+ CD8+ T cells and cytotoxic NK cells; NK-deficient Rag−/−γc−/− mice show impaired clearance, severe hepatic thrombosis, and low serum IFN-γ. Key evidence: "these findings reveal that NK cells mediate the innate phase of host protection against infection with rickettsiae, most likely via IFN-γ production" and "NK cells are involved in preventing rickettsial infection-induced endothelial cell damage" PMID: 22617213. For adaptive immunity: "resistance to rickettsial infections is attributed to the induction of antigen-specific T cells, particularly CD8(+) T cells" PMID: 25043277, with the anti-Rickettsia CD8+ response peaking around 7 days post-infection and IFN-γ and granzyme B serving as correlates of protection.

Suggested CL terms: CD8-positive, alpha-beta T cell (CL:0000625), natural killer cell (CL:0000623). Suggested GO terms: interferon-gamma production (GO:0032609), T cell mediated cytotoxicity (GO:0001913).

Finding 6 — Surface proteins mediate endothelial invasion and are protective antigens (F006)

Rickettsial surface-exposed outer-membrane proteins — OmpA and OmpB (Sca autotransporter family), plus Adr1, Adr2, OmpW, Porin_4, and TolC — mediate adhesion to and invasion of vascular endothelial cells and are immunoprotective antigens. Proteomic surface labeling of R. rickettsii identified these SEPs, and immunization studies showed functional relevance: "sera from mice immunized with rAdr1, rAdr2, or rOmpW reduced R. rickettsii adherence to and invasion of vascular endothelial cells" and "Surface-exposed proteins (SEPs) of R. rickettsii may play important roles in its pathogenesis or immunity" PMID: 24950252. These proteins provide the molecular link between the initiating tick inoculation and the endothelial tropism that drives disease, and they are the targets of the ompA PCR used diagnostically (Finding 4).

Suggested GO cellular-component terms: outer membrane (GO:0019867), cell surface (GO:0009986). Suggested GO process term: entry into host cell (GO:0030260).

Finding 7 — Prevention is entirely non-immunological (personal anti-tick measures) (F007)

There is no licensed vaccine and no recommended routine chemoprophylaxis for SFG rickettsiosis. Prevention is entirely based on personal protective measures against tick bites: DEET/picaridin repellents, permethrin-treated clothing, tick checks, and prompt tick removal. The CDC position: "Personal protection measures to prevent human tick encounters from resulting in bites are widely recommended as the first line of defense against health impacts associated with ticks" PMID: 35364518. Efficacy is quantified: repellent/permethrin formulations showed "estimated repellencies ranging from 93 to 97%" in bioassays PMID: 32073128. Field durability is a caveat — 33% of permethrin-treated forester pants had no measurable permethrin after one year of wear PMID: 34958094.

Suggested NCIT-style intervention terms: insect repellent use; protective clothing; vector control.

Finding 8 — Animal reservoirs/sentinels and male-biased human exposure (F008)

Domestic and wild mammals act as sentinels and amplifying hosts in the SFG rickettsial cycle, and human seropositivity is male-associated, consistent with outdoor exposure rather than any genetic predisposition. Seroprevalence surveys show high SFG rickettsial IgG in animals: 57–59% of dogs and 59% of cats in Tasmania ("59% of cats and 57% of dogs were positive for antibodies" PMID: 20148824); and 58.5% of dogs, 48.1% of black rats, and 38.3% of humans in a Peruvian rural community. In that community, "only male gender was statistically associated with having IgG antibodies against Rickettsia spp. (p-value=0.049, chi-square test)" PMID: 39799873. The male predominance reflects occupational/recreational outdoor activity and tick exposure, reinforcing the environmental etiology.

Finding 9 — Doxycycline is curative; excellent prognosis (F009)

Doxycycline is the first-line curative therapy for STT and related SFG rickettsioses, producing rapid recovery with very rare sequelae. "Sequellae are very rare and treatment with doxycycline is recommended" PMID: 24034636, and a recent case series confirms "All patients were treated with doxycycline and recovered without complications" PMID: 40608626. The excellent prognosis, combined with the absence of a vaccine and reliance on vector avoidance (Finding 7), completes the management picture. Suggested NCIT term: Doxycycline (NCIT:C542); CHEBI: doxycycline (CHEBI:50845).

Full Disease-Knowledge-Base Entry (15 Sections)

1. Disease Information

STT is an acute febrile zoonotic infection of the SFG rickettsioses. Identifiers: MONDO:0001154; MeSH "Rickettsiosis, Siberian Tick" / "spotted fever"; ICD-10 A77.2 (Spotted fever due to Rickettsia sibirica); ICD-11 1C30.2. It is not an OMIM/Orphanet Mendelian entry (infectious, not genetic). Synonyms: North Asian tick typhus, North Asian tick-borne rickettsiosis, Siberian tick-borne typhus, Rickettsia sibirica infection. Information is derived from aggregated disease-level resources (case series, seroprevalence surveys, molecular surveillance) rather than individual EHR data.

2. Etiology

Causal factor: infectious — inoculation of R. sibirica through the bite of an infected ixodid tick (Finding 1). There are no genetic risk factors; susceptibility loci, causal variants, and modifier genes are not applicable to this infectious disease. Environmental/behavioral risk factors: outdoor occupational or recreational activity in endemic Eurasian foci (Siberia, Mongolia, northern China, Central Asia), spring–summer tick season, contact with tick-infested vegetation or animals; male sex is statistically associated with seropositivity as a proxy for exposure (Finding 8). Protective factors are behavioral (tick avoidance, repellents, protective clothing — Finding 7), not genetic. Gene–environment interactions: not applicable.

3. Phenotypes

Phenotype	Type	HPO term	Frequency / notes
Fever	Symptom	HP:0001945	Near-universal; acute onset after incubation
Inoculation eschar (tache noire)	Clinical sign	HP:0200042 (skin ulcer)	Hallmark at bite site
Maculopapular rash	Physical manifestation	HP:0000988	Common
Regional lymphadenopathy	Clinical sign	HP:0002716	Common, esp. in LAR
Lymphangitis (LAR, mongolitimonae)	Clinical sign	—	~1/3 of mongolitimonae cases (Finding 2)
Headache / myalgia	Symptoms	HP:0002315 / HP:0003326	Frequent constitutional
Thrombocytopenia	Lab abnormality	HP:0001873	Reported in rickettsial infection

Characteristics: adult-onset (exposure-driven, any age); acute onset; severity generally mild–moderate and self-limited; monophasic course resolving with treatment. Quality-of-life impact is transient and low given rapid response to doxycycline and rare sequelae.

4. Genetic/Molecular Information

Not applicable in the human-host sense — there are no causal human genes, pathogenic variants, modifier genes, epigenetic lesions, or chromosomal abnormalities. The relevant molecular genetics are pathogen-side: the R. sibirica genes ompA (outer membrane protein A) and gltA (citrate synthase) are used for molecular typing and phylogeny (Findings 1, 4), and surface-protein genes ompB, adr1, adr2, ompW encode virulence/adhesion factors (Finding 6).

5. Environmental Information

Infectious agent: Rickettsia sibirica (including subsp. sibirica and subsp. mongolitimonae). Vectors/environment: ixodid ticks — Dermacentor nuttalli (principal), other Dermacentor spp., Haemaphysalis, and (for mongolitimonae) Hyalomma and Rhipicephalus ticks in the broader region. Transmission occurs in natural steppe/forest-steppe habitats. No toxin, radiation, or pollution etiology.

6. Mechanism / Pathophysiology

Ordered causal chain:

An infected ixodid tick bites the human host and inoculates R. sibirica into the dermis (initiating exposure). → leads to
Bacteria use surface-exposed outer-membrane proteins (OmpA/OmpB, Adr1/Adr2) to adhere to and invade vascular endothelial cells at and beyond the bite site (Finding 6). → results in
Intracellular replication and cell-to-cell spread causing local endothelial injury and the inoculation eschar (tache noire); lymphatic spread produces regional lymphadenopathy and, for mongolitimonae, lymphangitis (LAR) (Finding 2). → leads to
Hematogenous dissemination and disseminated small-vessel vasculitis with endothelial injury (Finding 3). → results in
Procoagulant activation — thromboxane-A2-dependent platelet activation, thrombin generation, endothelial dysfunction (↑endothelin-1) — and increased vascular permeability (Finding 3). → produces
The clinical manifestations: maculopapular rash, fever, and (rarely) more severe vascular complications. Branch: in parallel, the host mounts a protective response —
NK cells (innate) and CD8+ T cells (adaptive), via IFN-γ and granzyme B, clear infected endothelium and prevent endothelial damage/thrombosis (Finding 5), leading to resolution — accelerated by doxycycline (Finding 9).

Steps 2, 3, 5, and 7 are supported by direct experimental evidence (largely from closely related SFG agents R. rickettsii and R. conorii, extrapolated to R. sibirica, which is noted as an inference where species-specific data are lacking). Molecular pathways: bacterial cell entry, host inflammatory response, coagulation cascade. Cell types: endothelial cells (target); NK cells, CD8+ T cells (protection). GO/CL/UBERON terms as listed under Findings 3, 5, 6.

7. Anatomical Structures Affected

Primary organ/tissue: vascular endothelium (systemic small vessels) — UBERON:0004638 (blood vessel endothelium); skin (UBERON:0002097) at eschar and rash.
Secondary: lymphatic vessels/nodes (lymphangitis, lymphadenopathy — UBERON:0000029 lymph node); potential liver/vascular complications in severe disease.
Body systems: cardiovascular (vascular), integumentary, lymphatic/immune.
Cell level: endothelial cell (CL:0000115). Subcellular: cytoplasm (intracellular replication) — GO cytoplasm (GO:0005737).
Lateralization: eschar typically unilateral/localized (single bite site); rash generalized/bilateral.

8. Temporal Development

Onset: acute, after a short incubation following the tick bite; any age (exposure-dependent, adult-predominant). Course: monophasic, self-limited, resolving over days to weeks; prompt doxycycline shortens course. Progression: generally mild and non-progressive; sequelae very rare (Findings 2, 9). Remission: treatment-induced (rapid) or spontaneous in mild cases. Critical period: early doxycycline initiation optimizes outcome.

9. Inheritance and Population

Epidemiology: endemic across Siberia, Mongolia, northern China, Kazakhstan, and Central Asia; seasonal (tick-activity months). Animal seroprevalence is high (dogs 57–58.5%, cats 59%, rats 48%), indicating widespread enzootic circulation (Finding 8). Inheritance: not applicable (infectious). Penetrance/expressivity/anticipation/founder effects/consanguinity/carrier frequency: all not applicable. Demographics: male predominance in seropositivity (p=0.049), attributable to outdoor exposure (Finding 8); no ethnic genetic predisposition. Geographic distribution tracks the range of Dermacentor/Haemaphysalis vectors and their small-mammal reservoirs.

10. Diagnostics

Serology: IFA (reference standard) — seroconversion or ≥4-fold titer rise (Finding 4). Molecular: PCR of ompA and gltA with sequencing, from eschar biopsy or swab (non-invasive), or from blood/rash biopsy (Finding 4). Supportive labs: thrombocytopenia may be present. Clinical criteria: compatible triad (eschar + fever + rash) plus endemic tick exposure. Differential diagnosis: other SFG rickettsioses (MSF/R. conorii, R. slovaca TIBOLA/SENLAT, R. raoultii, R. aeschlimannii), tularemia, Lyme borreliosis, typhus group, and other eschar-forming tick-borne illnesses. Genetic/omics/newborn screening: not applicable.

11. Outcome/Prognosis

Excellent. With doxycycline, recovery is rapid and complete; "All patients... recovered without complications" PMID: 40608626. Mortality is very low for R. sibirica (in contrast to more virulent SFG agents such as R. rickettsii). Sequelae are very rare PMID: 24034636. Complications (severe vasculitis, thrombosis) are uncommon and associated with delayed treatment. Prognostic factors: timeliness of doxycycline, host immune competence (NK/CD8+ IFN-γ response — Finding 5), and comorbidity.

12. Treatment

First-line: Doxycycline (tetracycline-class; inhibits bacterial protein synthesis) — curative, rapid response (Finding 9). Alternatives for SFG rickettsioses include other tetracyclines and, in specific circumstances, chloramphenicol or fluoroquinolones/macrolides (agent- and patient-dependent). No advanced therapeutics (gene, cell, RNA, targeted, or immunotherapy) are relevant. Supportive care for fever/pain as needed. Pharmacogenomics: not applicable. NCIT/CHEBI: Doxycycline (NCIT:C542; CHEBI:50845).

13. Prevention

Entirely non-immunological (Finding 7). Primary prevention: personal anti-tick measures — DEET/picaridin repellents, permethrin-treated clothing (93–97% repellency), tick checks, prompt tick removal; environmental/vector control in high-risk settings. Secondary/tertiary: early recognition and doxycycline. Immunization: no licensed vaccine. Prophylaxis: routine post-bite antibiotics not recommended. Public health: health education for outdoor workers/travelers in endemic zones; note permethrin durability declines over ~1 year of wear (Finding 7 caveat).

14. Other Species / Natural Disease

Taxonomy of hosts/reservoirs: small mammals (rodents), dogs (Canis lupus familiaris, NCBITaxon:9615), cats (Felis catus, NCBITaxon:9685), and rats serve as reservoirs/sentinels with high seroprevalence (Finding 8). Vector: Dermacentor nuttalli and related ixodids. Zoonotic potential: STT is a zoonosis maintained in a tick–mammal cycle; humans are incidental hosts. Domestic animals are largely asymptomatic amplifying/sentinel hosts. Comparative pathology: the endothelial-tropism mechanism is conserved across SFG Rickettsia species and their mammalian hosts.

15. Model Organisms

Mouse models are the principal experimental system for SFG rickettsial immunity and pathogenesis: resistant/susceptible mouse strains, Rag−/−γc−/− NK-deficient mice, and challenge/immunization studies define the NK/CD8+/IFN-γ correlates of protection (Findings 5, 6). In vitro: vascular endothelial cell infection assays model adhesion/invasion (Finding 6). Most mechanistic data derive from R. rickettsii/R. conorii models and are extrapolated to R. sibirica; species-specific R. sibirica models are a knowledge gap. Cattle Cowdria (Ehrlichia) ruminantium work PMID: 9573061 provides comparative evidence that infected endothelial cells present antigen to protective T cells.

Mechanistic Model / Interpretation

 TICK BITE (Dermacentor nuttalli inoculates R. sibirica)
      │
      ▼
 [Surface proteins OmpA/OmpB, Adr1/Adr2]  ── adhere & invade ──►  VASCULAR ENDOTHELIAL CELLS
      │                                                          │
      ▼                                                          ▼
   Local injury → ESCHAR (tache noire)                     Hematogenous dissemination
   Lymphatic spread → lymphadenopathy / LAR (mongolitimonae)            │
                                                        ▼
                            DISSEMINATED SMALL-VESSEL VASCULITIS
                                                        │
                    ┌───────────────────────────────────┤
                    ▼                                   ▼
    Procoagulant activation                     Increased vascular
    (TXA2 → platelets, thrombin,                permeability
     ↑endothelin-1)                                     │
                    └───────────────┬───────────────────┘
                                    ▼
                    FEVER + MACULOPAPULAR RASH
                                    │
┌───────────────────────────────────────────┘
▼ (host defense branch)
 NK cells (innate) + CD8+ T cells (adaptive) ── IFN-γ, granzyme B ──► clear infected endothelium
│
▼
 RESOLUTION  ◄──── accelerated by DOXYCYCLINE ────►  EXCELLENT PROGNOSIS, rare sequelae

The disease is best understood as a linear infectious cascade with a protective immune branch. The single initiating lesion (tick inoculation) is amplified through endothelial tropism into a systemic vasculitis; the same surface proteins that drive invasion are the antigens recognized by protective cellular immunity and the genetic targets of molecular diagnostics. Because there is no host genetic component, the disease's "risk," "protection," and "prevention" all operate at the level of exposure — explaining the male, outdoor-associated epidemiology and the vector-avoidance basis of prevention.

Evidence Base

PMID	Title (abbrev.)	Supports	Evidence type
35934699	Rickettsia in D. nuttalli, Inner Mongolia	F001 vector & agent	Molecular surveillance
24092850	Tick-borne rickettsioses worldwide	F001 taxonomy, F004 eschar swab	Review
24034636	LAR by R. sibirica mongolitimonae	F002 clinic, F009 doxycycline	Clinical review
33969876	LAR by R. sibirica mongolitimonae	F002 ~1/3 lymphangitis	Clinical review
20797742	R. conorii meningoencephalitis	F003 vasculitis	Clinical/mechanistic
8584998	R. conorii coagulation activation	F003 procoagulant	Human in vivo
23168048	MSF in Trakya, Turkey	F004 ompA/gltA PCR	Clinical series
22617213	NK cells vs. rickettsiae	F005 innate immunity	Mouse model
25043277	Anti-Rickettsia CD8+ response	F005 adaptive immunity	Mouse model
24950252	R. rickettsii surface proteins	F006 invasion/antigens	Proteomics + immunization
35364518	Personal protection vs. ticks	F007 prevention	Review/guidance
32073128	Repellent efficacy vs. ticks	F007 93–97% repellency	Bioassay
34958094	Permethrin uniform durability	F007 durability caveat	Field study
39799873	SFG rickettsiae, Peru	F008 male exposure	Seroprevalence
20148824	SFG in cats/dogs, Tasmania	F008 animal sentinels	Seroprevalence
40608626	Rickettsiosis case series, Turkey	F009 doxycycline outcome	Clinical series
26384814	Rickettsioses in Europe	Context: LAR classification	Review
9573061	Cowdria T-cell immunity	Comparative endothelial immunity	Cattle model

Key strength: the mechanistic and immunological findings are internally consistent and cross-supported by multiple SFG species. Key caveat: much of the mechanistic/immunological detail derives from R. rickettsii and R. conorii rather than R. sibirica directly, and is applied by inference within the SFG.

Limitations and Knowledge Gaps

Species-specific data scarcity. Most pathophysiology (Findings 3, 5, 6) comes from R. conorii and R. rickettsii. R. sibirica-specific endothelial-invasion, immune-correlate, and virulence studies are limited; extrapolation within the SFG is reasonable but not proven for STT.
Epidemiology from proxies. The male-predominance and seroprevalence findings (F008) derive from non-endemic comparators (Peru, Tasmania) rather than core Eurasian STT foci; precise STT incidence/prevalence per 100,000 in Siberia/Mongolia/China was not quantified here.
No quantitative severity/QoL data. Phenotype frequencies are qualitative or drawn from related agents; formal QoL instruments have not been applied to STT.
Diagnostic performance figures (e.g., 72.6% PCR positivity) come from MSF series, not STT-specific cohorts.
No host-genetics dimension exists for this infectious disease, so Sections 4 and much of 9 are "not applicable" by nature rather than by data gap.
Vaccine/therapeutic pipeline for SFG rickettsioses remains preclinical; the protective-antigen work (F006) is promising but not yet translated.

Proposed Follow-up Actions

Quantify STT-specific epidemiology by mining Russian/Chinese/Mongolian surveillance and registry literature for incidence, seasonality, and age/sex distribution in core endemic foci.
Confirm R. sibirica-specific mechanisms: seek in vitro endothelial-invasion and murine immunity studies using R. sibirica itself to validate the extrapolated OmpA/OmpB/Adr and NK/CD8+/IFN-γ findings.
Compile a differential-diagnosis matrix distinguishing STT from co-circulating eschar-forming rickettsioses (R. slovaca, R. raoultii, R. aeschlimannii, R. conorii) by vector, geography, eschar location, and lymphadenopathy pattern.
Assess subspecies delineation: further characterize R. sibirica subsp. mongolitimonae (LAR) vs. subsp. sibirica clinical and molecular distinctions.
Evaluate protective-antigen vaccine candidates (Adr1/Adr2/OmpW) for cross-protection across SFG species, given the shared endothelial mechanism.
Ontology curation: finalize HPO/GO/CL/UBERON/NCIT/CHEBI mappings proposed above for knowledge-base ingestion.

Report compiled from 5 investigation iterations, 9 confirmed cited findings, and 23 reviewed papers. Evidence types span human clinical series, mouse and cattle models, in vitro assays, molecular surveillance, and seroprevalence surveys. Where R. sibirica-specific data were unavailable, findings from closely related spotted fever group Rickettsia are applied by explicit inference.

Artifacts

Reference Validation

Checked with linkml-reference-validator 0.3.0rc1.

Outcome	Count
References checked	18
Resolved	18
Unresolved (possible confabulation)	0
Unverifiable	0
References weighed for topical relevance	18
On topic	8
Off topic	0

All extracted references resolved successfully.

Term Validation

Checked with linkml-term-validator 0.4.5, through the ols: adapter.

Outcome	Count
Terms checked	29
Resolved	28
Unresolved (possible confabulation)	0
Obsolete	1
Unverifiable	0
Terms whose name was checked	6
Terms named correctly	2
Terms named as a different term	4

Terms the report names something else

These identifiers resolve, so nothing about them looks wrong, and the ontology calls them something unrelated to what the report calls them. That usually means the identifier is not the one the sentence needs:

HP:0001945 (2 mentions) - the report calls it "Symptom"; HP calls it Fever
HP:0000988 (2 mentions) - the report calls it "Physical manifestation"; HP calls it Skin rash
HP:0002716 (2 mentions) - the report calls it "Clinical sign"; HP calls it Lymphadenopathy
HP:0001873 (1 mention) - the report calls it "Lab abnormality"; HP calls it Thrombocytopenia

Obsolete terms

These terms are real but deprecated. Citing one is not a fabrication; it does mean the report is naming something the ontology has retired:

GO:0030260 (GO_0030260) (1 mention) - replaced by GO:0044409

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Phenotypes

Medical Actions

Diagnosis

Progression

Epidemiology

Infectious Agent

Transmission

Source YAML

References & Deep Research

References

Deep Research

Key Findings

Finding 1 — Etiology and vector (F001)

Finding 2 — Clinical triad, LAR subspecies, and benign course (F002)

Finding 3 — Pathophysiology: endothelial infection, vasculitis, and procoagulant activation (F003)

Finding 4 — Diagnosis by IFA serology and ompA/gltA PCR (F004)

Finding 5 — Protective immunity is cell-mediated (NK cells + CD8+ T cells + IFN-γ) (F005)

Finding 6 — Surface proteins mediate endothelial invasion and are protective antigens (F006)

Finding 7 — Prevention is entirely non-immunological (personal anti-tick measures) (F007)

Finding 8 — Animal reservoirs/sentinels and male-biased human exposure (F008)

Finding 9 — Doxycycline is curative; excellent prognosis (F009)

Full Disease-Knowledge-Base Entry (15 Sections)

1. Disease Information

2. Etiology

3. Phenotypes

4. Genetic/Molecular Information

5. Environmental Information

6. Mechanism / Pathophysiology

7. Anatomical Structures Affected

8. Temporal Development

9. Inheritance and Population

10. Diagnostics

11. Outcome/Prognosis

12. Treatment

13. Prevention

14. Other Species / Natural Disease

15. Model Organisms

Mechanistic Model / Interpretation

Evidence Base

Limitations and Knowledge Gaps

Proposed Follow-up Actions

Artifacts

Reference Validation

Term Validation

Terms the report names something else

Obsolete terms