Pneumonic Tularemia

Infectious Disease MONDO:0002212 Pathograph 18 Show in embeddings browser Tularemia

Pneumonic tularemia is the inhalational and pulmonary form of Francisella tularensis infection in which aerosolized bacteria reach the lung, escape the macrophage phagosome into the cytosol, and trigger acute inflammatory pneumonia.

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Classifications

Harrison's Part
INFECTIOUS DISEASES
⚙

Pathophysiology

7
Inhaled Francisella tularensis Exposure
Aerosolized F. tularensis is inhaled into the lung and seeds the pulmonary portal of entry that defines pneumonic tularemia.
lung UBERON:0002048 Uberon multi-species anatomy ontology (UBERON) Relation: this pathophysiological event occurs in this anatomical location This pathophysiological event occurs in lung (UBERON:0002048). UBERON:0002048 is an anatomical location from the Uberon multi-species anatomy ontology.
Downstream
Macrophage Phagosomal Escape and Cytosolic Replication Inhaled F. tularensis enters pulmonary macrophages and establishes an intracellular cytosolic niche.
Show evidence (1 reference)
PMID:37916743 SUPPORT REVIEW SYNTHESIS Other
"Pulmonary form appears after inhalation of bacteria."
Establishes inhaled bacteria as the route that produces the pulmonary form of tularemia.
Macrophage Phagosomal Escape and Cytosolic Replication
F. tularensis uses its Francisella Pathogenicity Island-encoded type VI secretion system to escape the macrophage phagosome and replicate in the cytosol.
macrophage CL:0000235 Cell Ontology (CL) Relation: this pathophysiological event involves this cell type This pathophysiological event involves macrophage (CL:0000235). CL:0000235 is a cell type from the Cell Ontology.
symbiont-mediated disruption of host phagosome GO:0141160 Gene Ontology (GO) Relation: this pathophysiological event involves this biological process This pathophysiological event involves symbiont-mediated disruption of host phagosome (GO:0141160). GO:0141160 is a biological process from the Gene Ontology.
Downstream
Atypical Lipid A TLR4 Evasion Francisella surface lipid A weakly activates TLR4, delaying early innate recognition while cytosolic replication is established.
GBP-IRGB10 Francisella Bacteriolysis Replicating cytosolic Francisella can be attacked and lysed by interferon-inducible GBPs and IRGB10, releasing bacterial DNA for AIM2.
Show evidence (1 reference)
PMID:37941380 SUPPORT REVIEW SYNTHESIS Other
"The main virulence attribute of F. tularensis is the type 6 secretion system (T6SS) and its effectors that promote escape from the phagosome."
Identifies T6SS-mediated phagosomal escape as the central Francisella virulence mechanism enabling cytosolic replication.
Atypical Lipid A TLR4 Evasion
Francisella produces an atypical lipid A that is poorly recognized by TLR4 and cationic antimicrobial peptides, helping the bacterium blunt early innate recognition in the lung.
negative regulation of toll-like receptor 4 signaling pathway GO:0034144 ↑ INCREASED Gene Ontology (GO) Relation: this pathophysiological event involves this biological process This pathophysiological event involves increased negative regulation of toll-like receptor 4 signaling pathway (GO:0034144). GO:0034144 is a biological process from the Gene Ontology.
Downstream
Pulmonary Inflammation Early TLR4 evasion allows higher pulmonary Francisella burden before the delayed inflammatory phase.
Show evidence (1 reference)
PMID:28807561 SUPPORT In vitro / ex vivo
"It produces an atypical lipid A, whose structure precludes an efficient recognition by both innate immune players, TLR4 and cationic antimicrobial peptides."
Mass-spectrometry work on Francisella lipid A states that the unusual lipid-A structure evades TLR4 and antimicrobial-peptide recognition.
GBP-IRGB10 Francisella Bacteriolysis
Interferon-inducible GBP2, GBP5, and IRGB10 attack cytosolic Francisella and liberate bacterial ligands that can be sensed by inflammasomes.
macrophage CL:0000235 Cell Ontology (CL) Relation: this pathophysiological event involves this cell type This pathophysiological event involves macrophage (CL:0000235). CL:0000235 is a cell type from the Cell Ontology.
Downstream
AIM2 Inflammasome Pyroptosis GBP- and IRGB10-mediated bacteriolysis releases bacterial DNA into the cytosol, exposing the AIM2 ligand.
Show evidence (2 references)
PMID:25774716 SUPPORT In vitro / ex vivo
"Mechanistically, these two GBPs targeted cytosolic F. novicida and promoted bacteriolysis."
F. novicida experiments identify GBP2 and GBP5 as cytosolic Francisella-targeting proteins that lyse bacteria to enable sensing.
PMID:27693356 SUPPORT In vitro / ex vivo
"IRGB10 directly targeted cytoplasmic bacteria through a mechanism requiring guanylate-binding proteins. Localization of IRGB10 to the bacterial cell membrane compromised bacterial structural integrity and mediated cytosolic release of ligands for recognition by inflammasome sensors."
The IRGB10 study independently places cytosolic Francisella bacteriolysis upstream of AIM2 DNA sensing.
AIM2 Inflammasome Pyroptosis
Cytosolic Francisella DNA activates AIM2/ASC inflammasomes, caspase-1, IL-1β and IL-18 release, and pyroptosis.
AIM2 inflammasome complex assembly GO:0140970 ↑ INCREASED Gene Ontology (GO) Relation: this pathophysiological event involves this biological process This pathophysiological event involves increased AIM2 inflammasome complex assembly (GO:0140970). GO:0140970 is a biological process from the Gene Ontology.
Downstream
Th1 IFN-gamma TNF-iNOS Control IL-18 contributes to IFN-gamma-biased anti-Francisella immunity.
Pulmonary Inflammation AIM2/caspase-1 activation releases inflammatory IL-1-family cytokines and causes pyroptotic macrophage death in Francisella infection.
Show evidence (1 reference)
PMID:21883803 SUPPORT In vitro / ex vivo
"assembly of the AIM2 inflammasome complex is critical for caspase-1 activation in response to Francisella infection."
Francisella macrophage experiments demonstrate that AIM2/ASC inflammasome assembly activates caspase-1 after cytosolic bacterial DNA sensing.
Th1 IFN-gamma TNF-iNOS Control
IL-18, IL-12, T-bet-dependent CD4+ T cells, IFN-gamma, and TNF drive the macrophage antimicrobial program needed to control intracellular Francisella, including nitric-oxide-mediated killing.
CD4-positive, alpha-beta T cell CL:0000624 Cell Ontology (CL) Relation: this pathophysiological event involves this cell type This pathophysiological event involves CD4-positive, alpha-beta T cell (CL:0000624). CL:0000624 is a cell type from the Cell Ontology.
Downstream
Pulmonary Inflammation Protective Th1 cytokine responses shape the inflammatory lung response to intracellular Francisella.
Show evidence (2 references)
PMID:38461051 SUPPORT REVIEW SYNTHESIS Other
"IFNγ and TNF producing Th1 T cells are required to control infection, although roles for IL-17, IL-2, and IL-12 have likewise been described"
Review synthesis places IFN-gamma/TNF-producing Th1 cells and IL-12 in protective control of Francisella infection.
PMID:24421047 SUPPORT Model organism
"In contrast, immune T-bet-KO lung lymphocytes were greatly impaired in controlling intramacrophage growth of LVS; this functional defect is the likely mechanism underpinning the lack of respiratory protection."
Mouse LVS infection experiments show that the Th1 transcription factor T-bet is required for effective lung Francisella immunity.
Pulmonary Inflammation
Pulmonary innate immune activation produces acute infectious pneumonia.
inflammatory response GO:0006954 ↑ INCREASED Gene Ontology (GO) Relation: this pathophysiological event involves this biological process This pathophysiological event involves increased inflammatory response (GO:0006954). GO:0006954 is a biological process from the Gene Ontology.
lung UBERON:0002048 Uberon multi-species anatomy ontology (UBERON) Relation: this pathophysiological event occurs in this anatomical location This pathophysiological event occurs in lung (UBERON:0002048). UBERON:0002048 is an anatomical location from the Uberon multi-species anatomy ontology.
Downstream
Pneumonia Lung inflammation manifests clinically as pneumonia after inhalational tularemia.
Fever Systemic inflammatory cytokines produce an acute febrile illness.
Cough Pulmonary inflammatory disease produces cough.
Tachypnea Pulmonary tularemia can present with rapid respiration.
Pleuritic Chest Pain Pleurisy produces pleuritic chest pain in pneumonic tularemia.
Pleural Effusion Severe pneumonic tularemia can produce pleural effusions.
Mediastinal Lymphadenopathy Thoracic inflammation can enlarge mediastinal or hilar lymph nodes.
Chills Systemic inflammation in acute tularemia produces chills.
Headache Acute systemic tularemia produces headache.
Myalgia Acute systemic tularemia produces myalgia.
Show evidence (1 reference)
PMID:21819572 SUPPORT Model organism
"Following pulmonary infection of mice with FT, there is an initial lag in recruitment of neutrophils as well as a minimal proinflammatory cytokine response in the first 24-48 hours following infection with FT"
The murine pulmonary tularemia model documents delayed early neutrophil and cytokine responses in the lung after F. tularensis infection.
⬡

Pathograph

Use Group by to collapse related nodes into one box. Use the checkboxes to hide or show graph categories. Hover nodes for evidence and cross-linked metadata.
Pathograph: causal mechanism network for Pneumonic Tularemia Interactive directed graph showing how pathophysiology mechanisms, phenotypes, genetic factors and variants, experimental models, environmental triggers, and treatments relate through causal and linked edges.
●

Phenotypes

10
Cardiovascular 1
Mediastinal Lymphadenopathy FREQUENT HP:0100721 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Mediastinal lymphadenopathy (HP:0100721). HP:0100721 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:37941380 SUPPORT REVIEW SYNTHESIS Other
"Symptoms include cough, chest pain, rapid respiration (polypnea), fever, and enlargement of lymph nodes localized in the chest region (mediastinal and/or hilar adenopathy)"
The review lists mediastinal or hilar adenopathy as a thoracic manifestation of pulmonary tularemia.
Immune 1
Pneumonia VERY_FREQUENT HP:0002090 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Pneumonia (HP:0002090). HP:0002090 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:11757506 SUPPORT Human clinical
"We conducted a case-control study of adults with pneumonic tularemia and investigated the environment to identify risk factors for primary pneumonic tularemia."
Documents primary pneumonic tularemia as the lung-centered clinical presentation studied in a human outbreak.
Metabolism 2
Fever VERY_FREQUENT HP:0001945 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Fever (HP:0001945). HP:0001945 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:37941380 SUPPORT REVIEW SYNTHESIS Other
"Tularaemia in humans presents in six clinical forms depending on the point of bacterial entry: ulceroglandular, glandular, oculoglandular, oropharyngeal, pulmonary, and typhoid. At onset, tularaemia symptoms are non-specific and include a flu-like syndrome with fever, headache, muscle and joint..."
Review synthesis includes pulmonary tularemia among the forms with nonspecific febrile onset.
Pleural Effusion OCCASIONAL HP:0002202 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Pleural effusion (HP:0002202). HP:0002202 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:38294108 SUPPORT REVIEW SYNTHESIS Human clinical
"Patients with pneumonic disease who received ciprofloxacin had no fatalities and the lowest rates of thoracentesis/pleural effusion drainage and intubation compared to those who received aminoglycosides and tetracyclines."
The systematic review's pneumonic-disease analysis included patients requiring thoracentesis or pleural-effusion drainage.
Nervous System 1
Headache FREQUENT HP:0002315 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Headache (HP:0002315). HP:0002315 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:37916743 SUPPORT REVIEW SYNTHESIS Other
"The disease has an acute onset, with the occurrence of fever (38–40 °C), chills, fatigue, generalized myalgia, and headaches, resembling flu."
Review synthesis places headache in the acute tularemia syndrome.
Respiratory 2
Cough FREQUENT HP:0012735 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Cough (HP:0012735). HP:0012735 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:37941380 SUPPORT REVIEW SYNTHESIS Other
"Symptoms include cough, chest pain, rapid respiration (polypnea), fever, and enlargement of lymph nodes localized in the chest region (mediastinal and/or hilar adenopathy)"
The review lists cough among pulmonary tularemia manifestations.
Tachypnea FREQUENT HP:0002789 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Tachypnea (HP:0002789). HP:0002789 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:37941380 SUPPORT REVIEW SYNTHESIS Other
"Symptoms include cough, chest pain, rapid respiration (polypnea), fever, and enlargement of lymph nodes localized in the chest region (mediastinal and/or hilar adenopathy)"
The review lists polypnea, rapid respiration, among pulmonary tularemia manifestations.
Constitutional 3
Pleuritic Chest Pain FREQUENT HP:0033771 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Pleuritic chest pain (HP:0033771). HP:0033771 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:37941380 SUPPORT REVIEW SYNTHESIS Other
"Symptoms include cough, chest pain, rapid respiration (polypnea), fever, and enlargement of lymph nodes localized in the chest region (mediastinal and/or hilar adenopathy)"
Chest pain in the pulmonary form supports pleuritic chest pain as a respiratory phenotype of pneumonic tularemia.
Chills FREQUENT HP:0025143 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Chills (HP:0025143). HP:0025143 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:37916743 SUPPORT REVIEW SYNTHESIS Other
"The disease has an acute onset, with the occurrence of fever (38–40 °C), chills, fatigue, generalized myalgia, and headaches, resembling flu."
Review synthesis places chills in the acute tularemia syndrome.
Myalgia FREQUENT HP:0003326 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Myalgia (HP:0003326). HP:0003326 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:37916743 SUPPORT REVIEW SYNTHESIS Other
"The disease has an acute onset, with the occurrence of fever (38–40 °C), chills, fatigue, generalized myalgia, and headaches, resembling flu."
Review synthesis places generalized myalgia in the acute tularemia syndrome.
💊

Medical Actions

1
Tularemia antibiotic therapy
Action: PharmacotherapyNCI Thesaurus (NCIT) Relation: this treatment is this clinical intervention This treatment is Pharmacotherapy (NCIT:C15986). NCIT:C15986 is a clinical intervention from the NCI Thesaurus. NCIT:C15986
Agent: streptomycin CHEBI:17076 Chemical Entities of Biological Interest (CHEBI) Relation: this treatment uses this therapeutic agent This treatment uses streptomycin (CHEBI:17076). CHEBI:17076 is a therapeutic agent from Chemical Entities of Biological Interest. gentamicin CHEBI:759884 Chemical Entities of Biological Interest (CHEBI) Relation: this treatment uses this therapeutic agent This treatment uses gentamicin (CHEBI:759884). CHEBI:759884 is a therapeutic agent from Chemical Entities of Biological Interest. ciprofloxacin CHEBI:100241 Chemical Entities of Biological Interest (CHEBI) Relation: this treatment uses this therapeutic agent This treatment uses ciprofloxacin (CHEBI:100241). CHEBI:100241 is a therapeutic agent from Chemical Entities of Biological Interest. doxycycline CHEBI:50845 Chemical Entities of Biological Interest (CHEBI) Relation: this treatment uses this therapeutic agent This treatment uses doxycycline (CHEBI:50845). CHEBI:50845 is a therapeutic agent from Chemical Entities of Biological Interest.
Platform: Small molecule
Aminoglycosides, fluoroquinolones, and tetracyclines are effective intracellularly active treatment classes for tularemia; streptomycin and gentamicin are historical treatments of choice, while ciprofloxacin and doxycycline are commonly used modern options.
Mechanism Target:
INHIBITS Macrophage Phagosomal Escape and Cytosolic Replication — Ciprofloxacin reduces the intracellular F. tularensis burden that drives pneumonic tularemia.
Show evidence (3 references)
PMID:38294108 SUPPORT REVIEW SYNTHESIS Other
"For pneumonic disease specifically, ciprofloxacin may have slight advantages compared to other antimicrobials."
Supports ciprofloxacin as a treatment option with review-level evidence specific to pneumonic tularemia.
PMID:29183485 SUPPORT REVIEW SYNTHESIS Other
"Streptomycin and gentamicin are currently considered the treatment of choice for tularemia. Quinolone is an effective alternative drug."
Bioterrorism-focused clinical guidance identifies aminoglycosides as the treatment of choice and quinolones as effective alternatives.
PMID:42641375 SUPPORT REVIEW SYNTHESIS Other
"The 2025 CDC guidelines establish fluoroquinolones and doxycycline as first-line therapeutic options."
The re-emergence review summarizes updated CDC guidance listing fluoroquinolones and doxycycline among first-line options.
🔬

Diagnosis

1
Tularemia Laboratory Diagnosis
Tularemia diagnosis relies principally on serology, with PCR and culture used for direct pathogen detection when available and safe.
laboratory procedure NCIT:C25294 NCI Thesaurus (NCIT)
Show evidence (1 reference)
PMID:20220165 SUPPORT Other
"Serology is still considered to be a cornerstone in tularemia diagnosis due to the low sensitivity of bacterial culture and the lack of standardization in PCR methodology for the direct identification of the pathogen."
Serodiagnostic test development summarizes why serology remains central while culture and PCR have sensitivity, biosafety, or standardization limitations.
📈

Progression

3
Aerosol pulmonary exposure
Pneumonic tularemia begins when aerosolized F. tularensis is inhaled into the lower respiratory tract.
Show evidence (1 reference)
PMID:37916743 SUPPORT REVIEW SYNTHESIS Other
"Pulmonary form appears after inhalation of bacteria."
Defines inhalation as the exposure route for the pulmonary clinical form.
Intracellular macrophage replication
Inhaled Francisella organisms enter pulmonary phagocytes, escape the phagosome through the Francisella pathogenicity island type VI secretion system, and replicate in the macrophage cytosol.
Show evidence (1 reference)
PMID:37941380 SUPPORT REVIEW SYNTHESIS Other
"The main virulence attribute of F. tularensis is the type 6 secretion system (T6SS) and its effectors that promote escape from the phagosome."
Places type VI secretion-mediated phagosomal escape in the intracellular replication phase.
Acute inflammatory pneumonia
Intracellular replication, cytosolic bacteriolysis, AIM2/caspase-1 activation, and delayed pulmonary innate responses progress to inflammatory pneumonia.
Show evidence (1 reference)
PMID:21883803 SUPPORT In vitro / ex vivo
"Francisella tularensis is a facultative intracellular pathogen known to trigger a cytosolic innate immune response upon phagosomal escape."
Places phagosomal escape upstream of Francisella-triggered cytosolic innate sensing.
🌍

Epidemiology

2
Martha's Vineyard primary pneumonic outbreaks
Primary pneumonic tularemia is rare in the United States, but Martha's Vineyard had recognized outbreaks in 1978 and 2000, and the 2000 outbreak case-control study implicated lawn mowing and brush cutting as aerosol-generating risk factors.
Show evidence (1 reference)
PMID:11757506 SUPPORT Human clinical
"The only previously reported outbreak of pneumonic tularemia in the United States also occurred on the island in 1978."
Places the 2000 Martha's Vineyard outbreak in context as the second recognized U.S. outbreak of primary pneumonic tularemia.
High-mortality pulmonary form
Pneumonic tularemia has the highest mortality among tularemia clinical forms, with untreated tularemia carrying roughly 30% mortality in modern review summaries.
Show evidence (2 references)
PMID:38461051 SUPPORT REVIEW SYNTHESIS Other
"Tularemia is caused by subspecies of Francisella tularensis and can manifest in a variety of disease states, with the pneumonic presentation resulting in the greatest mortality."
The vaccine review identifies pneumonic tularemia as the highest-mortality disease state.
PMID:42641375 SUPPORT REVIEW SYNTHESIS Other
"Tularemia is classified as a Category A bioterrorism agent by the CDC due to its extraordinary virulence; as few as 10 bacterial cells can establish infection, and untreated cases carry 30% mortality."
Recent review synthesis ties Francisella's high virulence to the approximately 30% untreated mortality figure.
🦠

Infectious Agent

1
Francisella tularensis
Intracellular Gram-negative coccobacillus that causes tularemia, including its inhalational pneumonic form.
Francisella tularensis NCBITaxon:263 NCBI Taxonomy (NCBITaxon)
Show evidence (1 reference)
PMID:38294108 SUPPORT REVIEW SYNTHESIS Other
"Francisella tularensis, the causative agent of tularemia, is endemic throughout the Northern Hemisphere and requires as few as 10 organisms to cause disease"
Identifies F. tularensis as the causative agent of tularemia and supports the low infectious dose relevant to inhalational disease.
↔️

Transmission

1
Inhalation of infectious aerosols
Humans acquire pneumonic tularemia when they inhale aerosolized F. tularensis from contaminated animal or environmental material.
Show evidence (2 references)
PMID:37916743 SUPPORT REVIEW SYNTHESIS Other
"Pulmonary form appears after inhalation of bacteria."
Links inhalation of F. tularensis to pulmonary tularemia.
PMID:11757506 SUPPORT Human clinical
"Study of this outbreak of primary pneumonic tularemia implicates lawn mowing and brush cutting as risk factors for this infection."
The Martha's Vineyard outbreak tied aerosol-generating landscaping to primary pneumonic tularemia.
{ }

Source YAML

click to show 
name: Pneumonic Tularemia
creation_date: "2026-09-29T22:52:21Z"
description: >-
  Pneumonic tularemia is the inhalational and pulmonary form of Francisella
  tularensis infection in which aerosolized bacteria reach the lung, escape
  the macrophage phagosome into the cytosol, and trigger acute inflammatory
  pneumonia.
category: Infectious Disease
disease_term:
  preferred_term: pneumonic tularemia
  term:
    id: MONDO:0002212
    label: pneumonic tularemia
parents:
- Tularemia
synonyms:
- Pulmonary tularemia
notes: >-
  This entry is scoped to primary pneumonic tularemia after aerosol inhalation
  of Francisella tularensis. Other tularemia entries carry vector-borne,
  ulceroglandular, oculoglandular, or oropharyngeal portals when those routes
  drive the clinical form. Pneumonic tularemia is retained separately because
  it is the highest-mortality tularemia form and carries pulmonary diagnostic
  and treatment urgency after aerosol exposure.
review_notes: >-
  Deliberately lumped. F. tularensis type A, type B, and type A-east/A-west
  strain strata differ in virulence, geography, and typical severity, but this
  pneumonic-form entry is organized by inhalational route and lung disease
  rather than by agent subspecies.
infectious_agent:
- name: Francisella tularensis
  infectious_agent_term:
    preferred_term: Francisella tularensis
    term:
      id: NCBITaxon:263
      label: Francisella tularensis
  description: >-
    Intracellular Gram-negative coccobacillus that causes tularemia, including
    its inhalational pneumonic form.
  evidence:
  - reference: PMID:38294108
    reference_title: >-
      Systematic Review: Clinical Features, Antimicrobial Treatment, and
      Outcomes of Human Tularemia, 1993-2023.
    supports: SUPPORT
    evidence_source: OTHER
    quote_role: REVIEW_SYNTHESIS
    snippet: >-
      Francisella tularensis, the causative agent of tularemia, is endemic
      throughout the Northern Hemisphere and requires as few as 10 organisms to
      cause disease
    explanation: >-
      Identifies F. tularensis as the causative agent of tularemia and
      supports the low infectious dose relevant to inhalational disease.
agent_life_cycle:
  description: >-
    Francisella tularensis persists in a broad zoonotic cycle involving
    lagomorphs, rodents, more than 250 animal species, arthropod vectors, and
    contaminated soil or water; humans are incidental clinical hosts exposed to
    infectious aerosols, infected animals, or contaminated environmental
    material.
  hosts:
  - preferred_term: Homo sapiens
    role: incidental clinical host
    term:
      id: NCBITaxon:9606
      label: Homo sapiens
  - preferred_term: lagomorphs
    role: animal source
    term:
      id: NCBITaxon:9975
      label: Lagomorpha
  - preferred_term: rodents
    role: animal source
    term:
      id: NCBITaxon:9989
      label: Rodentia
  vectors:
  - Lone star tick (Amblyomma americanum)
  - American dog tick (Dermacentor variabilis)
  - Mosquitoes (Culicidae)
  evidence:
  - reference: PMID:37941380
    reference_title: "Pathogenicity and virulence of Francisella tularensis."
    supports: SUPPORT
    evidence_source: OTHER
    quote_role: REVIEW_SYNTHESIS
    snippet: >-
      Hares or small rodents (voles, mice, rats, coypu, squirrels, etc.) are
      the primary sources of direct contamination, but over 250 animal species
      have been identified as carrying or being infected with F. tularensis
      [17].
    explanation: >-
      Supports the broad animal cycle that seeds environmental material able to
      aerosolize and cause pneumonic tularemia.
classifications:
  harrisons_chapter:
  - classification_value: INFECTIOUS_DISEASES
transmission:
- name: Inhalation of infectious aerosols
  description: >-
    Humans acquire pneumonic tularemia when they inhale aerosolized F.
    tularensis from contaminated animal or environmental material.
  evidence:
  - reference: PMID:37916743
    reference_title: "Tularemia - a re-emerging disease with growing concern."
    supports: SUPPORT
    evidence_source: OTHER
    quote_role: REVIEW_SYNTHESIS
    snippet: Pulmonary form appears after inhalation of bacteria.
    explanation: >-
      Links inhalation of F. tularensis to pulmonary tularemia.
  - reference: PMID:11757506
    reference_title: An outbreak of primary pneumonic tularemia on Martha's Vineyard.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Study of this outbreak of primary pneumonic tularemia implicates lawn
      mowing and brush cutting as risk factors for this infection.
    explanation: >-
      The Martha's Vineyard outbreak tied aerosol-generating landscaping to
      primary pneumonic tularemia.
pathophysiology:
- name: Inhaled Francisella tularensis Exposure
  role: trigger
  description: >-
    Aerosolized F. tularensis is inhaled into the lung and seeds the pulmonary
    portal of entry that defines pneumonic tularemia.
  biological_scale: TISSUE
  locations:
  - preferred_term: lung
    term:
      id: UBERON:0002048
      label: lung
  downstream:
  - target: Macrophage Phagosomal Escape and Cytosolic Replication
    causal_link_type: DIRECT
    description: >-
      Inhaled F. tularensis enters pulmonary macrophages and establishes an
      intracellular cytosolic niche.
  evidence:
  - reference: PMID:37916743
    reference_title: "Tularemia - a re-emerging disease with growing concern."
    supports: SUPPORT
    evidence_source: OTHER
    quote_role: REVIEW_SYNTHESIS
    snippet: Pulmonary form appears after inhalation of bacteria.
    explanation: >-
      Establishes inhaled bacteria as the route that produces the pulmonary
      form of tularemia.
- name: Macrophage Phagosomal Escape and Cytosolic Replication
  description: >-
    F. tularensis uses its Francisella Pathogenicity Island-encoded type VI
    secretion system to escape the macrophage phagosome and replicate in the
    cytosol.
  biological_scale: CELLULAR
  cell_types:
  - preferred_term: macrophage
    term:
      id: CL:0000235
      label: macrophage
  biological_processes:
  - preferred_term: symbiont-mediated disruption of host phagosome
    term:
      id: GO:0141160
      label: symbiont-mediated disruption of host phagosome
  downstream:
  - target: Atypical Lipid A TLR4 Evasion
    causal_link_type: DIRECT
    description: >-
      Francisella surface lipid A weakly activates TLR4, delaying early innate
      recognition while cytosolic replication is established.
  - target: GBP-IRGB10 Francisella Bacteriolysis
    causal_link_type: DIRECT
    description: >-
      Replicating cytosolic Francisella can be attacked and lysed by
      interferon-inducible GBPs and IRGB10, releasing bacterial DNA for AIM2.
  evidence:
  - reference: PMID:37941380
    reference_title: "Pathogenicity and virulence of Francisella tularensis."
    supports: SUPPORT
    evidence_source: OTHER
    quote_role: REVIEW_SYNTHESIS
    snippet: >-
      The main virulence attribute of F. tularensis is the type 6 secretion
      system (T6SS) and its effectors that promote escape from the phagosome.
    explanation: >-
      Identifies T6SS-mediated phagosomal escape as the central Francisella
      virulence mechanism enabling cytosolic replication.
- name: Atypical Lipid A TLR4 Evasion
  description: >-
    Francisella produces an atypical lipid A that is poorly recognized by TLR4
    and cationic antimicrobial peptides, helping the bacterium blunt early
    innate recognition in the lung.
  biological_scale: MOLECULAR
  biological_processes:
  - preferred_term: negative regulation of toll-like receptor 4 signaling pathway
    modifier: INCREASED
    term:
      id: GO:0034144
      label: negative regulation of toll-like receptor 4 signaling pathway
  downstream:
  - target: Pulmonary Inflammation
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    description: >-
      Early TLR4 evasion allows higher pulmonary Francisella burden before the
      delayed inflammatory phase.
  evidence:
  - reference: PMID:28807561
    reference_title: Mass spectrometry analysis of intact Francisella bacteria identifies lipid A structure remodeling in response to acidic pH stress.
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: >-
      It produces an atypical lipid A, whose structure precludes an efficient
      recognition by both innate immune players, TLR4 and cationic
      antimicrobial peptides.
    explanation: >-
      Mass-spectrometry work on Francisella lipid A states that the unusual
      lipid-A structure evades TLR4 and antimicrobial-peptide recognition.
- name: GBP-IRGB10 Francisella Bacteriolysis
  description: >-
    Interferon-inducible GBP2, GBP5, and IRGB10 attack cytosolic Francisella
    and liberate bacterial ligands that can be sensed by inflammasomes.
  biological_scale: CELLULAR
  cell_types:
  - preferred_term: macrophage
    term:
      id: CL:0000235
      label: macrophage
  downstream:
  - target: AIM2 Inflammasome Pyroptosis
    causal_link_type: DIRECT
    description: >-
      GBP- and IRGB10-mediated bacteriolysis releases bacterial DNA into the
      cytosol, exposing the AIM2 ligand.
  evidence:
  - reference: PMID:25774716
    reference_title: Guanylate-binding proteins promote activation of the AIM2 inflammasome during infection with Francisella novicida.
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: >-
      Mechanistically, these two GBPs targeted cytosolic F. novicida and
      promoted bacteriolysis.
    explanation: >-
      F. novicida experiments identify GBP2 and GBP5 as cytosolic
      Francisella-targeting proteins that lyse bacteria to enable sensing.
  - reference: PMID:27693356
    reference_title: IRGB10 Liberates Bacterial Ligands for Sensing by the AIM2 and Caspase-11-NLRP3 Inflammasomes.
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: >-
      IRGB10 directly targeted cytoplasmic bacteria through a mechanism
      requiring guanylate-binding proteins. Localization of IRGB10 to the
      bacterial cell membrane compromised bacterial structural integrity and
      mediated cytosolic release of ligands for recognition by inflammasome
      sensors.
    explanation: >-
      The IRGB10 study independently places cytosolic Francisella bacteriolysis
      upstream of AIM2 DNA sensing.
- name: AIM2 Inflammasome Pyroptosis
  description: >-
    Cytosolic Francisella DNA activates AIM2/ASC inflammasomes, caspase-1,
    IL-1β and IL-18 release, and pyroptosis.
  biological_scale: CELLULAR
  biological_processes:
  - preferred_term: AIM2 inflammasome complex assembly
    modifier: INCREASED
    term:
      id: GO:0140970
      label: AIM2 inflammasome complex assembly
  downstream:
  - target: Th1 IFN-gamma TNF-iNOS Control
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    description: IL-18 contributes to IFN-gamma-biased anti-Francisella immunity.
  - target: Pulmonary Inflammation
    causal_link_type: DIRECT
    description: >-
      AIM2/caspase-1 activation releases inflammatory IL-1-family cytokines
      and causes pyroptotic macrophage death in Francisella infection.
  evidence:
  - reference: PMID:21883803
    reference_title: Elevated AIM2-mediated pyroptosis triggered by hypercytotoxic Francisella mutant strains is attributed to increased intracellular bacteriolysis.
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: >-
      assembly of the AIM2 inflammasome complex is critical for caspase-1
      activation in response to Francisella infection.
    explanation: >-
      Francisella macrophage experiments demonstrate that AIM2/ASC inflammasome
      assembly activates caspase-1 after cytosolic bacterial DNA sensing.
- name: Th1 IFN-gamma TNF-iNOS Control
  description: >-
    IL-18, IL-12, T-bet-dependent CD4+ T cells, IFN-gamma, and TNF drive the
    macrophage antimicrobial program needed to control intracellular
    Francisella, including nitric-oxide-mediated killing.
  biological_scale: CELLULAR
  cell_types:
  - preferred_term: CD4-positive, alpha-beta T cell
    term:
      id: CL:0000624
      label: CD4-positive, alpha-beta T cell
  downstream:
  - target: Pulmonary Inflammation
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    description: >-
      Protective Th1 cytokine responses shape the inflammatory lung response
      to intracellular Francisella.
  evidence:
  - reference: PMID:38461051
    reference_title: Current vaccine strategies and novel approaches to combatting Francisella infection.
    supports: SUPPORT
    evidence_source: OTHER
    quote_role: REVIEW_SYNTHESIS
    snippet: >-
      IFNγ and TNF producing Th1 T cells are required to control infection,
      although roles for IL-17, IL-2, and IL-12 have likewise been described
    explanation: >-
      Review synthesis places IFN-gamma/TNF-producing Th1 cells and IL-12 in
      protective control of Francisella infection.
  - reference: PMID:24421047
    reference_title: T-bet regulates immunity to Francisella tularensis live vaccine strain infection, particularly in lungs.
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: >-
      In contrast, immune T-bet-KO lung lymphocytes were greatly impaired in
      controlling intramacrophage growth of LVS; this functional defect is the
      likely mechanism underpinning the lack of respiratory protection.
    explanation: >-
      Mouse LVS infection experiments show that the Th1 transcription factor
      T-bet is required for effective lung Francisella immunity.
- name: Pulmonary Inflammation
  description: >-
    Pulmonary innate immune activation produces acute infectious pneumonia.
  biological_scale: TISSUE
  locations:
  - preferred_term: lung
    term:
      id: UBERON:0002048
      label: lung
  biological_processes:
  - preferred_term: inflammatory response
    modifier: INCREASED
    term:
      id: GO:0006954
      label: inflammatory response
  downstream:
  - target: Pneumonia
    causal_link_type: DIRECT
    description: >-
      Lung inflammation manifests clinically as pneumonia after inhalational
      tularemia.
  - target: Fever
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    description: Systemic inflammatory cytokines produce an acute febrile illness.
  - target: Cough
    causal_link_type: DIRECT
    description: Pulmonary inflammatory disease produces cough.
  - target: Tachypnea
    causal_link_type: DIRECT
    description: Pulmonary tularemia can present with rapid respiration.
  - target: Pleuritic Chest Pain
    causal_link_type: DIRECT
    description: Pleurisy produces pleuritic chest pain in pneumonic tularemia.
  - target: Pleural Effusion
    causal_link_type: DIRECT
    description: Severe pneumonic tularemia can produce pleural effusions.
  - target: Mediastinal Lymphadenopathy
    causal_link_type: DIRECT
    description: Thoracic inflammation can enlarge mediastinal or hilar lymph nodes.
  - target: Chills
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    description: Systemic inflammation in acute tularemia produces chills.
  - target: Headache
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    description: Acute systemic tularemia produces headache.
  - target: Myalgia
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    description: Acute systemic tularemia produces myalgia.
  evidence:
  - reference: PMID:21819572
    reference_title: A galU mutant of Francisella tularensis is attenuated for virulence in a murine pulmonary model of tularemia.
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: >-
      Following pulmonary infection of mice with FT, there is an initial lag in
      recruitment of neutrophils as well as a minimal proinflammatory cytokine
      response in the first 24-48 hours following infection with FT
    explanation: >-
      The murine pulmonary tularemia model documents delayed early neutrophil
      and cytokine responses in the lung after F. tularensis infection.
progression:
- phase: Aerosol pulmonary exposure
  notes: >-
    Pneumonic tularemia begins when aerosolized F. tularensis is inhaled into
    the lower respiratory tract.
  evidence:
  - reference: PMID:37916743
    reference_title: "Tularemia - a re-emerging disease with growing concern."
    supports: SUPPORT
    evidence_source: OTHER
    quote_role: REVIEW_SYNTHESIS
    snippet: Pulmonary form appears after inhalation of bacteria.
    explanation: >-
      Defines inhalation as the exposure route for the pulmonary clinical form.
- phase: Intracellular macrophage replication
  notes: >-
    Inhaled Francisella organisms enter pulmonary phagocytes, escape the
    phagosome through the Francisella pathogenicity island type VI secretion
    system, and replicate in the macrophage cytosol.
  evidence:
  - reference: PMID:37941380
    reference_title: "Pathogenicity and virulence of Francisella tularensis."
    supports: SUPPORT
    evidence_source: OTHER
    quote_role: REVIEW_SYNTHESIS
    snippet: >-
      The main virulence attribute of F. tularensis is the type 6 secretion
      system (T6SS) and its effectors that promote escape from the phagosome.
    explanation: >-
      Places type VI secretion-mediated phagosomal escape in the intracellular
      replication phase.
- phase: Acute inflammatory pneumonia
  notes: >-
    Intracellular replication, cytosolic bacteriolysis, AIM2/caspase-1
    activation, and delayed pulmonary innate responses progress to inflammatory
    pneumonia.
  evidence:
  - reference: PMID:21883803
    reference_title: Elevated AIM2-mediated pyroptosis triggered by hypercytotoxic Francisella mutant strains is attributed to increased intracellular bacteriolysis.
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: >-
      Francisella tularensis is a facultative intracellular pathogen known to
      trigger a cytosolic innate immune response upon phagosomal escape.
    explanation: >-
      Places phagosomal escape upstream of Francisella-triggered cytosolic
      innate sensing.
phenotypes:
- name: Pneumonia
  description: >-
    Pneumonic tularemia presents with acute infectious pneumonia after
    inhalational acquisition.
  frequency: VERY_FREQUENT
  phenotype_term:
    preferred_term: Pneumonia
    term:
      id: HP:0002090
      label: Pneumonia
  evidence:
  - reference: PMID:11757506
    reference_title: An outbreak of primary pneumonic tularemia on Martha's Vineyard.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      We conducted a case-control study of adults with pneumonic tularemia and
      investigated the environment to identify risk factors for primary
      pneumonic tularemia.
    explanation: >-
      Documents primary pneumonic tularemia as the lung-centered clinical
      presentation studied in a human outbreak.
- name: Fever
  description: Acute pneumonic tularemia commonly begins as a febrile illness.
  frequency: VERY_FREQUENT
  phenotype_term:
    preferred_term: Fever
    term:
      id: HP:0001945
      label: Fever
  evidence:
  - reference: PMID:37941380
    reference_title: "Pathogenicity and virulence of Francisella tularensis."
    supports: SUPPORT
    evidence_source: OTHER
    quote_role: REVIEW_SYNTHESIS
    snippet: >-
      Tularaemia in humans presents in six clinical forms depending on the
      point of bacterial entry: ulceroglandular, glandular, oculoglandular,
      oropharyngeal, pulmonary, and typhoid. At onset, tularaemia symptoms are
      non-specific and include a flu-like syndrome with fever, headache, muscle
      and joint aches (myalgia, and/or arthralgia).
    explanation: >-
      Review synthesis includes pulmonary tularemia among the forms with
      nonspecific febrile onset.
- name: Cough
  description: Cough is a respiratory symptom of pulmonary tularemia.
  frequency: FREQUENT
  phenotype_term:
    preferred_term: Cough
    term:
      id: HP:0012735
      label: Cough
  evidence:
  - reference: PMID:37941380
    reference_title: "Pathogenicity and virulence of Francisella tularensis."
    supports: SUPPORT
    evidence_source: OTHER
    quote_role: REVIEW_SYNTHESIS
    snippet: >-
      Symptoms include cough, chest pain, rapid respiration (polypnea), fever,
      and enlargement of lymph nodes localized in the chest region (mediastinal
      and/or hilar adenopathy)
    explanation: The review lists cough among pulmonary tularemia manifestations.
- name: Tachypnea
  description: Pulmonary tularemia can cause rapid breathing.
  frequency: FREQUENT
  phenotype_term:
    preferred_term: Tachypnea
    term:
      id: HP:0002789
      label: Tachypnea
  evidence:
  - reference: PMID:37941380
    reference_title: "Pathogenicity and virulence of Francisella tularensis."
    supports: SUPPORT
    evidence_source: OTHER
    quote_role: REVIEW_SYNTHESIS
    snippet: >-
      Symptoms include cough, chest pain, rapid respiration (polypnea), fever,
      and enlargement of lymph nodes localized in the chest region (mediastinal
      and/or hilar adenopathy)
    explanation: >-
      The review lists polypnea, rapid respiration, among pulmonary tularemia
      manifestations.
- name: Pleuritic Chest Pain
  description: Pulmonary tularemia can cause pleuritic chest pain.
  frequency: FREQUENT
  phenotype_term:
    preferred_term: Pleuritic chest pain
    term:
      id: HP:0033771
      label: Pleuritic chest pain
  evidence:
  - reference: PMID:37941380
    reference_title: "Pathogenicity and virulence of Francisella tularensis."
    supports: SUPPORT
    evidence_source: OTHER
    quote_role: REVIEW_SYNTHESIS
    snippet: >-
      Symptoms include cough, chest pain, rapid respiration (polypnea), fever,
      and enlargement of lymph nodes localized in the chest region (mediastinal
      and/or hilar adenopathy)
    explanation: >-
      Chest pain in the pulmonary form supports pleuritic chest pain as a
      respiratory phenotype of pneumonic tularemia.
- name: Pleural Effusion
  description: Pneumonic tularemia can be complicated by pleural effusion.
  frequency: OCCASIONAL
  phenotype_term:
    preferred_term: Pleural effusion
    term:
      id: HP:0002202
      label: Pleural effusion
  evidence:
  - reference: PMID:38294108
    reference_title: >-
      Systematic Review: Clinical Features, Antimicrobial Treatment, and
      Outcomes of Human Tularemia, 1993-2023.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: REVIEW_SYNTHESIS
    snippet: >-
      Patients with pneumonic disease who received ciprofloxacin had no
      fatalities and the lowest rates of thoracentesis/pleural effusion
      drainage and intubation compared to those who received aminoglycosides
      and tetracyclines.
    explanation: >-
      The systematic review's pneumonic-disease analysis included patients
      requiring thoracentesis or pleural-effusion drainage.
- name: Mediastinal Lymphadenopathy
  description: >-
    Pneumonic tularemia can enlarge thoracic lymph nodes, including hilar or
    mediastinal nodes.
  frequency: FREQUENT
  phenotype_term:
    preferred_term: Mediastinal lymphadenopathy
    term:
      id: HP:0100721
      label: Mediastinal lymphadenopathy
  evidence:
  - reference: PMID:37941380
    reference_title: "Pathogenicity and virulence of Francisella tularensis."
    supports: SUPPORT
    evidence_source: OTHER
    quote_role: REVIEW_SYNTHESIS
    snippet: >-
      Symptoms include cough, chest pain, rapid respiration (polypnea), fever,
      and enlargement of lymph nodes localized in the chest region (mediastinal
      and/or hilar adenopathy)
    explanation: >-
      The review lists mediastinal or hilar adenopathy as a thoracic
      manifestation of pulmonary tularemia.
- name: Chills
  description: Chills accompany the acute flu-like phase of tularemia.
  frequency: FREQUENT
  phenotype_term:
    preferred_term: Chills
    term:
      id: HP:0025143
      label: Chills
  evidence:
  - reference: PMID:37916743
    reference_title: "Tularemia - a re-emerging disease with growing concern."
    supports: SUPPORT
    evidence_source: OTHER
    quote_role: REVIEW_SYNTHESIS
    snippet: >-
      The disease has an acute onset, with the occurrence of fever (38–40 °C),
      chills, fatigue, generalized myalgia, and headaches, resembling flu.
    explanation: Review synthesis places chills in the acute tularemia syndrome.
- name: Headache
  description: Headache accompanies the acute flu-like phase of tularemia.
  frequency: FREQUENT
  phenotype_term:
    preferred_term: Headache
    term:
      id: HP:0002315
      label: Headache
  evidence:
  - reference: PMID:37916743
    reference_title: "Tularemia - a re-emerging disease with growing concern."
    supports: SUPPORT
    evidence_source: OTHER
    quote_role: REVIEW_SYNTHESIS
    snippet: >-
      The disease has an acute onset, with the occurrence of fever (38–40 °C),
      chills, fatigue, generalized myalgia, and headaches, resembling flu.
    explanation: Review synthesis places headache in the acute tularemia syndrome.
- name: Myalgia
  description: Generalized myalgia accompanies the acute flu-like phase of tularemia.
  frequency: FREQUENT
  phenotype_term:
    preferred_term: Myalgia
    term:
      id: HP:0003326
      label: Myalgia
  evidence:
  - reference: PMID:37916743
    reference_title: "Tularemia - a re-emerging disease with growing concern."
    supports: SUPPORT
    evidence_source: OTHER
    quote_role: REVIEW_SYNTHESIS
    snippet: >-
      The disease has an acute onset, with the occurrence of fever (38–40 °C),
      chills, fatigue, generalized myalgia, and headaches, resembling flu.
    explanation: >-
      Review synthesis places generalized myalgia in the acute tularemia
      syndrome.
diagnosis:
- name: Tularemia Laboratory Diagnosis
  description: >-
    Tularemia diagnosis relies principally on serology, with PCR and culture
    used for direct pathogen detection when available and safe.
  diagnosis_term:
    preferred_term: laboratory procedure
    term:
      id: NCIT:C25294
      label: Laboratory Procedure
  evidence:
  - reference: PMID:20220165
    reference_title: Evaluation of an immunochromatographic test for rapid and reliable serodiagnosis of human tularemia and detection of Francisella tularensis-specific antibodies in sera from different mammalian species.
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      Serology is still considered to be a cornerstone in tularemia diagnosis
      due to the low sensitivity of bacterial culture and the lack of
      standardization in PCR methodology for the direct identification of the
      pathogen.
    explanation: >-
      Serodiagnostic test development summarizes why serology remains central
      while culture and PCR have sensitivity, biosafety, or standardization
      limitations.
treatments:
- name: Tularemia antibiotic therapy
  description: >-
    Aminoglycosides, fluoroquinolones, and tetracyclines are effective
    intracellularly active treatment classes for tularemia; streptomycin and
    gentamicin are historical treatments of choice, while ciprofloxacin and
    doxycycline are commonly used modern options.
  therapeutic_modality: SMALL_MOLECULE
  treatment_term:
    preferred_term: Pharmacotherapy
    term:
      id: NCIT:C15986
      label: Pharmacotherapy
    therapeutic_agent:
    - preferred_term: streptomycin
      term:
        id: CHEBI:17076
        label: streptomycin
    - preferred_term: gentamicin
      term:
        id: CHEBI:759884
        label: gentamicin
    - preferred_term: ciprofloxacin
      term:
        id: CHEBI:100241
        label: ciprofloxacin
    - preferred_term: doxycycline
      term:
        id: CHEBI:50845
        label: doxycycline
  target_mechanisms:
  - target: Macrophage Phagosomal Escape and Cytosolic Replication
    treatment_effect: INHIBITS
    description: >-
      Ciprofloxacin reduces the intracellular F. tularensis burden that drives
      pneumonic tularemia.
  evidence:
  - reference: PMID:38294108
    reference_title: >-
      Systematic Review: Clinical Features, Antimicrobial Treatment, and
      Outcomes of Human Tularemia, 1993-2023.
    supports: SUPPORT
    evidence_source: OTHER
    quote_role: REVIEW_SYNTHESIS
    snippet: >-
      For pneumonic disease specifically, ciprofloxacin may have slight
      advantages compared to other antimicrobials.
    explanation: >-
      Supports ciprofloxacin as a treatment option with review-level evidence
      specific to pneumonic tularemia.
  - reference: PMID:29183485
    reference_title: Bichat guidelines for the clinical management of tularaemia and bioterrorism-related tularaemia.
    supports: SUPPORT
    evidence_source: OTHER
    quote_role: REVIEW_SYNTHESIS
    snippet: >-
      Streptomycin and gentamicin are currently considered the treatment of
      choice for tularemia. Quinolone is an effective alternative drug.
    explanation: >-
      Bioterrorism-focused clinical guidance identifies aminoglycosides as the
      treatment of choice and quinolones as effective alternatives.
  - reference: PMID:42641375
    reference_title: "Tularemia: a re-emerging zoonosis."
    supports: SUPPORT
    evidence_source: OTHER
    quote_role: REVIEW_SYNTHESIS
    snippet: >-
      The 2025 CDC guidelines establish fluoroquinolones and doxycycline as
      first-line therapeutic options.
    explanation: >-
      The re-emergence review summarizes updated CDC guidance listing
      fluoroquinolones and doxycycline among first-line options.
epidemiology:
- name: Martha's Vineyard primary pneumonic outbreaks
  description: >-
    Primary pneumonic tularemia is rare in the United States, but Martha's
    Vineyard had recognized outbreaks in 1978 and 2000, and the 2000 outbreak
    case-control study implicated lawn mowing and brush cutting as
    aerosol-generating risk factors.
  evidence:
  - reference: PMID:11757506
    reference_title: An outbreak of primary pneumonic tularemia on Martha's Vineyard.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      The only previously reported outbreak of pneumonic tularemia in the
      United States also occurred on the island in 1978.
    explanation: >-
      Places the 2000 Martha's Vineyard outbreak in context as the second
      recognized U.S. outbreak of primary pneumonic tularemia.
- name: High-mortality pulmonary form
  description: >-
    Pneumonic tularemia has the highest mortality among tularemia clinical
    forms, with untreated tularemia carrying roughly 30% mortality in modern
    review summaries.
  evidence:
  - reference: PMID:38461051
    reference_title: Current vaccine strategies and novel approaches to combatting Francisella infection.
    supports: SUPPORT
    evidence_source: OTHER
    quote_role: REVIEW_SYNTHESIS
    snippet: >-
      Tularemia is caused by subspecies of Francisella tularensis and can
      manifest in a variety of disease states, with the pneumonic presentation
      resulting in the greatest mortality.
    explanation: >-
      The vaccine review identifies pneumonic tularemia as the highest-mortality
      disease state.
  - reference: PMID:42641375
    reference_title: "Tularemia: a re-emerging zoonosis."
    supports: SUPPORT
    evidence_source: OTHER
    quote_role: REVIEW_SYNTHESIS
    snippet: >-
      Tularemia is classified as a Category A bioterrorism agent by the CDC due
      to its extraordinary virulence; as few as 10 bacterial cells can establish
      infection, and untreated cases carry 30% mortality.
    explanation: >-
      Recent review synthesis ties Francisella's high virulence to the
      approximately 30% untreated mortality figure.
📚

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Pneumonic Tularemia — Comprehensive Disease Characteristics Report
openscientist-autonomous 44 citations 2026-09-29T16:11:19.498852

Pneumonic Tularemia — Comprehensive Disease Characteristics Report

Disease: Pneumonic Tularemia MONDO ID: MONDO:0002212 Category: Infectious Disease Causative agent: Francisella tularensis (Gram-negative facultative intracellular coccobacillus)

Summary

Pneumonic tularemia is the pulmonary and most lethal clinical form of tularemia, an acute zoonosis caused by the Gram-negative facultative intracellular bacterium Francisella tularensis. It arises either as primary pneumonic disease following inhalation of aerosolized organisms (e.g., landscaping activities, laboratory accidents, or a deliberate bioterrorism release) or as secondary pneumonic disease through hematogenous spread from other clinical forms. Among the classical clinical forms (ulceroglandular, glandular, oculoglandular, oropharyngeal, typhoidal, and pneumonic), the pneumonic presentation carries the greatest mortality, and it is the form of greatest bioterrorism concern because F. tularensis is one of the most infectious bacteria known — as few as ~10 organisms inhaled can initiate infection. The organism is a CDC Category A (Tier 1) select agent.

Mechanistically, disease follows a well-characterized intracellular pathway: the bacterium invades alveolar macrophages and dendritic cells, escapes the phagosome within hours via a Type VI secretion system encoded on the Francisella Pathogenicity Island (FPI), and replicates in the cytosol. Virulent type A strains actively subvert early innate immunity through an atypical, under-acylated lipid A that evades TLR4 recognition. Once in the cytosol, bacterial DNA — liberated by interferon-inducible guanylate-binding proteins (GBPs) and IRGB10 — is sensed by the AIM2 inflammasome, driving caspase-1 activation, IL-1β/IL-18 secretion, and pyroptosis. Protective adaptive immunity is Th1-polarized and depends on IFN-γ, TNF-α, iNOS, and CD4⁺ T cells (T-bet).

Clinically, untreated pneumonic tularemia carries roughly 30% mortality, but prompt antibiotic therapy reduces case-fatality to below ~2%. Aminoglycosides (streptomycin, gentamicin) are the historical treatment of choice; fluoroquinolones (ciprofloxacin) and doxycycline are effective alternatives, and the 2025 CDC guidelines list fluoroquinolones and doxycycline as first-line options. Diagnosis relies chiefly on serology (microagglutination) and PCR because culture is insensitive and biohazardous. No licensed human vaccine exists. Tularemia is re-emerging across Europe and North America (2024–2025), reinforcing the need for clinical awareness, rapid diagnostics, and preventive measures.

Section 1 — Disease Information

Overview. Pneumonic (respiratory) tularemia is the lung-centered manifestation of infection by Francisella tularensis. It presents with fever, cough, dyspnea, pleuritic chest pain, and radiographic infiltrates, often with hilar lymphadenopathy and pleural effusion. Primary pneumonic disease results from inhalation of infectious aerosols; secondary pneumonic disease develops when bacteria seed the lungs from bloodstream dissemination of ulceroglandular, typhoidal, or other forms.

Key identifiers: - MONDO: MONDO:0002212 (tularemia; pneumonic subtype) - MeSH: Tularemia (D014406); "Tularemia, Pulmonary" as a subheading concept - ICD-10: A21.2 (pulmonary tularemia); A21.9 (tularemia, unspecified) - ICD-11: 1B94 (Tularaemia) - SNOMED CT: Pulmonary tularemia (disorder) - Orphanet: Tularemia is catalogued as a rare bacterial infectious disease (ORPHA:855 for the parent entity) - NCBI Taxonomy (pathogen): Francisella tularensis — txid263

Synonyms / alternative names: Pulmonary tularemia; respiratory tularemia; pneumonic form of tularemia; "rabbit fever" (lung form); "deer-fly fever" (lung form); Ohara disease / Francis disease (historical, whole-disease synonyms).

Data source type: Information is derived from aggregated disease-level resources — clinical case series, outbreak investigations, systematic reviews, and experimental animal/in vitro studies — rather than from individual EHR-derived patient records. A 2024 systematic review aggregated 870 cases spanning 1993–2023.

Section 2 — Etiology

Primary cause (infectious). Pneumonic tularemia is caused entirely by infection with Francisella tularensis; it is not a genetic disease. Human infection is initiated by inhalation of aerosolized bacteria. F. tularensis is among the most infectious bacteria known — inoculation or inhalation of as few as 10 organisms initiates infection (Finding F002; PMID: 38294108; PMID: 29183485).

"requires as few as 10 organisms to cause disease, making this potential bioterrorism agent one of the most infectious bacterial pathogens known" — PMID: 38294108

Environmental / occupational risk factors: - Aerosol-generating landscaping activities — lawn mowing and brush cutting were significant risk factors in the Martha's Vineyard primary pneumonic outbreak (odds ratio 9.2, 95% CI 1.6–68.0) (Finding F008; PMID: 11757506). - Occupational exposure — laboratory workers, landscapers, farmers, hunters, and those handling infected animals (rabbits, hares, rodents). - Arthropod vectors — ticks (Dermacentor, Amblyomma), deer flies, mosquitoes (predominant in Scandinavia) — though these more commonly cause ulceroglandular disease. - Animal contact — lagomorphs, rodents, and domestic cats/dogs. Dog-related exposures accounted for 3.3% of U.S. cases, of which 13% were pneumonic (PMID: 30556330). - Deliberate aerosol release — the pneumonic form is the most likely presentation after intentional release (PMID: 29183485). - Sex/age — systemic disease occurs more commonly in older patients (PMID: 22911645).

Genetic risk / protective factors: No human germline susceptibility or protective variants are established for tularemia; this is an environmentally/infectiously acquired disease. Host-genetic determinants of severity are described almost exclusively in mouse models (e.g., inflammasome genes Aim2, Nlrp3), not in humans. Gene-environment interactions in the classical human-disease sense are therefore not applicable; the relevant "gene–environment" axis is the interaction between host innate-immune genes and the inhaled bacterial dose/strain virulence (see Section 6).

Section 3 — Phenotypes

Pneumonic tularemia is an acute, adult-predominant (though all ages affected) febrile respiratory illness with an incubation period typically of 3–5 days (range 1–14 days).

Phenotype Type HPO suggestion Frequency / notes
Fever Symptom/sign HP:0001945 (Fever) Near-universal; abrupt onset
Cough (often nonproductive) Symptom HP:0012735 (Cough) Common
Dyspnea Symptom HP:0002094 (Dyspnea) Common in severe disease
Pleuritic chest pain Symptom HP:0033771 (Pleuritic chest pain) Frequent
Pneumonia / pulmonary infiltrate Clinical sign / imaging HP:0002090 (Pneumonia) Defining feature
Pleural effusion Clinical sign HP:0002202 (Pleural effusion) Common; may require drainage
Hilar lymphadenopathy Clinical sign HP:0100721 (Hilar lymphadenopathy) Characteristic radiographic finding
Chills / rigors Symptom HP:0025143 (Chills) Common
Malaise / fatigue Symptom HP:0003394 / HP:0012378 Common
Headache Symptom HP:0002315 (Headache) Frequent
Myalgia Symptom HP:0003326 (Myalgia) Frequent
Cavitary pneumonia / empyema Complication HP:0006528 / HP:0002101 Reported; e.g., pulmonary empyema cases (PMID: 24655540)
Elevated inflammatory markers (ESR, CRP) Lab abnormality HP:0003565 (Elevated ESR) Common

Characteristics: - Age of onset: Any age; primarily adult in occupational/aerosol settings. - Severity: Moderate to severe; pneumonic form is the most severe clinical presentation (Finding F001). - Progression: Acute and potentially rapidly progressive; can advance to respiratory failure, sepsis, and multi-organ involvement if untreated. - Frequency among affected individuals: In U.S. case series, pneumonic disease constituted ~12% of all tularemia cases (PMID: 22911645); in dedicated aerosol outbreaks it predominates (11 of 15 cases primary pneumonic on Martha's Vineyard; PMID: 11757506).

Quality-of-life impact: As an acute, treatable infection, long-term QoL burden is limited in survivors treated promptly; however, delayed treatment can result in prolonged convalescence, pleural complications requiring intervention, and, rarely, death. No disease-specific EQ-5D/SF-36 datasets exist for pneumonic tularemia.

Section 4 — Genetic / Molecular Information

Not applicable in the human-host genetic sense. Pneumonic tularemia is an infectious disease with no causal human genes, pathogenic germline variants, modifier genes, human epigenetic signatures, or chromosomal abnormalities. There is no OMIM Mendelian entry, no ClinVar variant set, and no inheritance pattern.

The relevant molecular determinants are bacterial: - Francisella Pathogenicity Island (FPI): a ~16–19 gene cluster including the iglABCD operon encoding a Type VI secretion system (T6SS) required for phagosomal escape and intramacrophage growth; FPI mutants are highly attenuated (Finding F003; PMID: 17395722, PMID: 17233889). - Regulators: mglA/mglB control FPI expression. - Effector opiA (a bacterial PI3-kinase) modifies phagosomal PI(3)P to promote escape (PMID: 30057173). - LPS/lipid A biosynthesis genes (lpxD1/lpxD2, galU) shape immune evasion (PMID: 28478203, PMID: 21819572).

Host modifier genes (model-organism level): In mice, Aim2, Nlrp3, Tbx21 (T-bet), Ifng, Tnf, and Nos2 modify susceptibility/severity (Sections 5–6).

Section 5 — Environmental Information

Infectious agent (taxon): Francisella tularensis, NCBI Taxon 263. Two clinically important subspecies: - subsp. tularensis (Type A) — North America; highly virulent. Subdivided into type A-west and the more severe type A-east (Finding F009; PMID: 16836829). - subsp. holarctica (Type B) — Holarctic (Europe, Asia, North America); less virulent, rarely fatal.

"type A-west infections are less severe than either type B or type A-east infections" — PMID: 16836829

Environmental persistence: F. tularensis Type A survives in brackish water and salt-influenced soil similarly to Type B, which may explain why Martha's Vineyard sustains pneumonic transmission (PMID: 21136042). Diverse Francisella species are detectable in environmental water/sediment/soil at active foci (PMID: 19669828).

Environmental / lifestyle factors: Aerosol-generating outdoor work (mowing, brush cutting), hunting/skinning lagomorphs, farming, and laboratory handling. Waterborne outbreaks (contaminated drinking water) are common in Turkey and drive oropharyngeal rather than pneumonic disease (PMID: 42343287). No specific dietary or smoking association is established for the pneumonic form.

Section 6 — Mechanism / Pathophysiology

Ordered causal chain (inhalation → clinical pneumonia)

  1. Inhalation of aerosolized F. tularensis (≥ ~10 organisms) deposits bacteria in the alveolar space → leads to uptake by alveolar macrophages and dendritic cells (and alveolar epithelial cells).
  2. Bacterial invasion of macrophages/DCs → results in formation of the Francisella-containing phagosome (FCP).
  3. FPI/Type VI secretion system activity (IglABCD; effector OpiA remodels phagosomal PI(3)P) → causes disruption of the phagosomal membrane and phagosomal escape within a few hours (demonstrated in vitro and in macrophages) (PMID: 32694562, PMID: 30057173).
  4. Cytosolic replication → leads to high intracellular bacterial burdens.
  5. In parallel, atypical tetra-acylated lipid A on the bacterial surface precludes efficient TLR4 recognition and cationic antimicrobial peptide binding → results in blunted/delayed early innate signaling (chemokines, neutrophil recruitment) — an active immune-evasion branch (demonstrated: prior type A aerosol exposure antagonizes pulmonary LPS response; galU mutant reverses this) (PMID: 28807561, PMID: 26510639, PMID: 21819572).
  6. Cytosolic bacterial DNA is liberated by interferon-inducible GBP2/GBP5 and IRGB10, which attack the bacterial membrane causing bacteriolysis → leads to DNA release (PMID: 25774716, PMID: 27693356).
  7. AIM2 inflammasome senses cytosolic DNA → activates caspase-1 → drives processing/secretion of IL-1β and IL-18 and pyroptosis (demonstrated for F. novicida/LVS) (PMID: 21883803).
  8. Branch: An ASC-dependent, caspase-1-independent (caspase-8) pathway also generates IL-18, boosting NK-cell IFN-γ (PMID: 23975862).
  9. IL-18 + IL-12 → NK/T-cell IFN-γ; with TNF-α these activate iNOS (NOS2) in macrophages → results in nitric-oxide-mediated bacterial killing (demonstrated in LVS aerosol model) (PMID: 19237526).
  10. Th1 adaptive response (T-bet–dependent CD4⁺ T cells, plus antibody including IgA) → mediates control and clearance; loss of T-bet or CD4⁺ T cells → results in overwhelming infection (PMID: 24421047, PMID: 19211773).
  11. Net effect on tissue: If bacterial replication outpaces innate/adaptive control → widespread pyroptotic cell death, inflammatory infiltration, necrotizing pneumonia, pleural effusion, bacteremic dissemination → clinical pneumonic tularemia, potentially sepsis and death.

Detail by category

  • Molecular pathways: cytosolic DNA sensing → AIM2/ASC/caspase-1; TLR4/MyD88 (subverted by lipid A); interferon (type I & II)-inducible GBP/IRGB10 antibacterial program; iNOS/NO production.
  • Cellular processes: phagocytosis, phagosomal escape, intracellular replication, pyroptosis (GO:0070269), inflammasome assembly, inflammation (GO:0006954), autophagy/xenophagy (ATG5 modulates immunity, PMID: 42514097).
  • Protein dysfunction (bacterial virulence): T6SS effector delivery; PI3-kinase effector OpiA alters phosphoinositide signaling.
  • Immune involvement: Th1/IFN-γ-dominant protective immunity; excessive early NLRP3 signaling can be host-detrimental (PMID: 34690967); antibody (IgG2a, IgA) contributes but requires host IFN-γ/T cells to protect (PMID: 8039881).
  • Metabolic: macrophage selenoproteins restrict intracellular replication (PMID: 34777335); acidic-pH lipid A remodeling (PMID: 28807561).
  • Tissue damage mechanisms: necrotizing granulomatous inflammation, pyroptotic cell death, neutrophil-mediated injury, pleural inflammation.

GO term suggestions: GO:0070269 (pyroptosis), GO:0006954 (inflammatory response), GO:0032731 (positive regulation of IL-1β production), GO:0045087 (innate immune response), GO:0042742 (defense response to bacterium), GO:0071222 (cellular response to LPS). CL term suggestions: CL:0000235 (macrophage), CL:0000583 (alveolar macrophage), CL:0000451 (dendritic cell), CL:0000623 (natural killer cell), CL:0000624 (CD4⁺ T cell), CL:0000775 (neutrophil).

Section 7 — Anatomical Structures Affected

Organ level: - Primary: Lung (UBERON:0002048), including alveoli (UBERON:0002299) and bronchi. - Secondary: Pleura/pleural cavity (UBERON:0002402) — effusion/empyema; hilar/mediastinal lymph nodes (UBERON:0002509); with dissemination: spleen (UBERON:0002106), liver (UBERON:0002107), bone marrow, and rarely heart (myocarditis reported, PMID: 30656604). - Body systems: Respiratory system (primary); reticuloendothelial/lymphatic system; potentially cardiovascular (sepsis, rare myocarditis).

Tissue and cell level: - Alveolar epithelium; pulmonary interstitium. - Target cells: alveolar macrophages (CL:0000583), dendritic cells (CL:0000451), and other mononuclear phagocytes are the principal intracellular niche; neutrophils recruited to lung.

Subcellular level (GO Cellular Component): - Phagosome (GO:0045335) → Francisella-containing vacuole; escape into cytosol/cytoplasm (GO:0005829) — the replicative compartment. AIM2 inflammasome assembles in the cytosol.

Localization / lateralization: Bilateral or unilateral patchy infiltrates; pleural effusions may be unilateral. Hilar adenopathy commonly bilateral.

Section 8 — Temporal Development

  • Onset: Acute, after an incubation of 3–5 days (range 1–14). Median incubation ~3 days in Missouri case review (PMID: 22911645).
  • Progression: Rapid systemic febrile illness; can progress to respiratory failure and sepsis within days if untreated. Not staged like cancer; described as early (febrile, cough) → established pneumonia (infiltrates, effusion) → severe/complicated (empyema, respiratory failure, bacteremia).
  • Course pattern: Acute, monophasic; self-limited only rarely — most severe cases require antibiotics. With treatment, recovery is the rule; convalescence over 1–4 weeks.
  • Duration: Days to weeks (acute); not a chronic lifelong disease.
  • Remission: Treatment-induced resolution is standard with appropriate antibiotics. Relapse can occur with bacteriostatic agents (tetracyclines) or short courses.
  • Critical periods: Early antibiotic initiation is the key intervention window; delayed therapy increases complication and mortality risk (PMID: 42601640, PMID: 22652404).

Section 9 — Inheritance and Population

Inheritance: Not applicable — infectious, non-heritable.

Epidemiology: - Tularemia is a rare, reportable zoonosis. The pneumonic form is a minority of cases except in aerosol outbreaks. - Geographic distribution: Northern hemisphere — North America (esp. south-central USA: Arkansas, Missouri, Oklahoma; and Martha's Vineyard for pneumonic), Scandinavia, Central/Eastern Europe, Turkey, Russia, Japan. - Re-emergence (2024–2025): rising incidence — Austria 117, Slovenia 38, France 150, Spain/Castile-León 206, and United States 220 cases in 2024 (Finding F012; PMID: 42641375). Germany reached a peak incidence in 2024 (PMID: 42601640). - Primary pneumonic tularemia is exceptionally rare — Martha's Vineyard is the site of the only two recognized U.S. primary pneumonic outbreaks (1978, 2000) (Finding F008; PMID: 17442781).

"Martha's Vineyard, Massachusetts, is the site of the only two recognized outbreaks of primary pneumonic tularemia in the United States" — PMID: 17442781

Demographics: - Sex ratio: Male predominance in many series (e.g., 65% male in Missouri, PMID: 22911645), reflecting occupational/recreational exposure; varies by outbreak. - Age: All ages; systemic/severe disease more common in older adults. - Population-specific variants: Type A (North America) vs. Type B (Eurasia) geographic segregation; type A-east most virulent.

Section 10 — Diagnostics

Serology (cornerstone): - Microagglutination test (MAT): titer ≥ 1/160 considered positive; seroconversion (≥4-fold rise) in paired sera is confirmatory (Finding F006; PMID: 22090310). Antibodies may take 2+ weeks to develop, limiting early diagnosis. - Serology is preferred because culture has low sensitivity and biosafety risk, and PCR lacks standardization (PMID: 20220165).

"Serology is still considered to be a cornerstone in tularemia diagnosis due to the low sensitivity of bacterial culture and the lack of standardization in PCR methodology" — PMID: 20220165

  • Rapid immunochromatographic test: 98.3% sensitivity, 96.5% specificity vs. MAT (PMID: 20220165).

Molecular (PCR): - Validated targets: ISFtu2 insertion element, tul4 (17-kDa), fopA (43-kDa), 23-kDa gene (PMID: 14662930). Multitarget real-time TaqMan assays improve detection in complex specimens. - PCR positive in ~91% of lymph node aspirates where cultures were negative (Finding F006).

Culture: Requires cysteine-enriched media; slow-growing; must be handled at BSL-3 due to aerosol infection risk. Low clinical sensitivity.

Imaging: Chest X-ray/CT show patchy infiltrates, hilar/mediastinal lymphadenopathy, pleural effusion, and occasionally cavitation (PMID: 24655540).

Laboratory: Nonspecific — elevated ESR/CRP; leukocytosis variable (more frequent in pediatric cases, PMID: 42343287).

Clinical criteria / differential diagnosis: Consider in patients with pneumonia unresponsive to β-lactams plus relevant exposure (landscaping, animal/tick contact, endemic area). Differential: community-acquired bacterial pneumonia, Q fever, psittacosis, plague, anthrax, Legionella, tuberculosis, fungal pneumonia. Tularemia is frequently initially misdiagnosed (PMID: 22911645).

Screening: No population screening; genetic/omics diagnostics not applicable.

Section 11 — Outcome / Prognosis

  • Untreated mortality: ~30% (Finding F012; PMID: 42641375); pneumonic form has the highest mortality of all clinical forms (Finding F001; PMID: 38461051).

"with the pneumonic presentation resulting in the greatest mortality" — PMID: 38461051

  • Treated case-fatality (all forms, 870-case systematic review): 0.7% (aminoglycosides), 0.9% (fluoroquinolones), 1.2% (tetracyclines) — overall low with prompt therapy (Finding F004; PMID: 38294108).
  • Complications: pleural effusion/empyema (may require drainage), cavitary pneumonia, respiratory failure, bacteremia/sepsis, rare myocarditis, necrotizing abscess formation.
  • Recovery: Excellent with early appropriate antibiotics; full recovery is typical. Prognosis worsens with delayed diagnosis, older age, type A-east strain, and high inhaled dose.
  • Prognostic factors: speed of antibiotic initiation, subspecies/strain (type A-east worst), inoculum size, host age/comorbidity.
Treatment class Case-fatality (all forms) Notes
Aminoglycosides (streptomycin, gentamicin) 0.7% Treatment of choice historically
Fluoroquinolones (ciprofloxacin) 0.9% No fatalities & lowest pleural intervention in pneumonic subset
Tetracyclines (doxycycline) 1.2% Bacteriostatic; higher relapse

Section 12 — Treatment

Pharmacotherapy (NCIT term suggestions in parentheses): - Aminoglycosides — streptomycin (NCIT:C839), gentamicin (NCIT:C575): historical treatment of choice; bactericidal (Finding F004; PMID: 29183485).

"Streptomycin and gentamicin are currently considered the treatment of choice for tularemia. Quinolone is an effective alternative drug." — PMID: 29183485

  • Fluoroquinolones — ciprofloxacin (NCIT:C405): effective oral alternative; in the 870-case review, pneumonic patients on ciprofloxacin had no fatalities and the lowest rates of pleural intervention. Oral ciprofloxacin successfully treated cavitary pneumonic disease after drainage (PMID: 24655540).
  • Tetracyclines — doxycycline (NCIT:C692): bacteriostatic; requires ≥14–21 day courses; higher relapse.
  • 2025 CDC guidelines now establish fluoroquinolones and doxycycline as first-line options (Finding F012; PMID: 42641375).

"The 2025 CDC guidelines establish fluoroquinolones and doxycycline as first-line therapeutic options" — PMID: 42641375

Post-exposure prophylaxis: streptomycin, gentamicin, doxycycline, or ciprofloxacin (PMID: 29183485).

Interventional/supportive: Pleural drainage for empyema/large effusion; oxygen/ventilatory support in respiratory failure; hydration and antipyretics. No patient isolation required for pneumonic tularemia (no person-to-person transmission) (PMID: 29183485).

Experimental/adjunctive: Post-exposure immunization with F. tularensis membrane protein fraction (MPF) augmented gentamicin efficacy (100% survival in a mouse pneumonic model) — proof of concept for immunotherapy adjuncts (PMID: 22652404).

Pharmacogenomics / targeted / gene / cell / RNA therapies: Not applicable.

Section 13 — Prevention

  • Primary prevention: Avoid aerosol-generating activities in endemic areas; use of masks/PPE during mowing/brush-cutting; safe handling of animal carcasses; tick/insect avoidance and repellents; laboratory biosafety (BSL-3 for cultures). Vector control and public health education.
  • Immunization: No licensed human vaccine (Finding F007; PMID: 38461051).

"there are no approved vaccines against F. tularensis in the United States" — PMID: 38461051

  • The unlicensed Live Vaccine Strain (LVS) protects mice against lethal intranasal/aerosol SCHU S4 challenge (CD4⁺ T-cell– and antibody/IgA-mediated) (PMID: 19211773).
  • Subunit/glycoconjugate candidates: glucan-particle LPS + FTT0814 subunit vaccine (partial protection, T-cell immunity in a rat aerosol model, PMID: 38713688); O-antigen glycoconjugate (PMID: 30872471); MPL-adjuvanted catanionic nanoparticle vaccine (PMID: 28077440). All remain experimental.
  • Secondary prevention: Prompt recognition and post-exposure prophylaxis after known aerosol exposure or lab accident.
  • Public health: Surveillance and reporting (nationally notifiable), water chlorination (for waterborne foci), rodent/lagomorph control.

Section 14 — Other Species / Natural Disease

  • Taxonomy of hosts (naturally infected): Lagomorphs — rabbits/hares (Sylvilagus, Lepus); rodents (voles, mice, muskrats, beavers); domestic cats (Felis catus, NCBI:9685) and dogs (Canis lupus familiaris, NCBI:9615). Ticks and deer flies are vectors/reservoirs.
  • Natural disease & veterinary relevance: Tularemia is an important zoonosis; cats can transmit to humans via bite/scratch (PMID: 30556330); domestic dogs facilitate transmission via retrieved carcasses and ticks. Lagomorphs suffer high mortality (epizootics).
  • Comparative pathology: Intracellular macrophage infection and phagosomal escape are conserved across mammalian hosts; mouse pathology closely mirrors human intracellular pathogenesis.
  • Zoonotic potential: High — a prototypical zoonosis. No human-to-human transmission, so pneumonic cases need no isolation.
  • Cross-species susceptibility: Broad mammalian host range; extreme susceptibility in mice and lagomorphs.

Section 15 — Model Organisms

  • Mouse (Mus musculus, NCBI:10090) — principal model. Intranasal/aerosol challenge with SCHU S4 (type A) or attenuated LVS; BALB/c and C57BL/6 strains widely used. Recapitulates pneumonic pathogenesis, intracellular replication, inflammasome activation, Th1 immunity, and treatment/vaccine responses (Findings F003, F005, F007, F010, F011).
  • Knockout models: Aim2⁻/⁻, Nlrp3⁻/⁻, Asc⁻/⁻, Casp1⁻/⁻, Tbx21⁻/⁻ (T-bet), Ifng⁻/⁻, Nos2⁻/⁻ — dissect inflammasome and Th1 pathways (PMID: 24421047, PMID: 21883803, PMID: 33875472, PMID: 34690967).
  • Rat (Rattus norvegicus, NCBI:10116): Fischer 344 inhalation model used for vaccine efficacy testing (PMID: 38713688).
  • In vitro / cellular: Bone-marrow-derived and cell-line macrophages (J774) to study phagosomal escape, cytosolic replication, and inflammasome activation (PMID: 32694562, PMID: 29482417).
  • F. novicida and F. tularensis LVS serve as reduced-biosafety surrogates for the virulent SCHU S4 strain.
  • Model limitations: F. novicida is attenuated in humans but hypervirulent in mice; LVS is attenuated relative to SCHU S4; mouse inflammasome biology and lipid A responses differ somewhat from humans, so protective correlates do not always translate (PMID: 41410566).

Mechanistic Model / Interpretation

 Inhaled F. tularensis (~10 organisms, type A)
      |
      v
   Alveolar macrophage / DC uptake ---> Francisella-containing phagosome
      |                                   |
      |  FPI / T6SS (IglABCD),            |  Atypical tetra-acylated
      |  effector OpiA (PI3K)             |  lipid A --> evades TLR4
      v                                   v  (blunted early innate signal)
     PHAGOSOMAL ESCAPE (hours) ----------> CYTOSOLIC REPLICATION
      |
      v
   GBP2/GBP5 + IRGB10 attack bacteria --> bacteriolysis --> DNA release
      |
      v
AIM2 inflammasome --> caspase-1 --> IL-1b / IL-18 + PYROPTOSIS
      |                                   |
      |  (ASC/caspase-8 branch also        |
      |   makes IL-18, caspase-1-indep.)   v
      v                          NK/T cells --> IFN-gamma
   IFN-gamma + TNF-a --> iNOS/NO in macrophages --> bacterial killing
      |
      v
   T-bet+ CD4+ Th1 cells + antibody (IgG2a, IgA) --> CLEARANCE
      |
   (If replication outpaces control) --> necrotizing pneumonia,
pleural effusion, bacteremia, sepsis --> CLINICAL PNEUMONIC TULAREMIA

Upstream vs downstream: Bacterial invasion, phagosomal escape, and lipid-A-mediated TLR4 evasion are the upstream drivers that permit unchecked cytosolic replication. The AIM2 inflammasome, GBP/IRGB10 bacteriolysis, IFN-γ/iNOS, and Th1/CD4⁺ responses are downstream host-protective mechanisms; when they are outpaced (high dose, virulent type A-east, delayed antibiotics), tissue injury and death follow. This model integrates 12 confirmed findings and is consistent across in vitro, mouse, rat, and human clinical/outbreak data.

Evidence Base

PMID Title (abbrev.) Supports finding Contribution
38461051 Vaccine strategies vs Francisella F001, F007 Pneumonic = greatest mortality; no approved vaccine
38294108 Systematic review 1993–2023 F002, F004 ~10-organism dose; comparative fatality by drug class
29183485 Bichat guidelines F001, F002, F004 Pneumonic = bioterrorism form; aminoglycoside first-line
32694562 Immune lymphocytes halt LVS F003 Phagosomal escape & cytosolic replication
17395722 Francisella Pathogenicity Island F003 FPI encodes T6SS
30057173 PI3K effector OpiA F003 Effector promotes phagosomal escape
19237526 Immune-mouse T cells F005 IFN-γ/TNF-α/iNOS dependence
19211773 Oral LVS protection F005, F007 CD4⁺ T cells/IgA mediate pulmonary protection
24421047 T-bet & lung immunity F005 T-bet critical for pulmonary immunity
20220165 Immunochromatographic test F006 Serology cornerstone; rapid test performance
22090310 Central Anatolia cases F006 MAT ≥1/160 threshold
14662930 Multitarget TaqMan PCR F006 Validated PCR gene targets
11757506 Martha's Vineyard outbreak F008 Landscaping OR 9.2 risk factor
17442781 Martha's Vineyard review F008 Only 2 US primary pneumonic outbreaks
16836829 US molecular epidemiology F009 Type A-east most severe
28807561 Lipid A remodeling F010 Atypical lipid A evades TLR4
26510639 Type A antagonizes TLR4 response F010 Active innate-immune suppression
21819572 galU mutant F010 WT FT suppresses early innate immunity
21883803 AIM2 & bacteriolysis F011 AIM2→caspase-1/IL-1β/IL-18/pyroptosis
25774716 GBP2/GBP5 & AIM2 F011 GBPs liberate DNA for AIM2
27693356 IRGB10 F011 IRGB10 liberates bacterial ligands
23975862 ASC/caspase-8 IL-18 F011 Caspase-1-independent IL-18/IFN-γ branch
42641375 Re-emerging zoonosis F012 30% untreated mortality; 2025 CDC first-line

Challenging/nuancing evidence: Aim2/Nlrp3 are dispensable for vaccine-induced adaptive immunity (PMID: 33875472), and NLRP3 can increase host susceptibility (PMID: 34690967) — indicating inflammasome roles are context-dependent (innate control vs. immunopathology).

Limitations and Knowledge Gaps

  1. Mechanistic data are largely from mouse/in vitro models using LVS or F. novicida surrogates, not virulent human type A SCHU S4 in humans. Translation to human pneumonic disease is inferred.
  2. Human pneumonic-specific datasets are sparse — most clinical series pool all tularemia forms; dedicated primary pneumonic cohorts are limited to rare outbreaks (Martha's Vineyard).
  3. No human transcriptomic/proteomic/metabolomic profiling of pneumonic tularemia patients was identified; omics diagnostics are not applicable/available.
  4. Correlates of protection remain undefined, hampering vaccine licensure; no licensed human vaccine exists.
  5. Fatality figures for antibiotics derive from all-form pooled reviews; pneumonic-only comparative RCTs are lacking (ethically/logistically constrained).
  6. Strain-virulence determinants (why type A-east > type B > type A-west) are incompletely mapped at the molecular level.
  7. PMID 42641375 provides key re-emergence and 2025-guideline figures but is a single review source; primary CDC guideline documents should be cross-checked.

Proposed Follow-up Experiments / Actions

  1. Human correlates-of-protection study in vaccinated (LVS-exposed lab personnel) or convalescent cohorts — define antibody/T-cell signatures predicting protection to guide vaccine endpoints.
  2. Primary CDC 2025 guideline verification — obtain and cite the definitive CDC/clinical-guideline document for first-line fluoroquinolone/doxycycline recommendations rather than relying on a review.
  3. Comparative-effectiveness analysis of ciprofloxacin vs. gentamicin specifically in pneumonic cases, leveraging pooled outbreak registries, to formalize the observed lower pleural-intervention rate.
  4. Host single-cell transcriptomics of infected lung (mouse aerosol SCHU S4) to resolve alveolar-macrophage vs. DC vs. neutrophil trajectories and map AIM2/IFN-γ programs spatially.
  5. Molecular dissection of type A-east virulence via comparative genomics/transposon screens to identify determinants of the severity gradient (type A-east > type B > type A-west).
  6. Advance the glucan-particle/glycoconjugate subunit vaccines toward dose-optimized aerosol-challenge efficacy and, ultimately, human immunogenicity trials.
  7. Adjunct immunotherapy translation — evaluate membrane-protein-fraction post-exposure immunization plus antibiotics (PMID: 22652404) in higher-order models toward a therapeutic-adjunct strategy.

Report compiled from 12 confirmed findings and ~60 reviewed papers across 5 investigative iterations. Evidence source types span human clinical/outbreak studies, mouse and rat model-organism experiments, and in vitro cellular assays, as annotated throughout.

Artifacts

Reference Validation

Checked with linkml-reference-validator 0.3.0rc3.

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References checked 44
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Quoted claims checked 8
Quoted claims found in source 8
Quoted claims not found in source 0
References weighed for topical relevance 44
On topic 31
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 45
Resolved 40
Unresolved (possible confabulation) 0
Obsolete 0
Unverifiable 5
Terms whose name was checked 30
Terms named correctly 18
Terms named as a different term 5
Terms whose name is worth a second look 7

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:

  • MONDO:0002212 (3 mentions) - the report calls it "if available", "tularemia; pneumonic subtype"; MONDO calls it pneumonic tularemia
  • GO:0070269 (2 mentions) - the report calls it "pyroptosis", "Cellular processes: phagocytosis, phagosomal escape, intracellular replication, pyroptosis"; GO calls it pyroptotic inflammatory response
  • NCIT:C839 (1 mention) - the report calls it "Aminoglycosides — streptomycin"; NCIT calls it Spiramycin
  • NCIT:C405 (1 mention) - the report calls it "Fluoroquinolones — ciprofloxacin"; NCIT calls it Cyclophosphamide
  • NCIT:C692 (1 mention) - the report calls it "Tetracyclines — doxycycline"; NCIT calls it Nimodipine

Terms whose name is worth a second look

The report's name for these is recognisably related to the term's own name without being one of them. A loose paraphrase reads the same way as a citation of the wrong sibling term - and so does a related synonym, which the ontology records precisely because it names something adjacent rather than the same thing - so these are listed rather than judged:

  • HP:0100721 (1 mention) - the report calls it "Hilar lymphadenopathy"; HP calls it Mediastinal lymphadenopathy
  • GO:0032731 (1 mention) - the report calls it "positive regulation of IL-1β production"; GO calls it positive regulation of interleukin-1 beta production, and lists "positive regulation of IL-1 beta production" among its other names
  • CL:0000583 (2 mentions) - the report calls it "alveolar macrophage", "Target cells: alveolar macrophages"; CL calls it alveolar macrophage**
  • CL:0000624 (1 mention) - the report calls it "CD4⁺ T cell"; CL calls it CD4-positive, alpha-beta T cell
  • UBERON:0002048 (1 mention) - the report calls it "Primary: Lung"; UBERON calls it lung**
  • UBERON:0002402 (1 mention) - the report calls it "Secondary: Pleura/pleural cavity"; UBERON calls it pleural cavity**
  • GO:0045335 (1 mention) - the report calls it "Phagosome"; GO calls it phagocytic vesicle, and lists "phagosome" among its other names

Terms named inconsistently

The report gives these identifiers more than one name of its own:

  • MONDO:0002212 - called "if available", "tularemia; pneumonic subtype"
  • GO:0070269 - called "pyroptosis", "Cellular processes: phagocytosis, phagosomal escape, intracellular replication, pyroptosis"
  • CL:0000583 - called "alveolar macrophage", "Target cells:** alveolar macrophages"

Prefixes with no resolver

Terms carrying these prefixes were not checked either way, because no configured ontology covers them. An unrecognised prefix may name an ontology this run could not reach as easily as one that does not exist, so nothing here is evidence of fabrication: ORPHA, NCBI.