Psittacosis

Infectious Disease MONDO:0005888 Pathograph 4 Show in embeddings browser Bacterial Respiratory Infection

Psittacosis (ornithosis, "parrot fever") is a zoonotic respiratory infection caused by Chlamydia (Chlamydophila) psittaci, an obligate intracellular bacterium transmitted to humans from birds (pet birds and poultry). After inhalation, the organism replicates intracellularly and produces an atypical pneumonia that is the predominant clinical presentation; severe cases can progress to acute respiratory distress syndrome and multi-organ dysfunction. Because the organism is intracellular, treatment requires a cell-penetrant antibiotic — tetracyclines (doxycycline) are first-line, with macrolides or fluoroquinolones as alternatives; beta-lactams are ineffective.

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3
Pathophys.
4
Phenotypes
4
Pathograph
1
Medical Actions
1
Datasets
⚙

Pathophysiology

3
Inhalation and Obligate Intracellular Chlamydial Infection
Psittacosis follows inhalation of aerosols from infected birds. Chlamydia psittaci is an obligate intracellular bacterium that replicates within host cells, an intracellular lifestyle that underlies the requirement for cell-penetrant antibiotics, because beta-lactams cannot reach the intracellular organism.
respiratory epithelial cell CL:0002632 Cell Ontology (CL) Relation: this pathophysiological event involves this cell type This pathophysiological event involves respiratory epithelial cell, annotated with epithelial cell of lower respiratory tract (CL:0002632). CL:0002632 is a cell type from the Cell Ontology.
symbiont entry into host cell GO:0046718 Gene Ontology (GO) Relation: this pathophysiological event involves this biological process This pathophysiological event involves symbiont entry into host cell (GO:0046718). GO:0046718 is a biological process from the Gene Ontology. biological process involved in interaction with host GO:0051701 Gene Ontology (GO) Relation: this pathophysiological event involves this biological process This pathophysiological event involves biological process involved in interaction with host (GO:0051701). GO:0051701 is a biological process from the Gene Ontology.
Downstream
Atypical Pneumonia and Systemic Illness Intracellular replication produces an atypical pneumonia that can become severe and multisystem.
Chlamydial Ribosomal Translation (Tetracycline Target) The organism's ribosome is the molecular target of tetracycline therapy.
Show evidence (2 references)
PMID:15895932 SUPPORT Other
"Chlamydia are obligate intracellular bacteria."
Establishes Chlamydia (including C. psittaci) as obligate intracellular bacteria, the basis for the intracellular-niche conformance. Evidence source is OTHER as this is a review article.
PMID:15895932 SUPPORT Other
"Chlamydophila psittaci causes psittacosis, a severe zoonotic pneumonia transmitted by birds."
Identifies C. psittaci as the cause of psittacosis, a zoonotic pneumonia transmitted by birds. Evidence source is OTHER as this is a review article.
Atypical Pneumonia and Systemic Illness
Pneumonia is the predominant clinical presentation of psittacosis; severe cases can progress to acute respiratory distress syndrome and multi-organ dysfunction.
inflammatory response GO:0006954 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. ↑ INCREASED
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.
Show evidence (1 reference)
PMID:42255501 SUPPORT Other
"Pneumonia was the predominant clinical presentation, and severe cases could progress to acute respiratory distress syndrome and multi-organ dysfunction."
Scoping review establishing pneumonia as the predominant presentation, with progression to ARDS and multi-organ dysfunction in severe cases. Evidence source is OTHER as this is a review article.
Chlamydial Ribosomal Translation (Tetracycline Target)
C. psittaci depends on its bacterial ribosome for protein synthesis. Doxycycline, a tetracycline with good intracellular bioavailability, binds the 30S ribosomal subunit and arrests bacterial protein synthesis — combining the ribosomal target with the intracellular penetration needed to reach the organism, which is why a tetracycline rather than a beta-lactam is first-line.
translation GO:0006412 Gene Ontology (GO) Relation: this pathophysiological event involves this biological process This pathophysiological event involves translation (GO:0006412). GO:0006412 is a biological process from the Gene Ontology.
Show evidence (1 reference)
PMID:24336183 SUPPORT Other
"The ribosome is one of the main antibiotic targets in the bacterial cell."
Establishes the bacterial ribosome as the target of tetracyclines and other protein-synthesis inhibitors, the step this node represents. Evidence source is OTHER as this is a review article.
⬡

Pathograph

Use the checkboxes to hide or show graph categories. Hover nodes for evidence and cross-linked metadata.
Pathograph: causal mechanism network for Psittacosis 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

4
Immune 1
Pneumonia 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:42255501 SUPPORT Other
"Pneumonia was the predominant clinical presentation, and severe cases could progress to acute respiratory distress syndrome and multi-organ dysfunction."
Pneumonia is the predominant clinical presentation of psittacosis. Evidence source is OTHER as this is a review article.
Metabolism 1
Fever 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:34817316 SUPPORT Human Clinical
"Frequent symptoms included fever (16/16, 100%), dyspnoea (16/16, 100%), cough (12/16, 75%), sputum (11/16, 69%) and headache (9/16, 56%)."
In this case series of C. psittaci pneumonia, fever was present in every patient, supporting fever as a characteristic manifestation.
Respiratory 2
Cough 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:34817316 SUPPORT Human Clinical
"Frequent symptoms included fever (16/16, 100%), dyspnoea (16/16, 100%), cough (12/16, 75%), sputum (11/16, 69%) and headache (9/16, 56%)."
Cough was documented in most patients in this case series of C. psittaci pneumonia, supporting cough as a frequent respiratory manifestation.
Dyspnea HP:0002094 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Dyspnea (HP:0002094). HP:0002094 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:34817316 SUPPORT Human Clinical
"Frequent symptoms included fever (16/16, 100%), dyspnoea (16/16, 100%), cough (12/16, 75%), sputum (11/16, 69%) and headache (9/16, 56%)."
Dyspnoea was present in every patient in this case series of severe C. psittaci pneumonia, supporting dyspnea as a manifestation that can progress to respiratory failure.
💊

Medical Actions

1
Doxycycline
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: 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.
Tetracycline antibiotic with good intracellular bioavailability that inhibits bacterial protein synthesis at the 30S ribosome; first-line treatment for psittacosis because it reaches the intracellular organism. Macrolides and fluoroquinolones are alternatives.
Mechanism Target:
INHIBITS Chlamydial Ribosomal Translation (Tetracycline Target) — Doxycycline binds the 30S ribosome and arrests C. psittaci protein synthesis.
INHIBITS Inhalation and Obligate Intracellular Chlamydial Infection — Doxycycline's intracellular bioavailability lets it reach the intracellular organism that beta-lactams cannot.
Show evidence (1 reference)
PMID:15895932 SUPPORT Other
"Treatment should use an antibiotic with good intracellular bioavailability such as tetracycline, macrolides and new generation fluoroquinolones."
Supports use of cell-penetrant antibiotics (tetracycline first-line) for intracellular chlamydial infection. Evidence source is OTHER as this is a review article.
📊

Related Datasets

1
Host inflammatory response is the major factor in the progression of Chlamydia psittaci pneumonia geo:GSE202947
To clarify the host inflammatory response in psittacosis,we compared transcriptome data and concentrations of serum cytokines and chemokines in pneumonia and bronchitis cases.
human BULK RNA SEQ n=29
PMID:36119044
Identified by GEO DataSets index search for Psittacosis (scripts/discover_datasets.py); accession and metadata verified against NCBI E-utilities on 2026-08-01. Title, sample count, and organism are GEO's own values.
{ }

Source YAML

click to show 
name: Psittacosis
creation_date: "2026-06-28T00:00:00Z"
description: >
  Psittacosis (ornithosis, "parrot fever") is a zoonotic respiratory infection
  caused by Chlamydia (Chlamydophila) psittaci, an obligate intracellular
  bacterium transmitted to humans from birds (pet birds and poultry). After
  inhalation, the organism replicates intracellularly and produces an atypical
  pneumonia that is the predominant clinical presentation; severe cases can
  progress to acute respiratory distress syndrome and multi-organ dysfunction.
  Because the organism is intracellular, treatment requires a cell-penetrant
  antibiotic — tetracyclines (doxycycline) are first-line, with macrolides or
  fluoroquinolones as alternatives; beta-lactams are ineffective.
category: Infectious Disease
parents:
- Bacterial Respiratory Infection
synonyms:
- Ornithosis
- Parrot fever
- Chlamydia psittaci infection
disease_term:
  preferred_term: psittacosis
  term:
    id: MONDO:0005888
    label: ornithosis
pathophysiology:
- name: Inhalation and Obligate Intracellular Chlamydial Infection
  role: trigger
  conforms_to: "intracellular_pathogen_persistence#Intracellular Niche and Beta-Lactam Exclusion"
  description: >
    Psittacosis follows inhalation of aerosols from infected birds. Chlamydia
    psittaci is an obligate intracellular bacterium that replicates within host
    cells, an intracellular lifestyle that underlies the requirement for
    cell-penetrant antibiotics, because beta-lactams cannot reach the intracellular
    organism.
  cell_types:
  - preferred_term: respiratory epithelial cell
    term:
      id: CL:0002632
      label: epithelial cell of lower respiratory tract
  biological_processes:
  - preferred_term: symbiont entry into host cell
    term:
      id: GO:0046718
      label: symbiont entry into host cell
  - preferred_term: biological process involved in interaction with host
    term:
      id: GO:0051701
      label: biological process involved in interaction with host
  evidence:
  - reference: PMID:15895932
    reference_title: "[Chlamydia: diagnostic and treatment]."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      Chlamydia are obligate intracellular bacteria.
    explanation: >-
      Establishes Chlamydia (including C. psittaci) as obligate intracellular
      bacteria, the basis for the intracellular-niche conformance. Evidence source
      is OTHER as this is a review article.
  - reference: PMID:15895932
    reference_title: "[Chlamydia: diagnostic and treatment]."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      Chlamydophila psittaci causes psittacosis, a severe zoonotic pneumonia
      transmitted by birds.
    explanation: >-
      Identifies C. psittaci as the cause of psittacosis, a zoonotic pneumonia
      transmitted by birds. Evidence source is OTHER as this is a review article.
  downstream:
  - target: Atypical Pneumonia and Systemic Illness
    description: >-
      Intracellular replication produces an atypical pneumonia that can become
      severe and multisystem.
    evidence:
    - reference: PMID:15895932
      reference_title: "[Chlamydia: diagnostic and treatment]."
      supports: SUPPORT
      evidence_source: OTHER
      snippet: >-
        Chlamydophila psittaci causes psittacosis, a severe zoonotic pneumonia
        transmitted by birds.
      explanation: >-
        C. psittaci infection produces psittacosis as a severe (atypical)
        pneumonia, the downstream pneumonia edge of inhalational infection.
        Evidence source is OTHER as this is a review article.
  - target: Chlamydial Ribosomal Translation (Tetracycline Target)
    description: >-
      The organism's ribosome is the molecular target of tetracycline therapy.
    evidence:
    - reference: PMID:24336183
      reference_title: "Ribosome-targeting antibiotics and mechanisms of bacterial resistance."
      supports: SUPPORT
      evidence_source: OTHER
      snippet: >-
        The ribosome is one of the main antibiotic targets in the bacterial cell.
      explanation: >-
        The bacterial ribosome is the molecular target of tetracyclines, the
        therapeutic-vulnerability node reached from chlamydial infection. Evidence
        source is OTHER as this is a review article.

- name: Atypical Pneumonia and Systemic Illness
  role: consequence
  description: >
    Pneumonia is the predominant clinical presentation of psittacosis; severe cases
    can progress to acute respiratory distress syndrome and multi-organ
    dysfunction.
  biological_processes:
  - preferred_term: inflammatory response
    term:
      id: GO:0006954
      label: inflammatory response
    modifier: INCREASED
  locations:
  - preferred_term: lung
    term:
      id: UBERON:0002048
      label: lung
  evidence:
  - reference: PMID:42255501
    reference_title: "The re-emergence of psittacosis in China: a scoping review of epidemiology, diagnostics, and One Health priorities."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      Pneumonia was the predominant clinical presentation, and severe cases could
      progress to acute respiratory distress syndrome and multi-organ dysfunction.
    explanation: >-
      Scoping review establishing pneumonia as the predominant presentation, with
      progression to ARDS and multi-organ dysfunction in severe cases. Evidence
      source is OTHER as this is a review article.
  downstream: []

- name: Chlamydial Ribosomal Translation (Tetracycline Target)
  role: therapeutic_vulnerability
  conforms_to: "bacterial_protein_synthesis_inhibition#Bacterial mRNA Translation by the Ribosome"
  description: >
    C. psittaci depends on its bacterial ribosome for protein synthesis. Doxycycline,
    a tetracycline with good intracellular bioavailability, binds the 30S ribosomal
    subunit and arrests bacterial protein synthesis — combining the ribosomal target
    with the intracellular penetration needed to reach the organism, which is why a
    tetracycline rather than a beta-lactam is first-line.
  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
    snippet: >-
      The ribosome is one of the main antibiotic targets in the bacterial cell.
    explanation: >-
      Establishes the bacterial ribosome as the target of tetracyclines and other
      protein-synthesis inhibitors, the step this node represents. Evidence source
      is OTHER as this is a review article.
  downstream: []
phenotypes:
- category: Respiratory
  name: Pneumonia
  description: >
    Atypical pneumonia is the predominant manifestation of psittacosis.
  phenotype_term:
    preferred_term: Pneumonia
    term:
      id: HP:0002090
      label: Pneumonia
  evidence:
  - reference: PMID:42255501
    reference_title: "The re-emergence of psittacosis in China: a scoping review of epidemiology, diagnostics, and One Health priorities."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      Pneumonia was the predominant clinical presentation, and severe cases could
      progress to acute respiratory distress syndrome and multi-organ dysfunction.
    explanation: >-
      Pneumonia is the predominant clinical presentation of psittacosis. Evidence
      source is OTHER as this is a review article.
- category: Constitutional
  name: Fever
  description: >
    Fever is characteristic (psittacosis is also called "parrot fever").
  phenotype_term:
    preferred_term: Fever
    term:
      id: HP:0001945
      label: Fever
  evidence:
  - reference: PMID:34817316
    reference_title: "Sixteen cases of severe pneumonia caused by Chlamydia psittaci in South China investigated via metagenomic next-generation sequencing."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Frequent symptoms included fever (16/16, 100%), dyspnoea (16/16, 100%),
      cough (12/16, 75%), sputum (11/16, 69%) and headache (9/16, 56%).
    explanation: >-
      In this case series of C. psittaci pneumonia, fever was present in every
      patient, supporting fever as a characteristic manifestation.
- category: Respiratory
  name: Cough
  description: >
    Cough accompanies the atypical pneumonia of psittacosis.
  phenotype_term:
    preferred_term: Cough
    term:
      id: HP:0012735
      label: Cough
  evidence:
  - reference: PMID:34817316
    reference_title: "Sixteen cases of severe pneumonia caused by Chlamydia psittaci in South China investigated via metagenomic next-generation sequencing."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Frequent symptoms included fever (16/16, 100%), dyspnoea (16/16, 100%),
      cough (12/16, 75%), sputum (11/16, 69%) and headache (9/16, 56%).
    explanation: >-
      Cough was documented in most patients in this case series of C. psittaci
      pneumonia, supporting cough as a frequent respiratory manifestation.
- category: Respiratory
  name: Dyspnea
  description: >
    Shortness of breath occurs, and severe disease can progress to respiratory
    failure/ARDS.
  phenotype_term:
    preferred_term: Dyspnea
    term:
      id: HP:0002094
      label: Dyspnea
  evidence:
  - reference: PMID:34817316
    reference_title: "Sixteen cases of severe pneumonia caused by Chlamydia psittaci in South China investigated via metagenomic next-generation sequencing."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Frequent symptoms included fever (16/16, 100%), dyspnoea (16/16, 100%),
      cough (12/16, 75%), sputum (11/16, 69%) and headache (9/16, 56%).
    explanation: >-
      Dyspnoea was present in every patient in this case series of severe
      C. psittaci pneumonia, supporting dyspnea as a manifestation that can
      progress to respiratory failure.
treatments:
- name: Doxycycline
  description: >
    Tetracycline antibiotic with good intracellular bioavailability that inhibits
    bacterial protein synthesis at the 30S ribosome; first-line treatment for
    psittacosis because it reaches the intracellular organism. Macrolides and
    fluoroquinolones are alternatives.
  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: Chlamydial Ribosomal Translation (Tetracycline Target)
    treatment_effect: INHIBITS
    description: >-
      Doxycycline binds the 30S ribosome and arrests C. psittaci protein synthesis.
  - target: Inhalation and Obligate Intracellular Chlamydial Infection
    treatment_effect: INHIBITS
    description: >-
      Doxycycline's intracellular bioavailability lets it reach the intracellular
      organism that beta-lactams cannot.
  evidence:
  - reference: PMID:15895932
    reference_title: "[Chlamydia: diagnostic and treatment]."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      Treatment should use an antibiotic with good intracellular bioavailability
      such as tetracycline, macrolides and new generation fluoroquinolones.
    explanation: >-
      Supports use of cell-penetrant antibiotics (tetracycline first-line) for
      intracellular chlamydial infection. Evidence source is OTHER as this is a
      review article.
notes: >
  Created as part of the Respiratory Infections project. Intracellular zoonotic
  atypical pneumonia (bird reservoir); conforms to the
  intracellular_pathogen_persistence module (intracellular niche) and the
  bacterial_protein_synthesis_inhibition module (tetracycline ribosomal target),
  mirroring the Q_Fever and Murine_Typhus doxycycline pattern. disease_term uses
  MONDO:0005888 (ornithosis, the MONDO label for psittacosis). The infectious_agent
  (NCBITaxon) block was omitted at creation and C. psittaci is described in text.
datasets:
- accession: geo:GSE202947
  title: Host inflammatory response is the major factor in the progression of Chlamydia psittaci pneumonia
  description: To clarify the host inflammatory response in psittacosis,we compared transcriptome data and concentrations of serum cytokines and chemokines in pneumonia and bronchitis cases.
  organism:
    preferred_term: human
    term:
      id: NCBITaxon:9606
      label: Homo sapiens
  data_type: BULK_RNA_SEQ
  sample_count: 29
  publication: PMID:36119044
  notes: Identified by GEO DataSets index search for Psittacosis (scripts/discover_datasets.py); accession and metadata verified against NCBI E-utilities on 2026-08-01. Title, sample count, and organism are GEO's own values.