Psittacosis is a relatively uncommon zoonosis in the United States and Europe, with an estimated incidence of 1–2 cases per 1 million people per year. Outbreaks are more frequently reported in occupational settings—pet shop workers, poultry farmers, veterinarians, and laboratory personnel. In developing regions where live‑bird markets are common, the disease may be under‑diagnosed, leading to higher local rates.

Symptoms

Symptoms typically appear 5–14 days after exposure, but the incubation period can range from 1 to 4 weeks. The clinical picture is variable; some people experience a mild, flu‑like illness, while others develop severe pneumonia.

Common manifestations

• Fever: Often high (≥ 38.5 °C / 101.5 °F) and may be persistent.
• Headache: Usually throbbing and may be accompanied by photophobia.
• Dry cough: Can become productive with sputum that may be yellow‑green.
• Myalgia & fatigue: Generalized muscle aches and profound tiredness.
• Chest pain: Pleuritic pain that worsens with deep breathing.

Less common but noteworthy signs

• Rounded “bird‑shaped” rash (rare).
• Gastrointestinal symptoms – nausea, vomiting, abdominal pain.
• Neurologic involvement – headache progressing to meningitis or encephalitis (≈ 5 % of severe cases).
• Hepatomegaly or mild liver enzyme elevation.
• Splenomegaly.

Severe disease

In about 10–15 % of infected adults, the infection progresses to atypical pneumonia, which may be complicated by:

• Respiratory failure requiring supplemental oxygen or mechanical ventilation.
• Septic shock.
• Endocarditis (very rare).

Causes and Risk Factors

What causes rabbit fever?

Psittacosis results from infection with Chlamydia psittaci, an obligate intracellular gram‑negative bacterium. The organism replicates within respiratory epithelial cells and macrophages, provoking an inflammatory response that produces the characteristic pneumonia.

Major sources of exposure

• Pet birds (parrots, cockatiels, lovebirds, budgerigars).
• Commercial poultry (turkeys, chickens, ducks) – especially during processing.
• Wild birds (pigeons, starlings, sparrows) – exposure in farms, aviaries, or when cleaning bird droppings.
• Rabbits and other mammals infected experimentally or via contaminated environments.

Who is at higher risk?

• Occupational exposure: Bird handlers, poultry workers, veterinarians, pet‑store employees, laboratory researchers.
• People with close indoor bird keeping: Owners of pet birds kept in poorly ventilated rooms.
• Immunocompromised individuals: HIV/AIDS, organ‑transplant recipients, patients receiving chemotherapy or high‑dose steroids.
• Elderly adults: Age‑related decline in immune function increases likelihood of severe disease.

Diagnosis

Diagnosing psittacosis can be challenging because its symptoms mimic other respiratory infections. A combination of clinical suspicion, exposure history, and laboratory testing is essential.

Step‑by‑step diagnostic approach

1. Clinical assessment: Fever, cough, and recent bird or rabbit contact raise suspicion.
2. Chest imaging:
   • X‑ray: Often shows patchy infiltrates, typically in the lower lobes; may be bilateral.
   • CT scan: Can reveal ground‑glass opacities and consolidation, helping to differentiate from typical bacterial pneumonia.
3. Laboratory tests:
   • Complete blood count (CBC): Usually shows a mild leukocytosis or leukopenia.
   • Liver function tests: Mild transaminase elevation in up to 30 % of cases.
4. Specific microbiologic testing:
   • Polymerase chain reaction (PCR): Detects C. psittaci DNA from sputum, nasopharyngeal swab, or blood. PCR is the most rapid and sensitive method (sensitivity ≈ 80‑90 %).
   • Serology: Paired acute‑ and convalescent‑phase sera showing a four‑fold rise in IgG titers. Single‑sample IgM may be useful early but has lower specificity.
   • Culture: Requires biosafety level‑3 (BSL‑3) facilities; rarely performed in routine practice.

Diagnostic criteria (CDC): A confirmed case requires a compatible illness plus either a positive PCR, a four‑fold rise in IgG, or isolation of C. psittaci. A probable case may rely on a single high IgG titer together with clinical and exposure data.

Treatment Options

Prompt antimicrobial therapy dramatically shortens illness duration and prevents complications.

First‑line antibiotics

• Tetracyclines – Doxycycline 100 mg orally twice daily for 10‑14 days (or 14‑21 days for severe disease). Preferred due to excellent intracellular penetration.
• Macrolides – Azithromycin 500 mg PO once daily for 5‑7 days (alternative for doxycycline‑intolerant patients, pregnant women, or children < 8 years).

Alternative agents

• Fluoroquinolones (e.g., levofloxacin 500 mg daily) – useful in cases of macrolide or tetracycline resistance, though resistance is uncommon.
• Chloramphenicol – historically used, now reserved for severe cases where first‑line agents cannot be given.

Supportive care

• Antipyretics (acetaminophen or ibuprofen) for fever and aches.
• Hydration and rest.
• Oxygen supplementation or mechanical ventilation for respiratory failure.
• Hospital admission is recommended for:
  • Severe pneumonia.
  • Pregnant patients.
  • Immunocompromised hosts.

Lifestyle and adjunct measures

• Smoking cessation – smoking impairs mucociliary clearance and worsens outcomes.
• Nutrition optimization – protein‑rich diet supports immune recovery.

Living with Rabbit Fever (Psittacosis)

Even after successful treatment, some patients experience lingering fatigue or cough. The following strategies help promote full recovery and reduce the risk of relapse.

Daily management tips

• Medication adherence: Complete the entire antibiotic course, even if you feel better after a few days.
• Monitor symptoms: Keep a log of temperature, cough frequency, and any new chest pain.
• Hydration: Aim for 2‑3 L of fluids daily unless fluid restriction is medically indicated.
• Gradual activity: Resume light activities (walking, stretching) after 48‑72 h of fever resolution; avoid strenuous exercise for at least 2 weeks.
• Pulmonary hygiene: Practice deep‑breathing exercises and use incentive spirometry if prescribed.
• Follow‑up appointments: Schedule a post‑treatment visit (typically 2‑3 weeks) for repeat chest X‑ray and serology if indicated.

Psychosocial considerations

Because psittacosis is often linked to pets, patients may feel guilty or fearful about keeping animals. Counseling about safe handling, environmental cleaning, and, when necessary, temporary relocation of the bird(s) can alleviate anxiety.

Prevention

Prevention hinges on minimizing exposure to infected animals and maintaining good hygiene.

For pet owners

• Obtain birds from reputable breeders who screen for C. psittaci.
• Quarantine new birds for at least 30 days and monitor for respiratory signs.
• Keep cages in well‑ventilated rooms; clean droppings daily using a damp cloth and a disinfectant effective against chlamydia (e.g., 0.1 % sodium hypochlorite).
• Wear a disposable N95 respirator or a surgical mask when cleaning cages or handling sick birds.
• Wash hands with soap and water for at least 20 seconds after any contact with birds, cages, or their waste.

For occupational settings

• Implement engineering controls: local exhaust ventilation in poultry houses and bird‑cage cleaning areas.
• Provide personal protective equipment (PPE) – N95 respirators, gloves, goggles.
• Conduct regular health surveillance (annual symptom questionnaires, antibody screening for high‑risk workers).
• Vaccination is not currently available; however, education programs reduce incidence markedly (CDC reports a 30‑40 % reduction after workplace training).

General public health measures

• Report outbreaks to local health departments; they can initiate environmental testing.
• Educate patients in live‑bird markets about safe handling practices.
• Encourage clinicians to consider psittacosis in any atypical pneumonia with a pet‑bird exposure history.

Complications

If untreated or inadequately treated, psittacosis can lead to serious complications:

• Atypical pneumonia: May progress to acute respiratory distress syndrome (ARDS).
• Septicemia: Bacterial spread to the bloodstream causing multi‑organ dysfunction.
• Endocarditis: Rare but reported in immunocompromised patients.
• Neurologic involvement: Meningitis, encephalitis, or Guillain‑Barré‑like syndrome.
• Hepatic dysfunction: Hepatitis with jaundice in 5–10 % of severe cases.
• Reproductive complications: In pregnant women, infection has been linked to miscarriage, preterm labor, or fetal death.

Mortality rates vary: CDC data indicate a case‑fatality rate of 1–5 % overall, rising to 10–15 % among the elderly or immunocompromised.

When to Seek Emergency Care

**References**

1. Mayo Clinic. Psittacosis (Parrot Fever). Accessed June 2024.
2. Centers for Disease Control and Prevention (CDC). Psittacosis (Parrot Fever). Updated 2023.
3. World Health Organization (WHO). Fact sheet: Psittacosis. 2022.
4. National Institutes of Health – National Library of Medicine. Clinical presentation and management of psittacosis. J Infect Dis. 2022.
5. Cleveland Clinic. Psittacosis (Parrot Fever). Reviewed 2023.