Fact-sheet: Tularemia
Updated on 01/08/2025 at 9:45 AM
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Definition
Tularemia is a rare zoonosis caused by the bacterium Francisella tularensis. It is a strictly aerobic, non-motile, gram-negative bacillus that is a strict intracellular organism in vivo.
Human contamination occurs through direct contact with infected animals, blood-feeding arthropods (ticks in particular), ingestion of contaminated water or meat, or inhalation. This latter route is of particular concern, as the bacterium can be used as a bioterrorism agent.
Clinical features
Incubation period of 2 to 10 days, followed by a flu-like syndrome with fever, chills, myalgia, and headache.
Different clinical forms may develop depending on the mode of contamination:
• Ulceroglandular form (75-85% of cases): Ulcer at the inoculation site with regional lymphadenopathy.
• Glandular form: Lymphadenopathy without ulceration.
• Oculoglandular form: Purulent conjunctivitis and corneal ulceration with lymphadenopathy.
• Oropharyngeal form: Pharyngitis or chronic Sore throat resistant to standard antibiotics.
• Typhoidal form: Isolated fever or fever following another form, which may progress to sepsis.
• Pulmonary form: Fever, dry cough, dyspnea, chest pain, hemoptysis. A sign of severity.
Severe forms with visceral involvement (pulmonary, pericardial, endocarditis, osseous), septicemia with DIC, rhabdomyolysis, acute renal failure, and acute Hepatitis may occur.
Laboratory findings
A systemic inflammatory response is common, with neutrophilic leukocytosis and elevated CRP.
Diagnosis is confirmed by serology (requiring two samples 15 days apart) or PCR (faster).
Bacteriological diagnosis.
Radiography
Chest radiography may show:
• A solitary mass resembling a consolidation, with lymphadenopathy and a small pleural effusion. This appearance is often mistaken for lung cancer in the absence of clinical features suggesting acute infection.
• Right paratracheal lymphadenopathy.
• Parenchymal nodules.
• Left hilar infiltration.
• Bilateral interstitial pattern.
• Right pleural effusion.
• Consolidations.
• Cavitated nodules.
Resolution of radiographic abnormalities is slow and may take up to three months.
Ultrasound
Ultrasound may be useful in cases of suppurative adenitis.
CT
Chest CT is the imaging modality of choice for the evaluation of pulmonary tularemia.
Main findings encountered:
• Mediastinal-hilar lymphadenopathy, often necrotic.
• Polymorphic unilateral or bilateral parenchymal infiltrates, predominating in the lung bases.
• Lung abcess.
• Pleural effusions.
• Pseudotumoral appearance.
• Granulomatous pleurisy.
• ARDS (Acute Respiratory Distress Syndrome).
Nuclear medicine
PET-CT may show hypermetabolism of mediastinal lymphadenopathy and help differentiate inflammatory from tumoral lymphadenopathy.
Management
• Notify laboratory personnel, as handling the bacterium requires strict precautions.
• Confirm the diagnosis by serology (requires two samples 15 days apart) or PCR (faster).
• Initiate appropriate antibiotic therapy: streptomycin (treatment of choice), tetracyclines (21 days), fluoroquinolones (14 days).
• Report the disease to health authorities, as it is a notifiable disease.
Differential diagnosis
• Atypical pneumonias
• Tuberculosis
• Histoplasmosis
• Q fever
• Anthrax
• Lung cancer
• Thoracic sarcoidosis, sarcoidosis of neck
• Lymphoma