Infectious Disease: Tularemia

Introduction

• Zoonotic infection caused by the bacterium Francisella tularensis.
• Gram-negative, aerobic bacteria.
• Also known as: Francis's disease, rabbit fever, deer fly fever.
• Transmission through contact with infected animals, tick bites, and exposure to dead animals.

Risk Factors

• Certain occupations: veterinarians, farmers, hunters, meat handlers, landscapers.
• Consuming undercooked wild meat, particularly rabbit meat.
• Camping (due to tick bites and exposure to infected animals).

Pathophysiology

• Highly virulent: 10-50 bacteria needed to cause illness.
• Facultative intracellular bacterium that infects macrophages.
• Macrophages phagocytize bacteria, which then replicate inside and eventually cause cell lysis, spreading the infection.
• Can also infect neutrophils.

Clinical Presentation

• Wide spectrum: asymptomatic to septic shock and death.
• F. tularensis has two subspecies: F. tularensis subspecies tularensis (more severe) and subspecies holarctica (less severe).
• Symptoms appear abruptly after 3-5 day incubation period, often nonspecific and systemic (fever, chills, malaise, fatigue).

Forms of Tularemia

1. Ulceroglandular
   • Most common form.
   • Skin lesion, swollen tender lymph nodes, fever, single erythematous ulcer with central eschar at inoculation site.
   • Possible subcutaneous nodules.
2. Glandular
   • Second most common form.
   • Tender lymph nodes without identifiable skin ulcer.
3. Oculoglandular
   • Infection of conjunctiva through eye rubbing or aerosols.
   • Red, swollen eye, pain, photophobia, increased tearing.
   • Possible corneal ulceration.
4. Pharyngeal
   • Through ingestion of contaminated food/drink.
   • Fever, sore throat, neck swelling, exudative pharyngitis, possible pharyngeal or tonsillar ulcers.
5. Pneumonic
   • Primary: direct inhalation of bacteria (farmers, lab workers, sheep shearers).
   • Secondary: spread from another infection site, usually involving bilateral lower lobes.
   • Symptoms: fever, cough, malaise, myalgia, erythema nodosum.
6. Typhoidal
   • Systemic febrile illness without regional lymphadenopathy.
   • Symptoms: fever, chills, anorexia, headaches, myalgia, sore throat, cough, abdominal pain, diarrhea.

Complications

• Chronic and recurrent fevers, long-standing fatigue, weight loss, weakness if left untreated.

Diagnosis

• Based on symptoms, risk factors, and clinical suspicion.
• Confirmatory tests: serology (positive antibody titers), bacterial culture (difficult but possible), PCR testing.

Treatment

• Antibiotics: streptomycin or gentamicin (intramuscular), fluoroquinolones, tetracyclines.
• Early diagnosis and treatment crucial to prevent long-term complications.

Conclusion

• Tularemia is a master of disguises with many clinical presentations.
• Important for those in infectious disease environments and high-risk occupations to recognize and understand the condition.
• Related infectious diseases: Q fever, Lyme disease.
• Support the educational channel if helpful.