Tularemia

Key Features

Essentials of Diagnosis

• A cutaneous or mucous membrane lesion at the site of inoculation and regional lymph node enlargement

• Sudden onset of fever, chills, and prostration

• History of contact with infected animals, principally wild rabbits, or history of tick exposure

• Positive culture or immunofluorest staining of samples from mucocutaneous ulcer or regional lymph nodes

• High serum antibody titer

General Considerations

• Caused by Francisella tularensis

• Ticks are the most important vector of tularemia and rabbits are the classic vector

• Occasionally infection is acquired from infected domestic dogs or cats; by contamination of the skin or mucous membranes with infected blood or tissues; by inhalation of infected material; by bites of fleas or deer flies that have been in contact with infected animals; or by ingestion of contaminated meat or water

• Incubation period is short, usually 3–7 days, but may vary from 2 to 25 days

Clinical Findings

Symptoms and Signs

• Several clinical types of tularemia occur in children

• Ulceroglandular form responsible for 60% of infections

  • Starts as a relatively nonpainful, reddened papule that may be pruritic and quickly ulcerates

  • Regional lymph nodes become large and tender

  • Fluctuance quickly follows

  • There may be marked systemic symptoms, including high fever, chills, weakness, and vomiting

  • Pneumonitis occasionally accompanies the ulceroglandular form or may be seen as the sole manifestation of infection (pneumonic form)

  • Detectable skin lesion may be absent, and localized lymphoid enlargement may exist alone (glandular form)

• Oculoglandular and oropharyngeal forms also occur

  • Latter is characterized by tonsillitis, often with membrane formation, cervical adenopathy, and high fever

  • In the absence of a primary ulcer or localized lymphadenitis, a prolonged febrile disease reminiscent of typhoid fever can occur (typhoidal form)

• Splenomegaly is common in all forms

Differential Diagnosis

• Ulceroglandular type resembles pyoderma caused by staphylococci or streptococci, plague, anthrax, and cat-scratch fever

• Oropharyngeal type must be distinguished from streptococcal or diphtheritic pharyngitis, mononucleosis, herpangina, or other viral pharyngitides

• Typhoidal form may mimic typhoid, brucellosis, miliary tuberculosis, Rocky Mountain spotted fever, and mononucleosis

• Pneumonic tularemia resembles atypical or mycotic pneumonitis

Diagnosis

• F tularensis can be recovered from ulcers, regional lymph nodes, blood, and sputum of patients with the pneumonic form

• Immunofluorescent staining of biopsy material or aspirates of involved lymph nodes is diagnostic, although it is not widely available

• WBC count is not remarkable

• Diagnosis is typically confirmed by demonstration of a fourfold antibody titer rise between acute and convalescent serum samples

Treatment

• Antipyretics and analgesics may be given as necessary

• Skin lesions are best left open

• Glandular lesions occasionally require incision and drainage

• Historically, streptomycin was the drug of choice

• However, gentamicin is efficacious, more available, and familiar to clinicians; a 10-day course is ...