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For further information, see CMDT Part 33-24: Tularemia

Key Features

Essentials of Diagnosis

  • History of outdoor activity

  • Possible contact with rabbits, other rodents, and biting arthropods (eg, ticks in summer) in endemic area

  • Fever, headache, nausea, and prostration

  • Papule progressing to ulcer at site of inoculation

  • Enlarged regional lymph nodes

  • Serologic tests or culture of ulcer, lymph node aspirate, or blood confirm the diagnosis

General Considerations

  • An infection of wild rodents—particularly rabbits and muskrats—with Francisella (Pasteurella) tularensis

  • Usually acquired by contact with animal tissues (eg, trapping muskrats, skinning rabbits), from ticks, or from biting flies

  • Risk factors for pneumonic tularemia include lawn-mowing and brush-cutting, underscoring the potential for probable aerosol transmission of the organism

  • The incubation period is 2–10 days

  • F tularensis has been classified as a high-priority agent for potential bioterrorism use because of its virulence and relative ease of dissemination

Clinical Findings

Symptoms and Signs

  • A papule at the site of inoculation develops and soon ulcerates

  • This local lesion may be on the skin of an extremity or in the eye

  • Widespread organ involvement may occur but may be entirely asymptomatic

  • Fever, headache, and nausea begin suddenly

  • Regional lymph nodes may become enlarged and tender and may suppurate

  • Pneumonia may develop from hematogenous spread of the organism or may be primary after inhalation of infected aerosols, which are responsible for human-to-human transmission

  • Following ingestion of infected meat or water, an enteric form may be manifested by gastrointestinal symptoms, stupor, and delirium

  • Hematogenous spread may produce meningitis, perisplenitis, pericarditis, pneumonia, and osteomyelitis

  • In any type of involvement, the spleen may be enlarged and tender and there may be nonspecific rashes, myalgias, and prostration

Differential Diagnosis

  • Anthrax

  • Cat-scratch disease

  • Infectious mononucleosis

  • Plague

  • Typhoid fever

  • Lymphoma

  • Rickettsial disease, eg, epidemic typhus, Q fever

  • Rat-bite fever

  • Meningococcemia

  • Sporotrichosis

  • Herpes simplex virus conjunctivitis

Diagnosis

Laboratory Tests

  • Culturing the organism from blood or infected tissue requires special media. For this reason and because cultures of F tularensis may be hazardous to laboratory personnel, the diagnosis is usually made serologically

  • A positive agglutination test (> 1:80) develops within 2 weeks and may persist for several years

  • Culture of ulcer, lymph node aspirate, or blood confirms the diagnosis

Treatment

Medications

  • Streptomycin

    • Dosage: 7.5–10.0 mg/kg every 12 hours intramuscularly or intravenously for 10 days

    • Drug of choice

  • Gentamicin

    • Dosage: 5 mg/kg once daily intramuscularly or intravenously for 10 days

    • Generally less toxic than streptomycin

    • However, some case series report lower treatment success rates

  • Doxycycline

    • Dosage: 200 mg/day orally

    • Also effective but has a higher relapse rate

    • Should only be used for the less seriously ill

Outcome

Complications

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