Tularemia

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Agent

Francisella tularensis

Tularemia is caused by the highly infectious F. tularensis bacteria. It is spread through exposure to infected arthropods (including deer flies and several species of ticks), contact with infected carcasses or animals (such as rabbits, hares, and rodents), contaminated food or water, or inhalation of aerosols (such as by mowing over an infected rabbit carcass).

Where Found

Tularemia has been reported in all states except Hawaii, but it is most common in the south-central United States, the Great Plains region, and parts of Massachusetts.

Tularemia ulcer on persons thumb

Incubation Period

3–5 days (range 1–21 days)

Signs and Symptoms

The clinical presentation of tularemia depends on many factors, including the route of inoculation and subtype of F. tularensis. Tularemia can be serious or fatal without adequate treatment. Unusual and severe clinical manifestations have been described in patients with immunocompromising conditions.

  • Fever, chills
  • Headache
  • Malaise, fatigue
  • Anorexia
  • Myalgia
  • Chest discomfort, cough
  • Sore throat
  • Vomiting, diarrhea
  • Abdominal pain

(Ulcero) Glandular

  • Localized lymphadenopathy
  • Cutaneous ulcer at infection site (not always present)

Oculoglandular

  • Photophobia
  • Vision impairment/loss
  • Conjunctivitis
  • Regional lymphadenopathy

Oropharyngeal

  • Severe throat pain
  • Exudative pharyngitis or tonsillitis
  • Regional lymphadenopathy

Pneumonic

  • Non-productive cough
  • Substernal tightness
  • Pleuritic chest pain
  • Hilar adenopathy, infiltrate, or pleural effusion may be present on chest X-ray

Typhoidal

  • Characterized by any combination of the general symptoms without the localizing symptoms of other syndromes
  • May have infiltrates in chest radiograph in the absence of respiratory symptoms

General Laboratory Findings

  • Hyponatremia
  • Leukocytosis
  • Thrombocytopenia
  • Elevated hepatic transaminases
  • Elevated creatine kinase
  • Elevated erythrocyte sedimentation rate
  • Myoglobinuria
  • Sterile pyuria

Laboratory Diagnosis

Isolation of F. tularensis in culture is optimal for diagnosis but can be challenging due to the slow-growing, fastidious nature of the organism. Appropriate specimens for culture include swabs or scrapings of ulcers, lymph node aspirates or biopsies, pharyngeal swabs, or respiratory specimens (e.g., pleural fluid), depending on the form of illness. Blood cultures are often negative.

Seroconversion from negative to positive IgM and/or IgG can also confirm the diagnosis when tularemia is suspected. Ideally, these are performed as paired acute and convalescent specimens, the latter collected 2-3 weeks after initial illness.

When available, other tests can be useful, including:

  • Direct immunofluorescence assay (DFA)
  • Immunohistochemical staining
  • PCR assay

Clinicians who suspect tularemia should alert the laboratory to the possible need for special safety procedures to minimize risk of laboratory transmission.

Treatment

These regimens may need to be adjusted depending on a person’s age, medical history, underlying health conditions, pregnancy status, or allergies. Consult an infectious disease specialist regarding individual patient treatment decisions.

Tularemia treatment regimen
Age Category Drug Dosage Maximum Duration (Days)
Adults Gentamicin* 5 mg/kg IM or IV daily (with desired peak serum levels of at least 5 mcg/mL) Monitor serum drug levels Minimum 10
Ciprofloxacin* 400 mg IV or 500 mg PO twice daily N/A 10–14
Doxycycline 100 mg IV or PO twice daily N/A 14–21
Children Gentamicin* 2.5 mg/kg IM or IV 3 times daily** Monitor serum drug levels and consult a pediatric infectious disease specialist Minimum 10
Ciprofloxacin* 15 mg/kg IV or PO twice daily 800 mg per day 10
Doxycycline 2.2mg/kg IV or PO twice daily 100mg IV or PO twice daily 14

-21

* Not a U.S. FDA-approved use but has been used successfully to treat patients with tularemia.
** Once-daily dosing could be considered in consultation with a pediatric infectious disease specialist and a pharmacist

NOTE: Gentamicin is preferred for treatment of severe tularemia. Dose should be adjusted for renal insufficiency.

NOTE: For tularemic meningitis, combination therapy should be considered in consultation with an infectious disease specialist.

See Tularemia For Clinicians for detailed treatment information.

Tularemia prophylaxis is recommended in cases of laboratory exposure to infectious materials.

  • Doxycycline (100 mg orally twice daily for 14 days) is generally recommended for prophylaxis in adults.
  • Ciprofloxacin (500 mg orally twice daily) is not FDA-approved for prophylaxis of tularemia but has demonstrated efficacy in various studies and may be an alternative for patients unable to take doxycycline.

References

Auwaerter PG, Penn RL. Francisella tularensis (Tularemia). In: Bennett J, Dolin R, Blaser M., editors. Mandell, Douglas, and Bennett’s Principles and Practice of Infectious Diseases. 9th ed. Elsevier Health Sciences; 2020.

Centers for Disease Control and Prevention. Tularemia—United States, 2001-2010. MMWR Morb Mortal Wkly Rep. 2013;62(47):963–966.

Dennis D, Inglesby TV, Henderson DA, et al. Tularemia as a biological weapon: medical and public health management. JAMA. 2001;285(21):2763–2773.

Feldman KA, Enscore RE, Lathrop SL, et al. An outbreak of primary pneumonic tularemia on Martha’s Vineyard. NEJM. 2001;345:1601–1606.

Johansson A, Berglund L, Sjöstedt A, et al. Ciprofloxacin for treatment of tularemia. Clin Infect Dis. 2001;33:267–8.

Tarnvik A. WHO Guidelines on tularaemia. Vol. WHO/CDS/EPR/2007.7. Geneva: World Health Organization, 2007.

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Page last reviewed: August 5, 2022
Content source: Centers for Disease Control and Prevention, National Center for Emerging and Zoonotic Infectious Diseases (NCEZID), Division of Vector-Borne Diseases (DVBD)