OPHEPR; Tularemia - Profile for Healthcare Workers

Routes of Exposure: Tularemia can be acquired by humans by inoculation of the skin or mucous membranes with blood or tissue from infected animals, or bites of infected deerflies, mosquitoes, or ticks. Less commonly, inhalation of contaminated dust or ingestion of contaminated foods or water can also cause human disease. The animal reservoirs of disease include rabbits, muskrats, and squirrels.

Infective Dose & Infectivity: 10-50 organisms

Incubation Period: The incubation period ranges from 1 to 14 days with an average of 3 to 5 days.

Clinical Effects: Different clinical forms of disease are seen depending on the route of exposure. Disease resulting from intentional aerosol release of F. tularensis would primarily cause typhoidal tularemia. Gastrointestinal symptoms such as diarrhea and pain may also be present. Typhoidal tularemia manifests with fever, prostration, weight loss, but with no adenopathy. Pneumonia is most common with the typhoidal form. Tularemia pneumonia is generally a severe atypical pneumonia that may be fulminating and can result from either inhalation of infectious aerosols or from aspiration of organisms from the pharynx. Tularemia pneumonia can also be secondary to a tularemia bacteremia. Tularemia pneumonia generally manifests with fever, headache, substernal discomfort, and non-productive cough. Radiographic evidence of pneumonia or mediastinal lymphadenopathy may or may not be present. Oculoglandular tularemia can result from inoculation of the conjunctivae with hand or fingers contaminated by tissue and/or fluids from an infected animal. The gastrointestinal form of tularemia manifests as abdominal pain, nausea, vomiting and diarrhea.

Lethality: The mortality rate without treatment is 33%. However, with appropriate treatment, the mortality rate is less than 2%.

Transmissibility: There is no known person-to-person transmission.

Primary contaminations & Methods of Dissemination: Tularemia would most likely be delivered via aerosolization, or sabotage of food and/or water.

Secondary Contamination & Persistence of organism: Secondary transmission is not an issue. However, F. tularensis can persist in cold, moist environments for extended periods.

Decontamination & Isolation:

Patients – Standard precautions should be practiced. Contact precautions should be used with skin lesions and secretions. Patients with direct exposure to aerosols, as well as their clothing, should be washed with soap and water.
Equipment, clothing & other objects – Heat, 0.5% hypochlorite solution (one part household bleach and 9 parts water = 0.5% solution) will kill the organisms and can be used for environmental decontamination.

Outbreak control: Following an intentional release, the risk of acquiring infection from local animals is minimal. The risk can be further minimized by educating the public in avoidance of sick animals as well as personal protective measures against bites from mosquitoes, deerflies, or ticks. Standard levels of chlorine in municipal water sources should protect against waterborne infection. In warm, arid environments, organisms in the soil are unlikely to survive for significant periods of time and are unlikely to present a hazard.

Laboratory testing: Serology is the most common diagnostic test; acute and convalescent serology is the most helpful. Identification of organisms by gram staining ulcer fluids or sputum is generally not helpful. Rapid testing of secretions, exudates and biopsies can be done by direct fluorescent antibody or PCR. Routine culture is difficult due to unusual growth requirements and/or overgrowth of commensal bacteria. Culturing is difficult and potentially dangerous. If tularemia is suspected, and cultures are obtained, the laboratory should be notified because of the high risk to laboratory workers due to transmissibility of the bacteria. F. tularensis can be grown from wounds, tissues, blood, and respiratory secretions.

Therapeutic Treatment: The recommended treatment for tularemia in a contained casualty setting is streptomycin or gentamicin*. Alternate choices include doxycycline, ciprofloxacin*, or chloramphenicol*. In a mass casualty setting where patients cannot be managed individually, the recommended treatments are doxycycline or ciprofloxacin.

Prophylactic Treatment: Exposed individuals can be treated prophylactically with doxycycline or ciprofloxacin.

Differential Diagnosis: The differential diagnoses should include typhoidal syndromes such as Salmonella, rickettsia, malaria, and any atypical pneumonic process.

References:

Chin J. Control of Communicable Diseases Manual, Seventeenth Edition, American Public Health Association; 2000.
Dennis DT, Inglesby TV, Henderson DA, et al. Tularemia as a Biological Weapon: Medical and Public Health Management. JAMA. 2001; 285: 2763–2773.
Kortepeter M, Christopher G, Cieslak T, et al. Medical Management of Biological Casualties Handbook, U.S. Army Medical Research Institute of Infectious Diseases, U.S. Department of Defense; 2001: 37-42
Evans ME, Friedlander AM. Tularemia. In: Zajtchuk R, Bellamy RF, eds. Medical Aspects of Chemical and Biological Warfare. Washington, DC: Office of the Surgeon General, U.S. Department of the Army; 1997: 503-512.

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* Gentamicin, Ciprofloxacin, and Chloramphenicol do not have FDA approved indication for tularemia.