Diagnosis Synopsis
Tularemia is caused by Francisella tularensis, a pleomorphic aerobic gram-negative coccobacillus that normally resides in a wide variety of animals. Humans acquire the infection either after direct contact with the bodily fluids of animal carriers or through insect vectors (ticks), or contaminated food and water. There are seven major clinical patterns of tularemia: glandular, ulceroglandular (most common), oculoglandular, typhoidal, pneumonic, oropharyngeal, and septicemic. Any form of tularemia can be complicated by hematogenous spread, resulting in secondary pleuropneumonia, sepsis, or meningitis (rare).
The CDC has classified tularemia as a Class A bioterrorism agent due to its ease of dissemination, morbidity, and ability to infect with as few as 10 bacterial organisms. The Soviet Union has developed weaponized antibiotic and vaccine resistant strains of F. tularensis. F. tularensis is so infective that exposure to an open culture plate can cause human infection. Tularemia is not directly contagious person-to-person. Aerosol dissemination of F. tularensis has been projected to result in the abrupt onset of large numbers of cases of acute, non-specific febrile illness with pleuropneumonitis as the predominant finding.
Tularemia typically has an abrupt onset consisting of fever, headache, chills and rigors, myalgia (especially the low back), coryza, and sore throat. In 42% of patients a pulse-temperature dissociation has been observed. The cough may be dry or slightly productive and there may be substernal pain or tightness. Signs of pneumonia may or may not be obvious. Nausea, vomiting, and diarrhea may also occur.
Post-exposure prophylaxis is not recommended for inhalational tularemia due to the short incubation period and incomplete protection of current vaccines. A live attenuated vaccine derived from the avirulent Live Vaccine Strain (LVS) has been used to protect laboratory personnel handling F. tularensis. Isolation is not recommended for tularemia patients due to the lack of human-to-human transmission, although due to the risk of secondary arthropod transmission, ambient ticks, fleas, lice, and mosquitoes should be controlled.
Tularemia is present throughout the United States, but is most prevalent in Missouri, Arkansas, Oklahoma, Texas, Virginia, Massachusetts, California, and Tennessee.
Hunters, game wardens, trappers and campers are particularly susceptible. Animals known to have transmitted tularemia include rabbits (most common), foxes, squirrels, skunks, muskrats, beavers, voles and even fish. Other routes of infectivity include contact with contaminated water or mud and aerosol droplets.
Prevalence is greatest from June through August (more tick-related infections) and in the fall (during hunting season).
Tularemia is a reportable disease in most states.
Precautions: Standard healthcare worker precautions.
Look For
Typhoidal:
GI symptoms (diarrhea, pain) may be the most prominent feature. Systemic symptoms and signs are seen without lymphadenitis, cutaneous or mucosal lesions.
Ulceroglandular:
At the start of flu-like symptoms a papule appears at the inoculation site that eventually becomes pustular and then ulcerates within a few days. An eschar may or may not form at the inoculation site. There is typically regional lymphadenopathy; the nodes may become fluctuant and rupture.
Oculoglandular:
This form results in a purulent conjunctivitis. Small yellow nodules develop on the conjunctiva and ulcerate and are usually unilateral. This may be accompanied by severe eyelid edema, vasculitis, and regional lymphadenitis.
Oropharyngeal:
Look for an ulcerative pharyngitis. Diffuse morbilliform, vesicular, papular, erythema multiforme and acneiform lesions. Urticaria and erythema nodosum-like lesions may occur.
Glandular:
The glandular form is characterized by lymphadenopathy without cutaneous manifestations.
Oropharyngeal:
Oropharyngeal can present with stomatitis or an exudative pharyngitis or tonsillitis. There also may be ulcers and cervical lymphadenopathy.
Pneumonic:
This form presents with acute signs of illness such as pharyngitis, bronchiolitis, pleuropneumonitis, and hilar lymphadenitis along with other signs of systemic illness. On X-ray or CT may show bronchial infiltrates, pleural effusions, and hilar lymphadenopathy.
Septicemic:
This is the most severe form of tularemia. In addition to the GI presentation of the typhoidal form, CNS symptoms such as confusion or coma may occur.
Diagnostic Pearls
Patients with tularemia are far more likely than those with inhalational anthrax to have pulmonary infiltrates.
Differential Diagnosis & Pitfalls
Pasteurella multocida infection
Sporotrichosis
Glanders
Melioidosis
Psittacosis
Leptospirosis
Plague
Anthrax, cutaneous
Anthrax, inhalational
Best Tests
ELISA; micro agglutination (titer greater than 1:160). Skin testing with the F. tularensis antigen is highly specific, but is only available through the CDC in Atlanta. Febrile agglutinins positive at 10 days. A titer of 1:160 considered diagnostic. A four-fold increase between acute and convalescent titers is diagnostic. ELISA is more sensitive than tube-agglutination.
PCR.
Blood cultures are only rarely positive. WBC is normal or low, but may be associated with polymorphonuclear leukocytosis. Rarely, thrombocytopenia, hyponatremia, elevated liver enzymes, increased CPK, myoglobinuria, and sterile pyuria are found.
Management Pearls
Streptomycin is the drug of choice, although gentamicin and tetracycline have been used effectively.
Therapy
Adults:
Streptomycin 0.5 grams IM bid for 10 days.
or
Gentamicin 2.5 mg/kg IM or IV qd for 10 days.
Children:
Streptomycin 15 mg/kg IM bid for 10 days.
or
Gentamicin 2.5 mg/kg iM or IV tid for 10 days.
Pregnant Women:
Gentamicin 5 mg/kg IM or IV qd for 10 days.
or
Streptomycin 1 g IM bid for 10 days.
Medical Disclaimer:
The information contained in this web page is intended to be an adjunct to traditional medical information sources. It is not intended to be a substitute for professional medical judgment.
Authors and Editors:
Tener Goodwin Veenema PhD, MPH, MS, CPNP
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