Tularemia is an acute, febrile, granulomatous, infectious zoonosis caused by Francisella tularensis, an aerobic, gram-negative, pleomorphic bacillus. F tularensis is one of the most infectious bacterial species known. See the image below.
Eschar on thumb and under thumbnail at the site of a rabbit bite in a patient with tularemia.
Signs and symptoms
The following are common findings in the various clinical forms of tularemia:
Abrupt onset of fever and chills – These symptoms typically last for several days, remit for a brief interval, and then recur
Malaise and fatigue or prostration
Secondary pneumonitis – May occur in 45-83% of patients with the typhoidal form of tularemia
As many as 20% of patients with tularemia have a rash, which may begin as blotchy, macular, or maculopapular and progress to pustular. Erythema nodosum and erythema multiforme are rare.
More specific signs and symptoms are as follows:
Ulceroglandular tularemia – Includes painful regional lymphadenopathy and an ulcerated skin lesion
Glandular tularemia – Tender lymphadenopathy without evidence of local cutaneous lesions
Oculoglandular tularemia – Unilateral conjunctivitis, corneal ulceration, lymphadenopathy, photophobia, lacrimation, lid edema, vision loss (rare)
Oropharyngeal tularemia – Stomatitis and exudative pharyngitis or tonsillitis; abdominal pain, nausea, and vomiting; cervical lymphadenopathy; diarrhea; gastrointestinal bleeding
Intestinal tularemia – Abdominal pain, vomiting, and diarrhea
Pneumonic tularemia – Dry cough, dyspnea, and pleuritic-type chest pain
Typhoidal tularemia – Fever, chills, myalgias, malaise, and weight loss
The diagnosis of tularemia is usually based on serology results. Tests vary from antibody detection (using latex agglutination or enzyme-linked immunosorbent assay [ELISA] testing) to the examination of a range of polymerase chain reaction (PCR) assay products.
An agglutination titer greater than 1:160 is considered presumptively positive, and treatment may be started if this result is obtained. A second titer, demonstrating a 4-fold increase after 2 weeks, confirms the diagnosis.
Indirect fluorescent antibody testing
Indirect fluorescent antibody testing of suppurative material is rapid and specific. Microscopic examination of tissue and smear specimens is possible using fluorescently labeled antibodies at reference laboratories, possibly providing rapid confirmation of disease.
Early tularemic lesions may demonstrate areas of focal necrosis surrounded by neutrophils and macrophages. Later, the necrotic areas become surrounded by epithelioid cells and lymphocytes. Caseating granulomata with or without multinucleated giant cells develops in some lesions.
Although F tularensis has been cultured from sputum, pleural fluid, wounds, blood, lymph node biopsy samples, and gastric washings, the yield is extremely low and culturing poses a danger to laboratory personnel.
Chest radiography – To evaluate for pneumonia; this is indicated in any patient in whom the diagnosis of tularemia is suspected
Ultrasonography – To examine lymph nodes for findings suggestive of infection; however, these findings lack specificity
Medical care in tularemia is directed primarily toward antibiotic eradication of F tularensis, with streptomycin being the drug of choice (DOC) for this treatment. Research increasingly supports the use of fluoroquinolones to treat the disease, but clinical experience and in vitro data regarding their efficacy are limited.
Symptomatic and supportive care is applied for accompanying conditions (eg, osteomyelitis, pericarditis, peritonitis) in patients with tularemia, as clinically indicated.
No tularemia vaccine is currently available. A vaccine based on a live strain of the bacterium was previously available but is no longer produced because of concerns about unknown attenuation, safety, and production.
Avoid tick-infested areas
Wear trousers and long-sleeved shirts to avoid tick bites
Use tick repellants
Frequently inspect the body and clothing for evidence of ticks
Avoid exposure to dead or wild mammals and wear gloves if such exposure is necessary; hands should be thoroughly washed afterwards