Tularemia

Infectious agent:

Francisella tularensis (formlerly Pasteurella tularensis), a small, gram-negative nonmotile coccobacillus.

Incubation:

Related to virulence of infecting strain and to size of inoculum; the range is 1-14 days, usually 3-5 days.

Mode of transmission:

Through bite of arthropods, including the wood tick, dog tick, lone star tick, and less commonly the deer tick.

Period of communicability:

Not directly transmitted person to person. Unless treated, the infectious agent may be found in the blood during the first 2 weeks of disease and in lesions for a month, sometimes longer. Flies can be infective for 14 days and ticks throughout their lifetime (about 2 years). Rabbit meat frozen at -15° C (5° F) has remained infective longer than 3 years.

Clinical Symptoms:

A zoonotic bacterial disease with a variety of clinical manifestations related to the route of introduction and the virulence of the disease agent. Ulceroglandular type: indolent ulcer at the site of introduction of the organism, together with swelling of the regional lymph nodes. Glandular type: no primary ulcer, but only one or more enlarged and painful lymph nodes that may suppurate. Oropharyngeal type: ingestion of organisms in contaminated food or water may produce a painful pharyngitis (with or without ulceration), abdominal pain, diarrhea, and vomiting. Tyhpoidal type: inhalation of infectious material may be followed by pneumonic involvement or a primary septicemic syndrome with a 30-60% case-fatality rate if untreated. Pleuropulmonary type: bloodborne organisms may localize in the lung or pleural spaces. Oculoglandular type: conjunctival sac is a rare route of introduction that results in clinical disease of painful purulent conjunctivitis with regional lymphadenitis. Pneumonia may complicate all clinical types and requires prompt identification and specific treatment to prevent a fatal outcome.

Prophylaxis if exposed:

Intramuscular streptomycin will prevent disease following documented exposure but not recommended following tick bites or animal contact.

Diagnosis:

Culture with special media available for blood, sputum, lymph node material, and wound exudates if diagnosis suspected. Serology is available to confirm diagnosis.

Precautions:

Standard precautions are recommended.

Source:

Control of Communicable Diseases Manual, Chin 17^th edition, 2000, and Biological Agent Information Papers, United States Army Institute of Infectious Diseases.