Tularemia
Tularemia is caused by Francisella tulaeresis, a gram-negative coccobacillus. Six clinical syndromes are recognized: ulceroglandular, glandular, typhoidal, pneumonic, oropharyngeal, and oculoglandular. As many as 80% of the cases are ulceroglandular, and are the result of direct contact with infected animals; the organisms are introduced through minor skin abrasions. They can also be caused by the bite of an animal, espically a cat, or an insect vector, particularly a tick or deer fly. After an incubation period of 2 to 10 days, there is an abrupt onset of fever, chills, headache, and myalgias. The primary lesion develops at the site of inoculation, usually the hand, is associated with regional lymphadenopathy, and occasionally, nodular lymphangitis. The primary lesion begins as a single, red, painful papule that develops a central ulcer with raised margins, often covered by a black eschar. Systemic toxicity can be marked.
Differential Diagnosis: Tularemia can be distinguished from cutaneous anthrax in the following manner.
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Tularemia |
Cutaneous anthrax |
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*Onset follows contact with cats, rabbits, foxes, squirrels, muskrats, beavers, and pheasants or potential exposure to tick or deer fly vector *Lesion is a painful papule or ulcer |
*Ulcer is painless * Ulcer and eschar are surrounded by characteristic non-pitting edema |
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