Plague
Plague is caused by Yersinia pestis, a gram-negative bacillus endemic to Arizona, Colorado, California, and New Mexico. Plague is a zoonosis that primarily affects rodents, with humans serving as an "accidental host." Three plague syndromes are recognized: bubonic, septecemic, and pneumonic. Transmission to humans occurs in one of five ways: bite or bites from an infected flea, human-to-human transmission of pneumonic plague, handling of infected animal carcasses, cat bites or scratches, or aerosolization of bacteria. Bubonic plague is the most common human presentation, and fleabites are the most common mode of transmission, followed by contact with infected animals.
The initial cutaneous manifestation of bubonic plague appears 2 to 8 days following the fleabite, and can easily be missed. The primary lesion, which consists of a small papule, or vesicopustule, develops at the site of the fleabite. This stage is soon followed by the abrupt onset of fever, chills, headache, weakness, and tender, proximal lymphadenopathy, most commonly occurring in the inguinal areas or axilla. Gastrointestinal symptoms such as nausea, vomiting, and abdominal pain may occur. The involved nodes become enlarged, matted, and associated with extensive overlying erythema and edema (buboes). Bacteremia may follow, resulting in sepsis and death. In the setting of bacteremia, petechiae and ecchymosis develop, and eschars and lesions similar to those of ecthyma gangrenosum may be seen. Eschars and ecthyma gangrenosum-like lesions can also develop at the site of the fleabite in the absence of bacteremia.
Differential Diagnosis: Plague can be distinguished from cutaneous anthrax in the following manner.
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Plague |
Cutaneous anthrax |
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* Patient has traveled to or resides in an endemic site (western United States) * Patient has been exposed to potential rodent or other animal vector *Fever and buboes develop *Signs of bacteremia and DIC (septic form) may be present |
* Tender lymphadenopathy may be present, but typically buboes are not common *Ulcers are painless * Ulcer and eschar surrounded by characteristic non-pitting edema |
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