buboes

In bubonic plague, Yersinia pestis is inoculated by the bite of a rat flea, Xenopsylla cheopis, travels to the draining node, and multiplies there, producing a hot, painful, matted node that may suppurate. Onset is abrupt with high fever and prostration, and untreated disease progresses to septicaemic plague with disseminated intravascular coagulation and acral gangrene, the 'black death', or to pneumonic plague, which alone transmits person to person by respiratory droplets and requires airborne precautions. Y. pestis is a gram-negative rod with bipolar 'safety pin' staining on Giemsa or Wright stain, and it uses a type III secretion system to inject Yop proteins that block phagocytosis. In the United States it is enzootic in prairie dogs and ground squirrels of the south-west. Treatment is streptomycin or gentamicin, with doxycycline or fluoroquinolone alternatives. Distinguishing features of other bubo-forming diseases: chancroid has a painful ulcer, lymphogranuloma venereum has a painless transient ulcer and the groove sign, and tularaemia follows rabbit or tick exposure.