ABSTRACT
Plague, a severe febrile illness caused by the Gram-negative bacterium Yersinia pestis, is a zoonosis usually transmitted by ¦ea bites. It is foremost a disease of rodents; over 200 species are reservoirs of Y. pestis [1,2]. When ¦eas feed on a bacteremic animal, the organism is taken with the blood meal into the midgut of the ¦ea where it multiplies, eventually forming a mass of aggregated bacteria that blocks the proventriculus, a valve-like structure leading to the midgut. This blockage starves the ¦ea, which then makes repeated, desperate attempts to feed. Because of the blockage, blood carrying Y. pestis is regurgitated into the bite wounds, thus spreading the disease to new hosts. The blocked ¦ea, also a victim of the disease, eventually starves to death [3]. Most often, humans become infected by ¦ea bite during an epizootic event. Less frequently, human disease is a result of contact with blood or tissues of infected animals (including ingestion of raw or undercooked meat), or exposure to aerosol droplets containing the organism [2,4]. Infectious aerosols can be generated by humans or animals with plague pneumonia, particularly cats [5,6].
