(Received 23 March 1978; accepted 14 June 1978)
Published Online: 1979
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Plague is an ancient bacterial disease of rodents that occurs in man in sporadic and epidemic forms. The causative organism is the Gram-negative bacterium Yersinia pestis, which multiplies in the stomach of fleas (particularly the Oriental rat flea Xenopsylla cheopis) [1,2]. Microscopic examination of infected fleas reveals large masses of bacteria in their stomachs. The bacterial masses eventually block passage of the victim's blood and when blockage occurs, bacteria are regurgitated into the wound and passed in the feces of the flea. Fortunately, the rat flea prefers the rat as a host but, if the rat dies, the flea seeks a new warm-blooded host. The nearest warm-blooded animal may be man, and when man is infected the symptoms are those of many febrile diseases and include fever, malaise, tachycardia, headache, vomiting, lymphadenopathy, delirium, and shaking chills. The flea bite is rarely seen, and if it is present a papule or vesicle is identified which is usually pustular. Sixty to seventy-five percent of lymphadenopathy occurs in the inguinal areas because the majority of flea bites occur on the legs. Enlarged inguinal nodes were named buboes, but the use of this term has been expanded to include other lymph node groups as well. Plague occurs in three forms: bubonic, septicemic (bacteremic), and pneumonic. Bubonic plague is now the most common form seen in man and fever, malaise, and buboes are the usual symptoms. Proliferation of plague organisms produces enlargement of the lymph node and the organisms may escape into the circulation, causing septicemia (bacteremia). Organisms may be trapped in the lungs, resulting in secondary plague pneumonia. The pneumonic form can result in man-to-man infection by aspiration of infected exhaled droplets from a plague victim and this mode of transmission potentially can produce an epidemic (primary plague pneumonia) . The last cases of primary plague pneumonia occurred in California in 1924 . Unfortunately, pulmonary findings in plague pneumonia may be lacking until the final day when the victim coughs up copious bloody sputum. In bubonic plague, the disease can be transmitted from man to man by the human flea, Pulex irritans. If septicemia occurs, subcutaneous hemorrhages can occur which, if massive, impart a “black” color to the patient and therefore the term “Black Death” evolved.
Associate medical investigator and assistant professor of pathology, Office of the Medical Investigator, School of Medicine, The University of New Mexico, Albuquerque,
New Mexico State epidemiologist, Sante Fe, N. Mex.
Resident, School of Medicine, The University of New Mexico, Albuquerque,
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