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ESSENTIALS OF DIAGNOSIS
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ESSENTIALS OF DIAGNOSIS
History of exposure to rodents in endemic area.
Sudden onset of high fever, muscular pains, and prostration.
Axillary, cervical, or inguinal lymphadenitis (bubo).
Pustule or ulcer at inoculation site.
Pneumonia or meningitis is often fatal.
Positive smear and culture from bubo and positive blood culture.
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GENERAL CONSIDERATIONS
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Plague is a zoonotic infection carried by wild rodents and caused by Yersinia pestis, a small bipolar-staining gram-negative rod. It is endemic in California, Arizona, Nevada, and New Mexico. Worldwide, Madagascar accounts for three-quarters of the global burden. It is transmitted among rodents and to humans by the bites of fleas or from contact with infected animals. Following a fleabite, the organisms spread through the lymphatics to the lymph nodes, which become greatly enlarged (buboes). They may then reach the bloodstream to involve all organs. When pneumonia or meningitis develops, the outcome is often fatal. The patient with pneumonia can transmit the infection to other individuals by droplets. The incubation period is 2–10 days. Because of its extreme virulence, its potential for dissemination and person-to-person transmission, and efforts to develop the organism as an agent of biowarfare, plague bacillus is considered a high-priority agent for bioterrorism.
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A. Symptoms and Signs
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The onset is sudden, with high fever, malaise, tachycardia, intense headache, delirium, and severe myalgias. The patient appears profoundly ill. If pneumonia develops, tachypnea, productive cough, blood-tinged sputum, and cyanosis also occur. There may be signs of meningitis. A pustule or ulcer at the site of inoculation may be observed. Axillary, inguinal, or cervical lymph nodes become enlarged and tender and may suppurate and drain. With hematogenous spread, the patient may rapidly become toxic and comatose, with purpuric spots (black plague) appearing on the skin.
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Primary pneumonic plague is a fulminant pneumonitis with bloody, frothy sputum and sepsis. It is usually fatal unless treatment is started within a few hours after onset.
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B. Laboratory Findings
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The plague bacillus may be found in smears from aspirates of buboes examined with Gram stain. Cultures from bubo aspirate or pus and blood are positive but may grow slowly. In convalescing patients, an antibody titer rise may be demonstrated by agglutination tests.
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DIFFERENTIAL DIAGNOSIS
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The lymphadenitis of plague is most commonly mistaken for the lymphadenitis accompanying staphylococcal or streptococcal infections of an extremity, sexually transmitted diseases such as lymphogranuloma venereum or syphilis, and tularemia. The systemic manifestations resemble those of enteric or rickettsial fevers, malaria, or influenza. The pneumonia resembles other bacterial pneumonias, and the meningitis is similar to those caused by other bacteria.
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Avoiding exposure to rodents and fleas in endemic areas is the best prevention strategy. Drug prophylaxis may ...