Plague

Key Features

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

General Considerations

• An zoonotic infection carried by wild rodents and caused by Yersinia pestis, a small bipolar-staining gram-negative rod

• It is transmitted among rodents and to humans by the bites of fleas or from contact with infected animals

• Following the flea bite, the organisms spread through the lymphatics to the lymph nodes, which become greatly enlarged (bubo). They may then reach the bloodstream to involve all organs

• If pneumonia develops in a patient with plague, the infection can be transmitted by droplets to other individuals

• 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

Demographics

• It is endemic in California, Arizona, Nevada, and New Mexico

• Worldwide, Madagascar accounts for three-quarters of the global burden

Clinical Findings

Symptoms and Signs

• The onset is sudden, with high fever, malaise, tachycardia, intense headache, delirium, and severe myalgias

• 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

• Signs of meningitis may develop

• With hematogenous spread, the patient may rapidly become toxic and comatose, with purpuric spots (black plague) appearing on the skin

• Primary plague pneumonia is a fulminant pneumonitis with bloody, frothy sputum and sepsis

• If pneumonia develops, tachypnea, productive cough, blood-tinged sputum, and cyanosis also occur

Differential Diagnosis

• Lymphadenitis accompanying staphylococcal or streptococcal infections of an extremity

• Sexually transmitted diseases, such as lymphogranuloma venereum or syphilis

• Tularemia

• Enteric or rickettsial fevers

• Malaria

• Influenza

• Other bacterial pneumonias

• Meningitis caused by other bacteria

Diagnosis

Laboratory Tests

• The plague bacillus may be found in Gram-stained smears from aspirates of buboes

• 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

Treatment

Medications

• Therapy should be started immediately once plague is suspected

• Either streptomycin (the agent with which there is greatest experience), 1 g every 12 hours intravenously, or gentamicin, administered as a 2 mg/kg loading dose, then 1.7 mg/kg every 8 hours intravenously, is ...