Plague

Plague: Excerpt from Handbook of Diseases

Plague, also known as the black death, is an acute infection caused by the gram-negative, nonmotile, nonsporulating bacillus Yersinia pestis (formerly called Pasteurella pestis).

Plague occurs in several forms. Bubonic plague, the most common, causes the characteristic swollen and sometimes suppurative lymph glands (buboes) that give this infection its name. Other forms include septicemic plague, a severe, rapid systemic form; and pneumonic plague, which can be primary or secondary to the other two forms.

Without treatment, mortality is about 60% in bubonic plague and approaches 100% in septicemic and pneumonic plagues. With treatment, mortality is approximately 18%, largely due to the delay between onset and treatment. The patient’s age and physical condition are also factors.

Causes

The bite of a flea from an infected rodent host — such as a rat, squirrel, prairie dog, or hare — is the typical transmission route to humans. Occasionally, transmission occurs from handling infected animals or their tissues. Bubonic plague is notorious for the historic pandemics in Europe and Asia during the Middle Ages, which in some areas killed up to two-thirds of the population. This form is rarely transmitted from person to person. However, the untreated bubonic form may progress to a highly contagious, secondary pneumonic form, which is transmitted by contaminated respiratory droplets. In the United States, the primary pneumonic form usually occurs after inhalation of Y. pestis in a laboratory.

Endemic areas in the United States are California, Utah, Arizona, Nevada, and New Mexico. Bubonic and pneumonic plague can occur.

Signs and symptoms

The three forms of plague vary in their incubation period, early symptoms, severity at onset, and clinical course.

Bubonic plague

With bubonic plague, the incubation period is 2 to 6 days. The milder form begins with malaise, fever, and pain or tenderness in regional lymph nodes, possibly associated with swelling. Lymph node damage (usually axillary or inguinal) eventually produces painful, inflamed, and possibly suppurative buboes. The classic sign of plague is an excruciatingly painful bubo. Hemorrhagic areas may become necrotic; in the skin, such areas appear dark — hence the name “black death.”

Bubonic plague can progress rapidly. A seemingly mildly ill person with fever and adenitis may become moribund within hours.

Bubonic plague may also begin dramatically, with a sudden high fever of 103° to 106° F (39.4° to 41.1° C), chills, myalgia, headache, prostration, restlessness, disorientation, delirium, toxemia, and staggering gait. Occasionally, it causes abdominal pain, nausea, vomiting, and constipation followed by diarrhea (frequently bloody), skin mottling, petechiae, and circula-tory collapse.

Septicemic plague

Septicemic plague usually develops without overt lymph node enlargement. With this form, the patient shows toxicity, hyperpyrexia, seizures, prostration, shock, and disseminated intravascular coagulation (DIC). Septicemic plague causes widespread nonspecific tissue damage — such as peritoneal or pleural effusions, pericarditis, and meningitis — and is fatal if the patient doesn’t receive prompt treatment.

Pneumonic plague

Primary pneumonic plague is an acutely fulminant, highly contagious form of plague that causes acute prostration, respiratory distress, and death — typically within 2 to 3 days after onset.

The incubation period for primary pneumonic plague is 2 to 3 days. It’s followed by a typically acute onset, including high fever, chills, severe headache, tachycardia, tachypnea, dyspnea, and a productive cough (first mucoid sputum; later frothy pink or red).

Secondary pneumonic plague, the pulmonary extension of the bubonic form, complicates about 5% of cases of untreated plague. A cough that produces bloody sputum signals this complication. The primary and secondary forms of pneumonic plague rapidly cause severe prostration, respiratory distress and, usually, death.

Diagnosis

Because plague is rare in the United States, it’s commonly overlooked until after the patient dies or multiple cases develop.

Bubonic plague

Characteristic buboes and a history of exposure to rodents strongly suggest bubonic plague. Stained smears and cultures of Y. pestis (obtained from a small amount of fluid aspirated from skin lesions) confirm this diagnosis.

Postmortem examination of a guinea pig inoculated with a sample of blood or purulent drainage allows isolation of the organism. Other labora-tory findings include a white blood cell count over 20,000/µl with increased polymorphonuclear leukocytes and hemoagglutination reactions (increased antibody titer).

Diagnosis should rule out tularemia, typhus, and typhoid.

Septicemic plague

Stained smear and blood culture containing Y. pestis are diagnostic in septicemic plague.

Pneumonic plague

Diagnosis of pneumonic plague requires a chest X-ray to show fulminating pneumonia and stained smear and culture of sputum to identify Y. pestis. Other bacterial pneumonias and psittacosis must be ruled out.

UNDER STUDY: Researchers have developed a rapid diagnostic test for bubonic and pneumonic plague. It uses monoclonal antibodies to the F antigen of Y. pestis and has a sensitivity and specificity of 100%. Results from the test are available within 15 minutes and have a shelf life of 21 days at 60° F (15.6° C).

Treatment

Because cultures of Y. pestis grow slowly, treatment of suspected plague (especially pneumonic and septicemic plagues) should begin immediately, even before laboratory confirmation is received. Generally, treatment consists of large doses of streptomycin, the drug proven most effective against Y. pestis. Other effective drugs include gentamicin, doxycycline, and chloramphenicol. Penicillins are ineffective against plague.

For septicemic and pneumonic plagues, life-saving antimicrobial treatment must begin within 18 hours of onset. Supportive management aims to control fever, shock, and seizures and to maintain fluid balance.

After antimicrobial therapy is initiated, glucocorticoids may be prescribed to combat life-threatening toxemia and shock; diazepam can be used to decrease restlessness. If the patient develops DIC, treatment may also include heparin.

Special considerations

❑ Make sure the patient is kept in strict isolation, until at least 48 hours after antimicrobial therapy begins, provided respiratory symptoms don’t develop.

❑ Use an approved insecticide to rid the patient and his clothing of fleas. Carefully dispose of soiled dressings and linens, feces, and sputum. If the patient has pneumonic plague, wear a gown, mask, and gloves. Handle all exudates, purulent discharge, and laboratory specimens with rubber gloves. For more information, consult your infection control officer.

❑ Treat buboes with hot, moist compresses. Never excise or drain them because this could spread the infection.

❑ When septicemic plague causes peripheral tissue necrosis, pad the bed’s side rails and avoid using restraints or armboards. This prevents further injury to necrotic tissue.

❑ Obtain a history of patient contacts so that they can be quarantined for 6 days of observation. Administer prophylactic tetracycline as ordered.

❑ Report suspected cases of plague to local public health department officials so that they can identify the source of infection.

❑ To help prevent plague, discourage contact with wild animals (especially those that are sick or dead), and support programs aimed at reducing insect and rodent populations. Even though the effect of immunization is transient, recommend immunization with the plague vaccine to people who travel to and reside in endemic areas.

Book Source Details

• Book Title: Handbook of Diseases
• Author(s): Springhouse
• Year of Publication: 2003
• Copyright Details: Handbook of Diseases, Copyright © 2003 Lippincott Williams & Wilkins.

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More About This Book: Title: Handbook of Diseases Authors: Springhouse Publisher: Lippincott Williams & Wilkins Copyright: 2003 ISBN: 1-58255-266-5

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