Tropical Diseases - Plague

Bubonic plague is transmitted to humans through direct or indirect contact with animals. At least three great epidemics of bubonic plague have been recorded, including the Black Death of the 14th century, when the disease claimed at least 50 million lives. While recent cases of the plague in North America have been relatively rare, cases of the plague still occur in the western United States. Increased outdoor activity in these areas has resulted in a higher incidence of the disease among humans in recent years.


The infection is transmitted from animals to man through the bite of a flea carrying the disease organism. Symptoms usually develop in several days but may take as long as two weeks after the flea bite. The victim experiences chills and fever, with the temperature rising above 102° F. He may experience headaches, a rapid heart beat, and difficulty walking. Vomiting and delirium also are among the symptoms of plague. There may be pain and tenderness of the lymph nodes, which become inflamed and swollen; the enlarged lymph nodes are known as buboes , a term that gives its name to the type of plague involved. The buboes occur most frequently in the legs and groin because these are the most frequent sites for flea bites.

The site of the flea bite may or may not be found after the symptoms develop. If present, it may be marked by a swollen, pus-filled area of the skin.

Diagnosis of plague can be confirmed by laboratory tests that might include examination of the bacteria taken in samples from buboes or other diseased areas of the body, inoculation of laboratory animals with suspected disease organisms, and studies of the white blood cells of the patient.

Complications can include pneumonia and hemorrhages, with bleeding from the nose or mouth or through the gastrointestinal or urinary tracts, and abscesses and ulcerations. The pneumonic form of plague can be transmitted from one person to another like colds or other infectious diseases; in other words, plague organisms are spread by being exhaled by one person and inhaled by another.

Treatment and Prevention

As in other infectious diseases, early treatment is most effective. Antibiotics are administered every day for a period of one to two weeks, and buboes are treated with hot, moist applications. The buboes may be drained if necessary after the patient has responded to antibiotic medications. Antibiotics have reduced the fatality rate from plague infections from a high of 90 percent to a maximum of about 10 percent. Vaccines are available but are of limited and temporary value. Prevention requires eradication of rats and other possibly infected rodents (some 200 species are known to carry the disease), use of insecticides to control fleas, and avoidance of contact with wild animals in areas where plague is known to exist. Domestic animals also should be protected from contact with possibly infected wild animals.

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