A. Rocky Mountain spotted fever

Rocky Mountain spotted fever, a disease caused by Rickettsia rickettsii, is transmitted by wood ticks and dog ticks. Symptoms appear approximately one week after infection and include fever, headache, and a rash which usually appears 3 to 5 days later on the wrists and ankles, spreading to chest and abdomen. The greatest incidence is reported in the states Oklahoma, North and South Carolina, Arkansas, Georgia, and Virginia.

B. Legionnaire's Disease

Legionnaire's Disease, a bacterial pneumonia, is caused by an infection of the lung with Legionella pneumophila. Legionella is ubiquitous in soil and water and may grow in cooling towers of central air-conditioning systems. Infection usually occurs by inhalation of aerosolized bacteria from air-conditioning systems. The disease typically occurs in individuals with a compromised immune system (smoking, alcohol, old age) while healthy children and adults are relatively resistant.

C. Cholera

Cholera is caused by the ingestion of food or water contaminated with the feces of an infected individual. The causative agent is the bacterium Vibrio cholerae, which can grow in the intestines after ingestion and produces a toxin leading to massive diarrhea and fluid loss.

D. Plague

Plague can occur in two different clinical manifestations: bubonic plague and pneumonic plague. Bubonic plague is typically transmitted by infected fleas, not ticks. Yersinia pestis, the causative agent, enters the body of the victim as the flea is feeding. The bacteria are then transported to the local lymph nodes where they multiply and cause the characteristic swellings (bubo). Pneumonic plague can result when the bacteria spread from the lymph nodes via the blood stream to the lungs or directly by inhalation of aerosolized bacteria from a patient with pneumonic plague.

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The Biology Project
University of Arizona
Tuesday, August 4, 1998
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