Rocky Mountain spotted fever is a serious disease that is often fatal in humans. It is caused by a kind of bacterium called rickettsia. The bacteria infects the Rocky Mountain wood tick and the American dog tick. The ticks become infected when they bite small mammals, such as field mice and dogs, that are infected with the bacteria. When the tick bites a person, it transfers the rickettsia to that person’s bloodstream. Doctors first discovered the fever in the Rocky Mountain area of the United States, but it occurs throughout the country. It is most common in the Southeastern and Middle Atlantic States. About 600 cases are reported every year, usually in late spring or early summer. It begins with chills and fever, and severe pains in the leg muscles and the joints. Then a rash develops. The fever resembles many of the typhus diseases (see Typhus ).
Tetracyclines, such as doxycycline << `DOC`see sy klihn, >> and other antibiotics are effective in treatment. Vaccines against the disease have proved relatively ineffective. Recovery from the fever gives complete immunity.
See also Rickettsia .
