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Spotted fevers, which are caused by Rickettsia spp. in the spotted fever group (SFG), have been recognized in people for more than a hundred years. The clinical signs are broadly similar in all of these diseases, but the course ranges from mild and self-limited to severe and life-threatening. For a long time, spotted fevers were thought to be caused by only a few organisms, including Rickettsia rickettsii (Rocky Mountain spotted fever) in the Americas, R. conorii (Mediterranean spotted fever) in the Mediterranean region and R. australis (Queensland tick typhus) in Australia. Many additional species have been recognized as human pathogens since the 1980s. These infections are easily misidentified with commonly used diagnostic tests. For example, some illnesses once attributed to R. rickettsii are caused by R. parkeri, a less virulent organism.

Animals can be infected with SFG rickettsiae, and develop antibodies to these organisms. With the exception of Rocky Mountain spotted fever and possibly Mediterranean spotted fever in dogs, there is no strong evidence that these organisms are pathogenic in animals. It is nevertheless possible that illnesses have not been recognized, or have been attributed to another agent. Rocky Mountain spotted fever, which is a recognized illness among dogs in the North America, was only recently documented in dogs in South America.

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Iowa State University



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