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Title: Rocky Mountain spotted fever in Argentina

item PADDOCK, C.
item SUMNER, J.
item Reeves, Will

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 7/1/2007
Publication Date: 9/19/2007
Citation: Paddock, C.D., Fernandez, S., Echenique, G., Sumner, J.W., Reeves, W.K., Remondegui, C.E. 2007. Rocky Mountain spotted fever in Argentina. 21st Meeting of the American Society for Rickettsiology, Colorado Springs, CO. 19 Sept. 2007. Meeting Abstract.

Interpretive Summary:

Technical Abstract: Cases of epidemic typhus have been documented in Argentina since 1919; however, no confirmed reports of spotted fever rickettsiosis were described in this country until 1999. We describe the first molecular confirmation of Rickettsia rickettsii, the etiologic agent of Rocky Mountain spotted fever (RMSF), in a tick vector, Amblyomma cajennense (the Cayenne tick), and in a patient with fatal infection, from Jujuy Province in northwestern Argentina. Three boys and 1 man from the Departments of San Salvador de Jujuy and Santa Bárbara died following illnesses of approximately 1 week duration during September and October, 2003-2004. All had tick bites shortly before illness onset and all developed fever, headache, myalgias and a petechial rash. Serum specimens were available for 2 patients who had IgG antibody titers reactive with R. rickettsii > 128. Autopsy specimens were available for 2 patients and both demonstrated abundant spotted fever group rickettsiae in endothelial cells by an immunohistochemical stain. A 590-bp segment of the rompA gene was subsequently amplified from fixed splenic tissue from this patient that demonstrated 100% homology to the corresponding segment of the rompA gene of R. rickettsii. Additionally, questing A. cajennense ticks were collected from or near sites of presumed or confirmed cases of spotted fever rickettsiosis in Jujuy Province and evaluated by PCR ssays for spotted fever group rickettsiae. A 608-bp segment of the rompA gene was amplified from a pool of 5 nymphal A. cajennense ticks collected near the home of 2 children who had died from spotted fever years earlier, and showed 100% identity to the corresponding sequences of R. rickettsii. The findings reported here conclusively demonstrate the occurrence of RMSF in Argentina and emphasize the need for clinicians and public health officials throughout the Americas to consider RMSF in the differential diagnoses of febrile rash illnesses.