Rickettsia parkeri in Uruguay

To the Editor: During 1990 in Uruguay, a rickettsiosis in the spotted fever group was presumptively diagnosed for 3 patients who had fever, an initial small maculopapulous lesion at the site of a tick bite on the scalp, and subsequent regional lymphadenopa-thy. Microimmunofluorescent sero-logic assay, with Rickettsia conorii as the sole antigen source, gave positive results for all patients, and these infections were presumptively identified as spotted fever caused by R. of 23 patients who had a history of tick bite, some of whom had exanthe-ma and inoculation eschars, were identified from Canelones County, Uruguay. These patients had antibod-ies against R. conorii, according to microimmunofluorescence testing; however, R. conorii was again the sole antigen source used in the assay (2). Because 1 of the major limitations of serologic testing for diagnosis of rickettsioses is the cross-reactivity between different Rickettsia species, the association of R. conorii with the spotted fever group cases in Uruguay was considered inappropriate (3). In addition, R. conorii has never been found in the Western Hemisphere (3). Amblyomma triste, a neotropical tick species with a variety of hosts, is the main tick species that feeds on humans in Uruguay and the primary candidate vector for tickborne rickettsioses in that country (4). A recent investigation demonstrated DNA of R. parkeri in A. triste ticks collected from humans and animals, indicating that this rickettsia could be the pathogenic agent of spotted fever group rickettsioses in Uruguay (5). In the United States, where A. macula-tum ticks infected with R. parkeri have been reported since the 1930s, the role of this rickettsial agent as a human pathogen was confirmed only recently (3). Our study is the first to isolate R. parkeri from A. triste collected in Uruguay and confirms the presence of this emerging pathogen in South America. During September 2004, 78 adult flat ticks (25 males, 53 females) identified as A. triste were collected from vegetation in the suburban area of Toledo Chico (34°44′53″S, 56°06′ 19″´W) in Canelones County, southern Uruguay. At the laboratory, the legs of live ticks were extirpated for DNA extraction, and the tick bodies were immediately frozen at −80°C. Each group of legs from 1 tick was subjected to DNA extraction by boiling at 100°C for 20 min as described (6). DNA extracted from each tick was tested by PCR by using primers CS-78 and CS-323 (Table), which targeted a 401-bp fragment of the citrate synthase …