Rickettsia parkeri Rickettsiosis, Argentina

Abstract

Rickettsia parkeri, a recently identified cause of spotted fever rickettsiosis in the United States, has been found in Amblyomma triste ticks in several countries of South America, including Argentina, where it is believed to cause disease in humans. We describe the clinical and epidemiologic characteristics of 2 patients in Argentina with confirmed R. parkeri infection and 7 additional patients with suspected R. parkeri rickettsiosis identified at 1 hospital during 2004-2009. The frequency and character of clinical signs and symptoms among these 9 patients closely resembled those described for patients in the United States (presence of an inoculation eschar, maculopapular rash often associated with pustules or vesicles, infrequent gastrointestinal manifestations, and relatively benign clinical course). Many R. parkeri infections in South America are likely to be misdiagnosed as other infectious diseases, including Rocky Mountain spotted fever, dengue, or leptospirosis.

Figure 1

Confirmed and suspected cases of Rickettsia parkeri rickettsiosis, Argentina. The box (A) enlarged in panel (B) shows the extent of the area in which Argentinean provinces, representing patient exposure locations to ticks, are labeled and highlighted. A previous study (10) identified ticks collected from the Paraná Delta near the city of Campana. Numbers of suspected and confirmed cases of R. parkeri rickettsiosis, by province during 2004–2009, are shown in parentheses. The national capital city of Buenos Aires continues to experience rapid population growth into adjacent lands in and near the Paraná Delta. Rocky Mountain spotted fever, a more severe tick-borne rickettsiosis, has been described in the province of Jujuy in the northwestern corner of Argentina (15,16).

Figure 2

Cutaneous lesions of patients with suspected and confirmed Rickettsia parkeri rickettsiosis in Argentina. A) Eschar at the nape of the neck at the site of recent tick bite. B, C) Papulovesicular rash involving the back and lower extremities. D) Histopathologic appearance of a papule biopsy specimen, showing perivascular mononuclear inflammatory cell infiltrates and edema of the adjacent superficial dermis and an intact epidermis (hematoxylin and eosin stain; original magnification ×100).