Rickettsia parkeri Rickettsiosis, Argentina

Rickettsia parkeri, a recently identifi ed 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 confi rmed R. parkeri infection and 7 additional patients with suspected R. parkeri rickettsiosis identifi ed 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.R ickettsia parkeri, a tick-borne bacterium discovered in 1937, was considered nonpathogenic until 2004.Since 2004, >25 cases of R. parkeri rickettsiosis have been reported in persons living within the recognized range of the tick vector, Amblyomma maculatum, in the United States (1-4; Centers for Disease Control and Prevention, unpub.data).The clinical features of this newly recognized disease appear less severe than those produced by R. rickettsii bacteria, the agent of Rocky Mountain spotted fever (RMSF).For many years, investigators in several countries of South America, including Argentina, Brazil, and Uruguay, have recognized eschar-associated infections that clinically resemble R. parkeri rickettsiosis (5-7).These reports, and the discoveries of R. parkeri in A. triste ticks collected from these same countries, suggest that human infections with R. parkeri also occur in South America (8-10); to our knowledge, no confi rmed cases of disease caused by this Rickettsia species have been reported from this continent.The Paraná Delta, situated in the provinces of Buenos Aires and Entre Ríos in Argentina, represents the terminus of the Paraná River as it approaches and drains into the Uruguay River and subsequently into the Río de la Plata.This alluvial ecosystem, where braided river branches create a network of islands and wetlands, covers ≈14,000 km 2 (5,405 mi 2 ) and extends for ≈320 km (200 mi).This region also contains abundant populations of A. triste ticks (10).The Paraná Delta has always been a major agricultural and farming region.Recently, this area has become increasingly developed; roads have been built to allow greater access for tourism and recreational activities by many of the ≈14 million inhabitants of nearby Buenos Aires.In 2005, an eschar-associated febrile infection was diagnosed in a male beekeeper from the Paraná Delta; the infection was later confi rmed as a spotted fever group (SFG) rickettsiosis by serology and immunohistochemistry (5).He had been bitten by a tick not far from several sites where R. parkeri was subsequently detected in A. triste ticks (10).We report confi rmed cases of R. parkeri rickettsiosis in 2 patients in Argentina and describe additional suspected cases of this disease, or similar infections, in patients from the provinces of Buenos Aires, Chaco, and Entre Ríos.