Detection of a novel spotted fever group rickettsia in Amblyomma parvum ticks (Acari: Ixodidae) from Argentina

Abstract

The present study evaluated the rickettsial infection in Amblyomma parvumticks collected in Northwestern Córdoba Province, Argentina. Each tick was subjected toDNA extraction and tested by polymerase chain reaction (PCR) targeting fragments of therickettsial genes gltA and ompB. Nine (69.2%) out of 13 adult ticks yielded expected PCRproducts for the two rickettsial genes. Products from the ompB PCR were sequenced,generating DNA sequences 100% identical for the nine PCR-positive ticks. Three of theseticks were tested in another battery of PCR targeting fragments of the rickettsial genes gltA,htrA, and ompA. Products from the gltA, htrA, and ompA PCRs were sequenced generatingDNA sequences 100% identical for the three PCR-positive ticks. The rickettsia detected inthe A. parvum ticks was designated as Rickettsia sp. strain Argentina. Phylogenetic analysesperformed with partial sequences of the rickettsial genes gltA, htrA, ompB, and ompAshowed that Rickettsia sp. strain Argentina belonged to the spotted fever group, being distinctfrom all known Rickettsia species and genotypes available in GenBank, representingpossibly a new Rickettsia species. This was the Wrst evidence of rickettsial infection in thetick A. parvum, and the third report of rickettsial infection among the Argentinean tickfauna. The role of Rickettsia sp. strain Argentina as a human pathogen is unknown. Furtherstudies are needed to obtain tissue-cultured isolates of Rickettsia sp. strain Argentina, inorder to better characterize it and to determine its taxonomic status as a new species.