A tick-borne rickettsia of the spotted-fever group, similar to Rickettsia amblyommii, in French Guyana

Rickettsiae of the spotted-fever group (SFG) are obligatory intracellular Gramnegative bacteria, belonging to the genus Rickettsia, that are associated with arthropods, mainly ticks, which may act as vectors and sometimes as reservoirs (Parola et al., 2005). Between 1984 and 2005, 11 species or subspecies of rickettsia have been identified as emerging agents of tick-borne rickettsioses of humans throughout the world (Parola et al., 2005). Many Rickettsiae of the SFG have, however, only yet been isolated from ticks, and the pathogenicity of these bacteria to humans is still unknown (Parola et al., 2005). Several SFG Rickettsiae have been reported in South America. Two known human pathogens have been isolated in this region: Rickettsia rickettsii from the ticks Amblyomma cajennense and A. aureolatum in Brazil (Dias and Martins, 1939; Sanguioni et al., 2005), and R. parkeri from A. triste in Uruguay (Venzal et al., 2004). Other Rickettsiae of unknown pathogenicity, including R. bellii (Labruna et al., 2004a), ‘R. andeanae’ (Blair et al., 2004), Rickettsia strain Cooperi (Labruna et al., 2004b), and ‘R. amblyommii’ (Labruna et al., 2004a), have also been recorded in South America. In French Guyana — a French territory in South America — virtually nothing is known of the prevalence of SFG Rickettsiae in ticks. The results of a molecular survey on ticks collected from reptiles and mammals in French Guyana are therefore presented here. The 57 ticks investigated — six Amblyomma humerale from two tortoises, 13 A. coelebs from two white-lipped peccaries, one A. cajennense from another white-lipped peccary, and 37 A. rotundatum from three snakes — were collected near the French army’s training centre in the Equatorial forest at Regina (4u189N, 52u089W), in September 2004. They were all identified by morphology, using the taxonomic keys of Floch and Fauran (1958), and stored in 70% ethanol until DNA could be extracted from them. For the extraction, each tick was washed twice with distilled water, dried on sterile filter paper, and then cut in half. The DNA in one half of each tick was extracted using the QIAamp DNA mini kit (Qiagen, Hilden, Germany), following the manufacturer’s instructions, and then tested, in PCR-based assays, for the rickettsial ompA gene, using the 190.70 and 190.701 primers (Parola et al., 2001), and for the rickettsial gltA gene, using the Rp877p and Rp1258n primers (Roux et al., 1997). Both negative controls, in which the test DNA in the reaction mixture was replaced with DNA extracted from laboratory-reared ticks or with distilled water, and a positive control (DNA from R. montanensis), were included in each batch of assays. The PCR products were purified and sequenced as previously described (Parola et al., 2001). All the rickettsial ompA gene sequences obtained were assembled, edited and compared with the relevant sequences in the GenBank database (Parola et al., 2003). The ClustalW and TreeView software packages (http://taxonomy.zoology.gla.ac.uk/rod/rod.html) were then used to construct phylogenetic trees based on the sequence data. Two of the 13 A. coelebs collected from white-lipped peccaries and the positive control were found positive for rickettsial Annals of Tropical Medicine & Parasitology, Vol. 101, No. 2, 185–188 (2007)