Survey of Rickettsia spp. in Amblyomma dubitatum Neumann 1899 and Amblyomma triste Koch 1844 ticks from Brazil and Uruguay, respectivily / Pesquisa de Rickettsia spp. em carrapatos Amblyomma dubitatum Neumann 1899 e Amblyomma triste Koch 1844, provenientes do Brasil e Uruguai, respectivamente

AUTOR(ES)
DATA DE PUBLICAÇÃO

2007

RESUMO

Owing to the potential role of the tick Amblyomma dubitatum and Amblyomma triste in the transmission of the Spotted Fever Group (SFG) Rickettsia, this study evaluated infection by Rickettsia in ticks collected in Brazil and Uruguay, where rickettsial infection is endemic. A total of 841 (367 males e 474 females) A. dubitatum adult ticks were collected in Pedreira, an area of Brazilian Spotted Fever (BSF) endemicity in the state of São Paulo, and 78 adult ticks (25 males, 53 females) identified as A. triste were collected from vegetation in the suburban area of Toledo Chico, southern Uruguay. At the laboratory, all samples were individually processed by the hemolymph test with Gimenez staining and PCR targeting a fragment of the rickettsial gene gltA, present in all Rickettsia species. From 841 A. dubitatum ticks tested by the hemolymph test, 153 (18.18%) samples were positive, 452 (53.74%) were negative, and 236 (28.06%) were inconclusive. All 78 samples of A. triste ticks from Uruguay were negative by the hemolymph test. All 841 samples of A. dubitatum were submitted to PCR, being 378 (44.94%) positive and afterwards tested by PCR targeting a 150-bp fragment of the ompA (a major outer membrane protein A present only in SFG Rickettsia), being all samples negative. From the 378 PCR-positive samples of A. dubitatum, DNA sequence was determined for 93 samples, being all identified as Rickettsia bellii according to GenBank available sequences. For the A. triste samples, only 2 ticks (1 male, 1 female) yielded expected amplicons by PCR. Rickettsia isolation in cell culture was attempted by using the shell vial technique from these two PCR-positive ticks. Rickettsiae were successfully isolated and established in Vero cell culture from the female tick. This isolate, designated as At#5-URG, has been deposited as a reference strain in the Rickettsial Collection of Faculty of Veterinary Medicine in the University of São Paulo. DNA extracted from infected cells of the third passage was tested by a battery of PCRs that used primer pairs targeting fragments of 3 rickettsial genes: gltA, ompB (a major outer membrane protein B), and ompA. PCR products of expected size were obtained in all reactions and subjected to DNA sequencing. Fragments of 1,084, 775, and 491 bp of the gltA, ompB, and ompA genes, respectively, were obtained and showed 100% identity to the corresponding sequences available in GenBank for the Maculatum strain of Rickettsia parkeri from United States.

ASSUNTO(S)

rickettsia bellii amblyomma dubitatum amblyomma dubitatum rickettsia parkeri amblyomma triste ticks carrapatos rickettsia parkeri rickettsia bellii amblyomma triste

ACESSO AO ARTIGO

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