Banca de DEFESA: THAÍS SILVA OLIVEIRA

Uma banca de DEFESA de MESTRADO foi cadastrada pelo programa.
STUDENT : THAÍS SILVA OLIVEIRA
DATE: 25/02/2026
TIME: 13:00
LOCAL: Videoconferência
TITLE:

Tick diversity and molecular detection of Rickettsia spp. in Conservation Units in the state of Rio de Janeiro, Brazil

KEY WORDS:

Molecular biology, integrative taxonomy, nested PCR, PCR-RFLP, coinfection.

PAGES: 87
BIG AREA: Ciências Agrárias
AREA: Medicina Veterinária
SUBÁREA: Medicina Veterinária Preventiva
SPECIALTY: Doenças Parasitárias de Animais
SUMMARY:

Ticks are arthropod vectors of several pathogens and can represent a significant risk to public health, especially in interface areas between forest fragments and human flow, such as Conservation Units dedicated to ecotourism. In this context, the objective of this study was to survey the diversity and spatial distribution of ticks on trails within two Conservation Units in the state of Rio de Janeiro, followed by the molecular detection of Rickettsia spp. The methodology involved acarological surveys using flagging, dragging, and walking trap methods on trails located in the Guapiaçu Ecological Reserve (Cachoeiras de Macacu) and the Cicuta Forest Area of Relevant Ecological Interest (Volta Redonda). Adult and nymphal specimens were morphologically identified to the species level, while larvae were identified to the genus level. DNA extraction was performed using the HotSHOT method, with phenol-chloroform re-extraction for samples that failed to amplify. To obtain comprehensive data regarding species diversity, Polymerase Chain Reaction - Restriction Fragment Length Polymorphism (PCR-RFLP) was employed for larval species identification and to confirm nymphal identification. This technique was based on the amplification of the 16S rDNA and COI genes, followed by enzymatic digestion using the restriction endonucleases DraI and VspI, and PstI and MboI, respectively. The investigation of Rickettsia spp. infection and coinfection involved conventional PCR, nested PCR, and PCR-RFLP assays targeting the gltA, ompA, ompB, sca2, and sca9 genes. A total of 582 ticks were collected, distributed across six species: Amblyomma calcaratum, Amblyomma sculptum, Amblyomma dubitatum, Amblyomma varium, Amblyomma ovale, and Ixodes loricatus. Sample positivity varied according to the Rickettsia target gene. For the gltA gene, conducted via conventional PCR, 62 and 41 A. varium samples were positive for the 401 bp and 834 bp fragments, respectively. In the Spotted Fever Group nested PCRs, ompA (360 bp) and ompB (511 bp), positivity was detected in 69 and 60 A. varium samples, respectively, and in one A. ovale specimen. PCR-RFLP and sequencing identified Rickettsia parkeri strain Atlantic Rainforest in A. ovale and Rickettsia amblyommatis in A. varium. Additionally, nested PCRs for sca2 (764 bp) and sca9 (727 bp) detected Rickettsia bellii in the single specimen of I. loricatus and in two A. ovale specimens, revealing a coinfection of R. parkeri strain Atlantic Rainforest and R. bellii in an A. ovale larvae. This study presents the first report of R. amblyommatis in A. varium in the Southeast region and the first reports of R. bellii infection in I. loricatus and coinfection in A. ovale in the state of Rio de Janeiro. It is concluded that the combined use of nested PCR and PCR-RFLP techniques represents an effective and low-cost strategy for larval identification and detection of rickettsial coinfections. The application of these methodologies allows for a more robust epidemiological characterization, revealing pathogen-host interactions that frequently remain underestimated.

COMMITTEE MEMBERS:
Presidente - 3247559 - BRUNA DE AZEVEDO BAETA
Interna - 3103478 - MARISTELA PECKLE PEIXOTO
Externo à Instituição - HERMES RIBEIRO LUZ - UFMA
Externa à Instituição - IZABELA MESQUITA ARAÚJO - UFRRJ
Externo à Instituição - RODRIGO GREDILHA DUARTE - UNIRIO