Banca de DEFESA: DAVI GUIMARAES DE ALMEIDA

Uma banca de DEFESA de DOUTORADO foi cadastrada pelo programa.
STUDENT : DAVI GUIMARAES DE ALMEIDA
DATE: 23/12/2025
TIME: 08:00
LOCAL: Videoconferência
TITLE:

Diagnosis of Rickettsia spp. in free-living ticks and those collected from wild animals in the Atlantic Forest, Cerrado, and Amazon biomes.

KEY WORDS:

Ticks; Rickettsia; Amazon; Atlantic Forest; Cerrado.

PAGES: 74
BIG AREA: Ciências Agrárias
AREA: Medicina Veterinária
SUBÁREA: Medicina Veterinária Preventiva
SPECIALTY: Doenças Parasitárias de Animais
SUMMARY:

Species of the genus Rickettsia are widely distributed in Brazil, including Rickettsia rickettsii, Rickettsia parkeri, Rickettsia bellii, Rickettsia felis, and Rickettsia amblyommatis, with R. rickettsii being the main causative agent of Brazilian spotted fever. Despite the well-recognized importance of ticks in maintaining these agents, comparative studies across different biomes remain scarce. This study aimed to investigate tick diversity and the occurrence of Rickettsia spp. in free-living ticks and those collected from wild hosts in the Amazon, Atlantic Forest, and Cerrado biomes. A total of 460 ticks were analyzed, with a predominance of the genus Amblyomma (99.7%), collected in the Amazon (n = 303), Cerrado (n = 64), and Atlantic Forest (n = 93). Specimens were morphologically identified and subjected to molecular detection of Rickettsia spp. by conventional PCR targeting the gltA, htrA (17 kDa), and ompA genes, followed by sequencing and phylogenetic analysis. Overall, 9.22% of the samples were positive for Rickettsia spp., with detection restricted to the Amazon and Atlantic Forest biomes. The tick species associated with positive samples were Amblyomma cajennense sensu stricto, Amblyomma sculptum, Amblyomma dubitatum, Amblyomma ovale, Amblyomma geayi, and Ixodes loricatus. In the Amazon, A. cajennense s.s. and A. geayi were detected in Tapirus terrestris, Bradypus variegatus, and in the environment, indicating high ecological plasticity. In the Atlantic Forest, A. sculptum and A. dubitatum parasitizing Hydrochoerus hydrochaeris showed high positivity, reinforcing the role of capybaras as amplifier hosts in enzootic cycles. No Rickettsia spp. was detected in the Cerrado. Positive nymphs were predominantly infected with R. amblyommatis, with a single detection of R. felis in an A. sculptum nymph. No DNA of R. rickettsii was detected in the analyzed samples; however, spotted fever group rickettsiae, such as R. parkeri and R. amblyommatis, were identified. These results demonstrate that the circulation of rickettsiae varies among biomes, reflecting ecological, vector-related, and host-related differences. The study highlights the importance of ticks in maintaining enzootic cycles and emphasizes the need for integrated surveillance at the human–animal–environment interface under a One Health perspective.

COMMITTEE MEMBERS:
Presidente - 3247559 - BRUNA DE AZEVEDO BAETA
Interna - 3103528 - CLAUDIA BEZERRA DA SILVA
Interna - 3103478 - MARISTELA PECKLE PEIXOTO
Externo à Instituição - RODRIGO GREDILHA DUARTE - UNIRIO
Externa à Instituição - IZABELA MESQUITA ARAÚJO - UFRRJ
Externo à Instituição - ADLILTON PACHECO DE OLIVEIRA - IFES
Externo à Instituição - JOSÉ LUIS RODRÍGUEZ BAUTISTA