Rondônia is the only state in the North Region of Brazil to have registered confirmed cases of Brazilian Spotted Fever (BSF). The present study investigated the epidemiological cycle of Rickettsia spp. by surveying free-living ixodofauna and tick parasitism of dogs in the municipality of Porto Velho, Rondônia State. Ticks and dogs were tested for the presence of Rickettsia spp. DNA and dog serum was tested for reactivity to anti-Rickettsia spp. antibodies. Tick collection and dog blood sampling were performed in peri-urban and rural environments at 11 locations. Eight free-living Amblyomma species and one Haemaphysalis species were collected: A. scalpturatum, A. naponense, A. oblongoguttatum, A. coelebs, A. latepunctatum, A. pacae, A. ovale, Amblyomma sp., and H. juxtakochi. Three tick species were found parasitizing dogs: Rhipicephalus sanguineus sensu lato, A. oblongoguttatum and A. ovale. Molecular analysis did not identify the presence of the gltA gene fragment in any tick specimen. Results from an indirect immunofluorescent assay (IFA) showed that 20.8% of peri-urban and 15.4% of rural dog sera exhibited reactivity to Rickettsia rhipicephali, Rickettsia amblyommatis, Rickettsia bellii and Rickettsia parkeri antigens. Antibody prevalence in dogs was 16.4%. This study is the first to describe the prevalence of Rickettsia spp. infection in dogs from Porto Velho municipality. Our findings enhance current knowledge of Rickettsia spp. circulation in the Western Amazon.

朗多尼亚州（Rondônia）是巴西北部地区唯一登记确诊的巴西斑点热病（BSF）病例的州。本研究调查了立克次体的流行病学周期。通过对朗多尼亚州波尔图韦略市的狗的自由活动ixodofauna和tick虱寄生进行调查。检验cks和狗是否存在立克次体。测试了DNA和狗血清对抗立克次氏菌的反应性。抗体。在城郊和乡村环境中的11个地点进行了ick虫收集和狗血采样。收集了八种自由生存的盲膜物种和一种血肿物种：A. scalpturatum，A. naponense，A. oblongoguttatum，A. coelebs，A. latepunctatum，A. pacae，A.未闭，花蜱属，和H. juxtakochi。发现了三种tick虫寄生虫犬：Rhipicephalus sanguineus sensu lato，A。oblongoguttatum和A.卵形犬。分子分析未发现任何壁虱标本中存在gltA基因片段。从间接免疫荧光试验（IFA）结果表明，近郊的20.8％和农村狗血清的15.4％显示出反应性的立克次氏体rhipicephali，立克次体amblyommatis，立克次体bellii和立克次体parkeri抗原。狗中的抗体患病率为16.4％。这项研究是首次描述立克次体的流行。波尔图韦略市的狗感染。我们的发现增强了对立克次体的最新知识。亚马逊西部地区的流通。