Labruna Marcelo B, Krawczak Felipe S, Gerardi Monize, Binder Lina C, Barbieri Amalia R M, Paz Gustavo F, Rodrigues Daniel S, Araújo Ricardo N, Bernardes Marcela Lanza, Leite Romario C
Department of Preventive Veterinary Medicine and Animal Health, Faculty of Veterinary Medicine, University of São Paulo, São Paulo, SP, Brazil.
Department of Preventive Veterinary Medicine and Animal Health, Faculty of Veterinary Medicine, University of São Paulo, São Paulo, SP, Brazil.
Vet Parasitol Reg Stud Reports. 2017 May;8:82-85. doi: 10.1016/j.vprsr.2017.02.007. Epub 2017 Feb 23.
Brazilian spotted fever (BSF) is a tick-borne disease caused by the bacterium Rickettsia rickettsii, the deadliest spotted fever of the world, transmitted in southeastern Brazil mainly by the tick Amblyomma sculptum, a member of the Amblyomma cajennense species complex. In the present study, over 5000 adults of A. sculptum ticks were collected by dry ice traps in the Municipal Ecological Park, alongside the Pampulha Lake region, a BSF-endemic area of Belo Horizonte city, state of Minas Gerais, southeastern Brazil. Ticks were taken alive to the laboratory, where a sample of 2100 specimens was processed for isolation of R. rickettsii. For this purpose, ticks were macerated and intraperitoneally inoculated into guinea pigs. Only one out of 21 inoculated guinea pigs presented high fever within 21days post inoculation with tick homogenates. This febrile animal was euthanized and its internal organs were macerated and inoculated into additional guinea pigs (guinea pig passage). A spleen sample from a febrile guinea pig was used to inoculate Vero cells, resulting in a successful isolation and in vitro establishment of rickettsiae. Rickettsia-infected Vero cells were used for molecular characterization of the rickettsial isolate through PCR and DNA sequencing of fragments of three rickettsial genes (gltA, ompA, and ompB), which were all 100% identical to corresponding sequences of R. rickettsii from GenBank. The present R. rickettsii isolate was designated as strain Pampulha. A minimal infection rate of 0.05% R. rickettsii-infected ticks was estimated for A. sculptum population of the Pampulha Lake region. Our results, coupled with epidemiological evidences, suggest that R. rickettsii strain Pampulha, isolated from A. sculptum ticks in the present study, is the strain responsible for human clinical cases of BSF in the Pampulha Lake region of Belo Horizonte city.
巴西斑点热（BSF）是一种由立氏立克次体引起的蜱传疾病，是世界上最致命的斑点热，主要通过蜱类安氏革蜱在巴西东南部传播，安氏革蜱是卡氏安氏革蜱物种复合体的成员。在本研究中，在巴西东南部米纳斯吉拉斯州贝洛奥里藏特市的BSF流行区潘普利亚湖地区的市生态公园内，通过干冰诱捕器收集了5000多只成年安氏革蜱。蜱被活体带回实验室，对2100个样本进行处理以分离立氏立克次体。为此，将蜱研磨后经腹腔接种到豚鼠体内。在接种蜱匀浆后的21天内，21只接种的豚鼠中只有1只出现高热。这只发热的动物被安乐死，其内脏被研磨后接种到另外的豚鼠体内（豚鼠传代）。用一只发热豚鼠的脾脏样本接种Vero细胞，成功分离出立克次体并在体外建立了培养。感染立克次体的Vero细胞用于通过PCR和对三个立克次体基因（gltA、ompA和ompB）片段进行DNA测序对立克次体分离株进行分子鉴定，这些基因与GenBank中立氏立克次体的相应序列100%相同。目前的立氏立克次体分离株被命名为潘普利亚菌株。估计潘普利亚湖地区安氏革蜱种群中立氏立克次体感染蜱的最低感染率为0.05%。我们的结果与流行病学证据相结合，表明在本研究中从安氏革蜱分离出的立氏立克次体潘普利亚菌株是贝洛奥里藏特市潘普利亚湖地区人类BSF临床病例的致病菌株。
