Molecular detection of Rickettsia genus in chigger mites (Trombidiformes: Trombiculidae) collected on small mammals in southeastern brazilian

Abstract Chiggers are ectoparasites of vertebrates and may cause trombiculiasis or transmit pathogens to their hosts. Specimens collected from rodents and marsupials were morphologically identified as Herpetacarus hertigi, Eutrombicula tinami, Kymocta sp., Quadraseta brasiliensis, Quadraseta falconensis, Quadraseta flochi, Quadraseta mackenziei, Quadraseta pazca, Quadraseta trapezoides, Quadraseta sp., Serratacarus sp., and Trombewingia bakeri. These mites were submitted individually to molecular analyses for the detection of bacteria of the genus Coxiella, Hepatozoon and Rickettsia. Samples were positive to Rickettsia only. Obtained sequences for the gltA (350 pb) and ompA (488 pb) genes were identical to “Candidatus Rickettsia colombianensi”, a species previously detected in ticks. In addition, molecular identification of mites based on 18S rDNA sequences are provided for H. hertigi, Kymocta sp., Q. brasiliensis, Q. pazca, Q. trapezoides, Quadraseta sp., and T. bakeri for the first time. This is the first report of the detection of a Rickettsia sp. in chigger mites collected on rodents in Brazil.

摘要 恙螨（Chiggers）是脊椎动物的外寄生生物，可引发恙螨病（trombiculiasis），亦可向宿主传播病原体。本研究从啮齿类与有袋类动物体表采集的标本经形态学鉴定，分别为赫氏蠕形恙螨（Herpetacarus hertigi）、Tinami真恙螨（Eutrombicula tinami）、Kymocta属未定种（Kymocta sp.）、巴西四毛恙螨（Quadraseta brasiliensis）、Falcon四毛恙螨（Quadraseta falconensis）、Floch四毛恙螨（Quadraseta flochi）、Mackenzie四毛恙螨（Quadraseta mackenziei）、Pazca四毛恙螨（Quadraseta pazca）、梯形四毛恙螨（Quadraseta trapezoides）、Quadraseta属未定种（Quadraseta sp.）、Serratacarus属未定种（Serratacarus sp.）以及Baker氏恙翼螨（Trombewingia bakeri）。将上述螨类标本单独进行分子分析，以检测柯克斯体属（Coxiella）、肝簇虫属（Hepatozoon）及立克次体属（Rickettsia）的细菌。结果仅在立克次体属细菌的检测中呈阳性。所获得的gltA与ompA基因的序列（分别对应350个碱基对、488个碱基对），与此前在蜱（ticks）中检出的“候选哥伦比亚立克次体（Candidatus Rickettsia colombianensi）”完全一致。此外，本研究首次基于18S rDNA序列完成了赫氏蠕形恙螨（H. hertigi）、Kymocta属未定种、巴西四毛恙螨（Q. brasiliensis）、Pazca四毛恙螨（Q. pazca）、梯形四毛恙螨（Q. trapezoides）、Quadraseta属未定种以及Baker氏恙翼螨（T. bakeri）的分子鉴定。本研究系首次在巴西啮齿类动物体表采集的恙螨中检测到立克次体属物种。