The purpose of this study was to investigate the presence and diversity of Rickettsia species among ticks in northern Florida. Samples of host-seeking adult ticks of five species collected from public recreation areas in northern Florida were screened for Rickettsia species DNA using a genus-specific nested PCR assay that amplifies a portion of the highly conserved 17-kDa protein gene. Positive samples were then tested with PCR primers that amplify a portion of the 190-kDa outer membrane protein (rOmpA) gene of spotted fever group Rickettsia species. The rOmpA fragments from representative positive samples from each tick species were sequenced, and used to construct a phylogenetic tree for comparison with reference strain sequence data. Samples of all tick species harbored Rickettsia. Differences in Rickettsia infection prevalence by tick species and sex were noted. The rOmpA sequences obtained from Amblyomma americanum from Florida were 99 to 100% identical to reference strain sequences of R. ambloyommii. Sequences from A. maculatum were identical to reference strains of R. parkeri. Dermacentor variabilis rOmpA sequences were identical to other strains of R. rhipicephali. Sequences derived from Ixodes scapularis were 99 to 100% identical to strains designated as the I. scapularis endosymbiont (R. coolyei). The rOmpA sequences from I. affinis were most similar (96 to 98% identical) to the I. scapularis endosymbiont (R. coolyei) strains, and may represent a similar, but unique and previously unrecognized, Rickettsia species endosymbiont.
Species 1: Acari Ixodidae Amblyomma maculatum (Gulf Coast tick)
Species 2: Acari Ixodidae Dermacentor variabilis (American dog tick)
Species 3: Acari Ixodidae Ixodes scapularis (blacklegged tick)
Keywords: endosymbiont, phylogenetics
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