RICKETTSIA-PEACOCKII SP-NOV, A NEW SPECIES INFECTING WOOD TICKS, DERMACENTOR-ANDERSONI, IN WESTERN MONTANA

Rickettsia peacockii, a new species of spotted fever group rickettsiae , was identified from Rocky Mountain wood ticks (Dermacentor andersoni ) collected in the Sapphire Mountain Range on the eastern side of Bitt erroot Valley, Montana, DNA from R, peacockii Skalkaho(T) (T = type st rain) in naturally infected tick tissue was amplified by a PCR assay w ith primer sets derived from eubacterial 16S ribosomal DNA (rDNA), ric kettsial citrate synthase, and 190-kDa surface antigen (rOmpA) genes, Partial 16S rDNA and rOmpA gene sequences exhibited levels of similari ty of 99.7 and 93.2%, respectively, with the sequences of the spotted fever agent Rickettsia rickettsii R, By using Gimenez staining, fluore scent antibody tests, a PCR assay, and a restriction fragment length p olymorphism analysis, 76 of 115 female ticks (minimal field infection rate, 66.1%) collected between 1992 and 1995 were found to be infected . The organism is passed transstadially and transovarially (minimal ve rtical transmission rate, 73.3%), and infections are localized in ovar ial tissues, Attempts to cultivate R. peacockii were unsuccessful.