CHARACTERIZATION OF AN ENDOSYMBIONT INFECTING WOOD TICKS, DERMACENTOR-ANDERSONI, AS A MEMBER OF THE GENUS FRANCISELLA

A microorganism (Dermacantor andersoni symbiont [DAS]) infecting Rocky Mountain wood ticks (D. andersoni) collected in the Bitterroot Mounta ins of western Montana was characterized as an endosymbiont belonging to the genus Francisella. Previously described as Wolbachia like, the organism's DNA was amplified from both naturally infected tick ovarial tissues and Vero cell cultures by PCR assay with primer sets derived from eubacterial 16S ribosomal DNA (rDNA) and Francisella membrane pro tein genes. The 16S rDNA gene sequence of the DAS was most similar (95 .4%) to that of Francisella tularensis subsp. tularensis. Through a co mbination of Gimenez staining, PCR assay, and restriction fragment len gth polymorphism analysis, 102 of 108 female ticks collected from 1992 to 1996 were infected. Transovarial transmission to female progeny wa s 95.6%, but we found no evidence of horizontal transmission.