Detection of a spotted fever group rickettsia in Amblyomma cajennense (Acari: Ixodidae) in south Texas. Academic Article uri icon


  • Thai tick typhus rickettsia (strain TT-118), a spotted fever group rickettsia of indeterminant pathogenicity, was isolated from a mixed pool of larval Ixodes and Rhipicephalus ticks collected from Thailand in 1962. Here we report the surprising finding of a spotted fever group rickettsia with closest sequence homology to the Thai tick typhus rickettsia in Amblyomma cajennense (F.) ticks from south Texas. Sequence analysis was performed on segments of 3 genes that differentiate rickettsial species; all 3 genes sequenced, the 17-kDa, glta, and rompA, when compared with those of other rickettsiae, showed the highest degree of similarity to the Thai tick typhus rickettsia with 99.5, 99.5, and 100% homology, respectively. This is the 1st finding of a rickettsial species in A. cajennense ticks in Texas and the United States. If this rickettsia is pathogenic, exposure to infected A. cajennense ticks may pose a previously unrecognized health risk to people who have been fed upon by these ticks.

published proceedings

  • J Med Entomol

author list (cited authors)

  • Billings, A. N., Yu, X. J., Teel, P. D., & Walker, D. H.

citation count

  • 35

complete list of authors

  • Billings, AN||Yu, XJ||Teel, PD||Walker, DH

publication date

  • July 1998