Detection of a spotted fever group rickettsia in Amblyomma cajennense (Acari: Ixodidae) in south Texas.
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.
Department of Pathology, University of Texas Medical Branch, Galveston 77555-0609, USA.
A N
AN
Billings
X J
XJ
Yu
P D
PD
Teel
D H
DH
Walker
D000818:Animals; D001425:Bacterial Outer Membrane Proteins / Q000235:genetics*; D001426:Bacterial Proteins / Q000235:genetics*; D001483:Base Sequence; D002417:Cattle; D002418:Cattle Diseases / Q000469:parasitology*; D004269:DNA, Bacterial; D005798:Genes, Bacterial; D005970:Glutamate Synthase / Q000235:genetics*; D008969:Molecular Sequence Data; D016133:Polymerase Chain Reaction; D012281:Rickettsia / Q000235:genetics / Q000302:isolation & purification*; D017422:Sequence Analysis, DNA; D013781:Texas; D013984:Tick Infestations / Q000469:parasitology / Q000662:veterinary*; D013987:Ticks / Q000382:microbiology*
D001425:Bacterial Outer Membrane Proteins; D001426:Bacterial Proteins; D004269:DNA, Bacterial; C080205:rOmpA, Rickettsia; C107166:glutamate synthase A; D005970:Glutamate Synthase