Detection and identification of spotted fever group rickettsiae in dermacentor species from Southern California

Mary E. Wikswo, Renjie Hu, Gregory A. Dasch, Laura Krueger, Aaron Arugay, Keith Jones, Barry Hess, Stephen Bennett, Vicki Kramer, Marina E. Eremeeva

Research output: Contribution to journalArticlepeer-review

79 Scopus citations

Abstract

Dermacentor occidentalis Marx and Dermacentor variabilis (Say) commonly bite humans in California. These Dermacentor species may play a role in transmitting spotted fever group (SFG) rickettsiae to humans in many parts of the state where Dermacentor andersoni Stiles, a known vector for the etiologic agent of Rocky Mountain spotted fever, Rickettsia rickettsii, is absent. However, the specific rickettsial agents present in these ticks and their current prevalence are poorly understood. In total, 365 D. occidentalis and 10 D. variabilis were collected by flagging vegetation at 16 sites in five counties of southern California. The presence of SFG rickettsial DNA in these ticks was detected with rOmpA and GltA gene polymerase chain reaction (PCR) assays. The rickettsial species were identified by sequencing PCR amplicons. Of 365 D. occidentalis, 90 (24.7%) contained R. rhipicephali DNA, 28 (7.7%) contained DNA of unclassified genotype 364D, two (0.55%) contained R. bellii DNA, and one (0.3%) contained R. rickettsii DNA. Of 10 D. variabilis, four (40%) contained only R. rhipicephali. Four new genotypes of R. rhipicephali were discovered. For the first time, we detected R. rickettsii in D. occidentalis. Our study provides the first molecular data on the prevalence and species identification of SFG rickettsiae circulating in populations of these California ticks. Because neither D. variabilis nor R. rickettsii were abundant, 364D should be evaluated further as a potential cause of human SFG rickettsioses in southern California.

Original languageEnglish
Pages (from-to)509-516
Number of pages8
JournalJournal of Medical Entomology
Volume45
Issue number3
DOIs
StatePublished - May 2008

Scopus Subject Areas

  • Parasitology
  • General Veterinary
  • Insect Science
  • Infectious Diseases

Keywords

  • Dermacentor occidentalis
  • Dermacentor variabilis
  • Rickettsia rhipicephali
  • Rickettsia rickettsii
  • Rocky mountain spotted fever

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