Ixodes pacificus (Acari: Ixodidae) as a Vector of Ehrlichia equi (Rickettsiales: Ehrlichieae)

P. J. Richter, R. B. Kimsey, John E Madigan, J. E. Barlough, J. S. Dumler, D. L. Brooks

Research output: Contribution to journalArticlepeer-review

139 Scopus citations


Ehrlichia equi, a rickettsia described from horses in California 30 yr ago, causes equine granulocytic ehrlichiosis throughout the Americas and possibly Europe. Here, we report experimental transmission of E. equi from infected to susceptible horses through bites of western blacklegged ticks, Ixodes pacificus (Cooley & Kohls). In preliminary field studies, only I. pacificus consistently infested horses and vegetation at 3 locations with contemporary cases of equine ehrlichosis, and in particular, I. pacificus was the only species found attached to all of the infected horses. Exposure to bites of ticks in the genus Ixodes poses previously unrecognized and serious health risks to humans and animals.

Original languageEnglish (US)
Pages (from-to)1-5
Number of pages5
JournalJournal of Medical Entomology
Issue number1
StatePublished - Jan 1996


  • Disease
  • Ehrlichia
  • Ixodes
  • Ticks
  • Vector
  • Zoonosis

ASJC Scopus subject areas

  • Insect Science
  • veterinary(all)


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