Molecular evidence of Bartonella spp. in questing adult Ixodes pacificus ticks in California

Ticks are tile vectors of many zoonotic diseases in the United States, incl uding Lyme disease, human monocytic and granulocytic ehrlichioses, and Rock y Mountain spotted fever. Most known Bartonella species are arthropod borne . Therefore, it is important to determine if some Bartonella species, which are emerging pathogens, could he carried or transmitted by ticks. In this study, adult Ixodes pacificus ticks were collected by flagging vegetation i n three sites in Santa Clara County, Calif. PCR-restriction fragment length polymorphism and partial sequencing of 273 bp of the gltA gene were applie d for Bartonella identification. Twenty-nine (19.2%) of 151 individually te sted ticks were PCR positive for Bartonella. Male ticks were more likely to he infected with Bartonella than female ticks (26 versus 12%, P = 0.05). N one of the nine ticks collected at Baird Ranch was PCR positive for Bartone lla. However, 7 (50%) of 14 ticks from Red Fern Ranch and 22 (17%) of 128 t icks from the Windy Hill Open Space Reserve were infected with Bartonella. In these infected ticks, molecular analysis showed a variety of Bartonella strains, which were closely related to a cattle Bartonella strain and to se veral known human-pathogenic Bartonella species and subspecies: Bartonella henselae B. quintana, R. washoensis, and B. vinsonii subsp. berkhoffii. The se findings indicate that I. pacificus ticks may play an important role in Bartonella transmission among animals and humans.