title: Vector competence of Ixodes pacificus and Dermacentor occidentalis (Acari: Ixodidae) for various isolates of Lyme disease spirochetes.
abstract: The vector competence of the western black-legged tick, Ixodes pacificus Cooley & Kohls, and the Pacific Coast tick, Dermacentor occidentalis Marx, for the Lyme disease spirochete (Borrelia burgdorferi Johnson, Schmid, Hyde, Steigerwalt & Brenner) was compared. Rabbits, hamsters, and the deer mouse, Peromyscus maniculatus (Wagner), were injected with cultured spirochetes or infected tick-suspensions, or were fed upon by spirochete-infected ticks. Five of seven isolates used as inocula were reisolated from vertebrates with the ear-punch biopsy technique. Three isolates (CA4, 5, 7) that were infectious for both vertebrates and ticks possessed prominent low-molecular-weight protein bands that had relative mobilities of approximately 24-26 kd. The ability of ticks to acquire and maintain various inocula of B. burgdorferi was evaluated by feeding uninfected larvae xenodiagnostically on all three hosts 0-63 d postinjection. Low percentages (0-10.6%) of the I. pacificus and none of the D. occidentalis became infected. By contrast, 33% of I. pacificus and 40% of Ixodes scapularis Say (= I. dammini Spielman, Clifford, Piesman & Corwin) that fed on hamsters infected by tick-bite acquired and transstadially passed spirochetes; 10% of D. occidentalis fed on infected hamsters similarly acquired but did not maintain spirochetes. Ixodes pacificus nymphs efficiently transmitted B. burgdorferi to deer mice and a hamster. Feeding by one spirochete-infected nymph was sufficient to produce patent infections in each of five mice.
authors.affiliation: Department of Environmental Science, Policy and Management, University of California, Berkeley 94720.
authors.forename: R S
authors.initials: RS
authors.lastname: Lane
authors.forename: R N
authors.initials: RN
authors.lastname: Brown
authors.forename: J
authors.initials: J
authors.lastname: Piesman
authors.forename: C A
authors.initials: CA
authors.lastname: Peavey
mesh_terms: D000818:Animals; D001096:Arachnid Vectors / Q000382:microbiology*; D015748:Borrelia burgdorferi Group / Q000276:immunology / Q000302:isolation & purification*; D006224:Cricetinae; D003870:Dermacentor / Q000382:microbiology; D005260:Female; D006801:Humans; D008193:Lyme Disease / Q000635:transmission; D010542:Peromyscus; D011817:Rabbits; D013045:Species Specificity; D013987:Ticks / Q000382:microbiology*