title: The Eco-epidemiology of Pacific Coast Tick Fever in California.
abstract: Rickettsia philipii (type strain "Rickettsia 364D"), the etiologic agent of Pacific Coast tick fever (PCTF), is transmitted to people by the Pacific Coast tick, Dermacentor occidentalis. Following the first confirmed human case of PCTF in 2008, 13 additional human cases have been reported in California, more than half of which were pediatric cases. The most common features of PCTF are the presence of at least one necrotic lesion known as an eschar (100%), fever (85%), and headache (79%); four case-patients required hospitalization and four had multiple eschars. Findings presented here implicate the nymphal or larval stages of D. occidentalis as the primary vectors of R. philipii to people. Peak transmission risk from ticks to people occurs in late summer. Rickettsia philipii DNA was detected in D. occidentalis ticks from 15 of 37 California counties. Similarly, non-pathogenic Rickettsia rhipicephali DNA was detected in D. occidentalis in 29 of 38 counties with an average prevalence of 12.0% in adult ticks. In total, 5,601 ticks tested from 2009 through 2015 yielded an overall R. philipii infection prevalence of 2.1% in adults, 0.9% in nymphs and a minimum infection prevalence of 0.4% in larval pools. Although most human cases of PCTF have been reported from northern California, acarological surveillance suggests that R. philipii may occur throughout the distribution range of D. occidentalis.
authors.affiliation: Division of Communicable Disease Control, California Department of Public Health, Richmond, California, United States of America.
authors.forename: Kerry A
authors.identifier: http://orcid.org/0000-0002-9535-3401
authors.initials: KA
authors.lastname: Padgett
authors.affiliation: Division of Communicable Disease Control, California Department of Public Health, Richmond, California, United States of America.
authors.forename: Denise
authors.initials: D
authors.lastname: Bonilla
authors.affiliation: Jian-Ping Hsu College of Public Health, Georgia Southern University, Statesboro, Georgia, United States of America.
authors.forename: Marina E
authors.initials: ME
authors.lastname: Eremeeva
authors.affiliation: Division of Communicable Disease Control, California Department of Public Health, Richmond, California, United States of America.
authors.forename: Carol
authors.initials: C
authors.lastname: Glaser
authors.affiliation: Department of Environmental Science, Policy and Management, University of California, Berkeley, California, United States of America.
authors.forename: Robert S
authors.initials: RS
authors.lastname: Lane
authors.affiliation: Division of Communicable Disease Control, California Department of Public Health, Richmond, California, United States of America.
authors.forename: Charsey Cole
authors.initials: CC
authors.lastname: Porse
authors.affiliation: Division of Communicable Disease Control, California Department of Public Health, Richmond, California, United States of America.
authors.forename: Martin B
authors.initials: MB
authors.lastname: Castro
authors.affiliation: Division of Communicable Disease Control, California Department of Public Health, Richmond, California, United States of America.
authors.forename: Sharon
authors.initials: S
authors.lastname: Messenger
authors.affiliation: Division of Communicable Disease Control, California Department of Public Health, Richmond, California, United States of America.
authors.forename: Alex
authors.initials: A
authors.lastname: Espinosa
authors.affiliation: Division of Communicable Disease Control, California Department of Public Health, Richmond, California, United States of America.
authors.forename: Jill
authors.initials: J
authors.lastname: Hacker
authors.affiliation: Division of Communicable Disease Control, California Department of Public Health, Richmond, California, United States of America.
authors.forename: Anne
authors.initials: A
authors.lastname: Kjemtrup
authors.affiliation: Lake County Vector Control District, Lakeport, California, United States of America.
authors.forename: Bonnie
authors.initials: B
authors.lastname: Ryan
authors.affiliation: Lake County Vector Control District, Lakeport, California, United States of America.
authors.forename: Jamesina J
authors.initials: JJ
authors.lastname: Scott
authors.affiliation: Division of Communicable Disease Control, California Department of Public Health, Richmond, California, United States of America.
authors.forename: Renjie
authors.initials: R
authors.lastname: Hu
authors.affiliation: Division of Communicable Disease Control, California Department of Public Health, Richmond, California, United States of America.
authors.forename: Melissa Hardstone
authors.initials: MH
authors.lastname: Yoshimizu
authors.affiliation: Rickettsial Zoonoses Branch, National Center for Zoonotic, Vector-borne and Enteric Diseases, Centers for Disease Control and Prevention, Atlanta, Georgia, United States of America.
authors.forename: Gregory A
authors.initials: GA
authors.lastname: Dasch
authors.affiliation: Division of Communicable Disease Control, California Department of Public Health, Richmond, California, United States of America.
authors.forename: Vicki
authors.initials: V
authors.lastname: Kramer
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000818:Animals; D000907:Antibodies, Bacterial / Q000097:blood; D001096:Arachnid Vectors / Q000382:microbiology*; D002140:California / Q000453:epidemiology; D002648:Child; D002675:Child, Preschool; D003870:Dermacentor / Q000382:microbiology*; D005260:Female; D005334:Fever; D006801:Humans; D007074:Immunoglobulin G / Q000097:blood; D007814:Larva / Q000382:microbiology; D008297:Male; D008875:Middle Aged; D009758:Nymph / Q000382:microbiology; D015995:Prevalence; D012281:Rickettsia / Q000235:genetics / Q000276:immunology / Q000302:isolation & purification* / Q000472:pathogenicity; D012282:Rickettsia Infections / Q000175:diagnosis / Q000453:epidemiology* / Q000382:microbiology / Q000635:transmission*; D055815:Young Adult
chemical_list: D000907:Antibodies, Bacterial; D007074:Immunoglobulin G