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PLoS Negl Trop Dis. 2016 Oct 5;10(10):e0005020. doi: 10.1371/journal.pntd.0005020. eCollection 2016 Oct.

The Eco-epidemiology of Pacific Coast Tick Fever in California.

Author information

1
Division of Communicable Disease Control, California Department of Public Health, Richmond, California, United States of America.
2
Jian-Ping Hsu College of Public Health, Georgia Southern University, Statesboro, Georgia, United States of America.
3
Department of Environmental Science, Policy and Management, University of California, Berkeley, California, United States of America.
4
Lake County Vector Control District, Lakeport, California, United States of America.
5
Rickettsial Zoonoses Branch, National Center for Zoonotic, Vector-borne and Enteric Diseases, Centers for Disease Control and Prevention, Atlanta, Georgia, United States of America.

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.

PMID:
27706171
PMCID:
PMC5051964
DOI:
10.1371/journal.pntd.0005020
[Indexed for MEDLINE]
Free PMC Article

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