Graduation Date

Spring 2025

Document Type

Thesis

Program

Master of Science degree with a major in Biology

Committee Chair Name

Jianmin Zhong

Committee Chair Affiliation

Cal Poly Humboldt Faculty or Staff

Second Committee Member Name

Christopher Paddock

Second Committee Member Affiliation

Community Member or Outside Professional

Third Committee Member Name

Andrea Swei

Third Committee Member Affiliation

Community Member or Outside Professional

Fourth Committee Member Name

Catalina Cuellar Gempeler

Fourth Committee Member Affiliation

Cal Poly Humboldt Faculty or Staff

Keywords

Rickettsia, qPCR, ELISA, G022, Rickettsia tillamookensis, Rickettsia rickettsii subsp californica, Rickettsia rhipicephali, Northern California, Humboldt, Sonoma, Ticks

Subject Categories

Biology

Abstract

Pathogenic Rickettsia are responsible for causing febrile diseases in humans and animals. Ixodes pacificus is a clinically important vector of vector borne diseases along the Pacific Northwest of the United States. Little is known about the transmission mechanisms and pathogenic potential of Rickettsia species in I. pacificus. Rickettsia species phylotype G022 (G022) and Rickettsia tillamookensis both have a low infection prevalence in I. pacificus, suggesting that these Rickettsia species utilize amplifier hosts for maintenance. G022 and R. tillamookensis share a close phylogenetic history with known human pathogens but still retain an unknown pathogenicity. A molecular and serological survey of domestic dogs was conducted to evaluate the potential of G022 and R. tillamookensis to infect mammalian hosts. Whole blood was collected from 175 dogs in Humboldt and Sonoma Counties, originating from two veterinary hospitals and an animal shelter. The buffy coat fraction was screened for DNA from G022 and R. tillamookensis using quantitative real-time PCR (qPCR), while blood plasma was screened for anti-rickettsial antibodies using microimmunofluorescence (MIF), and an enzyme-linked immunosorbent assay (ELISA). Rickettsial antigens were derived from whole cell cultures for MIF, while partially purified antigens from R. tillamookensis, Rickettsia rickettsii subsp californica subsp nov (R. rickettsii californica), and Rickettsia rhipicephali isolates were used for the ELISA. In total, 1.71% (3/175; 95% CI: 0.58%-4.9%) of dogs were seropositive for Rickettsia, as detected by MIF and ELISA, suggesting these dogs were previously exposure to Rickettsia species. Among dogs from Sonoma County, 3.88% (3/104; 95% CI: 0.6%-8.2%) were seropositive by MIF and ELISA, while all the dogs from Humboldt County were seronegative for both methods. Although the ELISA results cannot be considered species-specific, three plasma samples demonstrated the greatest seroreactivity against the R. tillamookensis, R. rickettsii californica, and R. rhipicephali isolates, respectively. This data suggests prior exposure to Rickettsia species with similar antigenicity to R. tillamookensis, R. rickettsii californica, and R. rhipicephali, respectively. No DNA was detected for G022 or R. tillamookensis by qPCR. This is the first study to use a combined molecular and serological approach for the detection of R. tillamookensis and the first molecular survey of dogs for the detection of G022.

Comments

This data belongs to Nicholas Woronchuk and Jianmin Zhong and any usage or reference to this research must be properly cited to give credit to these individuals.

Citation Style

Woronchuk, Nicholas, "The molecular and serological detection of Rickettsia species phylotype G022 and Rickettsia tillamookensis in the blood of domestic dogs in northern California" (2025). Cal Poly Humboldt theses and projects.

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Available for download on Wednesday, May 02, 2029

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