# The Ecology and Classification of Rickettsia Species Phylotype G022, an Uncharacterized Bacterium from Ixodes pacificus Ticks

> **NIH NIH R16** · HUMBOLDT STATE UNIVERSITY · 2022 · $147,500

## Abstract

Project Summary/Abstract
 While both ticks and tick-borne disease agents have rapidly become a serious and growing threat to human and
veterinary public health, mounting evidence indicates that many tick-borne diseases due to rickettsial infection may be
under-reported in Northern America because of their uncharacteristic symptoms in humans and domestic animals. Ixodes
pacificus is a principal vector for pathogenic and endosymbiotic bacteria on the Pacific West Coast of the United States.
Compared to pathogenic rickettsiae identified in other tick species in California, the ecology and biology of pathogenic
rickettsiae in I. pacificus remains largely unexplored. Our lab detected a novel Rickettsia species, Rickettsia species
phylotype G022, in questing adult ticks of I. pacificus in three counties of Northern California in 2011, 2013, and 2020.
Due to phylotype G022’s low prevalence (2-4.5%) in adult I. pacificus and published phylogenetic trees placing the
bacterium within other pathogenic spotted fever group rickettsiae, our hypothesis is that phylotype G022 is a pathogenic
Rickettsia. The proposed study ultimately serves as a continuation of our previous findings regarding the ecology and
pathogenesis of Rickettsia species in I. pacificus. Our research pursues the following specific aims: 1) We will conduct a
survey to estimate the prevalence of Rickettsia species phylotype G022 in nymphal ticks of I. pacificus by collecting the
nymphs from the field and detecting the bacterium by real-time PCR; 2) We will study transmission routes of Rickettsia
species phylotype G022 in I. pacificus by collecting all life stages of the ticks via feeding on New Zealand white rabbits
and detecting the bacterium by real-time PCR; 3) We will perform the propagation and isolation of the Rickettsia
phylotype G022 isolate from I. pacificus using tick embryonic cell lines and limiting dilution assay; 4) We will perform
the molecular typing of the Rickettsia species phylotype G022 isolate by Multilocus Sequence Typing; 5) We will
investigate the presence of Rickettsia species phylotype G022 infection in domestic dogs from Northern California. This
study will not only result in the official naming of phylotype G022 by typing the pure bacterial isolate, but also enable us
to start gathering data on transmission dynamics of the bacterium as well as its potential pathogenicity, the long-term
research goal of our lab, to humans and animal hosts in Northern California.

## Key facts

- **NIH application ID:** 10412445
- **Project number:** 1R16AI167834-01
- **Recipient organization:** HUMBOLDT STATE UNIVERSITY
- **Principal Investigator:** Jianmin Zhong
- **Activity code:** R16 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2022
- **Award amount:** $147,500
- **Award type:** 1
- **Project period:** 2022-09-12 → 2026-08-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10412445

## Citation

> US National Institutes of Health, RePORTER application 10412445, The Ecology and Classification of Rickettsia Species Phylotype G022, an Uncharacterized Bacterium from Ixodes pacificus Ticks (1R16AI167834-01). Retrieved via AI Analytics 2026-05-23 from https://api.ai-analytics.org/grant/nih/10412445. Licensed CC0.

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