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Abstract Pacific Coast tick fever is a recently described zoonotic disease in California caused by a spotted fever group rickettsia, Rickettsia rickettsii subsp. californica (formerly Rickettsia 364D) and transmitted by the Pacific Coast tick, Dermacentor occidentalis. Like many emerging vector-borne diseases, knowledge regarding the transmission cycle, contribution from potential amplifying hosts, and geographic distribution of R. rickettsii californica is limited. We paired molecular analysis with comparative spatial niche modeling to identify vertebrate hosts potentially involved in the transmission cycle of this pathogen. We identified R. rickettsii californica DNA in three mammal species (Otospermophilus beecheyi, Lepus californicus, and Sylvilagus audubonii). This is the first record of R. rickettsii californica detected in mammals and may indicate potential amplifying hosts for this human pathogen. Species niche modeling of uninfected and infected D. occidentalis identified areas of high suitability along the coast and Sierra Nevada foothills of California. These findings support the hypothesis that amplifying host(s) may support higher infection prevalence in the infected tick regions compared to other parts of the tick’s range. Potential host species distribution models (SDMs) were constructed from museum records and niche overlap statistics were used to compare habitat suitability with R. rickettsii californica-infected tick SDMs. We found higher than null overlap of infected ticks with California ground squirrels (O. beecheyii) and trending, but nonsignificant, overlap with two lagomorph species. Pairing molecular and niche modeling may be a useful approach to identify species that are involved in the maintenance of emerging tick-borne zoonoses.
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Estimating the distribution of Oryzomys palustris , a potential key host in expanding rickettsial tick‐borne disease risk
Abstract Increasingly, geographic approaches to assessing the risk of tick‐borne diseases are being used to inform public health decision‐making and surveillance efforts. The distributions of key tick species of medical importance are often modeled as a function of environmental factors, using niche modeling approaches to capture habitat suitability. However, this is often disconnected from the potential distribution of key host species, which may play an important role in the actual transmission cycle and risk potential in expanding tick‐borne disease risk. Using species distribution modeling, we explore the potential geographic range ofOryzomys palustris, the marsh rice rat, which has been implicated as a potential reservoir host ofRickettsia parkeri, a pathogen transmitted by the Gulf Coast tick (Amblyomma maculatum) in the southeastern United States. Due to recent taxonomic reclassification ofO. palustrissubspecies, we reclassified geolocated collections records into the newer clade definitions. We modeled the distribution of the two updated clades in the region, establishing for the first time, range maps and distributions of these two clades. The predicted distribution of both clades indicates a largely Gulf and southeastern coastal distribution. Estimated suitable habitat forO. palustrisextends into the southern portion of the Mid‐Atlantic region, with a discontinuous, limited area of suitability in coastal California. Broader distribution predictions suggest potential incursions along the Mississippi River. We found considerable overlap of predictedO. palustrisranges with the distribution ofA. maculatum, indicating the potential need for extended surveillance efforts in those overlapping areas and attention to the role of hosts in transmission cycles.
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- Award ID(s):
- 2016265
- PAR ID:
- 10401980
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Ecosphere
- Volume:
- 14
- Issue:
- 3
- ISSN:
- 2150-8925
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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