Ectoparasites of Microtus californicus and Possible Emergence of an Exotic Ixodes Species Tick in California.

California voles (Microtus californicus Peale) harbor fleas and ticks, may be infected with vector-borne pathogens, and could themselves suffer from disease and serve as a source of infection for people and other animals. Here we summarize publications, museum archives, and recent records of ticks and fleas from California voles. There have been 18 flea species reported on California voles with geographic locations reported for 13. During recent statewide surveys, we found six flea species, with the highest species richness in Humboldt County. We found three of five previously reported tick species as well as a tick resembling the eastern North American tick Ixodes minor Neumann (which we here designate Ixodes "Mojave morphotype") on isolated Amargosa voles and Owens Valley voles (Microtus californicus vallicola Bailey) in Inyo County in 2012 and 2014. Additional incidental observations of this Mojave morphotype tick were on a western harvest mouse (Reithrodontomys megalotis Baird) at the Mojave site and a montane vole (Microtus montanus Peale) in the Owens Valley, both in March, 2014. We cannot rule out that this tick species has been present in remote areas of California but gone unrecognized, but these data are consistent with recent introduction of this tick, possibly from migrating birds. Changes in the ectoparasite fauna suggest changing ecologies of vectors and vector-borne pathogens that could influence animals and people as well.

Borrelia burgdorferi and Anaplasma phagocytophilum Genospecies in Northern California.

The sensu lato (s.l.) complexes of Borrelia burgdorferi and Anaplasma phagocytophilum include pathogenic genospecies each with distinct ecologies in northern California, yet, most work conflates the genospecies of each pathogen into one sensu lato species. Detailed understanding of the differences in geographic distributions and ecology among genospecies is lacking. We aimed to evaluate whether two B. burgdorferi and two A. phagocytophilum genospecies in high-risk locations in coastal northern California were spatially clustered and if presence of a particular genospecies was associated with geographical site, host species, or other demographic or ecological variables. DNA sequencing was performed to differentiate genospecies of Borreliae and Anaplasma from PCR-positive dusky-footed woodrats (Neotoma fuscipes) and sciurids (chipmunks, Tamias spp., and Douglas squirrels, Tamiasciurus douglasii) at four sites in northwestern California. Logistic regression was performed to assess associations of genospecies with the predictor variables host species, host sex, site, season, and year. Spatial clustering was assessed using a Poisson spatial scan statistic in SaTScan. Host species was a significant predictor for Borrelia bissettiae, B. burgdorferi sensu stricto (s.s.), A. phagocytophilum s.s., and the DU1 Anaplasma genospecies. Woodrats were significantly more likely to be PCR-positive for B. bissettiae and A. phagocytophilum DU1 genospecies, while A. phagocytophilum s.s. and B. burgdorferi s.s. were significantly associated with sciurids. We report a single Borrelia lanei in an Allen's chipmunk (Tamias senex) from the Hoopa Valley Tribal Reservation. A significant spatial cluster of A. phagocytophilum s.s. was detected at Hendy Woods State Park in Mendocino County. These results highlight the need to better understand genospecies partitioning according to host species to further assess human risks, aid in future surveillance, and inform targeted research.

Diet composition analysis provides new management insights for a highly specialized endangered small mammal.

The critically endangered Amargosa vole (Microtus californicus scirpensis) is found only in rare marsh habitat near Tecopa, California in a plant community dominated by three-square bulrush (Schoenoplectus americanus). Since the earliest research on the Amargosa vole, the existing paradigm has been that these voles are obligatorily dependent on bulrush as their only food source and for the three-dimensional canopy and litter structure it provides for predator avoidance. However, no prior research has confirmed the diet of the Amargosa vole. In this study we characterized the Amargosa vole' nutritional needs, analyzed the quality of bulrush by forage analysis, and performed microhistological and metabarcoding analyses of vole feces to determine what foods were consumed in the wild. All bulrush plant tissues analyzed were low in fat (from 0.9% of dry matter in roots to 3.6% in seeds), high in neutral detergent fiber (from 5.9% in rhizomes to 33.6% in seeds), and low in protein (7.3-8.4%). These findings support the conclusion that bulrush alone is unlikely to support vole survival and reproduction. Fecal microhistology and DNA metabarcoding revealed relatively diverse diets including plants in 14 families, with rushes (Juncaceae), bulrushes (Cyperaceae), and grasses (Poaceae) being the most common diet items. On microhistology, all analyzed samples contained bulrush, sedges (Carex sp.), rushes (Juncus sp.), and beaked spikerush (Eleocharis rostrellata) even from marshes where non-bulrush plants were uncommon. There was evidence of insects at <1% in two marshes but none in the remaining marshes. Metabarcoding detected ten genera of plants. When considering non-Schoenoplectus targets, for which metabarcoding had poor sensitivity, saltgrass (Distichlis spicata) was the most commonly detected species, with prominent contributions from seaside arrowgrass (Triglochin concinna) and yerba mansa (Anemopsis californica) as well. Diversity of vole diets generally increased with increasing site plant diversity, but differences were not statistically significant. Confirming details about dietary behaviors is critical for informing appropriate conservation planning including habitat management and reintroduction of voles into new sites.

A Tale of Two Valleys: Disparity in Sin Nombre Virus Antibody Reactivity Between Neighboring Mojave Desert Communities.

INTRODUCTION: Hantaviruses are a group of globally distributed rodent-associated viruses, some of which are responsible for human morbidity and mortality. Sin Nombre orthohantavirus, a particularly virulent species of hantavirus associated with Peromyscus spp. mice, is actively monitored by the Department of Public Health in California (CDPH). Recently, CDPH documented high (40%) seroprevalence in a potentially novel reservoir species, the cactus mouse (Peromyscus eremicus) in Death Valley National Park. METHODS: This study was performed in the extremely isolated Mojave Desert Amargosa River valley region of southeastern Inyo County, California, 105 km from Death Valley, approximately over the same time interval as the CDPH work in Death Valley (between 2011 and 2016). Similar rodent species were captured as in Death Valley and were tested for select hantaviruses using serology and RT-PCR to assess risk to human health and the conservation of the endemic endangered Amargosa vole. RESULTS: Among 192 rodents tested, including 56 Peromyscus spp., only one seropositive harvest mouse (Reithrodontomys megalotis) was detected. DISCUSSION: These data highlight the heterogeneity in the prevalence of hantavirus infection even among nearby desert communities and suggest that further studies of hantavirus persistence in desert environments are needed to more accurately inform the risks to public health and wildlife conservation.

Subpopulation augmentation among habitat patches as a tool to manage an endangered Mojave Desert wetlands-dependent rodent during anthropogenic restricted water climate regimes.

Intensive management may be necessary to protect some highly vulnerable endangered species, particularly those dependent on water availability regimes that might be disrupted by ongoing climate change. The Amargosa vole (Microtus californicus scirpensis) is an increasingly imperiled rodent constrained to rare wetland habitat in the Mojave Desert. In 2014 and 2016, we trapped and radio-collared 30 voles, 24 were translocated and six remained at donor and recipient marshes as resident control voles. Soft-release was performed followed by remote camera and radio-telemetry monitoring. Although comparative metrics were not statistically significant, the mean maximum known distance moved (MDM) was longer for translocated (82.3 ± 14.6 m) vs. resident-control voles (74.9 ± 17.5 m) and for female (98.4 ± 19.9 m) vs. male (57.8 ± 9.1 m) voles. The mean area occupied (AO) tended to be greater in female (0.15 ± 0.04 ha) vs. male (0.12 ± 0.03 ha) voles, and control voles (0.15 ± 0.05 ha) compared with translocated voles (0.13 ± 0.03 ha). The mean minimum known time alive (MTA) was 38.2 ± 19.4 days for resident-control voles and 47.0 ± 10.6 days for translocated voles. Female survival (55.7 ± 14.3 days) exceeded that of males (31.5 ± 9.4 days) regardless of study group. Activity in bulrush/rushes mix and bulrush vegetation types was strongly and significantly overrepresented compared with salt grass and rushes alone, and habitat selection did not differ between resident and translocated voles. Our results provide ecological and methodological insights for future translocations as part of a strategy of promoting long-term survival of an extremely endangered small mammal in a wild desert environment.

Distribution and Diversity of Borrelia burgdorferi Sensu Lato Group Bacteria in Sciurids of California.

California has a remarkable diversity of squirrel and chipmunk species (sciurids), and five named and several unnamed genospecies in the Borrelia burgdorferi sensu lato group (BBSL) of bacteria as well, many of which utilize sciurids as reservoirs. We investigated the prevalence, spatial distribution, and diversity of BBSL in sciurids of California by literature search, PCR of 585 ear tissue samples from 15 sciurid species prospectively collected across 19 California counties, and DNA sequencing when possible. Seven publications documented BBSL infections in western gray squirrels (Sciurus griseus), fox squirrels (Sciurus niger), eastern gray squirrels (Sciurus carolinensis), Douglas squirrels (Tamiasciurus douglasii), and redwood chipmunks (Tamias ochrogenys) in northern California. Prospective sampling added new BBSL infection records for long-eared chipmunks (Tamias quadrimaculatus), Allen's chipmunks (Tamias senex), and Siskiyou chipmunks (Tamias siskiyou). Infection was detected in the Mendocino, North Coast, West Sierra, and Central Valley regions of California. The overall PCR prevalence was 9.4% (n = 585), and exceeded 40% (n = 84) in Mendocino and farther north along the Pacific coast. Redwood (40.7%, n = 81) and Siskiyou (22.2%, n = 18) chipmunks had the highest prevalence of BBSL infection. BBSL infections were associated with arboreal and semiarboreal sciurid species and species occurring in conifer forests. Western gray squirrels and Allen's chipmunks in Humboldt County and redwood chipmunks in Mendocino County were infected with B. burgdorferi sensu stricto, while we identified Borrelia bissettiae in Douglas squirrels and Siskiyou chipmunks in Humboldt and Del Norte Counties. This indicates that further study of sciurids can aid in describing the ecology of BBSL in California.

Distribution and prevalence of vector-borne diseases in California chipmunks (Tamias spp.).

California, with 13 chipmunk (Tamias) species, has more than any other state or country, occupying habitats ranging from chaparral to the high peaks of the Sierra Nevada. Chipmunks host zoonotic pathogens including Yersinia pestis, Anaplasma phagocytophilum, relapsing fever (RF) Borrelia spp., Borrelia burgdorferi, and spotted fever group (SFG) Rickettsia species. Chipmunk species are often not differentiated by public health workers, yet different species utilize different ecological niches and may have intrinsically different capacities for maintaining vector-borne pathogens and infecting vectors. We surveyed over 700 individuals from nine species of chipmunks throughout California for exposure to and infection by Y. pestis, A. phagocytophilum, RF Borrelia spp., Borrelia burgdorferi, and SFG Rickettsia species. DNA of all five pathogens was found and all chipmunks except Merriam's chipmunk (T. merriami) were PCR-positive for at least one of the pathogens. Anaplasma phagocytophilum was most common (40.0%, 2/5) in Sonoma chipmunks (T. sonomae) from Marin county and B. burgdorferi most common (37.5%, 27/72) in redwood chipmunks (T. ochrogenys) from Mendocino county. RF Borrelia spp. was detected in 2% (6/297) of redwood chipmunks in Mendocino county and 10% (1/10) of both least (T. minimus) and lodgepole (T. speciosus) chipmunks in the western Sierra. Exposure to SFG Rickettsia spp. was found in the Northern Coastal region (Del Norte, Humboldt and Mendocino counties) and in the northern and western Sierra in several species of chipmunks. Y. pestis infection was found only in the western Sierra-in a yellow-pine (T. amoenus) and a long-eared (T. quadrimaculatus) chipmunk. Though more data are needed to thoroughly understand the roles that different chipmunk species play in disease transmission, our findings suggest that some chipmunk species may be more important to the maintenance of vector-borne diseases than others within each geographic area.

PREVALENCE AND POTENTIAL IMPACT OF TOXOPLASMA GONDII ON THE ENDANGERED AMARGOSA VOLE (MICROTUS CALIFORNICUS SCIRPENSIS), CALIFORNIA, USA.

We investigated the prevalence of Toxoplasma gondii in 2011-15 to assess its potential threat on the endangered Amargosa vole ( Microtus californicus scirpensis) in California, US. Surveillance was simultaneously performed on populations of syntopic rodent species. We detected antibodies to T. gondii in sera from 10.5% of 135 wild-caught Amargosa voles; 8% of 95 blood samples were PCR-positive for the T. gondii B1 gene, and 5.0% of 140 sympatric rodent brain samples were PCR-positive. Exposure to T. gondii did not change the probability that an animal would be recaptured in the field study. Behavioral response to domestic cat ( Felis catus ) and bobcat ( Lynx rufus ) urine was evaluated in five nonendangered Owens Valley voles ( Microtus californicus vallicola) as surrogates for Amargosa voles and seven uninfected controls. Voles showed mild attraction to mouse urine and had neutral reactions to domestic cat urine whether or not infected. Time spent near bobcat urine was approximately twice as high in infected than in uninfected voles (although not statistically significant). The presence of T. gondii in wild Amargosa vole and sympatric rodent populations may hinder the endangered Amargosa vole population's ability to recover in the wild.