Publications by authors named "Janet Foley"

211 Publications

Will new ticks invade North America? How to identify future invaders.

Trends Parasitol 2022 Sep 9;38(9):805-814. Epub 2022 Jul 9.

Department of Medicine and Epidemiology, School of Veterinary Medicine, University of California, Davis, CA 95616, USA. Electronic address:

Invasive tick species and the pathogens they transmit pose increasing threats to human and animal health around the world. Little attention has been paid to the characteristics enabling tick species to invade. Here we analyze examples of tick invasion events in North America to identify factors that facilitated the invasion. Commonalities among invasive ticks are that they thrive in anthropogenically modified habitats, feed on either domestic animals or wildlife occurring in high density, and can survive across a broad range of climatic conditions. Invasive tick species varied widely in life history and reproductive habits, suggesting that invasion occurs when multiple characteristics converge. The combination of potential characteristics leading to invasion, however, improves our ability to predict future invaders and inform surveillance.
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http://dx.doi.org/10.1016/j.pt.2022.06.004DOI Listing
September 2022

Nasopulmonary mites (Acari: Halarachnidae) as potential vectors of bacterial pathogens, including Streptococcus phocae, in marine mammals.

PLoS One 2022 16;17(6):e0270009. Epub 2022 Jun 16.

California Department of Fish and Wildlife, Marine Wildlife Veterinary Care and Research Center, Santa Cruz, California, United States of America.

Nasopulmonary mites (NPMs) of the family Halarachnidae are obligate endoparasites that colonize the respiratory tracts of mammals. NPMs damage surface epithelium resulting in mucosal irritation, respiratory illness, and secondary infection, yet the role of NPMs in facilitating pathogen invasion or dissemination between hosts remains unclear. Using 16S rRNA massively parallel amplicon sequencing of six hypervariable regions (or "16S profiling"), we characterized the bacterial community of NPMs from 4 southern sea otters (Enhydra lutris nereis). This data was paired with detection of a priority pathogen, Streptococcus phocae, from NPMs infesting 16 southern sea otters and 9 California sea lions (Zalophus californianus) using nested conventional polymerase chain reaction (nPCR). The bacteriome of assessed NPMs was dominated by Mycoplasmataceae and Vibrionaceae, but at least 16 organisms with pathogenic potential were detected as well. Importantly, S. phocae was detected in 37% of NPM by nPCR and was also detected by 16S profiling. Detection of multiple organisms with pathogenic potential in or on NPMs suggests they may act as mechanical vectors of bacterial infection for marine mammals.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0270009PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC9202935PMC
June 2022

Host species and environment drivers of ectoparasite community of rodents in a Mojave Desert wetlands.

PLoS One 2022 2;17(6):e0269160. Epub 2022 Jun 2.

Department of Medicine and Epidemiology, School of Veterinary Medicine, University of California, Davis, California, United States of America.

Drivers of patterns of ectoparasitism in rodents in patchy Mojave Desert wetlands were investigated. A total of 1,571 ectoparasites in Mesostigmata, Trombidiformes, Siphonaptera and Ixodida were collected from 341 rodents (Microtus californicus scirpensis, Mus musculus, Reithrodontomys megalotis, Peromyscus eremicus, and Neotoma lepida) at eleven marshes. Trombiculids accounted for 82.5% of mites, followed by the mesostigmatid Ornithonyssus bacoti (17.5%), with chiggers predominating on voles and harvest mice. There were at least three genera of chiggers (Eutrombicula alfreddugesi, Euschoengastia sp. novel, and Blankaartia sp. novel). Fleas included Orchopeas leucopus (90.3% of all fleas) and O. sexdentatus (9.7%), and ticks were the novel endemic Ixodes mojavensis (82.1% of ticks) and Dermacentor similis (17.9%). On all hosts and at all marshes, coverage-based rarefaction sampling was over 96%, indicating coverage sufficient for analysis. Dissimilarities in ectoparasite community structure were driven mainly by chiggers, I. mojavensis and O. leucopus. Northern marshes were dominated by chiggers; central marshes by I. mojavensis; and southern marshes by O. leucopus. Primary determinants of ectoparasite community structure were host species, patch size, and parasite interspecific interactions. Host species richness and environmental factors such as patch distance and water and plant availability were not significantly associated with patterns of ectoparasitism. There were nine (60%) significant negative pairwise associations between ectoparasite taxa and no significant positive relationships. Ixodes mojavensis had the highest number of negative associations (with five other species), followed by chiggers and O. bacoti with two negative associations each. The study area is among the most arid in North America and supports numerous rare and endemic species in increasingly isolated wetland habitat patches; knowledge of ectoparasite ecology in this region identifies potential ectoparasite vectors, and provides information needed to design and implement programs to manage vector-borne diseases for purposes of wildlife conservation.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0269160PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC9162374PMC
June 2022

Benefits, companion animal zoonotic disease prevalence and public perceptions of pet ownership among people experiencing homelessness in northern California.

Zoonoses Public Health 2022 May 23. Epub 2022 May 23.

Department of Medicine and Epidemiology, School of Veterinary Medicine, University of California Davis, Davis, California, USA.

California has the highest proportion of unhoused individuals in the country, and up to 25% of unhoused individuals own pets, providing substantial benefits but unique challenges including access to housing, transportation and unfounded grounds for social stigmatization. Unhoused individuals and pets may also be at risk for diseases due to impaired access to sanitation facilities. The purpose of this cross-sectional survey was to evaluate differences in perceived benefits, challenges and public perceptions among pet owners of varying housing security and the prevalence of diseases among their pets. Questionnaires were administered to housed and unhoused pet owners and pet blood screened for rickettsiosis, bartonellosis, ehrlichiosis, anaplasmosis, borreliosis, West Nile fever and heartworm. Among 147 canine and 16 feline blood samples, seropositivity of ectoparasitic diseases did not vary by housing status. Among 45 housed and 56 unhoused owners, unhoused owners were significantly more likely to report protective benefits, challenges obtaining housing, finding a flea on their pet, using bottled water for their pet and their pet sleeping in their bed. Housed owners were significantly more likely to report companionship and entertainment benefits, challenges with pet sitting and consistently administering parasite preventatives. Similar (96-98%) percentages stated they would not give up their pet for better housing and 31% of housed pet owners believed that people should not own pets if they do not have secure housing. Social stigma against unhoused pet owners is present within the community, requiring education to change public perception and guide policy regarding housing for pet owners experiencing homelessness.
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http://dx.doi.org/10.1111/zph.12970DOI Listing
May 2022

Spatial distribution patterns of tick community structure in sympatric jaguars (Panthera onca) and pumas (Puma concolor) from three ecoregions in Mexico.

Med Vet Entomol 2022 Sep 28;36(3):371-380. Epub 2022 Apr 28.

Department of Medicine and Epidemiology, School of Veterinary Medicine, University of California, Davis, California, USA.

We examined tick communities on wild felid hosts in three ecoregions of Mexico. We collected 186 ticks of 7 species from 10 pumas (Puma concolor) and 9 jaguars (Panthera onca). Tick community composition varied across the ecoregions, and across host species within each region. Overall, Ixodes affinis, Amblyomma ovale, and Amblyomma tenellum were the most abundant species; however, only the latter two ticks were distributed across all three ecoregions, while I. affinis, along with Ixodes spinipalpis, Amblyomma inornatum, and Amblyomma parvum were restricted to more limited geographical regions. Ixodes affinis occurred strictly in southern tropical rainforest ecoregions and was significantly more abundant in Selva Lacandona compared with the Yucatán Peninsula. Amblyomma ovale was significantly more common in the tropical dry forest in the Pacific coastal ecoregion. Amblyomma tenellum abundance tended to be higher on jaguars, while I. affinis abundance was higher on pumas. Regional distribution patterns of some tick species (e.g., I. affinis and I. spinipalpis) may be determined by off-host environmental conditions rather than host factors. In contrast, at the local scale, occurrence and abundance of some tick species (e.g., A. tenellum, A. ovale and Rhipicephalus microplus) might be driven by ecological-host factors, such as habitat use or predator-prey relationships.
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http://dx.doi.org/10.1111/mve.12575DOI Listing
September 2022

Detection and Isolation of Rickettsia tillamookensis (Rickettsiales: Rickettsiaceae) From Ixodes pacificus (Acari: Ixodidae) From Multiple Regions of California.

J Med Entomol 2022 Jul;59(4):1404-1412

Rickettsial Zoonoses Branch, Centers for Disease Control and Prevention, Atlanta, GA, USA.

The western black-legged tick (Ixodes pacificus) is the most frequently identified human-biting tick species in the western United States and the principal vector of at least three recognized bacterial pathogens of humans. A potentially pathogenic Rickettsia species, first described in 1978 and recently characterized as a novel transitional group agent designated as Rickettsia tillamookensis, also exists among populations of I. pacificus, although the distribution and frequency of this agent are poorly known. We evaluated DNA extracts from 348 host-seeking I. pacificus nymphs collected from 9 locations in five California counties, and from 916 I. pacificus adults collected from 24 locations in 13 counties, by using a real-time PCR designed specifically to detect DNA of R. tillamookensis. DNA of R. tillamookensis was detected in 10 (2.9%) nymphs (95% CI: 1.6-5.2%) and 17 (1.9%) adults (95% CI: 1.2-3.0%) from 11 counties of northern California. Although site-specific infection rates varied greatly, frequencies of infection remained consistently low when aggregated by stage, sex, habitat type, or geographical region. Four novel isolates of R. tillamookensis were cultivated in Vero E6 cells from individual adult ticks collected from Alameda, Nevada, and Yolo counties. Four historical isolates, serotyped previously as 'Tillamook-like' strains over 40 yr ago, were revived from long-term storage in liquid nitrogen and confirmed subsequently by molecular methods as isolates of R. tillamookensis. The potential public health impact of R. tillamookensis requires further investigation.
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http://dx.doi.org/10.1093/jme/tjac038DOI Listing
July 2022

Sarcoptic mange outbreak decimates South American wild camelid populations in San Guillermo National Park, Argentina.

PLoS One 2022;17(1):e0256616. Epub 2022 Jan 21.

One Health Institute, School of Veterinary Medicine, University of California, Davis, California, United States of America.

Sarcoptic mange epidemics can devastate wildlife populations. In 2014, mange was first detected in vicuñas (Vicugna vicugna) and guanacos (Lama guanicoe) in San Guillermo National Park (SGNP), Argentina. This study describes the temporal dynamics of the outbreak, its effects on the park's wild camelid populations between 2017-2019, and investigates the potential source of the epidemic. From May 2017 to June 2018, transect surveys indicated a sharp decrease in the density of living vicuñas and guanacos by 68% and 77%, respectively. By April 2019 no vicuñas or guanacos were recorded on transect surveys, suggesting their near-extinction in the park. Clinical signs consistent with mange (e.g., intense scratching, hyperkeratosis, alopecia) were observed in 24% of living vicuñas (n = 478) and 33% of living guanacos (n = 12) during surveys, as well as in 94% of vicuña carcasses (n = 124) and 85% of guanaco carcasses (n = 20) examined. Sarcoptes scabiei was identified as the causal agent by skin scrapings, and the cutaneous lesions were characterized by histopathology (n = 15). Genetic characterization revealed that mites recovered from seven vicuñas (n = 13) and three guanacos (n = 11) shared the same genotype, which is consistent with a single source and recent origin of the epidemic. Tracing the potential source, we identified a governmental livestock incentive program which introduced llamas (Lama glama) in areas adjacent to SGNP in 2009, some of which had alopecic scaling consistent with sarcoptic mange. Though at the time of our study no llamas with mange were available for confirmatory sampling, we hypothesize that the introduction of mange-infected llamas may have triggered the outbreak in wild camelids. This unprecedented event in SGNP had devastating effects on dominating herbivores with potentially profound cascading effects at the community and ecosystem levels.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0256616PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8782313PMC
February 2022

PARASITES OF AN ENDANGERED HARVEST MOUSE (REITHRODONTOMYS RAVIVENTRIS HALICOETES) IN A NORTHERN CALIFORNIA MARSH.

J Wildl Dis 2022 01;58(1):122-136

Department of Wildlife, Fish, and Conservation Biology, University of California, Davis, One Shields Avenue, Davis, California 95616, USA.

Disease may limit recovery of endangered species. We surveyed parasites in the federally endangered salt marsh harvest mouse (SMHM; Reithrodontomys raviventris halicoetes) and sympatric rodents in Suisun Marsh (Solano County, California, USA) from April 2018 through March 2019. We investigated individual SMHM risk factors (age, sex, reproductive status, and body condition) for infection and relationships among the estimated parasite prevalence and season and habitat management (natural tidal habitats versus diked, nontidal habitats). We captured 625 individual rodents, including 439 SMHM, and tested these for infection with Bartonella spp., Borrelia spp., Rickettsia spp., Francisella tularensis, Leptospira spp., Cryptosporidium spp., Giardia spp., and Toxoplasma gondii by PCR. Over one-third (34.6%, confidence interval [CI], 30.2-39.3%) of SMHM tested positive for at least one parasite. Four percent (CI, 2.8-6.3%) of SMHM were infected with F. tularensis holarctica, a virulent bacterium that causes mortality in rodents shortly after infection. Additionally, we detected three species of Bartonella (B. henselae, B. rochalimae, B. vinsonii arupensis), Leptospira borgpetersenii serovar Ballum, Cryptosporidium sp. (deer mouse [Peromyscus maniculatus] genotype), Cryptosporidium parvum, Giardia intestinalis, and an unidentified Borrelia sp. The only parasite that was associated with habitat management was Bartonella spp., which was more prevalent in diked than tidal areas. Male SMHM were more likely to be parasitized than females, and individuals in modestly poor body condition were most likely to be infected with Bartonella spp. The estimated sample prevalence of multiple parasites varied by season and by host species. This is the first major parasite assessment in a long-endangered species, and these results will assist managers to incorporate parasitic disease into recovery planning and provide a critical baseline for future investigations, including how climatically induced habitat and species composition changes could alter disease dynamics.
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http://dx.doi.org/10.7589/JWD-D-21-00059DOI Listing
January 2022

Nasopulmonary mites (Halarachnidae) of coastal Californian pinnipeds: Identity, prevalence, and molecular characterization.

Int J Parasitol Parasites Wildl 2021 Dec 14;16:113-119. Epub 2021 Aug 14.

School of Veterinary Medicine, Department of Medicine and Epidemiology, University of California Davis, 1320D Tupper Hall, Davis, CA, 95616, USA.

Mites from the family Halarachnidae Oudemans 1906 are obligate endoparasites that colonize the respiratory tracts of free-living and captive marine mammals. Infestations can range from mild to severe and result in respiratory tract irritation or impairment. Nasopulmonary acariasis was determined to be a contributing cause of death among several southern sea otters Merriam 1904 in a longitudinal study of otter mortality, and proximity to Pacific harbor seals Gray 1864 was a significant risk factor for sea otter infestation. Beyond scattered opportunistic reports, each halarachnid mite species' affinity for particular hosts and the extent of mite transmission between host species is poorly understood. We investigated the identity and prevalence of nasopulmonary mites from Pacific harbor seals, California sea lions Lesson 1828, northern elephant seals Gill 1866, northern fur seals Linnaeus 1758, and Guadalupe fur seals Merriam 1897 to complement published nasopulmonary mite findings from sympatric southern sea otters during a comparable timeframe. Halarachnid mite infestation was common among California sea lions (74.1%), northern fur seals (73.3%), and northern elephant seals (46.6%), but was less common among harbor seals (18.7%) and Guadalupe fur seals (8.8%). Observed host-mite relationships suggest a distinct host specificity, with genus infesting otariids, and genus infesting phocids and lutrinids along the California coast. Harbor seals and southern sea otters were the primary hosts of , but one nothern elephant seal was infested with both and a single We also present the first high-resolution SEM images for and and possible evidence for a new host record for .
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http://dx.doi.org/10.1016/j.ijppaw.2021.08.005DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8403680PMC
December 2021

A Survey of Tick Surveillance and Control Practices in the United States.

J Med Entomol 2021 07;58(4):1503-1512

Division of Vector-Borne Diseases, Centers for Disease Control and Prevention, Fort Collins, CO.

Tickborne diseases are an increasing public health threat in the United States. Prevention and diagnosis of tickborne diseases are improved by access to current and accurate information on where medically important ticks and their associated human and veterinary pathogens are present, their local abundance or prevalence, and when ticks are actively seeking hosts. The true extent of tick and tickborne pathogen expansion is poorly defined, in part because of a lack of nationally standardized tick surveillance. We surveyed 140 vector-borne disease professionals working in state, county, and local public health and vector control agencies to assess their 1) tick surveillance program objectives, 2) pathogen testing methods, 3) tick control practices, 4) data communication strategies, and 5) barriers to program development and operation. Fewer than half of respondents reported that their jurisdiction was engaged in routine, active tick surveillance, but nearly two-thirds reported engaging in passive tick surveillance. Detection of tick presence was the most commonly stated current surveillance objective (76.2%). Most of the programs currently supporting tick pathogen testing were in the Northeast (70.8%), Upper and Central Midwest (64.3%), and the West (71.4%) regions. The most common pathogens screened for were Rickettsia spp. (Rickettsiales: Rickettsiaceae) and bacterial and viral agents transmitted by Ixodes (Acari: Ixodidae) ticks. Only 12% of respondents indicated their jurisdiction directly conducts or otherwise financially supports tick control. Responses indicated that their ability to expand the capacity of tick surveillance and control programs was impeded by inconsistent funding, limited infrastructure, guidance on best practices, and institutional capacity to perform these functions.
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http://dx.doi.org/10.1093/jme/tjaa094DOI Listing
July 2021

Detection of in Humans with Babesiosis Symptoms.

Diagnostics (Basel) 2021 May 25;11(6). Epub 2021 May 25.

Department of Medicine and Epidemiology, School of Veterinary Medicine, University of California Davis, Davis, CA 95616, USA.

Human babesiosis is a life-threatening infectious disease that causes societal and economic impact worldwide. Several species of cause babesiosis in terrestrial vertebrates, including humans. A one-day clinic was held in Ontario, Canada, to see if a red blood cell parasite, which is present in blacklegged ticks, , is present in humans. Based on PCR testing and DNA sequencing of the 18S rRNA gene, we unveiled in two of 19 participants. DNA amplicons from these two patients are almost identical matches with the type strains of in GenBank. In addition, the same two human subjects had the hallmark symptoms of human babesiosis, including night sweats, chills, fevers, and profound fatigue. Based on symptoms and molecular identification, we provide substantive evidence that is pathogenic to humans. Dataset reveals that serologically cross-reacts with . Clinicians must realize that there are more than two spp. in North America that cause human babesiosis. This discovery signifies the first report of causing human babesiosis.
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http://dx.doi.org/10.3390/diagnostics11060947DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8228967PMC
May 2021

Effect of Temperature on Host Preference in Two Lineages of the Brown Dog Tick, Rhipicephalus sanguineus.

Am J Trop Med Hyg 2021 04 5;104(6):2305-2311. Epub 2021 Apr 5.

Rhipicephalus sanguineus is a species complex of ticks that vector disease worldwide. Feeding primarily on dogs, members of the complex also feed incidentally on humans, potentially transmitting disease agents such as Rickettsia rickettsii, Rickettsia conorii, and Ehrlichia species. There are two genetic Rh. sanguineus lineages in North America, designated as the temperate and tropical lineages, which had occurred in discrete locations, although there is now range overlap in parts of California and Arizona. Rh. sanguineus in Europe are reportedly more aggressive toward humans during hot weather, increasing the risk of pathogen transmission to humans. The aim of this study was to assess the impact of hot weather on choice between humans and dog hosts among tropical and temperate lineage Rh. sanguineus individuals. Ticks in a two-choice olfactometer migrated toward a dog or human in trials at room (23.5°C) or high temperature (38°C). At 38°C, 2.5 times more tropical lineage adults chose humans compared with room temperature, whereas temperate lineage adults demonstrated a 66% reduction in preference for dogs and a slight increase in preference for humans. Fewer nymphs chose either host at 38°C than at room temperature in both lineages. These results demonstrate that risk of disease transmission to humans may be increased during periods of hot weather, where either lineage is present, and that hot weather events associated with climatic change may result in more frequent rickettsial disease outbreaks.
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http://dx.doi.org/10.4269/ajtmh.20-1376DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8176482PMC
April 2021

Detection of in Ticks Collected in Southern Ontario, Canada.

Pathogens 2021 Mar 10;10(3). Epub 2021 Mar 10.

Department of Medicine and Epidemiology, School of Veterinary Medicine, University of California Davis, Davis, CA 95616, USA.

Tick-borne zoonotic diseases have an economic and societal impact on the well-being of people worldwide. In the present study, a high frequency of , a red blood cell parasite, was observed in the Huronia area of Ontario, Canada. Notably, 71% (15/21) blacklegged ticks, , collected from canine and feline hosts were infected with . Consistent with U.S. studies, 12.5% (4/32) of questing adults collected by flagging in various parts of southwestern Ontario were positive for . Our data show that all strains in the present study have consistent genetic identity, and match type strains in the GenBank database. The high incidence of in the Huronia area indicates that this babesial infection is established, and is cycling enzootically in the natural environment. Our data confirm that has wide distribution in southern Ontario.
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http://dx.doi.org/10.3390/pathogens10030327DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7999371PMC
March 2021

Demodectic mange in threatened southern sea otters (Enhydra lutris nereis).

Vet Dermatol 2021 Jun 19;32(3):211-e55. Epub 2021 Mar 19.

Marine Wildlife Veterinary Care and Research Center, California Department of Fish and Wildlife, 151 McAllister Way, Santa Cruz, CA, 95060, USA.

Background: Southern sea otters (Enhydra lutris nereis) rely on intact pelage for thermoregulation, and thus clinically significant demodicosis and associated alopecia can cause morbidity and death.

Hypothesis/objectives: This study aimed to describe lesions associated with follicular Demodex sp. infestation, estimate the prevalence and intensity of infestation, describe mite distribution across key anatomical regions, and assess mite presence or absence in relation to lesions and host risk factors.

Animals: Twenty necropsied, wild southern sea otters that stranded along the central California coast from 2005 to 2018.

Methods And Materials: Grossly normal and abnormal integument from the head, perineum, genitals, mamillary papillae and limbs was assessed microscopically for mites and mite-associated pathological findings.

Results: Intrafollicular mites were observed in the integument of 55% of otters and 20% had clinical demodicosis. Demodicosis was considered to be contributory to death or euthanasia in two cases. Although Demodex sp. mites often were observed microscopically in grossly normal skin, the presence of multiple densely-packed intrafollicular mites generally was associated with pigmentary incontinence, ectatic follicles, lymphoplasmacytic perifolliculitis, and neutrophilic and lymphoplasmacytic, dermal inflammation. Other findings included epidermal hyperplasia, orthokeratotic hyperkeratosis of epidermis and follicular epithelium, concurrent pyoderma and cell necrosis. Perioral integument, especially of the chin, had the highest prevalence of mites and the highest mite density, suggesting facial contact as a means of mite transmission.

Conclusions And Clinical Importance: Our research confirmed demodectic mange as a contributor to morbidity and mortality in sea otters, with important implications for clinical care, rehabilitation and conservation.
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http://dx.doi.org/10.1111/vde.12947DOI Listing
June 2021

Diversity of rickettsiae in domestic, synanthropic, and sylvatic mammals and their ectoparasites in a spotted fever-epidemic region at the western US-Mexico border.

Transbound Emerg Dis 2022 Mar 5;69(2):609-622. Epub 2021 Mar 5.

Department of Medicine and Epidemiology, School of Veterinary Medicine, University of California, Davis, CA, USA.

Over one hundred cases of human rickettsiosis, many fatal, are reported annually across the US-Mexico transboundary region, representing a likely undercount. Although cases are often attributed to Rickettsia rickettsii, the agent of Rocky Mountain spotted fever, multiple other Rickettsia pathogens are present in North America. We conducted multiple-host surveillance of domestic, synanthropic, and sylvatic mammals and their ectoparasites to investigate the ecology of Rickettsia species in this region. A total of 499 mammals, including 83 dogs, 23 wild carnivores, five lagomorphs, and 388 rodents were sampled, and 413 fleas and 447 ticks belonging to 15 and 4 species, respectively, were collected during 2017 and 2018. We detected Rickettsia spp. DNA in one blood sample of coyote (Canis latrans), 11 ear tissues of rodents (10.6%), and 79 ectoparasites (9.5%). Of the 64 Rickettsia-positive fleas, 54 were Echidnophaga gallinacea and 10 were Pulex simulans, while of the 15 ticks, 11 were Rhipicephalus sanguineus s.l. and four Ixodes pacificus. The DNA sequence alignment of gltA and ompB regions revealed one and ten genetic variants of Rickettsia spp., respectively. These variants were clustered in clades of zoonotic species (R. felis, R. massiliae, R. parkeri, R. rickettsii, and R. typhi) and organisms of unknown pathogenic significance (R. asembonensis and Candidatus Rickettsia tarasevichiae). The finding of a coyote infected with R. rickettsii and the multiple zoonotic SFG rickettsial agents in the study area suggest that: 1) wild canids could serve as an amplifying host for RMSF, an alternate host for Rh. sanguineus s.l. ticks, and a means to spread infection and ticks over large areas; and 2) at least some of the human rickettsiosis cases attributed to R. rickettsii could be caused by other Rickettsia species. This study strongly supports the importance of multiple-host and vector eco-epidemiological studies and the One Health approach to better understand disease in a RMSF-epidemic region.
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http://dx.doi.org/10.1111/tbed.14027DOI Listing
March 2022

LEPTOSPIRA PREVALENCE AND ITS ASSOCIATION WITH RENAL PATHOLOGY IN MOUNTAIN LIONS (PUMA CONCOLOR) AND BOBCATS (LYNX RUFUS) IN CALIFORNIA, USA.

J Wildl Dis 2021 01;57(1):27-39

Department of Veterinary Medicine and Epidemiology, School of Veterinary Medicine, University of California, Davis, One Shields Avenue, Davis, California 95616, USA.

Leptospirosis is reported infrequently in wild and domestic felids. We estimated the prevalence of Leptospira spp. infection and exposure using real-time PCR and serology, respectively, in 136 mountain lions (Puma concolor) and 39 bobcats (Lynx rufus) that died or were euthanized between 2009 and 2017 from several regions of California, US. Felids were classified as Leptospira-positive if they were test-positive using real-time PCR targeting the LipL32 gene of pathogenic Leptospira spp. or microscopic agglutination test for six serovars of Leptospira spp. The overall Leptospira spp. prevalence was 46% (63/136) for mountain lions and 28% (11/39) for bobcats. The most common serovar detected in both felid species was Leptospira interrogans serovar Pomona. Age class and geographic location were significantly associated with Leptospira spp. in mountain lions, but not in bobcats. Interstitial nephritis, predominately lymphocytic, was diagnosed in 39% (41/106) of mountain lions and 16% (4/25) of bobcats evaluated histologically and was significantly associated with being Leptospira spp.-positive in both species. Our findings suggest that Leptospira spp. infection is common and widespread in California's wild felids and may have clinical impacts on renal and overall health of individuals. Key words: Bobcat, Leptospira spp., leptospirosis, Lynx rufus, mountain lion, nephritis, pathology, Puma concolor.
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http://dx.doi.org/10.7589/JWD-D-20-00070DOI Listing
January 2021

Tick Microbiomes in Neotropical Forest Fragments Are Best Explained by Tick-Associated and Environmental Factors Rather than Host Blood Source.

Appl Environ Microbiol 2021 03 11;87(7). Epub 2021 Mar 11.

University of California at Davis, School of Veterinary Medicine, Davis, California, USA.

The composition of tick microbiomes varies both within and among tick species. Whether this variation is intrinsic (related to tick characteristics) or extrinsic (related to vertebrate host and habitat) is poorly understood but important, as microbiota can influence the reproductive success and vector competence of ticks. We aimed to uncover what intrinsic and extrinsic factors best explain the microbial composition and taxon richness of 11 species of neotropical ticks collected from eight species of small mammals in 18 forest fragments across central Panama. Microbial richness varied among tick species, life stages, and collection sites but was not related to host blood source. Microbiome composition was best explained by tick life stage, with bacterial assemblages of larvae being a subset of those of nymphs. Collection site explained most of the bacterial taxa with differential abundance across intrinsic and extrinsic factors. and were highly prevalent, but their proportional abundance differed greatly among tick species, and we found both positive and negative cooccurrence between members of these two genera. Other tick endosymbionts (e.g., and ) were associated with specific tick species. In addition, we detected and in several tick species. Our results indicate that the microbial composition and richness of neotropical ticks are principally related to intrinsic factors (tick species and life stage) and collection site. Taken together, our analysis informs how tick microbiomes are structured and can help anchor our understanding of tick microbiomes from tropical environments more broadly. Blood-feeding arthropod microbiomes often play important roles in disease transmission, yet the factors that structure tick microbial communities in the Neotropics are unknown. Utilizing ticks collected from live animals in neotropical forest fragments, this study teases apart the contributions of intrinsic and extrinsic tick-associated factors on tick microbial composition as well as which specific microbes contribute to differences across tick species, tick life stages, the mammals they fed on, and the locations from where they were sampled. Furthermore, this study provides revelations of how notable tick-associated bacterial genera are interacting with other tick-associated microbes as well as the forest animals they encounter.
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http://dx.doi.org/10.1128/AEM.02668-20DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8091620PMC
March 2021

USE OF FLUMETHRIN-IMPREGNATED COLLARS TO MANAGE AN EPIDEMIC OF SARCOPTIC MANGE IN AN URBAN POPULATION OF ENDANGERED SAN JOAQUIN KIT FOXES ().

J Zoo Wildl Med 2020 Nov;51(3):631-642

School of Veterinary Medicine, Department of Medicine and Epidemiology, University of California, Davis, CA 95616, USA.

Sarcoptic mange epidemics can have long-lasting impacts on susceptible wildlife populations, potentially contributing to local population declines and extirpation. Since 2013, there have been 460 reported cases of sarcoptic mange in an urban population of endangered San Joaquin kit foxes () in Bakersfield, CA, with many of them resulting in fatality. As part of a multifaceted response to mitigate mange-caused mortalities and reduce this conservation threat, a 2-yr randomized field trial was conducted to assess the efficacy of long-acting flumethrin collars against sarcoptic mange in kit foxes. Thirty-five kit foxes living in a high-density population on a college campus were captured, examined, administered selamectin, and each fox randomly assigned to either receive a flumethrin collar placed within a VHF radio collar or a VHF radio collar without flumethrin. The survival and mange-infestation status of study animals was monitored via radio telemetry, remote cameras, and periodic recapture examinations and compared among treated and control kit foxes using a Cox proportional hazards model. The average time to onset of mange for treated kit foxes (176 days) was similar to controls (171 days) and treatment with flumethrin did not significantly reduce mange risk for all kit foxes. Kit foxes that had a mild mange infestation at the beginning of the study were four times more likely to develop mange again, regardless of flumethrin treatment, compared with kit foxes that had no signs at initial recruitment. This study demonstrates an approach to evaluating population-level protection and contributes to the limited literature on efficacy, safety, and practicality of acaricides in free-ranging wildlife.
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http://dx.doi.org/10.1638/2019-0197DOI Listing
November 2020

Impacts of Timber Harvest on Communities of Small Mammals, Ticks, and Tick-Borne Pathogens in a High-Risk Landscape in Northern California.

J Med Entomol 2021 05;58(3):1171-1187

Department of Medicine and Epidemiology, School of Veterinary Medicine, University of California, Davis, CA.

Timber harvest may impact tick-borne disease by affecting small mammal and tick community structures. We assessed tick and small mammal populations in older second-growth redwood (Sequoia sempervirens (D. Don) Endl) habitat at two harvested sites in Santa Cruz County, California, where local risk of tick-borne disease is high and determined the prevalence of tick-borne pathogens in ticks. After single-tree removal harvest in 2014, there was a modest reduction in canopy, primarily toward the end of the study. Harvested sites showed strong reductions in California mouse (Peromyscus californicus, (Gambel)) captures 2-yr after harvest, resolving such that treatments and controls were comparable by the end of the study. Following harvest, treated sites experienced a transient decreased tick infestation while control plots experienced an increase. Ixodes angustus (Neumann) infestation probability on harvested plots decreased immediately after harvest, increasing with time but remaining lower than control plots, whereas I. pacificus (Cooley and Kohls) prevalence was higher shortly after the harvest on harvested plots, and continued to increase. Mean abundance of ticks on vegetation increased on control plots. We detected Borrelia burgdorferi ((Johnson et al.) Baranton) and Anaplasma phagocytophilum ((Foggie 1949) Dumler) in 3.8 and 3.1% of ticks on rodents, but no differences were associated with harvest. Impacts of forest harvest on tick-borne disease depend on removal practice and intensity, whether or not hosts are habitat specialists, and whether or not ticks are host specialists.
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http://dx.doi.org/10.1093/jme/tjaa297DOI Listing
May 2021

PFAS soil and groundwater contamination industrial airborne emission and land deposition in SW Vermont and Eastern New York State, USA.

Environ Sci Process Impacts 2021 Mar;23(2):291-301

Bennington College, 1 College Drive, Bennington, VT 05201, USA.

In order to understand the extent to which airborne PFAS emission can impact soil and groundwater, we conducted a sampling campaign in areas of conserved forest lands near Bennington, VT/Hoosick Falls, NY. This has been home to sources of PFAS air-emissions from Teflon-coating operations for over 50 years. Since 2015, the Vermont and New York Departments of Environmental Conservation have documented ∼1200 residential wells and two municipal water systems across a 200 km2 area contaminated with perfluorooctanoic acid (PFOA). Given the large areal extent of the plume, and the fact that much of the contaminated area lies up-gradient and across rivers from manufactures, we seek to determine if groundwater contamination could have resulted primarily from air-emission, land deposition, and subsequent leaching to infiltrating groundwater. Sampling of soils and groundwater in the Green Mountain National Forest (GMNF) downwind of factories shows that both soil and groundwater PFOA contamination extend uninterrupted from inhabited areas into conserved forest lands. Groundwater springs and seeps in the GMNF located 8 km downwind, but >300 meters vertically above factories, contain up to 100 ppt PFOA. Our results indicate that air-emitted PFAS can contaminate groundwater and soil in areas outside of those normally considered down-gradient of a source with respect to regional groundwater flow.
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http://dx.doi.org/10.1039/d0em00427hDOI Listing
March 2021

Response of small mammal and tick communities to a catastrophic wildfire and implications for tick-borne pathogens.

J Vector Ecol 2020 12;45(2):269-284

Department of Medicine and Epidemiology, School of Veterinary Medicine, University of California, Davis, CA, 95616, U.S.A.

Through their potentially devastating impacts on the environment, wildfires may impact pathogen, vector, and host interactions, leading to changing risks of vector-borne disease in humans and other animals. Despite established risks for tick-borne disease and increasing frequency and severity of wildfires in the United States, impacts of wildfire on ticks and tick-borne pathogens are understudied. In 2015, the large Wragg fire extensively burned a long-term field site at Stebbins Cold Canyon University of California Reserve (CC). We characterized the tick, reservoir host and pathogen community over a two-year period after the burn, comparing our findings to pre-fire data and to data from Quail Ridge Reserve (QR), a nearby unburned site. After the fire, there were 5.5 times more rodent, primarily Peromyscus spp., captures at CC than QR (compared to 3.5 times more pre-fire). There were significantly fewer dusky-footed woodrats (Neotoma fuscipes) at both sites post-fire, likely due to drought but not fire. Pre-fire tick infestation prevalence on rodents was comparable across sites (12.5% at CC and 9.9% at QR) and remained low at CC post-fire (13.7%) but was significantly higher at QR (48.0%), suggesting that ticks or their habitat were destroyed during the burn. Normalized difference vegetation indices documented a 16-fold loss of vegetation post- compared to pre-fire at CC; loss of vegetation and direct impacts on fauna are likely the main drivers of the post-fire differences in ticks we saw at CC. These data contribute to our understanding of tick-associated disease risks in our increasingly disturbed landscapes.
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http://dx.doi.org/10.1111/jvec.12398DOI Listing
December 2020

Environmental factors associated With Exposure in Neotropical Primates of Costa Rica.

Front Vet Sci 2020 22;7:583032. Epub 2020 Oct 22.

Escuela de Biología, Universidad de Costa Rica, San Pedro, Costa Rica.

The apicomplexan parasite () has been found in more than 350 species of homoeothermic vertebrates in diverse climates and geographic areas. In most animals, produces mild or asymptomatic infection. However, acute and hyperacute toxoplasmosis is associated with high mortality rates observed in Neotropical primates (NP) in captivity. These primates are distributed in 20 countries across the Americas, and although infection has been reported in certain countries and species, toxoplasmosis in the wild and its impact on NP population survival is unknown. Differences among species in exposure rates and disease susceptibility may be due in part to differences in host behavior and ecology. Four species of NP are found in Costa Rica, i.e., howler (), spider (), capuchin (), and squirrel monkeys (). This study reports NP exposure to using the modified agglutination test in 245 serum samples of NP (198 wild and 47 from captivity) from Costa Rica. Associations of serostatus with environmental (forest cover, annual mean temperature), anthropogenic (human population density), and biological (sex) variables in howler and capuchin monkeys were evaluated. The seroprevalence among wild NP was 11.6% (95% CI = 7.7-17.34), compared with 60% in captive monkeys (95% CI = 44.27-73.63), with significant differences between species ( = 20.072; df = 3, = 0.000164), suggesting an effect of behavior and ecology. In general, antibody titers were low for wild NP (<1:128) and high for captive NP (>1:8192), suggesting higher exposure due to management factors and increased life span in captivity. Seropositivity in howler monkeys was positively related to forest cover and inversely related to annual rainfall. For capuchins, annual rainfall was inversely related to seropositivity. Surveillance of exposure in NP in captivity and in the wild is required to understand drivers of the infection and develop novel strategies to protect them.
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http://dx.doi.org/10.3389/fvets.2020.583032DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7642457PMC
October 2020

Concentrations of Retinol and α-Tocopherol in Tissue Samples From Anna's Hummingbirds ().

Front Vet Sci 2020 29;7:637. Epub 2020 Sep 29.

Department of Medicine and Epidemiology, School of Veterinary Medicine, University of California, Davis, Davis, CA, United States.

Retinol (vitamin A) and α-tocopherol (vitamin E) concentrations were measured in tissue samples (liver, heart, pectoral muscle, and brain) from Anna's Hummingbirds (). Hummingbirds were after-hatch year birds that were sourced from various rehabilitation centers throughout California. Tissues samples were analyzed using high-performance liquid chromatography (HPLC). Minimum, maximum, mean, standard deviation (SD), and median ppm concentrations were calculated for each vitamin and tissue sample type. A novel analytical method was developed to analyze small mass tissue samples, with the smallest sample mass being 0.05 g for which analysis can be performed. Mean ± standard deviation (SD) concentrations of retinol in hummingbird livers, hearts, and pectoral muscle samples were 269.0 ± 216.9 ppm, 1.8 ± 2.2 ppm, and 0.3 ± 0.1 ppm, respectively. Mean ± SD α-tocopherol concentrations were 6.9 ± 4.6 ppm, 5.5 ± 4.0 ppm, 3.7 ± 2.2 ppm, and 9.1 ± 3.2 ppm for liver, heart, pectoral muscle, and brain samples, respectively. Vitamin concentrations from varying tissue types were compared to determine which were best associated with liver concentrations, the most commonly analyzed tissue for these vitamins. For both retinol and α-tocopherol, heart samples were most strongly associated with the liver samples. The results of this study provide baseline retinol and α-tocopherol concentrations in different tissue types from Anna's hummingbirds. These baseline values may be utilized in conservation efforts to avoid hypervitaminosis and hypovitaminosis of rehabilitated and/or captive hummingbirds by providing guidelines for nutritional targets which could be assessed on post-mortem examinations. Post-mortem examination of birds and measurement of vitamin concentrations in tissues may allow for dietary changes that aid captive hummingbirds.
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http://dx.doi.org/10.3389/fvets.2020.00637DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7553074PMC
September 2020

Cross-sectional evaluation of multiple epidemiological cycles of species in peri-urban wildlife in California.

J Am Vet Med Assoc 2020 Oct;257(8):840-848

Objective: To perform a cross-sectional survey to estimate prevalence of and potential risk factors for spp infection and exposure in peri-urban wildlife throughout California.

Animals: 723 animals representing 12 wildlife species.

Procedures: Blood and urine samples were obtained from wildlife in California from 2007 to 2017. Live animals were captured in humane traps, anesthetized, and released. Carcasses were donated by wildlife services and necropsied for urine, blood, and kidney tissue samples. Samples were tested for antibodies against 6 serovars of spp with a microscopic agglutination test and for pathogenic spp DNA with a real-time PCR assay targeting the gene. Potential risk factors for spp exposure were assessed by logistic regression. Genetic relatedness of spp were assessed with DNA sequencing of the gene and multiple locus sequence analysis.

Results: Statewide spp seroprevalence was 39.1%, and prevalence of positive PCR assay results for spp DNA was 23.0%. Risk factors for spp exposure included being an adult, being from northern California, and being a western gray squirrel, coyote, striped skunk, raccoon, gray fox, or mountain lion. Antibodies against serovar Pomona predominated in most species, followed by serovar Copenhageni. Complete sequences were identified as and multiple locus sequence type analysis revealed sequence type 140.

Conclusions And Clinical Relevance: Pathogenic spp appeared to be common and widespread among peri-urban wildlife in California. Our data highlight the potential for exposure to infectious disease for both humans and domestic animals at the urban-wildland interface.
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http://dx.doi.org/10.2460/javma.257.8.840DOI Listing
October 2020

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

PLoS One 2020 2;15(10):e0240136. Epub 2020 Oct 2.

Department of Medicine and Epidemiology, School of Veterinary Medicine, University of California, Davis, CA, United States of America.

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.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0240136PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7531790PMC
December 2020

Detection of in Ticks Collected from Songbirds in Ontario and Quebec, Canada.

Pathogens 2020 Sep 24;9(10). Epub 2020 Sep 24.

Department of Medicine and Epidemiology, School of Veterinary Medicine, University of California Davis, Davis, CA 95616, USA.

Songbirds widely disperse ticks that carry a diversity of pathogens, some of which are pathogenic to humans. Among ticks commonly removed from songbirds, the blacklegged tick, , can harbor any combination of nine zoonotic pathogens, including species. From May through September 2019, a total 157 ticks were collected from 93 songbirds of 29 species in the Canadian provinces of Ontario and Québec. PCR testing for the 18S gene of species detected in 12.63% of nymphs parasitizing songbirds in Ontario and Québec; none of the relatively small numbers of , , or were PCR-positive. For ticks at each site, the prevalence of was 16.67% in Ontario and 8.89% and 5.26% in Québec. Of 31 live, engorged larvae and nymphs held to molt, 25 ticks completed the molt; five of these molted ticks were positive for . PCR-positive ticks were collected from six bird species-namely, Common Yellowthroat, Swainson's Thrush, Veery, House Wren, Baltimore Oriole, and American Robin. Phylogenetic analysis documented the close relationship of to and , the latter a known pathogen to humans. For the first time in Canada, we confirm the transstadial passage of in molting from larvae to nymphs. A novel host record reveals on a Palm Warbler. Our findings show that is present in all mobile life stages of , and it is widely dispersed by songbirds in Ontario and Québec.
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http://dx.doi.org/10.3390/pathogens9100781DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7598643PMC
September 2020

Molecular epidemiology of a fatal sarcoptic mange epidemic in endangered San Joaquin kit foxes (Vulpes macrotis mutica).

Parasit Vectors 2020 Sep 7;13(1):456. Epub 2020 Sep 7.

Department of Medicine and Epidemiology, University of California, Davis, CA, 95616, USA.

Background: In 2013, sarcoptic mange, caused by Sarcoptes scabiei mites, precipitated a catastrophic decline of the formerly stable urban population of endangered San Joaquin kit foxes (Vulpes macrotis mutica) in Bakersfield, California, USA. In 2019, a smaller sarcoptic mange outbreak affected kit foxes 58 km southwest of Bakersfield in the town of Taft, California. To determine whether the Taft outbreak could have occurred as spillover from the Bakersfield outbreak and whether epidemic control efforts must involve not only kit foxes but also sympatric dogs (Canis lupus familiaris), coyotes (Canis latrans), and red foxes (Vulpes vulpes), we evaluated genotypes and gene flow among mites collected from each host species.

Methods: We used 10 Sarcoptes microsatellite markers (SARM) to perform molecular typing of 445 S. scabiei mites collected from skin scrapings from twenty-two infested kit foxes, two dogs, five coyotes, and five red foxes from Bakersfield, Taft, and other nearby cities.

Results: We identified 60 alleles across all SARM loci; kit fox- and red fox-derived mites were relatively monomorphic, while genetic variability was greatest in Bakersfield coyote- and dog-derived mites. AMOVA analysis documented distinct mite populations unique to hosts, with an overall F of 0.467. The lowest F (i.e. closest genetic relationship, F = 0.038) was between Bakersfield and Taft kit fox-derived mites while the largest genetic difference was between Ventura coyote- and Taft kit fox-derived mites (F = 0.843).

Conclusions: These results confirm the close relationship between the Taft and Bakersfield outbreaks. Although a spillover event likely initiated the kit fox mange outbreak, mite transmission is now primarily kit fox-to-kit fox. Therefore, any large-scale population level intervention should focus on treating kit foxes within the city.
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http://dx.doi.org/10.1186/s13071-020-04328-3DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7487715PMC
September 2020

A stochastic structured metapopulation model to assess recovery scenarios of patchily distributed endangered species: Case study for a Mojave Desert rodent.

PLoS One 2020 13;15(8):e0237516. Epub 2020 Aug 13.

Department of Medicine and Epidemiology, School of Veterinary Medicine, University of California Davis, Davis, California, United States of America.

While metapopulation theory offers tractable means to understand extinction risks for patchily-distributed endangered species, real systems often feature discrepant patch quality and accessibility, complex influences of environmental stochasticity, and regional and temporal autocorrelation. Spatially structured metapopulation models are flexible and can use real data but often at the cost of generality. Particularly as resources for management of such species are often critically limited, endangered species management guided by metapopulation modeling requires incorporation of biological realism. Here we developed a flexible, stochastic spatially structured metapopulation model of the profoundly endangered Amargosa vole, a microtine rodent with an extant population of only a few hundred individuals within 1km2 of habitat in the Mojave Desert. Drought and water insecurity are increasing extinction risks considerably. We modelled subpopulation demographics using a Ricker-like model with migration implemented in an incidence function metapopulation model. A set of scenarios was used to assess the effect of anthropogenic stressors or management actions on expected time to extinction (Te) including: 1) wildland fire, 2) anthropogenically-mediated losses of hydrologic flows, 3) drought, 4) intentional expansion of existing patches into 'megamarshes' (i.e. via restoration/enhancement), and 5) additive impacts of multiple influences. In isolation, marshes could be sources or sinks, but spatial context within the full metapopulation including adjacency could alter relative impacts of subpopulations on all other subpopulations. The greatest reductions in persistence occurred in scenarios simulated with impacts from drought in combination with fire or anthropogenically-mediated losses of hydrologic flows. Optimal actions to improve persistence were to prevent distant and smaller marshes from acting as sinks through strategic creation of megamarshes that act as sources of voles and stepping-stones. This research reinforces that management resources expended without guidance from empirically-based modeling can actually harm species' persistence. This metapopulation-PVA tool could easily be implemented for other patchily-distributed endangered species and allow managers to maximize scarce resources to improve the likelihood of endangered species persistence.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0237516PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7425968PMC
October 2020

An exploratory analysis of demography and movement patterns of dogs: New insights in the ecology of endemic Rocky Mountain-Spotted Fever in Mexicali, Mexico.

PLoS One 2020 21;15(5):e0233567. Epub 2020 May 21.

School of Veterinary Medicine, University of California, Davis, California, United States of America.

An outbreak of Rocky Mountain spotted fever (RMSF) transmitted by the brown dog tick (Rhipicephalus sanguineus sensu lato) has emerged as a major human and animal health concern in Mexicali, Mexico. Due to high rates of brown dog tick infestation, susceptibility, and association with humans, dogs serve as sentinels and have a key role in the ecology of RMSF. A cross-sectional household questionnaire study was conducted in six rural and urban locations to characterize dog ecology and demography in RMSF high-and low-risk areas of Mexicali. In addition, we tracked movement patterns of 16 dogs using a GPS data logger. Of 253 households, 73% owned dogs, and dog ownership tended to be higher in high-risk areas, with a mean dog:human ratio of 0.43, compared with 0.3 in low-risk areas. Dogs in high-risk areas had higher fecundity and roamed more, but the dog density and numbers of free-roaming dogs were comparable. There was a higher proportion of younger dogs and lower proportion of older dogs in high-risk areas. The high proportion of immunologically naïve puppies in high risk areas could result in a lack of herd immunity leading to a more vulnerable dog and human population. The marked increase of space use of free-roaming dogs in high-risk areas suggests that unrestrained dogs could play an important role in spreading ticks and pathogens. As means to limit RMSF risk, practical changes could include increased efforts for spay-neuter and policies encouraging dog restraint to limit canine roaming and spread of ticks across communities; due to dog density is less impactful such policies may be more useful than restrictions on the number of owned dogs.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0233567PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7241830PMC
August 2020
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