'Remoteness was a blessing, but also a potential downfall': traditional/subsistence and store-bought food access in remote Alaska during the COVID-19 pandemic.

OBJECTIVE: This study employs a strengths-based approach to assess food access in remote Alaska during the COVID-19 pandemic, identifying both the negative consequences of the pandemic on store-bought and subsistence/traditional food access and compensatory strategies used. DESIGN: As a part of a larger study on the impacts of COVID-19 on daily life remote Alaskan communities, study data presented here were collected through key informant interviews (KII) and state-wide online surveys from 21 September 2020 to 31 March 2021 among remote Alaska community members. SETTING: This study was conducted with residents of remote communities in Alaska, defined as those off the road system. Remote communities often have small or no grocery stores and rely on subsistence or traditional sources of food. PARTICIPANTS: KII participants (n 36) were majority female (78 %) and Alaska Native (57 %). Survey participants (n 615) were also majority female, 25-54 years old and most had had some post-secondary education or training. RESULTS: Survey and interview data revealed that the pandemic had significant negative impacts on store-bought food access in remote Alaskan communities. Individuals also shared that locally available and wild harvested foods acted as a buffer to some of the loss of access to these store-bought foods, with some people sharing that the harvesting of wild and traditional foods served as a coping strategy during times of pandemic-related stress. CONCLUSIONS: The results from this study demonstrate that the remoteness of some Alaskan communities has been both a source of vulnerability and protection in terms of food access.

Phylogeography of Rhipicephalus sanguineus sensu lato and its relationships with climatic factors.

Brown dog ticks morphologically identifiable as Rhipicephalus sanguineus sensu lato, are distributed world-wide and their systematics is controversial. Results of genetic and reproductive compatibility studies of geographically distinct populations of R. sanguineus s.l. indicate that the R. sanguineus complex is paraphyletic. To further elucidate systematic relationships within R. sanguineus s.l. and geographic boundaries of its lineages, we conducted a phylogeographical study of 136 tick specimens from 23 countries. Voucher specimens were morphologically identified. A phylogenetic tree was constructed using concatenated partial mitochondrial 12S and 16S rDNA gene sequences and analyzed by the Neighbor-Joining method. A set of 19 bioclimatic variables within the WorldClim dataset were extracted and analyzed to assess correlations between distribution of R. sanguineus s.l. lineages and climatic variables. The following four branches are clearly recognized on the phylogenetic tree: R. sanguineus s.l.-tropical and temperate clades, R. leporis, and R. turanicus. DNA sequences of Rhipicephalus ticks from Israel differ from those of other groups. Strong association between geographical locations of major clades of R. sanguineus s.l. and temperature was identified. The tropical clade of R. sanguineus s.l. occupies areas with the annual mean temperature >20 °C, whereas the temperate clade is present in areas with the annual mean temperature <20 °C. Our results indicate that ticks in two closely related phylogenetic clades are adapted to different environmental conditions and support proposals for re-classification of R. sanguineus complex. Differences in R. sanguineus s.l. ecology and human/animal pathogens transmitted by different taxa of brown dog tick need to be studied.

Climate change and human health: a One Health approach.

Climate change adds complexity and uncertainty to human health issues such as emerging infectious diseases, food security, and national sustainability planning that intensify the importance of interdisciplinary and collaborative research. Collaboration between veterinary, medical, and public health professionals to understand the ecological interactions and reactions to flux in a system can facilitate clearer understanding of climate change impacts on environmental, animal, and human health. Here we present a brief introduction to climate science and projections for the next century and a review of current knowledge on the impacts of climate-driven environmental change on human health. We then turn to the links between ecological and evolutionary responses to climate change and health. The literature on climate impacts on biological systems is rich in both content and historical data, but the connections between these changes and human health is less understood. We discuss five mechanisms by which climate changes impacts on biological systems will be felt by the human population: Modifications in Vector, Reservoir, and Pathogen Lifecycles; Diseases of Domestic and Wild Animals and Plants; Disruption of Synchrony Between Interacting Species; Trophic Cascades; and Alteration or Destruction of Habitat. Each species responds to environmental changes differently, and in order to predict the movement of disease through ecosystems, we have to rely on expertise from the fields of veterinary, medical, and public health, and these health professionals must take into account the dynamic nature of ecosystems in a changing climate.

By-degree Health and Economic Impacts of Lyme Disease, Eastern and Midwestern United States.

Lyme disease (LD) is the most common vector-borne disease in the United States (U.S.). This paper assesses how climate change may influence LD incidence in the eastern and upper Midwestern U.S. and the associated economic burden. We estimated future Ixodes scapularis habitat suitability and LD incidence with a by-degree approach using variables from an ensemble of multiple climate models. We then applied estimates for present-day and projected habitat suitability for I. scapularis, present-day presence of Borrelia burgdorferi, and projected climatological variables to model reported LD incidence at the county level among adults, children, and the total population. Finally, we applied an estimate of healthcare expenses to project economic impacts. We show an overall increase in LD cases with regional variation. We estimate an increase in incidence in New England and the upper Midwestern U.S. and a concurrent decrease in incidence in Virginia and North Carolina. At 3°C of national warming from the 1986-2015 baseline climate, we project approximately 55,000 LD cases, a 38-percent increase from present-day estimates. At 6°C of warming, our most extreme scenario, we project approximately 92,000 LD cases in the region, an increase of 145 percent relative to current levels. Annual LD-related healthcare expenses at 3°C of warming are estimated to be $236 million (2021 dollars), approximately 38 percent greater than present-day. These results may inform decision-makers tasked with addressing climate risks, the public, and healthcare professionals preparing for treatment and prevention of LD.

Association of Temperature Thresholds with Heat Illness- and Cardiorespiratory-Related Emergency Visits during Summer Months in Alaska.

BACKGROUND: Recent record-breaking hot temperatures in Alaska have raised concerns about the potential human health implications of heat exposure among this unacclimated population. OBJECTIVES: We estimated cardiorespiratory morbidity associated with days above summer (June-August) heat index (HI, apparent temperature) thresholds in three major population centers (Anchorage, Fairbanks, and the Matanuska-Susitna Valley) for the years 2015-2019. METHODS: We implemented time-stratified case-crossover analyses of emergency department (ED) visits for International Classification of Diseases, 10th Revision codes indicative of heat illness and major cardiorespiratory diagnostic codes using data from the Alaska Health Facilities Data Reporting Program. Using conditional logistic regression models, we tested maximum hourly HI temperature thresholds between 21.1°C (70°F) and 30°C (86°F) for a single day, 2 consecutive days, and the absolute number of previous consecutive days above the threshold, adjusting for the daily average concentration of particulate matter ≤2.5µg. RESULTS: There were increased odds of ED visits for heat illness above a HI threshold as low as 21.1°C (70°F) [odds ratio (OR)=13.84; 95% confidence interval (CI): 4.05, 47.29], and this increased risk continued for up to 4 d (OR=2.43; 95% CI: 1.15, 5.10). Asthma and pneumonia were the only respiratory outcomes positively associated with the HI: ED visits for both were highest the day after a heat event (Asthma: HI>27°C(80°F) OR=1.18; 95% CI: 1.00, 1.39; Pneumonia: HI>28°C(82°F) OR=1.40; 95% CI: 1.06, 1.84). There was a decreased odds of bronchitis-related ED visits when the HI was above thresholds of 21.1-28°C (70-82°F) across all lag days. We found stronger effects for ischemia and myocardial infarction (MI) than for respiratory outcomes. Multiple days of warm weather were associated with an increased risk of health impacts. For each additional preceding day above a HI of 22°C (72°F), the odds of ED visits related to ischemia increased 6% (95% CI: 1%, 12%); for each additional preceding day above a HI of 21.1°C (70°F), the odds of ED visits related to MI increased 7% (95% CI: 1%, 14%). DISCUSSION: This study demonstrates the importance of planning for extreme heat events and developing local guidance for heat warnings, even in areas with historically mild summertime climates. https://doi.org/10.1289/EHP11363.

"In the beginning, I said I wouldn't get it.": Hesitant adoption of the COVID-19 vaccine in remote Alaska between November 2020 and 2021.

Achieving sufficient COVID-19 vaccination coverage has been hindered in many areas by vaccine hesitancy. Many studies based on large survey samples have characterized vaccine refusal, but there are fewer in-depth qualitative studies that explore hesitant adoption: the middle-ground between vaccine acceptance and refusal, and how individuals may move across this continuum depending on their lived experience. For this paper, we use the narratives of 25 adults living in off-road, predominately Alaska Native communities to describe the complex decision-making processes undertaken by 'hesitant adopters', defined in our study as those who completed their initial COVID-19 series despite reporting hesitancy. Interviewees' stories help illustrate how hesitant adopters' decision-making processes involved making sense of information through interactions with trusted individuals, lived experiences, observations, emotions, and personal motivations. For the majority of these hesitant adopters' (n = 20, 80%) interpersonal interactions were key in helping to make the decision to get vaccinated. Over half of the interviewees (n = 14, 56%) described how conversations with individuals they trusted, including healthcare providers, family, friends, and interactions through their professional network made them feel safe. One third of the hesitant adopters (n = 7, 28%) attributed their decision to get vaccinated based on the influence of Alaska Native Elders including their knowledge, personal experiences, as well as being motivated by the desire to protect them. Independent research was also important to about a quarter of hesitant adopters (n = 6, 24%), and for these interviewees it was the process of gathering information on their own and learning from others, especially healthcare providers who could answer their questions and alleviate their concerns. This paper illustrates the temporality of vaccine decision-making: vaccine acceptance for those who are hesitant may be an ongoing process that is influenced by personal experience, relationships, and context.

COVID-19 vaccine decision-making in remote Alaska between November 2020 and November 2021.

Vaccine hesitancy is an ongoing barrier to achieve sufficient COVID-19 vaccination coverage. Although there are many studies globally of vaccine hesitancy based on large survey samples, there are fewer in-depth qualitative studies that explore vaccine hesitancy and acceptance as a spectrum of decision-making. In this paper, we begin to describe vaccination decision-making among 58 adults living in remote Alaska based on three waves of online surveys and follow-up semi-structured interviews conducted between November 2020 and November 2021. The survey question of intention was not a predictor of adoption for about one third of the interviewees who were unvaccinated when they took the survey (n=12, 35%). Over half of all interviewees (n=37, 64%) had vaccine-related concerns, including 25 vaccinated individuals (representing 57% of vaccinated interviewees). Most interviewees reported that they learned about COVID-19 vaccines through interpersonal interactions (n=30, 52%) and/or a variety of media sources (n=29, 50%). The major facilitators of acceptance were trust in the information source (n=20, 48% of the 42 who responded), and learning from the experiences of family, friends, and the broader community (n=12, 29%). Further, trust and having a sense of agency appears to be important to interviewee decision-making, regardless of vaccination status and intention.

A blueprint for strengthening climate and health literacy through professional adaptability.

Responding effectively to intensifying climate change hazards to protect human health in personal and professional settings is an urgent and pressing challenge. This will require collaboration and subject matter expertise of people across the life course and occupations. In this perspective piece, we build on a previously published compilation of climate and health literacy elements to explore tangible opportunities to strengthen climate and health understanding among individuals spanning educational levels, professional settings, and societal needs. Educational materials addressing climate change and health linkages have historically focused on K-12, college, post-graduate education, and continuing medical education, with less attention devoted to reaching students in trade schools and other professional settings. Here, we outline a flexible blueprint for strengthening climate and health literacy among all people by targeting education in a way that is relevant for each age group or profession. In particular, we discuss the idea of professional adaptability as a way to design practical climate and health training for people currently in the workforce.

Ticks and tick-borne microbes identified through passive and active surveillance in Alaska.

Rapid environmental change in Alaska and other regions of the Arctic and sub-Arctic has raised concerns about increasing human exposure to ticks and the pathogens they carry. We tested a sample of ticks collected through a combination of passive and active surveillance from humans, domestic animals, and wildlife hosts in Alaska for a panel of the most common tick-borne pathogens in the contiguous United States to characterize the diversity of microbes present in this region. We tested 189 pooled tick samples collected in 2019-2020 for Borrelia spp., Anaplasma spp., Ehrlichia spp., and Babesia spp. using a multiplex PCR amplicon sequencing assay. We found established populations of Ixodes angustus Neumann (Acari: Ixodidae), Ixodes uriae White (Acari: Ixodidae), and Haemaphysalis leporispalustris Packard (Acari: Ixodidae) in Alaska, with I. angustus found on a variety of hosts including domestic companion animals (dogs and cats), small wild mammals, and humans. Ixodes angustus were active from April through October with peaks in adult and nymphal activity observed in summer months (mainly July). Although no known human pathogens were detected, Babesia microti-like parasites and candidatus Ehrlichia khabarensis were identified in ticks and small mammals. The only human pathogen detected (B. burgdorferi s.s.) was found in a tick associated with a dog that had recently traveled to New York, where Lyme disease is endemic. This study highlights the value of a combined passive and active tick surveillance system to detect introduced tick species and pathogens and to assess which tick species and microbes are locally established.

Perspectives on and prevalence of ticks and tick-borne diseases in Alaskan veterinary clinics.

Objective: To assess knowledge, attitudes, and practices (KAP) of veterinary personnel and pet owners regarding ticks and tick-borne diseases in Alaska and to conduct a serosurvey for tick-borne disease pathogens among domestic animals visiting veterinary clinics for preventative care. Sample: Across 8 veterinary clinics, we sampled 31 veterinary personnel, 81 pet owners, 102 client-owned dogs, and 1 client-owned cat. Procedures: Information on KAP among veterinary staff and pet owners was collected via self-administered questionnaires. Tick and tick-borne disease prevalence were assessed via tick checks and benchtop ELISA antibody tests detecting Anaplasma phagocytophilum, Anaplasma platys, Erlichia canis, Erlichia ewingii, and Borrelia burgdorferi. Results: The veterinary personnel KAP survey showed a low average knowledge score (53.5%) but a moderate attitude score (71.7%). In contrast, owner average knowledge score was higher (67.5%) and attitude score was comparatively low (50.6%). Both veterinary personnel and owners had low average practice scores (64.5% and 56.3%, respectively). One dog was positive for anaplasmosis (unknown species) antibody, and 1 dog was positive for B burgdorferi antibody. No ticks were found during the study. Clinical Relevance: This study was the first of its kind in the state and indicated a low prevalence of ticks and tick-borne diseases in the domestic pet population and highlighted significant knowledge gaps that could be targeted by public health efforts. Our results suggest the value of a One Health approach and of the veterinary-client relationship to address ticks and tick-borne diseases.

Modeling Geographic Uncertainty in Current and Future Habitat for Potential Populations of Ixodes pacificus (Acari: Ixodidae) in Alaska.

Ixodes pacificus Cooley & Kohls is the primary vector of Lyme disease spirochetes to humans in the western United States. Although not native to Alaska, this tick species has recently been found on domestic animals in the state. Ixodes pacificus has a known native range within the western contiguous United States and southwest Canada; therefore, it is not clear if introduced individuals can successfully survive and reproduce in the high-latitude climate of Alaska. To identify areas of suitable habitat within Alaska for I. pacificus, we used model parameters from two existing sets of ensemble habitat distribution models calibrated in the contiguous United States. To match the model input covariates, we calculated climatic and land cover covariates for the present (1980-2014) and future (2070-2100) climatologies in Alaska. The present-day habitat suitability maps suggest that the climate and land cover in Southeast Alaska and portions of Southcentral Alaska could support the establishment of I. pacificus populations. Future forecasts suggest an increase in suitable habitat with considerable uncertainty for many areas of the state. Repeated introductions of this non-native tick to Alaska increase the likelihood that resident populations could become established.

Utilizing the "One Health" Model to Study Human Aging in Urban Environments.

The "One Health" concept has resulted in a rich research literature that integrates human and animal systems, with a focus on zoonotic diseases; however, this narrow focus is at the expense of one of the leading causes of global human mortality: non-infectious, chronic diseases. Here, we provide a viewpoint that applying the integrated One Health framework to public health issues such as the impact of stressful urban environments on the process of human aging has the potential to elucidate potential causal mechanisms that have previously gone unnoticed. Given the success of the One Health paradigm in studying human health in rural areas, we posit that this model would be a useful tool for studying human, animal, and environmental interactions in urban settings.

Compounding Effects of Social Vulnerability and Recurring Natural Disasters on Mental and Physical Health.

OBJECTIVE: This study evaluated the relationships between the occurrence of recent and recurring natural disasters on the incidence of acute and chronic health outcomes at the census tract level in 500 cities across the United States between 2001 and 2015. METHODS: Using the Centers for Disease Control and Prevention (CDC) 500 cities data set, the CDC Social Vulnerability Index, and the US Small Business Administration (SBA) Disaster Loan Database, we modeled the incidence of self-reported, poor mental and physical health, or a clinical diagnosis of high blood pressure or asthma in census tracts (N = 27 204 tracts in 500 cities) that had experienced recent or recurring natural disasters while controlling for social and environmental risk factors. RESULTS: Communities that experienced a natural disaster in the previous 5 years compared to those that had not had a higher incidence of poor mental health (RR: 1.02, 95% CI: 1.01-1.02), poor physical health (RR: 1.03, 95% CI: 1.02-1.04), high blood pressure (RR: 1.04, 95% CI: 1.02-1.05), and asthma (RR: 1.01, 95% CI: 1.01-1.02). The incidence of these poor health outcomes increased 1-2% with each additional year that a community experienced a disaster. CONCLUSIONS: Prevention and preparedness plans that work to build resilience in communities before disasters should focus on closing the gap in environmental and social determinants that have been linked with disproportionate health burdens and slow recovery post-disaster.

Evolving perceptions of COVID-19 vaccines among remote Alaskan communities.

Given the dynamic nature of the ongoing pandemic, public knowledge and perceptions about COVID-19 are evolving. Limited transportation options, inconsistent healthcare resources, and lack of water and sanitation infrastructure in many remote Alaskan communities located off the road system have contributed to the experience of the COVID-19 pandemic in these areas. We used longitudinal surveys to evaluate remote Alaskan residents' early vaccine acceptance, vaccine uptake and motivations, risk perceptions regarding COVID-19 vaccines, and likelihood of getting a booster. Slightly over half of respondents showed early vaccine acceptance (November/December 2020), with the highest rate among those over the age of 65 years. However, by March 2021, 80.7% of participants reported receiving the COVID-19 vaccine or planning to get one. Of the unvaccinated, reasons for not getting a vaccine included concerns about side effects and not trusting the vaccine. By September 2021, 88.5% of people had received two doses of a COVID-19 vaccine and 79.7% said they would get the booster (third dose) when it became available. There were misconceptions about vaccine recommendations for pregnant women and effects on fertility and DNA. Although initial vaccine concerns may have subsided, the booster rollout and forthcoming vaccines for youth under 12 years of age present new hurdles for vaccine communication efforts.

Coping strategies and household stress/violence in remote Alaska: a longitudinal view across the COVID-19 pandemic.

The COVID-19 pandemic has introduced novel stressors. Remote/rural communities have experienced additional difficulties, while also potentially benefitting from unique sources of resilience against such stressors. However, very little research has been conducted in remote/rural communities regarding coping and stress/violence. This study examines coping strategies and household stress/violence in remote Alaska communities across the pandemic through three online survey waves (November 2020-September 2021) (total n = 1,020). Across all waves, personal care was reported most frequently followed by social activities, religious activities, and traditional/subsistence activities. Substance use combined (alcohol, nicotine, marijuana) and seeking counselling were less frequently reported, with significant differences across gender and age categories. Less than 10% of individuals reported physical violence towards children and/or other adults within the household. Overall, these findings indicate that individuals are primarily relying on positive coping strategies to contend with additional stress brought into their lives by the COVID-19 pandemic.

Modeling future climate suitability for the western blacklegged tick, Ixodes pacificus, in California with an emphasis on land access and ownership.

In the western United States, Ixodes pacificus Cooley & Kohls (Acari: Ixodidae) is the primary vector of the agents causing Lyme disease and granulocytic anaplasmosis in humans. The geographic distribution of the tick is associated with climatic variables that include temperature, precipitation, and humidity, and biotic factors such as the spatial distribution of its primary vertebrate hosts. Here, we explore (1) how climate change may alter the geographic distribution of I. pacificus in California, USA, during the 21st century, and (2) the spatial overlap among predicted changes in tick habitat suitability, land access, and ownership. Maps of potential future suitability for I. pacificus were generated by applying climate-based species distribution models to a multi-model ensemble of climate change projections for the Representative Concentration Pathway (RCP) 4.5 (moderate emission) and 8.5 (high emission) scenarios for two future periods: mid-century (2026-2045) and end-of-century (2086-2099). Areas climatically-suitable for I. pacificus are projected to expand by 23% (mid-century RCP 4.5) to 86% (end-of-century RCP 8.5) across California, compared to the historical period (1980-2014), with future estimates of total suitable land area ranging from about 88 to 133 thousand km2, or up to about a third of California. Regions projected to have the largest area increases in suitability by end-of-century are in northwestern California and the south central and southern coastal ranges. Over a third of the future suitable habitat is on lands currently designated as open access (i.e. publicly available), and by 2100, the amount of these lands that are suitable habitat for I. pacificus is projected to more than double under the most extreme emissions scenario (from ~23,000 to >51,000 km2). Of this area, most is federally-owned (>45,000 km2). By the end of the century, 26% of all federal land in the state is predicted to be suitable habitat for I. pacificus. The resulting maps may facilitate regional planning and preparedness by informing public health and vector control decision-makers.

Establishing a baseline for tick surveillance in Alaska: Tick collection records from 1909-2019.

The expanding geographic ranges of tick species that are known pathogen vectors can have implications for human, domestic animal, and wildlife health. Although Alaska is home to several hard tick species, it has historically been outside of the range of the most common medically important ticks in the contiguous United States and western Canada. To assess the status of tick species establishment in the state and to provide a baseline for tracking future change in the distribution of ticks, we reviewed and compiled historical tick records and summarized recent tick occurrence records collected through the development of the Alaska Submit-A-Tick Program and through tick drag sampling at sentinel sites in southcentral Alaska. Between 1909-2019, there were 1190 tick records representing 4588 individual ticks across 15 species in Alaska. The majority of ticks were species historically found in Alaska: Haemaphysalis leporispalustris, Ixodes angustus, Ixodes auritulus, Ixodes howelli, Ixodes signatus, and Ixodes uriae. Over half of all tick records in the state were collected in the last 10 yr. During this time, the number of tick records and the number of tick species recorded in Alaska each year has increased substantially. Between 2010-2019, there were 611 tick records representing 1921 individual ticks. The most common hosts for reported ticks were domestic animals (n = 343, 56 %) followed by small wild mammals (n = 147, 24 %), humans (n = 49, 8%), and wild birds (n = 31, 5%). Less than 5% of records (n = 25) were of unattached ticks found in the environment. Since 2007, non-native tick species have been documented in the state every year, including Amblyomma americanum, Dermacentor andersoni, Dermacentor occidentalis, Dermacentor variabilis, Ixodes pacificus, Ixodes ricinus, Ixodes scapularis, Ixodes texanus, and Rhipicephalus sanguineus sensu lato (s.l.). Almost half of the records (n = 68, 48 %) of non-native tick species from 2010 to 2019 represented ticks found on a host (usually a dog or a human) that had traveled outside of Alaska in the two weeks prior to collection. However, A. americanum, D. variabilis, I. pacificus, I. texanus, and R. sanguineus s.l. have been found on humans and domestic animals in Alaska without reported recent travel. In particular, there is evidence to suggest that there is local establishment of R. sanguineus s.l. in Alaska. A tick species historically found in the state, I. angustus was frequently found on human and dogs, suggesting a potential role as a bridge vector of pathogens. Given the inconsistency of tick monitoring in Alaska over the past century, it is difficult to draw many conclusions from temporal trends in the data. Continued monitoring through the Alaska Submit-A-Tick Program will allow a more accurate assessment of the changing risk of ticks and tick-borne diseases in the state and provide information for setting clinical and public health guidelines for tick-borne disease prevention.

Evaluating acarological risk for exposure to Ixodes scapularis and Ixodes scapularis-borne pathogens in recreational and residential settings in Washington County, Minnesota.

The distribution of I. scapularis, the tick vector of the bacteria that cause Lyme disease, has been expanding over the last two decades in the north-central United States in parallel with increasing incidence of human cases of Lyme disease in that region. However, assessments of residential risk for exposure to ticks are lacking from this region. Here, we measured the density of host-seeking I. scapularis nymphs in two suburban and two rural public recreational sites located in Washington County, Minnesota as well as in nearby residential properties. We sought to compare tick densities across land use types and to identify environmental factors that might impact nymphal density. We also assessed the prevalence of infection in the collected ticks with Lyme disease spirochetes (Borrelia burgdorferi sensu stricto, B. mayonii), and other I. scapularis-borne pathogens including B. miyamotoi, Babesia microti and Anaplasma phagocytophilum. Similar to studies from the eastern United States, on residential properties, I. scapularis nymphal densities were highest in the ecotonal areas between the forest edge and the lawn. Residences with the highest densities of nymphs were more likely to have a higher percentage of forest cover, log piles, and signs of deer on their property. In recreational areas, we found the highest nymphal densities both in the wooded areas next to trails as well as on mowed trails. Among the 303 host-seeking I. scapularis nymphs tested for pathogens, B. burgdorferi sensu stricto, A. phagocytophilum and B. miyamotoi were detected in 42 (13.8%), 14 (4.6%), and 2 (0.6%) nymphs, respectively.

Modeling Climate Suitability of the Western Blacklegged Tick in California.

Ixodes pacificus Cooley & Kohls (Acari: Ixodidae), the primary vector of Lyme disease spirochetes to humans in the far-western United States, is broadly distributed across Pacific Coast states, but its distribution is not uniform within this large, ecologically diverse region. To identify areas of suitable habitat, we assembled records of locations throughout California where two or more I. pacificus were collected from vegetation from 1980 to 2014. We then employed ensemble species distribution modeling to identify suitable climatic conditions for the tick and restricted the results to land cover classes where these ticks are typically encountered (i.e., forest, grass, scrub-shrub, riparian). Cold-season temperature and rainfall are particularly important abiotic drivers of suitability, explaining between 50 and 99% of the spatial variability across California among models. The likelihood of an area being classified as suitable increases steadily with increasing temperatures >0°C during the coldest quarter of the year, and further increases when precipitation amounts range from 400 to 800 mm during the coldest quarter, indicating that areas in California with relatively warm and wet winters typically are most suitable for I. pacificus. Other consistent predictors of suitability include increasing autumn humidity, temperatures in the warmest month between 23 and 33°C, and low-temperature variability throughout the year. The resultant climatic suitability maps indicate that coastal California, especially the northern coast, and the western Sierra Nevada foothills have the highest probability of I. pacificus presence.