Changes in the geographic distribution of the blacklegged tick, Ixodes scapularis, in the United States

Defining the tick-borne disease occupational risk among 4 high-risk vocations in South Carolina

Tick-borne diseases account for 75% of all vector-borne disease cases in the United States of America. The increase in incidence has been linked with increased exposure among outdoor workers, thus becoming occupational hazards. This brief study aimed to identify the potential occupational exposures among 4 vocational groups in South Carolina (SC) using a knowledge, attitudes, and practices questionnaire survey. A total of 176 individuals responded to the survey, across SC State Parks, SC Department of Natural Resources, SC Forestry Commission, and SC animal shelter and veterinary office employees. Veterinary-related employees had the lowest exposure risk, while forestry employees were the group with highest risk. The findings yielded discrepancies in perceived risk and preventive measures adopted; identifying a potential opportunity to develop an education and training program tailored to outdoor worker populations to maintain low tick bite exposures.

Duplex PCR assay to determine sex and mating status of Ixodes scapularis (Acari: Ixodidae), vector of the Lyme disease pathogen

Ticks are a major health threat to humans and other animals, through direct damage, toxicoses, and transmission of pathogens. An estimated half a million people are treated annually in the United States for Lyme disease, a disease caused by the bite of a black-legged tick (Ixodes scapularis Say, 1821) infected with the bacterial pathogen Borrelia burgdorferi. This tick species also transmits another 6 human-disease causing pathogens, for which vaccines are currently unavailable. While I. scapularis are sexually dimorphic at the adult life stage, DNA sequence differences between male and female I. scapularis that could be used as a sex-specific marker have not yet been established. Here we identify sex-specific DNA sequences for I. scapularis (male heterogametic system with XY), using whole-genome resequencing and restriction site-associated DNA sequencing. Then we identify a male-specific marker that we use as the foundation of a molecular sex identification method (duplex PCR) to differentiate the sex of an I. scapularis tick. In addition, we provide evidence that this molecular sexing method can establish the mating status of adult females that have been mated and inseminated with male-determining sperm. Our molecular tool allows the characterization of mating and sex-specific biology for I. scapularis, a major pathogen vector, which is crucial for a better understanding of their biology and controlling tick populations.

A systematic literature review of the efficacy of acaricidal plants, plant extracts, and tick assays used against dog-associated ticks

Dogs are an integral part of many households and important companion animals to humans. Their inquisitive and exploratory behaviour leads them to roam natural environments, making them susceptible to tick infestations that can also be transmitted to humans. To control these ticks, various plant extracts have been evaluated for their efficacy as acaricides and/or repellents against various species. This study was aimed at consolidating the data that has been published in terms of the plant species that have shown efficacy against ticks that parasitize dogs, it further evaluated the methods used in preparing these formulations. A keyword-Boolean strategy was created to extract a total of n = 103 articles that were included in the study. The leading countries in terms of the global distribution of acaricidal plant investigation outputs were Brazil at 23 %, India at 17 % and Turkey at 7 %. A total of n = 13 tick species were used in the evaluated studies. The dog tick Rhipicephalus sanguineus was the most widely used for efficacy testing at 43 % frequency. The Lamiaceae plant family had the highest frequency for reported use across the evaluated studies at 18 %, this was followed by the family Asteraceae at 11 %. Adult immersion test, larval packet test and larval immersion test were the most preferred assays for acaricidal efficacy studies. Leaves were the most preferred plant parts utilized for crude plant metabolites extraction (n = 43), while essential oils were the most highly reported extracts (n = 60). Lastly, extracts were primarily subjected to Gas chromatography for analysis of the plant compounds (n = 38). This paper gives the current global status of potential acaricidal plants utilized against ticks parasitizing dogs.

Lyme Disease

Lyme disease, caused by Borrelia burgdorferi, is the most common vector-borne disease in the United States, and the range of its tick vector continues to expand. Most Lyme disease cases are diagnosed with the onset of the erythema migrans rashes, which can be single or multiple and vary from a homogeneous erythema to bull's-eye patterns. Serologic antibody testing is of low sensitivity at onset but becomes highly sensitive after a few weeks. Early dissemination may lead to neurologic and cardiac complications. Mono- or oligoarticular arthritis may develop in untreated patients. Antibiotic treatment is highly effective, but approximately 10% of treated patients experience persistent symptoms.

Powassan Virus Encephalitis in Pediatric Patients

Powassan virus is a tickborne flavivirus that is a rare cause of encephalitis in humans. The incidence of cases is increasing in North America. We present 6 cases of Powassan virus encephalitis in pediatric patients diagnosed between 2018 and 2023 in the New England region of the United States. The age at diagnosis ranged from 14 months to 11 years. All patients presented with fever and confusion, and the majority also presented with seizures. All patients had lasting neurologic sequelae including seizures, movement disorders, behavioral problems, attention-deficit hyperactivity disorder (ADHD), learning problems, anxiety, and sleep disturbances. This is the largest pediatric case series of Powassan virus encephalitis to date. These cases demonstrate the emergence of Powassan virus as a rare, but severe, cause of encephalitis in children that has long-term neurologic consequences. We recommend increased clinical surveillance and public awareness of this increasingly prevalent tickborne disease.

Using pet insurance claims to predict occurrence of vector-borne and zoonotic disease in humans in the United States

Taking a One Health approach to infectious diseases common to both dogs and people, pet insurance claims from 2008 to 2022 in the United States were compared to publicly available CDC-based data on human cases for Lyme disease, giardia, and Valley Fever (coccidioidomycosis). Despite having very different causative agents and etiologies, the disease trends for these three diseases were very similar between people and dogs both geographically and temporally. We furthermore demonstrated that adding dog data as a predictor variable in addition to the human data improves prediction models for those same diseases when investigating incidence over time. With machine learning prediction tools for the pet insurance to predict changes in disease incidence sooner and give public health officials more time to prepare, pet insurance data could be a helpful tool to predict and detect diseases by estimating even earlier the effects of these common exposure diseases on human health. We also show the spatiotemporal distribution of intestinal worm diagnoses in dogs, and while it could not be directly compared to human data because the corresponding disease in humans (soil-transmitted helminths) has not been well monitored recently. However, these data can help inform researchers and public health workers.

Emerging babesiosis in the mid-Atlantic: autochthonous human babesiosis cases and Babesia microti (Piroplasmida: Babesiidae) in Ixodes scapularis (Acari: Ixodidae) and Ixodes keiransi (Acari: Ixodidae) ticks from Delaware, Maryland, Virginia, West Virginia, and the District of Columbia, 2009 to 2024

The range of Babesia microti (Franca, 1910)-infected ticks is expanding, resulting in locally acquired human babesiosis cases occurring in new areas: Maryland (2009), the District of Columbia (2013), Virginia (2016), and West Virginia (2017). We collected host-seeking ticks from old fields, ecotones, forested habitats and animal hosts in Delaware, Maryland, and Virginia, 2010 to 2024. Ixodes scapularis Say, the tick vector of babesiosis, was captured in all 3 states. PCR revealed B. microti in 2.7% (36/1310) of I. scapularis, with site prevalence ranging from <1% to 12.5% infected. The first B. microti-positive I. scapularis was collected in Northampton County, Virginia, 2012. Of the B. microti-infected ticks, 50% (18/36) were coinfected with Borrelia burgdorferi and one was triple-infected with B. microti, B. burgdorferi, and Anaplasma phagocytophilum. We collected Ixodes keiransi Beati, Nava, Venzal, and Guglielmone ticks from Delaware and Virginia. We found B. microti and B. burgdorferi in those from Virginia, and B. burgdorferi in ticks from a shrew in Delaware. To our knowledge, this is the first report of B. microti and B. burgdorferi-positive I. keiransi from Virginia, and the first report of B. burgdorferi-positive I. keiransi from Delaware. Ixodes keiransi ticks rarely bite humans but are involved in the maintenance and spread of pathogens when sympatric with I. scapularis. We tested a subset of both tick species for Babesia duncani; none were positive. Jurisdictions in the southern mid-Atlantic region should expect babesiosis cases, and Lyme disease and anaplasmosis coinfections, and healthcare providers should consider these tick-borne infections as part of the differential diagnosis.

Functional connectivity for white-tailed deer drives the distribution of tick-borne pathogens in a highly urbanized setting

Context

As cities seek to provide more habitat for wildlife, there may be unintended consequences of increasing tick-borne disease hazards. In the United States, the Northeast is both highly urban and a hotspot for blacklegged ticks (Ixodes scapularis) and tick-borne disease emergence. Though tick-borne disease was once considered a suburban and rural problem, tick-borne hazards in urban landscapes are increasing.

Objectives

We hypothesized that multi-scale ecological processes hierarchically contribute to tick-borne hazards across an urbanization gradient. Urban greenspaces with higher functional connectivity to deer movement would have higher deer occupancy at the 'ecological neighborhood' scale, resulting in increased blacklegged tick populations and pathogen infection at the scale of within greenspaces.

Methods

To evaluate our hypothesis, we used circuit theory methods to model the impact of functional connectivity on deer occupancy, blacklegged tick abundance, and pathogen infected ticks across an urbanization gradient. We sampled nymphal ticks during their peak activity and deployed wildlife cameras to detect deer at 38 greenspaces across New York City and Long Island, NY from 2022 to 2023.

Results

We found that functional connectivity significantly predicted deer occupancy with cascading effects on abundance of blacklegged nymphal ticks and Borrelia burgdorferi infection. We novelly identified a threshold of functional connectivity in urban areas necessary for deer occupancy, tick populations, and tick infection with B. burgdorferi, to emerge in urban environments.

Conclusions

We recommend targeted tick-borne hazard mitigation along this functional connectivity threshold as part of urban greenspace management plans. Additionally, we highlight the importance of examining multi-scale landscape drivers of host, tick, and pathogen interactions.

Supplementary Information

The online version contains supplementary material available at 10.1007/s10980-025-02101-4.

Climate-driven variation in the phenology of juvenile Ixodes pacificus on lizard hosts

BACKGROUND

Ectothermic arthropods, like ticks, are sensitive indicators of environmental changes, and their seasonality plays a critical role in the dynamics of tick-borne disease in a warming world. Juvenile tick phenology, which influences pathogen transmission, may vary across climates, with longer tick seasons in cooler climates potentially amplifying transmission. However, assessing juvenile tick phenology is challenging in arid climates because ticks spend less time seeking for blood meals (i.e. questing) due to desiccation pressures. As a result, traditional collection methods like dragging or flagging are less effective. To improve our understanding of juvenile tick seasonality across a latitudinal gradient, we examined Ixodes pacificus phenology on lizards, the primary juvenile tick host in California, and explored how climate factors influence phenological patterns.

METHODS

Between 2013 and 2022, ticks were removed from 1527 lizards at 45 locations during peak tick season (March-June). Tick counts were categorized by life stage (larvae and nymphs) and linked with remotely sensed climate data, including monthly maximum temperature, specific humidity and Palmer Drought Severity Index (PDSI). Juvenile phenology metrics, including tick abundances on lizards, Julian date of peak mean abundance and temporal overlap between larval and nymphal populations, were analyzed along a latitudinal gradient. Generalized additive models (GAMs) were applied to assess climate-associated variation in juvenile abundance on lizards.

RESULTS

Mean tick abundance per lizard ranged from 0.17 to 47.21 across locations, with the highest abundance in the San Francisco Bay Area and lowest in Los Angeles, where more lizards had zero ticks attached. In the San Francisco Bay Area, peak nymphal abundance occurred 25 days earlier than peak larval abundance. Temporal overlap between larval and nymphal stages at a given location varied regionally, with northern areas showing higher overlap, possibly due to the bimodal seasonality of nymphs. We found that locations with higher temperatures and increased drought stress were linked to lower tick abundances, although the magnitude of these effects depended on regional location.

CONCLUSIONS

Our study, which compiled 10 years of data, reveals significant regional variation in juvenile I. pacificus phenology across California, including differences in abundance, peak timing, and temporal overlap. These findings highlight the influence of local climate on tick seasonality, with implications for tick-borne disease dynamics in a changing climate.

Understanding climate-sensitive tick development and diapause with a structured population model

Introduction

Tick-borne diseases have become a growing public health concern globally. As climate change reshapes the environment, tick populations are expected to expand into previously unsuitable areas, further increasing human exposure to ticks and the pathogens they transmit. Understanding the environmental factors that sustain tick populations is crucial for enhancing prevention and control measures.

Methods

This study presents a multi-process structured population model that simulates nymph activity, development, and diapause in response to temperature and photoperiod. By integrating laboratory data and meteorological variables, the model captures the role of photoperiod in regulating diapause and the influence of temperature on development rates.

Results

With this model, we propose a mechanism to better understand how short- and long-day conditions synchronize nymph development, highlighting the importance of repeated sensing of external conditions for maintaining behavioral strategies to optimize fitness under changing environmental conditions. The model successfully replicates nymph development observed in laboratory conditions and extends to field applications, predicting seasonal activity under variable weather conditions.

Discussion

By providing a mechanistic understanding of tick phenology, our model establishes a foundation for assessing the impacts of climate on tick populations. The insights gained can inform public health tools and strategies, contributing to the mitigation of tick-borne disease risks in a changing environment.

Perspectives from federal and state public health departments on their participation in and the utility of Ixodes scapularis (Acari: Ixodidae) and Ixodes pacificus tick and tick-borne pathogen surveillance in the United States

In response to notable increases in tick-associated illnesses in the United States, recent public health policies encouraged multi-sector collaborative approaches to preventing vector-borne diseases. Primary prevention strategies focus on educating the public about risks for tick-borne diseases and encouraging adoption of personal protection strategies. Accurate descriptions of when and where people are at risk for tick-borne diseases aid in the optimization of prevention messaging. Tick and tick-borne pathogen data can be used to fill gaps in epidemiological surveillance. However, the utility of acarological data is limited by their completeness. National maps showing the distribution of medically important tick species and the pathogens they carry are often incomplete or non-existent. Recent policies encourage accelerated efforts to monitor changes in the distribution and abundance of medically important ticks and the presence and prevalence of human pathogens that they carry, and to provide actionable, evidence-based information to the public, health care providers and public health policy makers. In 2018, the Centers for Disease Control and Prevention initiated a national tick surveillance program focused on Ixodes ticks. The national program coordinated and expanded upon existing efforts led by public health departments and academic institutions. Here, we describe experiences of state public health departments engaged in Ixodes tick surveillance, including information on why they initiated Ixodes surveillance programs, programmatic objectives, and strategies for maintaining tick surveillance programs. We share experiences and challenges in interpreting or communicating tick surveillance data to stakeholders and explore how the acarological data are used to complement epidemiological data.

A scoping review of applied tick control research in North America: funding, implementation, and advancement

Geographic ranges of ticks and tick-borne pathogens within North America are shifting due to environmental changes and human-driven activities, with species of public health concern presenting a multifaceted risk to human health. Innovative strategies and continued collaboration to control tick populations are needed to combat this growing threat. We conducted a scoping review of the literature to describe the nature of applied tick control research conducted in North America (Canada, Mexico, and the United States) to date, with the goal of describing key concepts and identifying gaps in this research area. A total of 244 articles met our inclusion criteria and were reviewed for patterns in applied tick control authorship and funding, study location, target species, and control methodology. Most studies (83.6%) were conducted exclusively in the United States and 75% focused on ticks of public health concern, principally Amblyomma americanum (Linnaeus, Acari: Ixodidae), Dermacentor variabilis (Say, Acari: Ixodidae), Ixodes scapularis Say (Acari: Ixodidae), and Rhipicephalus sanguineus (Latreille, Acari: Ixodidae). The majority of funding was provided through US federal agencies, predominantly the Centers for Disease Control and Prevention and the United States Department of Agriculture. Ixodes scapularis was the target of over 50% of identified articles, with the majority of research conducted within 3 states in the Northeast region of the U.S. Only 8.2% of included studies evaluated integrated tick management interventions. We note gaps in tick control research regarding (i) non-Ixodes medically relevant tick species, (ii) endemic range coverage, and (iii) control methodologies evaluated.

Estimating the density of questing Ixodes scapularis nymphs in the eastern United States using climate and land cover data

Tick-borne diseases pose a persistent and increasing threat to public health. In the United States, the majority of human infections are caused by pathogens spread by the blacklegged tick, Ixodes scapularis. Most infections are reported during the summer months, when nymphal ticks are active in states in the Northeast and Upper Midwest. The density of questing I. scapularis nymphs (DON) provides an estimate for the risk of human encounters with nymphs, but it is a resource intensive metric to obtain from field sampling. Thus, DON estimates are limited in the US national tick surveillance database, the ArboNET Tick Module. We estimated DON across all counties in the eastern US using a zero-inflated negative binomial model utilizing tick surveillance data reported to ArboNET (2004-2023) as well as climate and land cover data. The model estimated generally low DON across the southeastern US and Great Plains states with higher estimates in the Upper Midwest and Northeast regions. We assigned counties to relative acarological encounter risk categories based on estimated DON: zero or lower quartile DON estimates were scored as low risk, whereas inter- and upper-quartile DON estimates were scored as moderate-high risk. Counties with moderate-high DON reported from field sampling were accurately categorized by the model as moderate-high encounter risk (99 % sensitivity). However, 80 % of sampled counties reporting low DON were classified as moderate-high risk (20 % specificity). These misclassified counties were typically situated in recently colonized areas in the Northeast and Upper Midwest and likely indicated areas potentially suitable for tick population expansion. Our model yielded a very high negative predictive value (96 %) indicating the model did very well estimating low relative encounter risk in counties where no or few nymphs were collected, and a fair positive predictive value (60 %) indicated that densities may not have reached an expected peak in some locations, particularly in the Northeast, Upper Midwest, and northern states in the Southeast. Further tick surveillance is needed to evaluate and to refine these predictions. The resulting maps are useful for estimating relative risk of nymphal encounters across the eastern US where field data are sparse and may aid in efforts aimed at promoting the use of personal protective measures in communities that are at risk for nymphal tick encounters.

Ticks (Acari: Ixodidae) and tick-borne diseases affecting communal cattle and the control methods practiced by farmers in the Eastern Cape Province of South Africa

Background and Aim

Ticks and tick-borne diseases (TBDs) pose significant threats to cattle farming, impacting livestock health, productivity, and economic sustainability. In communal farming systems, the challenges of tick control are exacerbated by limited resources, acaricide resistance, and climate change. This study assesses communal cattle farmers' knowledge, attitudes, and practices regarding ticks, TBDs, and the control measures implemented in the Eastern Cape Province (ECP) of South Africa.

Materials and Methods

A cross-sectional survey was conducted using structured questionnaires administered to 100 cattle farmers across 20 communities in four vegetation types: Albany coastal belt (ACB), Amathole montane grassland (AMG), Bhisho thornveld (BT), and Great fish thicket (GFT). Data were analyzed using descriptive statistics, Pearson's Chi-square tests, and Kruskal-Wallis tests to determine associations between farmer demographics, livestock management practices, and the prevalence of TBDs.

Results

Most respondents (85%) were male, with an average age of 60 years, and 65% had only primary education. Livestock ownership varied across vegetation types, with cattle numbers ranging between 12.8 ± 1.17 and 15.6 ± 1.35 per farmer. Tick infestation was perceived as a major constraint, with adult cattle more affected than calves (χ2 = 15.98, p < 0.001). The most commonly reported TBDs were redwater (100%), gallsickness (90%), and heartwater (43%), with heartwater absent in AMG. Tick control methods included plunge dipping (90%) and the use of alternative treatments such as used motor oil (54%) and Jeyes fluid (35%). Acaricide inefficacy, poor mixing practices, and the uncontrolled movement of cattle were identified as major constraints to effective tick management.

Conclusion

Communal cattle farmers in the ECP recognize ticks and TBDs as critical challenges, with variations in TBD prevalence linked to vegetation type. Ineffective acaricide use and resistance are growing concerns, necessitating improved extension services and farmer education. Sustainable tick management strategies should integrate scientific knowledge with indigenous practices to enhance livestock health and productivity in communal farming systems.

Historical Summary of Tick and Animal Surveillance Studies for Lyme Disease in Canada, 1975-2023: A Scoping Review

INTRODUCTION

Lyme disease (LD) is caused by infection with the bacteria Borrelia burgdorferi sensu lato (Bb) through the bite of an infected Ixodes spp. tick. LD has emerged as a public and animal health issue in Canada, with human incidence increasing in part due to the expansion of Ixodes scapularis ticks and their vertebrate hosts. We sought to provide the first comprehensive summary of published tick and animal surveillance literature regarding LD in Canada to describe changes in LD over time.

METHODS

We conducted a review to identify peer-reviewed LD-focused tick, mammal, and bird surveillance articles in three online databases between 1975 and 2023. Data on study characteristics, data collection years, and surveillance methods and findings were extracted. Descriptive statistics were reported.

RESULTS

In total, 115 studies were included for review. Results showed an increase in published surveillance literature and changes in study approaches and their provincial distribution over time, coinciding with increased LD cases in Canada. Seventy-four studies were published after 2014 when Canada's Federal Framework on Lyme Disease Act was introduced, and two-thirds of these studies focused on tick surveillance only. Overall, 58% of studies involved surveillance in Ontario but increases in all other provinces were observed after 2009.

CONCLUSIONS

Observed changes in five decades of LD-related tick and animal surveillance literature helps document the historical rapid spread of Ixodes and Bb across provinces. This can provide lessons for other regions that may transition from emerging to endemic status for LD in the coming years.

Whole Genome Sequencing Reveals Clade-Specific Genetic Variation in Blacklegged Ticks

Ticks and tick-borne pathogens represent the greatest vector-borne disease threat in the United States. Blacklegged ticks are responsible for most human cases, yet the disease burden is unevenly distributed across the northern and southern United States. Understanding the genetic characteristics influencing phenotypic differences in tick vectors is critical to elucidating disparities in tick-borne pathogen transmission dynamics. Applying evolutionary analyses to molecular variation in natural tick populations across ecological gradients will help identify signatures of local adaptation, which will improve control and mitigation strategies. In this study, we performed whole genome nanopore sequencing of individual (n = 1) blacklegged ticks across their geographical range (Minnesota, Pennsylvania, and Texas) to evaluate genetic divergence among populations. Our integrated analyses identified genetic variants associated with numerous biological processes and molecular functions that segregated across populations. Notably, northern populations displayed genetic variants in genes linked to xenobiotic detoxification, transmembrane transport, and sulfation that may underpin key phenotypes influencing tick dispersal, host associations, and vectorial capacity. Nanopore sequencing further allowed the recovery of complete mitochondrial and commensal endosymbiont genomes. Our study provides further evidence of genetic divergence in epidemiologically relevant gene families among blacklegged tick clades. This report emphasizes the need to elucidate the genetic basis driving divergence among conspecific blacklegged tick clades in the United States.

Climate-induced expansion of Lyme disease in east central Ohio

The geographical distribution of Lyme disease has been attributed to changes in Earth's climate and associated distribution of its vector, ticks of the genus Ixodes. This study focuses on the impact of climatic and meteorological conditions on Lyme disease transmission in East Central Ohio, an emerging hotspot of cases. Using county-level data from 2001 to 2023, we analyzed the relationship between Lyme disease cases and temperature, precipitation, and the Southern Oscillation Index (SOI) using a distributed lag nonlinear model (DLNM). Results show that warmer winter temperatures, higher precipitation, and negative SOI values (El Niño conditions) were significantly associated with increased Lyme disease incidence and displayed delayed effects of 6 to18 months. These findings suggest that climate change, with its potential to bring milder winters and increased spring and summer rainfall, may further exacerbate Lyme disease cases in Ohio.

Genomic and Proteomic Analyses of Bacterial Communities of Ixodes scapularis Ticks from Broome County, New York

The microbial communities of Ixodes scapularis, the primary vector of Lyme disease in North America, exhibit regional variations that may affect pathogen transmission and vector competence. We analyzed bacterial communities in I. scapularis ticks collected from Broome County, New York, using 16S rRNA gene sequencing (18 ticks) as well as mass spectrometry-based proteomics (36 ticks). According to the 16S rRNA analysis, the endosymbiont Rickettsia buchneri was the most abundant species, with significantly higher (p = 0.0011) abundance in females (54.76%) compared to males (31.15%). We detected Borreliella burgdorferi in 44.44% of ticks and Anaplasma phagocytophilum in two nymphs but in high relative abundances (12.73% and 46.46%). Male ticks exhibited higher bacterial diversity, although the community composition showed no significant clustering by sex or life stage. Co-occurrence analysis revealed negative associations between R. buchneri and Pseudomonas (p = 0.0245), but no associations with B. burgdorferi. Proteomic analysis identified 12 R. buchneri-specific proteins, additionally detecting the protozoan pathogen Babesia microti in 18.18% of females. These findings provide the first comprehensive characterization of I. scapularis microbiomes in the Southern Tier region of New York and suggest broader distribution of R. buchneri across tick life stages than previously recognized, with potential implications for pathogen transmission dynamics.

Acute Febrile Illness Accompanied by 7th and 12th Cranial Nerve Palsy Due to Lyme Disease Following Travel to Rural Ecuador: A Case Report and Mini-Review

The causative agent of Lyme disease, Borrelia burgdorferi, is endemic to Canada, the northeastern United States, northern California, and temperate European regions. It is rarely associated with a travel-related exposure. In this report, we describe a resident of southern Ontario, Canada who developed rash, fever, and cranial nerve VII and XII palsies following a 12 day trip to Ecuador and the Galapagos islands approximately four weeks prior to referral to our center. Comprehensive microbiological work-up was notable for reactive Borrelia burgdorferi serology by modified two-tier testing (MTTT), confirming a diagnosis of Lyme disease. This case highlights important teaching points, including the classic clinical presentation of acute Lyme disease with compatible exposure pre-travel in a Lyme-endemic region of Ontario, initial manifestations during travel following acquisition of arthropod bites in Ecuador, and more severe manifestations post-travel. Given the travel history to a South American country in which Lyme disease is exceedingly uncommon, consideration of infections acquired in Ecuador necessitated a broad differential diagnosis and more comprehensive microbiological testing than would have been required in the absence of tropical travel. Additionally, cranial nerve XII involvement is an uncommon feature of Lyme neuroborreliosis, and therefore warranted consideration of an alternative, non-infectious etiology such as stroke or a mass lesion, both of which were excluded in this patient through neuroimaging.

Seasonal activity patterns of Ixodes scapularis and Ixodes pacificus in the United States

Knowledge of seasonal activity patterns of human-biting life stages of tick species serving as vectors of human disease agents provides basic information on when during the year humans are most at risk for tick bites and tick-borne diseases. Although there is a wealth of published information on seasonal activity patterns of Ixodes scapularis and Ixodes pacificus in the United States, a critical review of the literature for these important tick vectors is lacking. The aims of this paper were to: (i) review what is known about the seasonal activity patterns of I. scapularis and I. pacificus in different parts of their geographic ranges in the US, (ii) provide a synthesis of the main findings, and (iii) outline key knowledge gaps and methodological pitfalls that limit our understanding of variability in seasonal activity patterns. Based on ticks collected while questing or from wild animals, the seasonal activity patterns were found to be similar for I. pacificus in the Far West and I. scapularis in the Southeast, with synchronous activity of larvae and nymphs, peaking in spring (April to June) in the Far West and from spring to early summer (April to July) in the Southeast, and continuous activity of adults from fall through winter and spring with peak activity from fall through winter (November/December to March). In the colder climates of the Upper Midwest and Northeast, I. scapularis adults have a bimodal seasonal pattern, with activity peaks in fall (October to November) and spring (April to May). The seasonal activity patterns for immatures differ between the Upper Midwest, synchronous for larvae and nymphs with peak activity in spring and summer (May to August), and the Northeast, where the peak activity of nymphs in spring and early summer (May to July) precedes that of larvae in summer (July to September). Seasonality of human tick encounters also is influenced by changes over the year in the level of outdoor activities in tick habitat. Studies on the seasonality of ticks infesting humans have primarily focused on the coastal Northeast and the Pacific Coast states, with fewer studies in the Southeast, inland parts of the Northeast, and the Upper Midwest. Discrepancies between seasonal patterns for peak tick questing activity and peak human infestation appear to occur primarily for the adult stages of I. scapularis and I. pacificus. Study design and data presentation limitations of the published literature are discussed. Scarcity of data for seasonal activity patterns of I. pacificus outside of California and for I. scapularis from parts of the Southeast, Northeast, and Upper Midwest is a key knowledge gap. In addition to informing the public of when during the year the risk for tick bites is greatest, high-quality studies describing current seasonal activity patterns also will generate the data needed for robust model-based projections of future climate-driven change in the seasonal activity patterns and provide the baseline needed to empirically determine in the future if the projections were accurate.

Climate-driven variation in the phenology of juvenile Ixodes pacificus on lizard hosts

Background

Ectothermic arthropods, like ticks, are sensitive indicators of environmental changes, and their seasonality plays a critical role in tick-borne disease dynamics in a warming world. Juvenile tick phenology, which influences pathogen transmission, may vary across climates, with longer tick seasons in cooler climates potentially amplifying transmission. However, assessing juvenile tick phenology is challenging in climates where desiccation pressures reduce the time ticks spend seeking blood meals. To improve our understanding of juvenile tick seasonality across a latitudinal gradient, we examine Ixodes pacificus phenology on lizards, the primary juvenile tick host in California, and explore how climate factors influence phenological patterns.

Methods

Between 2013 and 2022, ticks were removed from 1,527 lizards at 45 locations during peak tick season (March-June). Tick counts were categorized by life stage (larvae and nymphs) and linked with remotely sensed climate data. Juvenile phenology metrics, including abundance, date of peak abundance, and temporal overlap between larval and nymphal populations, were analyzed along a latitudinal gradient, including tick abundances on lizards, Julian date of peak mean abundance. Generalized Additive Models (GAMs) were applied to assess climate-associated variation in juvenile abundance on lizards.

Results

Mean tick abundance per lizard ranged from 0.17 to 47.21 across locations, with the highest in the San Francisco Bay Area and lowest in Los Angeles, where more lizards had zero ticks attached. In the San Francisco Bay Area, peak nymphal abundance occurred 25 days earlier than peak larval abundance. Temporal overlap between larval and nymphal stages at a given location varied regionally, with northern areas showing higher overlap. We found that locations with higher temperatures and increased drought stress were linked to lower tick abundances, though the magnitude of these effects depended on regional location.

Conclusion

Our study, which compiled 10 years of data, reveals significant regional variation in juvenile I. pacificus phenology across California, including differences in the abundance, peak timing, and temporal overlap. These findings highlight the influence of local climate on tick seasonality, with implications for tick-borne disease dynamics in a changing climate.

Spatial and temporal distribution of Ixodes scapularis and tick-borne pathogens across the northeastern United States

BACKGROUND

The incidence of tick-borne diseases is increasing across the USA, with cases concentrated in the northeastern and midwestern regions of the country. Ixodes scapularis is one of the most important tick-borne disease vectors and has spread throughout the northeastern USA over the past four decades, with established populations in all states of the region.

METHODS

To better understand the rapid expansion of I. scapularis and the pathogens they transmit, we aggregated and analyzed I. scapularis abundance and pathogen prevalence data from across the northeastern USA, including the states of Connecticut, Maine, New Hampshire, New York and Vermont, from 1989 to 2021. Maine was the only state to collect data during the entire time period, with the other states collecting data during a subset of this time period starting in 2008 or later. We harmonized I. scapularis abundance by county and tick season, where the nymph season is defined as May to September and the adult season is October to December, and calculated I. scapularis pathogen infection prevalence as the percentage of ticks that tested positive for Anaplasma phagocytophilum, Babesia microti, Borrelia burgdorferi, and Borrelia miyamotoi. We then explored temporal trends in I. scapularis abundance and pathogen prevalence data using linear models.

RESULTS

The resulting dataset is one of the most spatially and temporally comprehensive records of tick abundance and pathogen prevalence in the USA. Using linear models, we found small or insignificant changes in the abundance of nymphs and adults over time; however, A. phagocytophilum, B. microti and B. burgdorferi prevalence in both nymphs and adults has increased over time. For the period 2017-2021, the statewide average prevalence of B. burgdorferi ranged from 19% to 25% in I. scapularis nymphs and from to 49% to 54% in I. scapularis adults. The statewide average prevalence of all other pathogens in I. scapularis for 2017-2021, including A. phagocytophilum (4-6% for nymphs, 4-9% for adults), B. microti (4-8% for nymphs, 2-13% for adults) and B. miyamotoi (1-2% for nymphs, 1-2% for adults), was considerably less.

CONCLUSIONS

Our efforts revealed the complications of creating a comprehensive dataset of tick abundance and pathogen prevalence across time and space due to variations in tick collection and pathogen testing methods. Although tick abundance has not changed along the more southern latitudes in our study over this time period, and only gradually changed in the more northern latitudes of our study, human risk for exposure to tick-borne pathogens has increased due to increased pathogen prevalence in I. scapularis. This dataset can be used in future studies of I. scapularis and pathogen prevalence across the northeastern USA and to evaluate models of I. scapularis ecology and population dynamics.

Genetic investigation of glycosylphosphatidylinositol (GPI) anchored Bd37 orthologs in Babesia divergens group and potential use of recombinant protein for ecological survey in deer

The Babesia divergens/B. capreoli group includes parasites with confirmed or possible zoonotic potential to cause human babesiosis. Currently, diagnostic antigen of the group has not been established. In this study, we investigated the ortholog of Bd37, a glycosylphosphatidylinositol (GPI)-anchored major merozoite surface protein of B. divergens sensu stricto, in the Asia lineage of the group. From two genomic isolates from sporozoite/sporoblast stages, three Bd37 gene variants, namely Bd37 JP-A, JP-B, and JP-C, were isolated with 62.3-64.1% amino acid sequence identity. Discriminative blood direct PCR revealed that Bd37 JP-A was encoded in all parasites infecting wild sika deer examined (n=22). While Bd37 JP-B and JP-C genes were randomly detected in 12 and 11 specimens, respectively. Sequencing of all JP-A variants revealed that the gene was polymorphic, with a low ratio of non-synonymous to synonymous substitutions (dN/dS) and that a highly polymorphic region was not related to predicted B-cell epitopes. A recombinant JP-A-based ELISA showed an overall positive rate of 13.9% in sika deer in Japan from north (Hokkaido) to south (Kyushu island) across 24 prefectures (n=360). This positive rate was twice as high as that examined by 18S rRNA-based PCR (6.6%). The geographical trends in infection rates were consistent. This study demonstrated that direct examination was informative for revealing genetic background and selecting antigen candidates. Bd37 orthologs may serve diagnostic purposes in combination with indirect fluorescence assay, which requires biological isolates.

Identifying the geographic leading edge of Lyme disease in the United States with internet searches: A spatiotemporal analysis of Google Health Trends data

BACKGROUND

The geographic footprint of Lyme disease is expanding in the United States, which calls for novel methods to identify emerging endemic areas. The ubiquity of internet use coupled with the dominance of Google's search engine makes Google user search data a compelling data source for epidemiological research.

OBJECTIVE

We evaluated the potential of Google Health Trends to track spatiotemporal patterns in Lyme disease and identify the leading edge of disease risk in the United States.

MATERIALS AND METHODS

We analyzed internet search rates for Lyme disease-related queries at the designated market area (DMA) level (n = 206) for the 2011-2019 and 2020-2021 (COVID-19 pandemic) periods. We used maps and other exploratory methods to characterize changes in search behavior. To assess statistical correlation between searches and Lyme disease cases reported to Centers for Disease Control and Prevention (CDC) between 2011 and 2019, we performed a longitudinal ecological analysis with modified Poisson generalized estimating equation regression models.

RESULTS

Mapping DMA-level changes in "Lyme disease" search rates revealed an expanding area of higher rates occurring along the edges of the northeastern focus of Lyme disease. Bivariate maps comparing search rates and CDC-reported incidence rates also showed a stronger than expected signal from Google Health Trends in some high-risk adjacent states such as Michigan, North Carolina, and Ohio, which may be further indication of a geographic leading edge of Lyme disease that is not fully apparent from routine surveillance. Searches for "Lyme disease" were a significant predictor of CDC-reported disease incidence. Each 100-unit increase in the search rate was significantly associated with a 10% increase in incidence rates (RR = 1.10, 95% CI: 1.07, 1.12) after adjusting for environmental covariates of Lyme disease identified in the literature.

CONCLUSION

Google Health Trends data may help track the expansion of Lyme disease and inform the public and health care providers about emerging risks in their areas.

Geographic range and minimum infection rate of Borrelia burgdorferi, Anaplasma phagocytophilum, Babesia microti, and Borrelia miyamotoi in Ixodes scapularis (Acari: Ixodidae) ticks in Manitoba, Canada from 1995 to 2017

INTRODUCTION

The expanding geographical range of blacklegged ticks (BLTs), Ixodes scapularis, and its ability to transmit Borrelia burgdorferi, Anaplasma phagocytophilum, Babesia microti, and Borrelia miyamotoi poses an emerging public health risk. Our study determined the geographic distribution and the minimum infection rate (MIR) of B. burgdorferi-, A. phagocytophilum-, Ba. microti-, and B. miyamotoi-infected BLTs in Manitoba submitted to the Public Health Agency of Canada's passive tick surveillance programme from 1995 to 2017.

METHODS

Regression models were used to test the association of the MIR by year for each pathogen. Ticks were tested using PCR for B. burgdorferi since 1995, A. phagocytophilum since 2006, and Ba. microti and B. miyamotoi since 2013. The global positioning system coordinates of infected and uninfected ticks submitted during the surveillance period were plotted on a map of Manitoba using ArcGIS Pro version 3.1.2 to detect changes in the geographic distribution of ticks over time.

RESULTS

The overall MIR for B. burgdorferi was 139.7 (95% confidence interval [CI]: 129.0-150.5) per 1000 BLTs; however, it varied over time. After remaining stable from 1995 to 2005, the MIR increased by 12.1 per 1000 BLTs per year from 2005 to 2017 (95% CI: 7.0%-17.2%, p-value <0.01). The geographic distribution of B. burgdorferi-infected BLTs was centred around Winnipeg, Manitoba, and spread outward from this locality. The MIRs of A. phagocytophilum, Ba. microti, and B. miyamotoi were 44.8 per 1000 BLTs (95% CI: 38.1-51.6), 10.8 (95% CI: 6.6-15.0), and 5.2 (95% CI: 2.3-8.1) per 1000 BLTs, respectively, and showed no significant change over time.

CONCLUSION

Passive surveillance revealed the presence of A. phagocytophilum-, Ba. microti-, and B. miyamotoi-infected BLTs in southern Manitoba and revealed an increased risk of exposure to B. burgdorferi-infected BLTs due to the increasing geographic range and MIR.

Advocating for planetary health is an essential part of advocating for children's health

Burning of fossil fuels along with deforestation and ecological disruption have led to the warming of the Earth and climate change. Children are especially vulnerable to adverse health effects of climate change associated changes in the air, soil, and water as their organs are still developing, have a faster breathing rate, higher per pound ingested and inhaled exposures, and greater relative body surface area. To protect this vulnerable population, health care professionals need to play a leading role. In 2015, the American Academy of Pediatrics (AAP) updated their original 2007 Global Climate Change and Children's Health policy statement (again updated in 2024) stating that, "failure to take prompt, substantive action would be an act of injustice to all children." Health care professionals need to educate themselves and their patients of the health risks posed by climate change and incorporate climate change counseling into their practice. They also need to go beyond the framework of the healthcare system and work collaboratively with communities, corporations, and governments to advocate for policies and solutions to mitigate and adapt to climate change. The health and wellbeing of future generations rests upon the actions we take today. IMPACT: Summarizes the adverse effects of increased anthropogenic activity and burning of fossil fuels on planetary and human health Details the increased vulnerability of children to environmental assaults and their long-term effects Provides guidance and resources to health care professionals to empower them to act as advocates for systemic and structural changes that protect children's health.

The role of southern red-backed voles, Myodes gapperi, and Peromyscus mice in the enzootic maintenance of Lyme disease spirochetes in North Dakota, USA

Lyme disease has expanded into the Great Plains of the USA. To investigate local enzootic transmission, small mammals were trapped in two forested tracts in northeastern North Dakota during 2012 and 2013. Peromyscus mice and southern red-backed voles, Myodes gapperi, comprised over 90% of all mammals captured. One site was dominated by Peromyscus (79% of 100 mammals captured). At the other site, M. gapperi (59% of 107 mammals captured) was more abundant than Peromyscus (36%). Immature stages of two tick species parasitized small mammals: Dermacentor variabilis and Ixodes scapularis. Larval I. scapularis ectoparasitism was significantly higher on Peromyscus (81% infested; 3.7 larvae per infested mouse) than M. gapperi (47% infested; 2.6 larvae per infested vole) whereas larval and nymphal D. variabilis ectoparasitism were highest on M. gapperi. Over 45% of infested rodents were concurrently infested with both tick species. Testing engorged I. scapularis larvae from Peromyscus (n = 66) and M. gapperi (n = 20) yielded xenopositivity prevalence for Borrelia burgdorferi sensu lato (s.l.) in these rodents of 6% and 5%, respectively. Progeny of field collected M. gapperi were used to determine host infectivity for a local isolate of B. burgdorferi sensu stricto (s.s.). Five M. gapperi were injected with spirochetes, infested with pathogen-free I. scapularis larvae on days 10, 20, and 40 after infection, and engorged larvae molted to nymphs. Subsamples of nymphs were tested by PCR for B. burgdorferi s. s. DNA and yielded infection rates of 56% (n = 100 nymphs tested), 75% (n = 8) and 64% (n = 31), respectively. The remaining infected nymphs were fed on BALB/c Mus musculus mice and 7 d later, mice were euthanized, and tissues were cultured for B. burgdorferi s.s. Nymphs successfully transmitted spirochetes to 13 of 18 (72%) mice that were exposed to 1-5 infected ticks. Theoretical reservoir potentials - i.e., ability to generate B. burgdorferi infected nymphs - were compared between Peromyscus and M. gapperi. At one site, Peromyscus accounted for nearly all Borrelia-infected nymphs produced (reservoir potential value of 0.935). At the other site, the reservoir potentials for Peromyscus (0.566) and M. gapperi (0.434) were comparable. The difference was attributed to differences in the relative abundance of voles versus mice between sites and the higher level of ectoparasitism by larval I. scapularis on Peromyscus versus M. gapperi at both sites. The southern red-backed vole, M. gapperi, contributes to the enzootic maintenance of Lyme disease spirochetes in North Dakota and possibly other areas where this rodent species is abundant.

Salp14 epitope-based mRNA vaccination induces early recognition of a tick bite

Repeated exposure of animals to Ixodes scapularis ticks can result in acquired tick resistance (ATR). The first manifestation of ATR is erythema at the tick bite site, however, the specific peptide targets and mechanisms associated with this early aspect of ATR are not understood. In this study, we immunized guinea pigs with a lipid nanoparticle containing the mRNA encoding 25 amino acids in the carboxyl terminus of Salp14 (Salp14-C mRNA-LNP), an I. scapularis salivary protein. The animals produced high titers of IgG directed at the carboxyl terminus of Salp14. Guinea pigs immunized with Salp14-C mRNA-LNP and then exposed to I. scapularis, developed erythema at the tick bite site. Transcriptomics of the skin of guinea pigs at the I. scapularis bite sites elucidated selected pathways, including histamine activation, that are associated with the development of erythema. The study demonstrates that an mRNA vaccine encoding a small peptide can induce the initial phase of ATR in guinea pigs.

Microbial community characteristics and pathogens detection in Rhipicephalus sanguineus and Haemaphysalis hystricis from Hainan Island, China

Background

Microbial communities significantly influence the vector capacity of ticks, which, along with tick-borne diseases, pose an increasing global threat. Due to the substantial individual variability caused by various factors, it is essential to assess tick microbial communities and vectorial capacities under different environmental conditions. However, there is a relative scarcity of research on the microbial communities and pathogen transmission of ticks in different physiological states and environmental conditions, especially in Hainan Island, southern China.

Methods

From 2021 to 2022, we collected 4,167 tick samples, grouping them by blood meal status, developmental stage, sex, time, geographical location, and tick species. We selected 128 samples for full-length 16S rRNA sequencing to describe microbial community characteristics and identify potential biomarkers. Seven hundred seventy-two samples were tested for seven tick-borne pathogens (Rickettsia, Borrelia burgdorferi, Ehrlichia, Anaplasma, Theileria, Babesia, and Hepatozoon), and sera from 208 residents of Hainan Island were tested for IgG antibodies against Rickettsia and B. burgdorferi.

Results

Blood meal status, developmental stage, sex, time, geographical location, and tick species significantly influenced the microbial communities of ticks. We observed distinct microbial community characteristics across different states. We noted the non-random replacement of stable and transient species, with functional differences between parasitic and engorged ticks mainly driven by transient species. Functionally, we observed three distinct response patterns: driven by stable species, transient species, and both together in response to the six factors. We identified 273 potential biomarkers (200 robust core species and 73 robust differential species). Six genera and eight species of pathogens were detected in ticks, with an overall positivity rate of 12.44% (96/772). Among humans, 18.27% (38/208) of serum samples were positive for at least one tick-borne pathogen IgG.

Conclusion

Our findings indicate that these six factors significantly influence both tick microbial communities and vectorial capacity, with varying effects on vector competence for different pathogens and inconsistent impacts on microbial communities under different conditions. This study supplemented the understanding of tick microbial communities on Hainan Island, assessed the relatively high risk of tick-borne pathogens in the region, and evaluated the impact of these factors on both microbial communities and vectorial capacity.

The Spread of Lone Star Ticks (Amblyomma americanum) and Persistence of Blacklegged Ticks (Ixodes scapularis) on a Coastal Island in Massachusetts, USA

In the northeastern USA, the distribution of lone star ticks (Amblyomma americanum) has expanded northward in recent decades, overlapping with the range of blacklegged ticks (Ixodes scapularis). Blacklegged ticks carry pathogens for diseases such as Lyme, babesiosis, and anaplasmosis, while bites from lone star ticks cause other diseases and the alpha-gal syndrome allergy. Lone star ticks can become so abundant that they are perceived as more of a public health threat than blacklegged ticks. Using the island of Martha's Vineyard, Massachusetts, as a case study, we analyzed data from a total of 1265 yard surveys from 2011 to 2024 to document lone star tick presence and subsequent expansion from two peripheral areas, Chappaquiddick and Aquinnah, to all six towns. The timing of lone star tick expansion on Martha's Vineyard closely matched an increase in tick submissions to a pathogen testing center. At Chappaquiddick, drag sampling carried out in June 2023 and 2024 showed that both tick species were most common at wooded sites, where blacklegged nymphs were somewhat more abundant than lone star nymphs. However, lone star ticks occurred in a wider range of natural and peridomestic habitats than blacklegged nymphs, making them far more challenging for people to avoid and manage.

Lyme Disease Under-Ascertainment During the COVID-19 Pandemic in the United States: Retrospective Study

Background

The COVID-19 pandemic resulted in a massive disruption in access to care and thus passive, hospital- and clinic-based surveillance programs. In 2020, the reported cases of Lyme disease were the lowest both across the United States and North Carolina in recent years. During this period, human contact patterns began to shift with higher rates of greenspace utilization and outdoor activities, putting more people into contact with potential vectors and associated vector-borne diseases. Lyme disease reporting relies on passive surveillance systems, which were likely disrupted by changes in health care-seeking behavior during the pandemic.

Objective

This study aimed to quantify the likely under-ascertainment of cases of Lyme disease during the COVID-19 pandemic in the United States and North Carolina.

Methods

We fitted publicly available, reported Lyme disease cases for both the United States and North Carolina prior to the year 2020 to predict the number of anticipated Lyme disease cases in the absence of the pandemic using a Bayesian modeling approach. We then compared the ratio of reported cases divided by the predicted cases to quantify the number of likely under-ascertained cases. We then fitted geospatial models to further quantify the spatial distribution of the likely under-ascertained cases and characterize spatial dynamics at local scales.

Results

Reported cases of Lyme Disease were lower in 2020 in both the United States and North Carolina than prior years. Our findings suggest that roughly 14,200 cases may have gone undetected given historical trends prior to the pandemic. Furthermore, we estimate that only 40% to 80% of Lyme diseases cases were detected in North Carolina between August 2020 and February 2021, the peak months of the COVID-19 pandemic in both the United States and North Carolina, with prior ascertainment rates returning to normal levels after this period. Our models suggest both strong temporal effects with higher numbers of cases reported in the summer months as well as strong geographic effects.

Conclusions

Ascertainment rates of Lyme disease were highly variable during the pandemic period both at national and subnational scales. Our findings suggest that there may have been a substantial number of unreported Lyme disease cases despite an apparent increase in greenspace utilization. The use of counterfactual modeling using spatial and historical trends can provide insight into the likely numbers of missed cases. Variable ascertainment of cases has implications for passive surveillance programs, especially in the trending of disease morbidity and outbreak detection, suggesting that other methods may be appropriate for outbreak detection during disturbances to these passive surveillance systems.

Geographic variation in the distribution of Anaplasma phagocytophilum variants in host-seeking Ixodes scapularis nymphs and adults in the eastern United States elucidated using next generation sequencing

Human anaplasmosis cases, caused by Anaplasma phagocytophilum, are increasing in the United States. This trend is explained, in part, by expansion in the geographic range of the primary vector, Ixodes scapularis. Multiple variants of A. phagocytophilum have been identified in field collected ticks, but only a single variant (human active, or "Ap-ha," variant) has been shown to be pathogenic in humans. Until recently, laboratory methods used to differentiate variants were cumbersome and seldomly used in large scale assessments of the pathogen's geographic distribution. As a result, many surveys reported A. phagocytophilum without segregating variants. Lack of discrimination among A. phagocytophilum variants could lead to overestimation of anaplasmosis risk to humans. Next Generation Sequencing (NGS) assays were recently developed to efficiently detect multiple Ixodes scapularis-borne human pathogens including Ap-ha. In this study, we utilized NGS to detect and differentiate A. phagocytophilum variants (Ap-ha vs. non ha) in host-seeking I. scapularis nymphs and adults collected across 23 states in the eastern United States from 2012 to 2023 as part of national tick surveillance efforts and research studies. Many of the included ticks were tested previously using a TaqMan PCR assay that could detect A. phagocytophilum but could not differentiate variants. We retested A. phagocytophilum infected ticks with NGS to differentiate variants. Anaplasma phagocytophilum (any variant) was identified in 165 (35 %) of 471 counties from which ticks were tested, whereas Ap-ha was detected in 70 (15 %) of 469 counties where variants were differentiated. Both variants were identified in 32 % (n = 40) of 126 counties with either variant detected. Among states where A. phagocytophilum (any variant) was detected, prevalence ranged from 2 % to 19 % in unfed adults and from 0.2 % to 7.8 % in unfed nymphs; prevalence of Ap-ha variant ranged from 0.0 % to 16 % in adults, and 0.0 % to 4.6 % in nymphs.

Laboratory Management of Mammalian Hosts for Ixodes scapularis -Host-Pathogen Interaction Studies

Due to their hematophagous life cycle, hard-bodied ticks including the genus Ixodes are a potential vector for numerous pathogenic organisms including bacteria, protozoa, viruses, and infectious prions. The natural geographic range of several hard tick species, includig Ixodes scapularis, has expanded over recent decades. Consequently, there is an ongoing need to maintain, feed, and propagate ticks for host-pathogen interaction studies to better understand and mitigate their impact on human and animal health. Artificial membrane feeding of hard ticks has advanced in recent years, has study design advantages, and should be used, when possible, to reduce animal use, but it also has several limitations that require the continued use of mammalian hosts including mice, guinea pigs, and rabbits. In this overview, we discuss the best management practices for these relevant species with respect to biosafety, health, and optimal host comfort when used in studies that depend on tick feeding. The capsule-jacket method is preferred over the ear sock-E-collar method of tick feeding on rabbit hosts because of better host health, comfort, and increased study versatility.

Genome resequencing reveals population divergence and local adaptation of blacklegged ticks in the United States

Tick vectors and tick-borne disease are increasingly impacting human populations globally. An important challenge is to understand tick movement patterns, as this information can be used to improve management and predictive modelling of tick population dynamics. Evolutionary analysis of genetic divergence, gene flow and local adaptation provides insight on movement patterns at large spatiotemporal scales. We develop low coverage, whole genome resequencing data for 92 blacklegged ticks, Ixodes scapularis, representing range-wide variation across the United States. Through analysis of population genomic data, we find that tick populations are structured geographically, with gradual isolation by distance separating three population clusters in the northern United States, southeastern United States and a unique cluster represented by a sample from Tennessee. Populations in the northern United States underwent population contractions during the last glacial period and diverged from southern populations at least 50 thousand years ago. Genome scans of selection provide strong evidence of local adaptation at genes responding to host defences, blood-feeding and environmental variation. In addition, we explore the potential of low coverage genome sequencing of whole-tick samples for documenting the diversity of microbial pathogens and recover important tick-borne pathogens such as Borrelia burgdorferi. The combination of isolation by distance and local adaptation in blacklegged ticks demonstrates that gene flow, including recent expansion, is limited to geographical scales of a few hundred kilometres.

Increasing Risk for Tick-Borne Disease: What Should Clinicians Know?

This clinical insights article examines reasons behind the increase in tick-borne diseases and what clinicians should know about diagnosis and mitigation.

The Diel Activity Pattern of Haemaphysalis longicornis and Its Relationship with Climatic Factors

Haemaphysalis longicornis is one of the most medically important carriers of various pathogens. Although H. longicornis is an important vector, only basic ecological and biological information has been obtained, primarily focusing on its abundance and distribution. This study determined the most active time and meteorological conditions for the diel activity of H. longicornis. The diel activity pattern of H. longicornis was the highest between 10:00 and 14:00, and the lowest between 22:00 and 02:00. The major activity temperature of H. longicornis was between 25 °C and 40 °C, with the highest activity at 35 °C. The relative humidity was between 30% and 70% during the active period. Temperature had the highest correlation with diel activity (R = 0.679), followed by humidity (R = -0.649) and light intensity (R = 0.572). Our results provide basic information for the development of tick-borne disease vector control programs and tick surveillance.

Willingness and capacity of publicly-funded vector control programs in the USA to engage in tick management

BACKGROUND

The vast majority of vector-borne diseases in the USA are associated with mosquitoes or ticks. Mosquito control is often conducted as part of community programs run by publicly-funded entities. By contrast, tick control focuses primarily on individual residential properties and is implemented predominantly by homeowners and the private pest control firms they contract. We surveyed publicly-funded vector control programs (VCPs), presumed to focus mainly on mosquitoes, to determine what tick-related services they currently offer, and their interest in and capacity to expand existing services or provide new ones.

METHODS

We distributed a survey to VCPs in the Northeast, Upper Midwest and Pacific Coast states of the USA, where humans are at risk for bites by tick vectors (Ixodes scapularis or Ixodes pacificus) of agents causing Lyme disease and other tick-borne diseases. The data we report are based on responses from 118 VCPs engaged in vector control and with at least some activities focused on ticks.

RESULTS

Despite our survey targeting geographic regions where ticks and tick-borne diseases are persistent and increasing public health concerns, only 11% (12/114) of VCPs reported they took direct action to suppress ticks questing in the environment. The most common tick-related activities conducted by the VCPs were tick bite prevention education for the public (70%; 75/107 VCPs) and tick surveillance (48%; 56/116). When asked which services they would most likely include as part of a comprehensive tick management program, tick bite prevention education (90%; 96/107), tick surveillance (89%; 95/107) and tick suppression guidance for the public (74%; 79/107) were the most common services selected. Most VCPs were also willing to consider engaging in activities to suppress ticks on public lands (68%; 73/107), but few were willing to consider suppressing ticks on privately owned land such as residential properties (15%; 16/107). Across all potential tick-related services, funding was reported as the biggest obstacle to program expansion or development, followed by personnel.

CONCLUSIONS

Considering the hesitancy of VCPs to provide tick suppression services on private properties and the high risk for tick bites in peridomestic settings, suppression of ticks on residential properties by private pest control operators will likely play an important role in the tick suppression landscape in the USA for the foreseeable future. Nevertheless, VCPs can assist in this effort by providing locally relevant guidelines to homeowners and private pest control firms regarding best practices for residential tick suppression efforts and associated efficacy evaluations. Publicly-funded VCPs are also well positioned to educate the public on personal tick bite prevention measures and to collect tick surveillance data that provide information on the risk of human encounters with ticks within their jurisdictions.

Don't go chasing waterfalls: the phenology of Amblyomma americanum and increased collection of medically relevant ticks further away from hiking trails in the Piedmont of North Carolina, USA

Hiking is a popular recreational activity in North Carolina that may expose people to ticks and tick-borne pathogens. However, there is a lack of knowledge on how ticks are distributed on and near trails. Our study tested the hypothesis that ticks are more likely to be encountered when moving further away from trails by measuring differences in relative abundance at various distances. We tested 4 distances (middle of trail, edge of trail, 5 m, 20 m), as well as an on-trail and off-trail grouping. We collected significantly more ticks and ticks were more likely to be collected at our 20 m and 5 m sampling distances rather than directly on or adjacent to trails, and significantly more were collected during off-trail collections than on-trails. When looking only at Amblyomma americanum, post hoc comparisons revealed that significantly more juvenile stages were collected at 5 m and 20 m distances, but not for adults. Our monthly sampling also allowed us to describe the phenology of A. americanum in North Carolina, which is consistent with the phenology of this species in the southeastern United States with adults peaking May-Jun, nymphs Jun-Jul, and larvae in Jul-Aug. These results generally demonstrate the importance of utilizing established trails when hiking to decrease tick-borne disease risk and should be communicated to the public as a recommendation for reducing tick-encounter risk.

A next generation sequencing assay combining Ixodes species identification with pathogen detection to support tick surveillance efforts in the United States

The burden of tick-borne diseases continues to increase in the United States. Tick surveillance has been implemented to monitor changes in the distribution and prevalence of human disease-causing pathogens in ticks that frequently bite humans. Such efforts require accurate identification of ticks to species and highly sensitive and specific assays that can detect and differentiate pathogens from genetically similar microbes in ticks that have not been demonstrated to be pathogenic in humans. We describe a modification to a next generation sequencing pathogen detection assay that includes a target that accurately identifies Ixodes ticks to species. We show that the replacement of internal control primers used to ensure assay performance with primers that also act as an internal control and can additionally differentiate tick species, retains high sensitivity and specificity, improves efficiency, and reduces costs by eliminating the need to run separate assays to screen for pathogens and for tick identification.

Nuttalliella namaqua Bedford, 1931, a sole extant species of the genus Nuttalliella - a scoping review

Nuttalliella namaqua Bedford, 1931 is the sole extant tick species that belongs to the genus and family Nuttalliella and Nuttalliellidae respectively. With the characteristics that are respectively distinctive to hard and soft ticks, it is regarded as the species closest to the ancestral lineage of ticks as well as the missing link between the Argasidae and Ixodidae families. In this review, literature search of the articles reporting on N. namaqua was done in Google Scholar and PubMed databases. After relevance and eligibility screening, 12 articles were deemed eligible and appraised. The results showed that N. namaqua was respectively distinct to limited regions of Africa such as Botswana, Namibia, Mozambique, South Africa and Tanzania. The review also indicated that N. namaqua was collected from murid rodents, African Savanna hare, scrub hare, elephant shrews, rock hyraxes, black backed jackal, lizards and off-host in locations that include under a stone, rock crevices, on a rock wall and respectively in the nests of an eagle and a lesser striped swallow. Irrespective of all the reports, natural hosts of the nymphs are still not clearly defined. Numerous phylogeny studies have reported Nuttalliellidae as the sister-lineage to Argasidae and Ixodidae tick families. Moreover, a recent report indicated that the similarities between Nuttalliellidae and the fossil families Deinocrotonidae and Legionaris award them to be merged into one family, preferably Nuttalliellidae Thus, further research on this family, will perhaps provide more knowledge about its unclear distribution, life cycle as well as the evolution of ticks in general.

History of the geographic distribution of the western blacklegged tick, Ixodes pacificus, in the United States

Ixodes pacificus (the western blacklegged tick) occurs in the far western United States (US), where it commonly bites humans. This tick was not considered a species of medical concern until it was implicated in the 1980s as a vector of Lyme disease spirochetes. Later, it was discovered to also be the primary vector to humans in the far western US of agents causing anaplasmosis and hard tick relapsing fever. The core distribution of I. pacificus in the US includes California, western Oregon, and western Washington, with outlier populations reported in Utah and Arizona. In this review, we provide a history of the documented occurrence of I. pacificus in the US from the 1890s to present, and discuss associations of its geographic range with landscape, hosts, and climate. In contrast to Ixodes scapularis (the blacklegged tick) in the eastern US, there is no evidence for a dramatic change in the geographic distribution of I. pacificus over the last half-century. Field surveys in the 1930s and 1940s documented I. pacificus along the Pacific Coast from southern California to northern Washington, in the Sierra Nevada foothills, and in western Utah. County level collection records often included both immatures and adults of I. pacificus, recovered by drag sampling or from humans, domestic animals, and wildlife. The estimated geographic distribution presented for I. pacificus in 1945 by Bishopp and Trembley is similar to that presented in 2022 by the Centers for Disease Control and Prevention. There is no clear evidence of range expansion for I. pacificus, separate from tick records in new areas that could have resulted from newly initiated or intensified surveillance efforts. Moreover, there is no evidence from long-term studies that the density of questing I. pacificus ticks has increased over time in specific areas. It therefore is not surprising that the incidence of Lyme disease has remained stable in the Pacific Coast states from the early 1990s, when it became a notifiable condition, to present. We note that deforestation and deer depredation were less severe in the far western US during the 1800s and early 1900s compared to the eastern US. This likely contributed to I. pacificus maintaining stable, widespread populations across its geographic range in the far western US in the early 1900s, while I. scapularis during the same time period appears to have been restricted to a small number of geographically isolated refugia sites within its present range in the eastern US. The impact that a warming climate may have had on the geographic distribution and local abundance of I. pacificus in recent decades remains unclear.

Density of host-seeking Ixodes scapularis nymphs by region, state, and county in the contiguous United States generated through national tick surveillance

The majority of vector-borne disease cases reported annually in the United States are caused by pathogens spread by the blacklegged tick, Ixodes scapularis. The number and geographic distribution of cases have increased as the geographic range and abundance of the tick have expanded in recent decades. A large proportion of Lyme disease and other I. scapularis-borne diseases are associated with nymphal tick bites; likelihood of such bites generally increases with increasing nymphal densities. National tick surveillance was initiated in 2018 to track changes in the distribution and abundance of medically important ticks at the county spatial scale throughout the United States. Tick surveillance records, including historical data collected prior to the initiation of the national program, are collated in the ArboNET Tick Module database. Through exploration of ArboNET Tick Module data, we found that efforts to quantify the density of host-seeking I. scapularis nymphs (DON) were unevenly distributed among geographic regions with the greatest proportion of counties sampled in the Northeast and Upper Midwest. Submissions covering tick collections from 2004 through 2022 revealed extensive variation in DON estimates at collection site, county, state, and regional spatial scales. Throughout the entire study period, county DON estimates ranged from 0.0 to 488.5 nymphs/1,000 m2 . Although substantial variation was recorded within regions, DON estimates were greatest in the Northeast, Upper Midwest, and northern states within the Southeast regions (Virginia and North Carolina); densities were intermediate in the Ohio Valley and very low in the South and Northern Rockies and Plains regions. The proportion of counties classified as moderate or high DON was lower in the Northeast, Ohio Valley, and Southeast regions during the 2004 through 2017 time period (prior to initiation of the national tick surveillance program) compared to 2018 through 2022; DON estimates remained similarly low between these time periods in the South and the Northern Rockies and Plains regions. Despite the limitations described herein, the ArboNET Tick Module provides useful data for tracking changes in acarological risk across multiple geographic scales and long periods of time.

Estimating the Incidence and Economic Cost of Lyme Disease Cases in Canada in the 21st Century with Projected Climate Change

BACKGROUND

Lyme disease (LD) is emerging in Canada owing to the range expansion of the tick vector Ixodes scapularis (I. scapularis).

OBJECTIVES

Our objective was to estimate future LD incidence in Canada, and economic costs, for the 21st century with projected climate change.

METHODS

Future regions of climatic suitability for I. scapularis were projected from temperature output of the North American Coordinated Regional Climate Downscaling Experiment regional climate model ensemble using greenhouse gas Representative Concentration Pathways (RCPs) 4.5 and 8.5. Once regions became climatically suitable for ticks, an algorithm derived from tick and LD case surveillance data projected subsequent increasing LD incidence. Three scenarios (optimistic, intermediate, and pessimistic) for maximum incidence at endemicity were selected based on LD surveillance, and underreporting estimates, from the United States. Health care and productivity cost estimates of LD cases were obtained from the literature.

RESULTS

Projected annual LD cases for Canada ranged from 120,000 to > 500,000 by 2050. Variation in incidence was mostly due to the maximum incidence at endemicity selected, with minor contributions from variations among climate models and RCPs. Projected annual costs were substantial, ranging from CA $ 0.5  billion to $ 2.0  billion a year by 2050. There was little difference in projected incidence and economic cost between RCPs, and from 2050 to 2100, because projected climate up to 2050 is similar for RCP4.5 and RCP8.5 (mitigation of greenhouse gas emissions captured in RCP4.5 does not impact climate before the 2050s) and by 2050 the most densely populated areas of the study region are projected to be climatically suitable for ticks.

CONCLUSIONS

Future incidence and economic costs of LD in Canada are likely to be substantial, but uncertainties remain. Because densely populated areas of Canada are projected to become endemic under conservative climate change scenarios, mitigation of greenhouse gas emissions is unlikely to provide substantial health co-benefits for LD. https://doi.org/10.1289/EHP13759.

Evaluation of the association between climate warming and the spread and proliferation of Ixodes scapularis in northern states in the Eastern United States

Ixodes scapularis (the blacklegged tick) is widely distributed in forested areas across the eastern United States. The public health impact of I. scapularis is greatest in the north, where nymphal stage ticks commonly bite humans and serve as primary vectors for multiple human pathogens. There were dramatic increases in the tick's distribution and abundance over the last half-century in the northern part of the eastern US, and climate warming is commonly mentioned as a primary driver for these changes. In this review, we summarize the evidence for the observed spread and proliferation of I. scapularis being driven by climate warming. Although laboratory and small-scale field studies have provided insights into how temperature and humidity impact survival and reproduction of I. scapularis, using these associations to predict broad-scale distribution and abundance patterns is more challenging. Numerous efforts have been undertaken to model the distribution and abundance of I. scapularis at state, regional, and global scales based on climate and landscape variables, but outcomes have been ambiguous. Across the models, the functional relationships between seasonal or annual measures of heat, cold, precipitation, or humidity and tick presence or abundance were inconsistent. The contribution of climate relative to landscape variables was poorly defined. Over the last half-century, climate warming occurred in parallel with spread and population increase of the white-tailed deer, the most important reproductive host for I. scapularis adults, in the northern part of the eastern US. There is strong evidence for white-tailed deer playing a key role to facilitate spread and proliferation of I. scapularis in the US over the last century. However, due to a lack of spatially and temporally congruent data, climate, landscape, and host variables are rarely included in the same models, thus limiting the ability to evaluate their relative contributions or interactions in defining the geographic range and abundance patterns of ticks. We conclude that the role of climate change as a key driver for geographic expansion and population increase of I. scapularis in the northern part of the eastern US over the last half-century remains uncertain.

Tick-Borne Co-Infections: Challenges in Molecular and Serologic Diagnoses

Co-infections are a poorly understood aspect of tick-borne diseases. In the United States alone, nineteen different tick-borne pathogens have been identified. The majority of these agents are transmitted by only two tick species, Ixodes scapularis and Amblyomma americanum. Surveillance studies have demonstrated the presence of multiple pathogens in individual ticks suggesting a risk of polymicrobial transmission to humans. However, relatively few studies have explored this relationship and its impact on human disease. One of the key factors for this deficiency are the intrinsic limitations associated with molecular and serologic assays employed for the diagnosis of tick-borne diseases. Limitations in the sensitivity, specificity and most importantly, the capacity for inclusion of multiple agents within a single assay represent the primary challenges for the accurate detection of polymicrobial tick-borne infections. This review will focus on outlining these limitations and discuss potential solutions for the enhanced diagnosis of tick-borne co-infections.

Prevalence of five human pathogens in host-seeking Ixodes scapularis and Ixodes pacificus by region, state, and county in the contiguous United States generated through national tick surveillance

The majority of vector-borne disease cases reported in the United States (U.S.) are caused by pathogens spread by the blacklegged tick, Ixodes scapularis. In recent decades, the geographic ranges of the tick and its associated human pathogens have expanded, putting an increasing number of communities at risk for tick-borne infections. In 2018, the U.S. Centers for Disease Control and Prevention (CDC) initiated a national tick surveillance program to monitor changes in the distribution and abundance of ticks and the presence and prevalence of human pathogens in them. We assessed the geographical representativeness of prevalence data submitted to CDC as part of the national tick surveillance effort. We describe county, state, and regional variation in the prevalence of five human pathogens (Borrelia burgdorferi sensu stricto (s.s.), Borrelia mayonii, Borrelia miyamotoi, Anaplasma phagocytophilum, and Babesia microti) in host-seeking I. scapularis and I. pacificus nymphs and adults. Although I. scapularis and I. pacificus are widely distributed in the eastern and western U.S., respectively, pathogen prevalence was estimated predominantly in ticks collected in the Northeast, Ohio Valley, and Upper Midwest regions, where human Lyme disease cases are most commonly reported. Within these regions, we found that state and regional estimates of pathogen prevalence generally reached predictable and stable levels, but variation in prevalence estimates at the sub-state level was considerable. Borrelia burgdorferi s.s. was the most prevalent and widespread pathogen detected. Borrelia miyamotoi and A. phagocytophilum shared a similarly broad geographic range, but were consistently detected at much lower prevalence compared with B. burgdorferi s.s. Babesia microti was detected at similar prevalence to A. phagocytophilum, where both pathogens co-occurred, but was reported over a much more limited geographic range compared with A. phagocytophilum or B. burgdorferi s.s. Borrelia mayonii was identified at very low prevalence with a focal distribution within the Upper Midwest. National assessments of risk for tick-borne diseases need to be improved through collection and testing of ticks in currently under-represented regions, including the West, South, Southeast, and eastern Plains states.

Perception of Ticks and Tick-Borne Diseases Worldwide

In this comprehensive review study, we addressed the challenge posed by ticks and tick-borne diseases (TBDs) with growing incidence affecting human and animal health worldwide. Data and perspectives were collected from different countries and regions worldwide, including America, Europe, Africa, Asia, and Oceania. The results updated the current situation with ticks and TBD and how it is perceived by society with information bias and gaps. The study reinforces the importance of multidisciplinary and international collaborations to advance in the surveillance, communication and proposed future directions to address these challenges.