Tick-Borne Zoonoses in the United States: Persistent and Emerging Threats to Human Health

Behavioral manipulation of Ixodes scapularis by Ehrlichia muris eauclairensis: implications for tick-borne disease transmission

Tick-borne diseases pose significant risks to both animals and humans, with emerging pathogens like Ehrlichia muris eauclairensis (EME) underscoring the need for a deeper understanding of pathogen-vector interactions and tick fitness. This study investigates the impact of EME on Ixodes scapularis nymphs, revealing significant behavioral changes in EME-positive ticks. These ticks exhibited increased movement speed, faster bite site-seeking for attachment, and prolonged feeding durations compared to control ticks. Proteomic analyses of the tick synganglion during resting and feeding phases identified 196 differentially expressed proteins in EME-positive ticks, including multiple proteins associated with nicotinic acetylcholine signaling pathways. Our findings indicated altered neuropeptide expression related to stimulus response and activity, suggesting changes in neurophysiology. This research provides the first evidence of behavioral manipulation by an Ehrlichia species, indicating that the tick nervous system is a site of bacterial influence and a potential target for interventions. These findings offer new insights into pathogen-vector dynamics that could lead to the development of transmission-blocking therapies, significantly impacting tick fitness and disease transmission.IMPORTANCETick-borne diseases (TBDs) are increasingly affecting humans, pets, and livestock, with cases rising in recent years. Ticks can carry multiple harmful germs, and human activities and environment are contributing to new TBDs. This study shows that the bacteria Ehrlichia muris eauclairensis (EME) can change the behavior of nymphal black-legged ticks, which spread various diseases. Infected ticks moved faster, attached to hosts more quickly, and fed longer than uninfected ticks. These changes were linked to specific proteins in the tick's nervous system, suggesting that EME manipulates tick behavior. This is the first evidence that an Ehrlichia species can influence tick behavior, potentially increasing disease transmission. Understanding these interactions can help develop strategies to prevent TBDs by targeting the bacteria's influence on ticks, ultimately reducing disease spread and improving public health.

Methods of active surveillance for hard ticks and associated tick-borne pathogens of public health importance in the contiguous United States: a comprehensive systematic review

Tick-borne diseases in humans and animals have increased prevalence across the United States. To understand risk factors underlying tick-borne diseases it is useful to conduct regular surveillance and monitoring of ticks and the pathogens they carry, in a sustained and effective manner. Using the Preferred Reporting Items for Systematic Reviews and Meta-Analysis guidelines, this study aims to summarize the previously used methods for active surveillance of ticks and tick-borne pathogens, identify the existing knowledge gaps in ongoing surveillance, and highlight and guide the mechanisms required to inform those gaps for more effective and sustainable future surveillance efforts. After screening 2,500 unique studies between 1944 and 2018, we found 646 articles that performed active surveillance of hard ticks and/or their associated tick-borne pathogens of public health importance within the United States. An additional 103 articles were included for the 2019 to 2023 period. Active surveillance has been performed in ~42% of the counties (1944 to 2018) and ~23% of the counties (2019 to 2023) within the contiguous US, and states with the most coverage are in the Northeast, Upper Midwest, and along the West coast. The most reported tick was Ixodes scapularis (195 studies) and most commonly reported pathogen was Borrelia burgdorferi (143 studies). Overall, surveillance efforts have increased and become more diversified, and methods of tick and tick-borne pathogens testing have undergone changes, but those efforts are mainly concentrated in focal regions of a county. Future surveillance efforts should follow Centers for Disease Control and Prevention guidelines and target areas of United States with scarce reports of active surveillance and build collaborations and resources to increase surveillance.

Evaluating knowledge of ticks and tick-borne diseases among Indiana healthcare professionals

Ticks and tick-borne disease (TBD) risks are increasing in Indiana and North America. The successful prevention, diagnosis, and treatment of TBDs requires healthcare professionals be well-informed and prepared. This study reports the findings of a 2020 online survey of 465 Indiana healthcare professionals, designed to assess their knowledge of ticks and TBDs and identify factors influencing total knowledge scores. The survey included 24 discrete/ordinal questions and one open-ended question. Statistical analyses, including ANOVA, t-tests, and the Boruta algorithm, were conducted in R. Indiana healthcare professionals scored 30.8% for tick- and 57.9% for disease-related questions. Professionals scored higher on most disease-related questions, including (i) the importance of prompt tick removal to reduce TBD transmission risk, (ii) that not all Lyme disease cases present with bull's-eye rash, and (iii) the signs and symptoms of TBDs. They scored lower on tick-related questions, including (i) the tick species capable of transmitting diseases to humans, (ii) TBDs considered endemic, (iii) the distribution of Ixodes scapularis (deer tick), and (iv) regions considered higher risk for Lyme disease transmission in Indiana. Knowledge scores varied across demographic categories, with the use of online resources identified as the most important predictor of total knowledge scores. These findings highlight the importance of increasing awareness of existing resources, expanding online educational materials to cover TBDs beyond Lyme disease, and promoting self-guided learning. Achieving these goals will require collaboration among state and public health agencies, healthcare professionals, research institutions, and community outreach partners.

Rickettsia and Ehrlichia of Veterinary and Public Health Importance in Ticks Collected from Birds in the Great Plains of the United States

As the incidence of tick-borne disease expands globally, comprehensive understanding of pathogen reservoir hosts is crucial to protect humans and wildlife. While many components are understood, there are gaps in our knowledge regarding the role of alternative, non-mammalian hosts such as birds. Within the United States, birds have been identified as reservoirs for Borrelia and Rickettsia; however, local studies rarely examine the potential of birds as reservoirs and transporters of Ehrlichia-infected ticks, unlike studies in Europe and South America. To address this research gap, we extracted and sequenced important microorganisms within 90 larval and nymphal ticks which were removed from passerine and near-passerine birds in the Great Plains region of the United States between May and October 2023. We found that 11% of birds hosted ticks infected with one or more Rickettsia or Ehrlichia species. Additionally, we collected a larval Haemaphysalis leporispalustris infected with Ehrlichia chaffeensis from a Northern Cardinal, the first North American songbird implicated in the Ehrlichia transmission cycle. Our research intertwines multiple bird and tick species in the North American pathogen system, highlighting the need for continued research focusing on birds as tick hosts and pathogen reservoirs in understudied parts of the United States.

Rickettsial Pathogens in Dogs and Ticks During an Epidemic of Rocky Mountain Spotted Fever in Ensenada, Baja California, México

A Rocky Mountain spotted fever (RMSF) epidemic has spread through the state of Baja California, Mexico over the last decade and a half, beginning in Mexicali, and subsequently to Tijuana and to Ensenada by 2018. In October of 2022, we surveyed dogs and homes in randomly selected Áreas Geoestadisticas Básicas (AGEBs) with and without reported human cases. Brown dog ticks (Rhipicephalus sanguineus sensu lato) were found on 33.9% of dogs and in the yards of 23.6% of homes. Homes from AGEBs with cases had over a 6-fold increased odds of ticks being present in the yard than AGEBs without reported cases. Both dogs that were permitted to roam and the presence of roaming dogs in the neighborhood were strongly associated with tick infestation of dogs and homes. No ticks or blood samples were polymerase chain reaction-positive for Rickettsia (R.) rickettsii, the causative agent of RMSF, although 54.6% of dogs were seropositive for spotted fever group rickettsiae, and 17.4% were seropositive for typhus group rickettsiae. R. massiliae and R. felis were detected in eight (1.3%) and 29 (4.8%) ticks, respectively; and R. felis was also detected in eight (4.6%) dog blood samples. Although the pathogenic potential of these other rickettsial species and their role in RMSF transmission remains unclear, our data on tick burdens in dogs and homes as risk factors for RMSF exposure provide further support to the pivotal need to reduce tick burdens and the numbers of roaming dogs to successfully manage the RMSF epidemic in northern Mexico.

Congeneric Rodents Differ in Immune Gene Expression: Implications for Host Competence for Tick-Borne Pathogens

Mice in the genus Peromyscus are abundant and geographically widespread in North America, serving as reservoirs for zoonotic pathogens, including Borrelia burgdorferi (B. burgdorferi), the causative agent of Lyme disease, transmitted by Ixodes scapularis ticks. While the white-footed mouse (Peromyscus leucopus (P. leucopus)) is the primary reservoir in the United States, the deer mouse (P. maniculatus), an ecologically similar congener, rarely transmits the pathogen to biting ticks. Understanding the factors that allow these similar species to serve as a poor and competent reservoir is critical for understanding tick-borne disease ecology and epidemiology, especially as climate change expands the habitats where ticks can transmit pathogens. Our study investigated immunological differences between these rodent species. Specifically, we compared the expression of six immune genes (i.e., TLR-2, IFN-γ, IL-6, IL-10, GATA-3, TGF-β) broadly involved in bacterial recognition, elimination, and/or pathology mitigation in ear biopsies collected by the National Ecological Observatory Network (NEON) as part of their routine surveillance. A principal components analysis indicated that immune gene expression in both species varied in two dimensions: TLR2, IFN-γ, IL-6, and IL-10 (comprising PC1) and TGF-β and GATA3 (comprising PC2) expression tended to covary within individuals. However, when we analyzed expression differences of each gene singly between species, P. maniculatus expressed more TLR2, IL-6, and IL-10 but less IFN-γ and GATA3 than P. leucopus. This immune profile could partly explain why P. leucopus is a better reservoir for bacterial pathogens such as B. burgdorferi.

Biodiversity, prevalence, and risk factors associated with tick infestation of Indigenous Nigerian breed of hunting dogs in Kwara State, Nigeria

Ticks are hematophagous arthropods that cause paralysis, toxicosis, and more importantly, they harbor and transmit different pathogens affecting humans and animals. This study was aimed to investigate the species composition, richness, diversity indices, prevalence, and risk factors associated with tick infestation of indigenous Nigerian breed of hunting dogs in Kwara State, Nigeria. The study was conducted on 240 hunting dogs from six local government areas in Kwara State. The dogs were subjected to integumentary examinations and the collected ticks were collected in 70% ethanol and transported to the Laboratory where they were morphologically identified using standard entomological keys. Of the 240 hunting dogs sampled, 157 were infested with ticks representing 65.4% with a 95% CI of 59.2-71.2. A total of 1206 ticks were collected belonging to Amblyomma variegatum, Haemaphysalis leachi, Hyalomma rufipes, Rhipicephalus decoloratus, Rhipicephalus microplus, and Rhipicephalus linnaei (Audouin, 1826), with Rhipicephalus linnaei being the most prevalent. The biodiversity and species richness indices, the prevalence of the infestation patterns, cumulative counts and mean load, species of ticks based on their developmental stages and sexes, as well as the degree of tick infestation were determined. Age was the only risk index significantly associated with the infestation of ticks among hunting dogs in the study. These findings underscore the importance of implementing tick control programs for hunting dogs, which may serve as reservoirs of ticks and tick-borne pathogens for domestic and pet dogs and humans.

Scent detection dogs detect a species of hard tick, Dermacentor albipictus, with comparable accuracy and efficiency to traditional tick drag surveys

BACKGROUND

Accurate surveillance data are critical for addressing tick and tick-borne pathogen risk to human and animal health. Current surveillance methods for detecting invading or expanding tick species are limited in their ability to scale efficiently to state or national levels. In this study we explored the potential use of scent detection dogs to assist field surveys for a hard tick species: Dermacentor albipictus.

METHODS

We used a series of indoor and in situ training simulations to teach scent detection dogs to recognize D. albipictus scent, distinguish tick scent from associated vegetation, and develop a cautious search pattern. After training, we deployed both a scent detection dog survey team and a human-only survey team on transect and surveillance plot surveys then compared the detection rates and efficiency of both methods.

RESULTS

Scent detection dogs required more time and money to train on field surveys but were comparable to traditional tick drags when accounting for cost per unit area surveyed. There was a lack of agreement on positive (ticks present) versus negative (ticks not present) sites between the two methods, implying that neither method is particularly reliable at detecting D. albipictus.

CONCLUSIONS

Estimating detection bias and false negative rates for tick surveillance methods such as tick drags will be important for accurately evaluating tick-borne disease risk across space and into the future. We found scent detection dogs to be a reasonable alternative sampling approach to consider when ticks are at low abundance or patchily distributed such as during tick range expansion or novel invasions. Scent detection dogs may also be useful for sampling for ticks in areas or along surfaces that are difficult to sample with the traditional tick drag technique like at ports of entry or livestock competitions.

Different drivers, same tick: Effect of host traits, habitat, and climate on the infestation of three rodent species by larval D ermacentor ticks

Tick-borne diseases (TBDs) pose a growing concern for public and wildlife health. Understanding how host traits and environmental factors influence tick infestation in small mammals is critical for improving TBD management strategies. We investigated the presence and load of Dermacentor spp. Larvae on three rodent species: Peromyscus leucopus, Sigmodon hispidus, and Onychomys leucogaster, in the arid brushland ecosystem of South Texas. We used generalized linear models to quantify how host, habitat structure, and climatic variables impact tick presence and load. Our results show that different drivers influenced tick infestation across species; O. leucogaster experienced higher tick loads in smaller individuals and habitats with more leaf litter, whereas for P. leucopus, infestation was determined by the reproductive state and sex of the host as well as larval activity throughout the year. None of the variables measured in this study adequately explained the presence and parasite load in S. hispidus. These findings highlight the importance of considering species-specific interactions between host traits and environmental factors for understanding the dynamics of ticks infestation in rodents. Our results contribute to a growing body of evidence on the complexity of tick-rodent host dynamics and offer insights for predicting changes in parasitism patterns and managing wildlife health in response to a changing environment in South Texas.

Serosurveillance Identifies Bourbon Virus-Neutralizing Antibodies in Bobcats, Coyotes, and Red Foxes in Missouri

Background: Bourbon virus (BRBV) is an emerging pathogen that can cause severe and fatal disease in humans. BRBV is vectored by Amblyomma americanum (lone star ticks), which are widely distributed across the central, southern, and eastern United States. Wildlife species are potentially important for the maintenance and transmission of BRBV, but little is known about which species are involved, and what other factors play a role in their exposure to BRBV. Methods: To assess the exposure risk to BRBV among wildlife in the St. Louis, Missouri, area, we collected sera from 98 individuals, representing 6 different mammalian species from two locations in St. Louis County: Tyson Research Center (TRC) and WildCare Park (WCP) from fall 2021 to spring 2023. The sera were used in a BRBV neutralization assay to detect neutralizing antibodies and RT-qPCR for viral RNA analysis. We also sampled and compared the abundance of A. americanum ticks at the two locations and modeled which factors influenced BRBV seropositivity across species. Results: In TRC, we observed a high rate of seropositivity in raccoons (Procyon lotor, 23/25), and white-tailed deer (Odocoileus virginianus, 18/27), but a low rate in opossums (Didelphis virginiana, 1/18). Neutralizing antibodies were also detected in sampled TRC bobcats (Lynx rufus, 4/4), coyotes (Canis latrans, 3/3), and a red fox (Vulpes vulpes, 1/1). The virological analysis did not detect BRBV RNA in any serum samples. In contrast to TRC, all sera screened from WCP were negative for BRBV-specific neutralizing antibodies, and significantly fewer ticks were collected at WCP (31) compared with TRC (2316). Conclusions: Collectively, these findings suggest that BRBV circulates in multiple wildlife species in the St. Louis area and that tick density and host community composition may be important factors in BRBV ecology.

Tick feeding or vaccination with tick antigens elicits immunity to the Ixodes scapularis exoproteome in guinea pigs and humans

Ixodes scapularis is a primary vector of tick-borne pathogens in North America. Repeated exposure to these ticks can induce a humoral response to tick antigens and acquired tick resistance. However, identifying antigens contributing to this resistance is challenging because of the vast number of I. scapularis proteins secreted during feeding. To address this, we developed I. scapularis rapid extracellular antigen monitoring (IscREAM), a technique to detect antibody responses to more than 3000 tick antigens. We validated IscREAM with immunoglobulin G (IgG) from guinea pigs vaccinated with tick antigens, including a cement antigen cocktail that induced tick resistance. Furthermore, we explored the natural response to tick bites by profiling antigens recognized by IgG isolated from a tick-resistant individual, as well as from others with Lyme disease and tick-bitten guinea pigs and mice, to identify 199 recognized antigens. We observed that several antigens contained histamine-binding domains. This work enhances our understanding of the host immune response to I. scapularis and defines immunogen candidates for future antitick vaccines.

Linked empirical studies reveal the cumulative impact of acquired tick resistance across the tick life cycle

Host defenses affect tick feeding success, and thus survival and reproduction, but defensive traits have rarely been studied relative to tick population dynamics. We explored the effects of anti-tick resistance of three natural hosts against Dermacentor andersoni, the Rocky Mountain wood tick. Larval ticks were fed on Deer mice (Peromyscus maniculatus) and Cottontail rabbits (Sylvilagus nuttallii), and nymph and adult ticks were fed on cattle (Bos taurus). We compared feeding success and fecundity of ticks fed on naïve (never infested by ticks) or exposed (one prior tick infestation) hosts. We used these measures to parameterize simulations of D. andersoni population growth in a discrete time, geometric population model to understand the population-level consequences of anti-tick resistance. Prior infestation triggered tick resistance in all three host species and impacted all tick life stages. On tick-exposed hosts, an average of 23 % fewer ticks reached adulthood and adult females produced 32 % fewer larvae. Modest effects of tick resistance at each life stage had strong cumulative effects across the tick life cycle. Simulated tick population dynamics revealed that mean population growth (λ) is reduced 68 % when the life cycle is completed on hosts with prior tick exposure. Simulated populations feeding on exposed hosts were more likely to decline (λ<1) under conditions of low off-host survival and host-finding. This suggests acquired tick resistance may interact with environmental conditions and host availability to affect tick population dynamics. These data shed new light on naturally occurring biotic factors that may affect tick abundance and tick-borne pathogen transmission.

Prevalence of Rickettsia species phylotype G022 and Rickettsia tillamookensis in Ixodes pacificus nymphs and adults from Northern California

Ticks are known vectors of various pathogenic bacteria, including species of Rickettsia. Two novel Rickettsia species have been identified in adult Ixodes pacificus: Rickettsia species phylotype G022 in 2011 and R. tillamookensis in 2021. Currently, the pathogenic potential of these species found in I. pacificus remains unknown. This study aimed to determine the prevalence of phylotype G022 and R. tillamookensis in I. pacificus nymphs across different mean annual temperature and relative humidity zones in California. Adult ticks were also tested for phylotype G022. Ticks were collected from multiple locations in seven northern California counties and tested by real-time PCR. The overall prevalence of phylotype G022 and R. tillamookensis in nymphs (n = 550) was 5.3 % (95 % CI = 3.7 %-7.5 %) and 1.6 % (95 % CI=0.8 %-3.3 %), respectively. The overall prevalence of phylotype G022 in adult I. pacificus (n = 720) was 9.0 % (95 % CI = 7.2 %-11.3 %). Phylotype G022 infects nymphal I. pacificus across a broad geographic range. The prevalence of phylotype G022 was higher in the 11.7-13.3 °C (53-56°F) temperature zone, at 6.4 % (95 % CI = 4.5 %-9.2 %), compared to the 13.9-15 °C (57-59°F) zone, where the prevalence was 0.8 % (95 % CI = 0.2 %-4.6 %). In contrast, the prevalence of R. tillamookensis did not show a statistically significant difference between the two temperature zones, with 1.9 % (95 % CI = 0.9 %-4.1 % in the 11.7-13.3 °C (53-56°F) zone and 0.9 % (95 % CI = 0.2 %-4.9 %) in the 13.9-15 °C (57-59°F) zone. The detection of phylotype G022 in both questing nymphs and adults of I. pacificus suggests that it is transmitted transstadially. qPCR testing revealed no coinfections of G022 and R. tillamookensis in any of the nymphs. Although R. tillamookensis exhibited a lower overall prevalence in nymphs compared to phylotype G022, both bacteria exhibited a similar geographic distribution.

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.

The Genome of the American Dog Tick (Dermacentor variabilis)

The American dog tick (Dermacentor variabilis) is a vector of zoonotic pathogens in North America that poses emerging threats to public health. Despite its medical importance, genomic resources for D. variabilis remain scarce. Leveraging long-read nanopore sequencing, we generated a high-quality genome assembly for D. variabilis with a final size of 2.15 Gb, an N50 of 445 kb, and a BUSCO completeness score of 95.2%. Comparative BUSCO analyses revealed fewer duplicate genes in our assembly than in other Dermacentor genomes, indicating improved haplotype resolution. The mitochondrial genome, assembled as a single circular contig, clustered monophyletically with D. variabilis isolates from the Upper Midwest, corroborating regional phylogenetic relationships. Repetitive element analysis identified 61% of the genome as repetitive, dominated by LINEs and LTR elements, with 24% remaining unclassified, underscoring the need for further exploration of transposable elements in tick genomes. Gene annotation predicted 21,722 putative genes, achieving a protein BUSCO completeness of 80.88%. Additionally, genome-wide methylation analysis revealed 9.9% global 5mC methylation, providing the first insights into epigenetic modifications in D. variabilis. Further, nanopore sequencing detected Rickettsia montanensis and a non-pathogenic Francisella-like endosymbiont. These findings expand our understanding of tick genomics and epigenetics, offering valuable resources for comparative studies and evolutionary analyses.

Behavioral Manipulation of Ixodes scapularis by Ehrlichia muris eauclairensis: Implications for Tick-Borne Disease Transmission

Tick-borne diseases pose significant risks to both animals and humans, with emerging pathogens like Ehrlichia muris eauclairensis (EME) underscoring the need for a deeper understanding of pathogen-vector interactions and tick fitness. This study investigates the impact of EME on Ixodes scapularis nymphs, revealing significant behavioral changes in EME-positive ticks. These ticks exhibited increased movement speed, faster bite site-seeking for attachment, and prolonged feeding durations compared to control ticks. Proteomic analyses of the tick synganglion during resting and feeding phases identified 196 differentially expressed proteins in EME-positive ticks, including multiple proteins associated with nicotinic acetylcholine signaling pathways. Our findings indicated altered neuropeptide expression related to stimulus response and activity, suggesting changes in neurophysiology. This research provides the first evidence of behavioral manipulation by an Ehrlichia species, indicating that the tick nervous system is a site of bacterial influence and a potential target for interventions. These findings offer new insights into pathogen-vector dynamics that could lead to the development of transmission-blocking therapies, significantly impacting tick fitness and disease transmission.

A review of filarial nematodes parasitizing tick vectors: unraveling global patterns in species diversity, host associations, and interactions with tick-borne pathogens

Ticks are well-known vectors of pathogens, including filarial nematodes, which can affect animal and human health. This review synthesizes current knowledge of filarial nematodes that utilize ticks as vectors, focusing on the Onchocercidae. Five genera of onchocercid filarial nematodes (Cercopithifilaria, Cherylia, Cruorifilaria, Monanema, and Yatesia) have demonstrated vector-parasite relationships with ticks, while Acanthocheilonema has only demonstrated molecular detection without confirmed vector competence. Vector competence has been experimentally proven for several species through documented development to infective stages. However, our understanding of tick-borne filarial nematodes remains limited owing to insufficient detection efforts and methodological challenges. Detection methods include traditional dissection, advanced imaging techniques such as microcomputed tomography (micro-CT), and molecular approaches, each with distinct advantages and limitations. To address knowledge gaps, future research should focus on conducting large-scale surveys of tick populations and wildlife to investigate vector competence, health impacts, and coinfection dynamics. Multi-disciplinary collaboration and community involvement in tick surveillance will advance our understanding of tick-borne filarial nematode ecology and epidemiology. Future research priorities include confirming vector competence where only molecular detection exists, investigating natural transmission patterns, and understanding the mechanisms influencing successful development in tick vectors. By addressing these knowledge gaps through systematic surveillance and experimental studies, we can better understand these complex host-parasite-vector relationships and their implications for animal health.

Tick Control Strategies: Critical Insights into Chemical, Biological, Physical, and Integrated Approaches for Effective Hard Tick Management

Ticks and tick-borne diseases significantly impact animal health, public health, and economic productivity globally, particularly in areas where the wildlife-livestock interface complicates management. This review critically examines the current control strategies, focusing on chemical, biological, physical, and integrated pest management (IPM) approaches. Chemical acaricides, while effective, are increasingly challenged by resistance development and environmental concerns. Biological approaches, including natural predators and entomopathogenic fungi, and physical interventions, such as habitat modification, provide sustainable alternatives but require further optimization. IPM stands out as the most promising long-term solution, integrating multiple approaches to enhance efficacy while reducing environmental risks. Emerging innovations, such as nanotechnology-enhanced acaricides and next-generation vaccines, offer promising avenues for improved tick control. Addressing the complex challenges of tick management requires tailored strategies, interdisciplinary collaboration, and sustained research investment in both veterinary and public health contexts.

A customizable multiplex protein microarray for antibody testing and its application for tick-borne and other infectious diseases

Tick-borne infections are the most common vector-borne diseases in the USA. Ticks harbor and transmit several infections with Lyme disease being the most common tickborne infection in the US and Europe. Lack of awareness about tick populations, specific diagnostic tests, and overlapping signs and symptoms of tick-borne infections can often lead to misdiagnosis affecting treatment and the prevalence data reported especially for non-Lyme tick-borne infections. The diagnostic tests currently available for tick-borne diseases are severely limited in their ability to provide accurate results and cannot detect multiple pathogens in a single run. The multiplex protein microarray developed at Vibrant was designed to detect multiple serological antibodies thereby detecting exposure to multiple pathogens simultaneously. Our microarray in its present form can accommodate 400 antigens (molecules that can bind to specific antibodies) and can multiplex across antigen types, whole cell lysates, recombinant proteins, and peptides. A designed array containing multiple antigens of several microbes including Borrelia burgdorferi, the Lyme disease spirochete, was manufactured and evaluated. The immunoglobulin M (IgM) and G (IgG) responses against several tick-borne microbes and other infectious agents were analyzed for analytical and clinical performance. The microarray improved IgM and IgG sensitivities and specificities of individual microbes when compared with the respective gold standards. The testing was also performed in a single run in comparison to multiple runs needed for comparable testing standards. In summary, our study presents a flexible multiplex microarray platform that can provide quick results with high sensitivity and specificity for evaluating exposure to varied infectious agents especially tick-borne pathogens.

Identification, seasonal prevalence, and preferred attachment sites of ixodid tick species infesting cattle in four municipalities of the province of Tiaret, northwest Algeria

Ixodid ticks are important disease vectors that significantly impact animal health and cause considerable economic losses, particularly in tropical and subtropical countries. The aim of the present study was to determine the identity, seasonal distribution, and preferred attachment sites of adult ixodid tick species of cattle in four municipalities (Aïn El Hadid, Sidi Bakhti, Mechraa Safa, and Sidi Hosni) of the Province of Tiaret (north-west Algeria) between May 2022 and May 2023. A total of 317 cattle were randomly selected and examined for tick infestation; 108 (34.07%; 95% CI 28-39) were found to be infested by one or more species of ticks. The mean intensity of tick infestation was 16.22 ± 18.45 ticks per individual, while the mean abundance was 5.53 ± 13.21 ticks per examined cattle. Overall, 1,752 adult ixodid ticks were collected and identified, including 1,353 males and 399 females. Three genus and nine tick species were identified, including, H. excavatum (43.78%), H. marginatum (20.15%), H. lusitanicum (18.32%), H. scupense (8.73%), R. bursa (7.53%), H. impeltatum (0.74%), R. (Boophilus) annulatus (0.46%), R. sanguineus sensu lato (0.23%), and D. marginatus (0.06%). The highest discrepancy indices (D) were recorded for H. impeltatum (0.98), while the lowest was observed for H. excavatum (0.88). The overall discrepancy (D) values range from 0.88 to 0.98, indicating significant seasonal variability in the aggregation of ixodid ticks. The highest infestation rate recorded was in Ain El Hadid at 100%, followed by Sidi Bakhti at 79.76%, Mechraa Safa at 10.53%, and Sidi Hosni at 9.79%. H. excavatum, H. marginatum, H. lusitanicum, H. scupense, H. impeltatum, R. bursa, and R. (Boophilus) annulatus displayed significant variation across municipalities (p < 0.001). Seasonally, the highest abundance of adult ixodid tick infestations occurred in summer (38.01%), while the lowest was observed in autumn (17.29%). Significant seasonal variations were observed in the abundance of H. excavatum, H. marginatum, H. lusitanicum, and R. bursa (p < 0.001). Tick distribution was highest in zone 5 (95.43%), which includes the sternum, abdomen, udder, scrotum, and inner sides of the hind legs, while the lowest occurrence was in zone 1 (0.06%), which includes the head and ears. H. excavatum and H. lusitanicum showed a significant preference for Zone 5 (p < 0.001). The findings from the current study serve as a foundation for creating effective strategies to control tick populations on cattle in the Tiaret province.

Surveillance of tick-borne pathogens present in ticks (Acari: Ixodidae) removed from companion animals in Louisiana, USA

Current knowledge of tick distribution and tick-borne pathogen presence across Louisiana is limited. Collaborating with veterinarians across the state, ticks removed from companion animals were recovered and assessed for the presence of zoonotic pathogens. A large number of ticks (n = 959) were removed from companion animals and subsequently screened using qPCR for Anaplasma phagocytophilum, Babesia microti, Borrelia burgdorferi, Bartonella henselae, Ehrlichia chaffeensis, and spotted fever group Rickettsia. Five different tick species, Ixodes scapularis (54.5%), Amblyomma americanum (18.4%), Amblyomma maculatum (12.5%), Dermacentor variabilis (11.2%), and Rhipicephalus sanguineus (0.3%) from different regions of Louisiana were collected from October 2018 to July 2019. There were 15 PCR-positive ticks for Rickettsia parkeri (1.6% prevalence), and four ticks were positive for Ehrlichia chaffeensis (0.4% prevalence). This survey identifies ticks and tick-borne pathogens associated with companion animals and areas for future active surveillance.

Detection of Amblyomma maculatum and Rickettsia parkeri in prairies of Central Missouri

The destruction and decline of prairie habitats due to landscape repurposing have profoundly impacted the diversity of plant, animal, and insect life. In the Central United States, the reconstruction of prairie habitats from farmland is a widely applied strategy to raise diversity and recreate a healthy, complex ecosystem. In Central Missouri, we examine the consequences of reconstruction efforts on the prevalence of zoonotic diseases and their associated pathogens by performing tick-flagging at two prairie sites. In doing so, we have observed large populations of Dog ticks, Dermacentor variabilis, and Lone Star ticks, Amblyomma americanum, as well as the first recorded instance of the Gulf Coast tick, Amblyomma maculatum, in Callaway County. The Gulf Coast tick is traditionally found mainly along the Atlantic and Gulf Coast regions but has been undergoing geographic expansion in the last decade. Since detection in 2020, the number of Gulf Coast ticks has increased. Upon screening 193 Gulf Coast ticks in 105 pools via PCR, we found that 6.67 % of ticks were positive for pathogenic Rickettsia parkeri, which causes spotted fever rickettsiosis in animals and humans, with most ticks coming from the reconstructed prairie site. These observations suggest that reconstruction of prairie habitat has the potential to support the sylvatic cycle of Rickettsia parkeri. Collectively, our observations show that the reconstructed prairie are capable of harboring large tick populations as compared to remnant prairies and demonstrates a potential increase in disease risk as a result. This works highlights the importance of proactive surveillance of ticks, especially with land-use change.

Evaluation of tick salivary and midgut extracellular vesicles as anti-tick vaccines in White-tailed deer (Odocoileus virginianus)

Current tick control measures are focused on the use of synthetic acaricides and personal protective measures. However, the emergence of acaricide resistance and the maintenance of tick populations in wildlife has precluded the efficient management of ticks. Thus, host-targeted, non-chemical control measures are needed to reliably reduce ticks parasitizing sylvatic reservoirs. This project aimed to evaluate extracellular vesicles (EVs) from Amblyomma americanum as vaccine candidates for white-tailed deer (Odocoileus virginianus; WTD). Salivary gland (SG) and midgut (MG) EVs were isolated by ultracentrifugation. Three deer were vaccinated with SG and MG EVs and received two boosters at days 28 and 50. Two control deer were injected with adjuvant and PBS only. On day 58, WTD were infested with 100 A. americanum nymphs, 50 females, and 50 males that were allowed to feed to repletion. On-host and off-host mortality, tick engorgement weight, nymph molting, time to oviposition, and egg hatchability were evaluated. Serum samples were recovered every seven days until the last day of tick drop off, and then at one year (Y1) and 1-year and 1-month (Y1M1). Vaccination resulted in seroconversion and significant increases in total IgG levels that remained significantly higher than controls and pre-vaccination levels at Y1 and Y1M1. No negative effects were observed in nymphs, but on-host mortality of female A. americanum was significantly higher in vaccinated animals. No effects were observed on reproductive parameters. These results indicate that proteins within female tick SG and MG vesicles are not good candidates for vaccine design against nymphs; however, the on-host adult mortality suggests that tick EVs harbor protective antigens against A. americanum females.

Features of Consistent Powassan Virus Lineage II Focus in Southern Maine, United States

Powassan virus lineage II or deer tick virus (DTV) is a rare but increasingly reported human infection in the United States transmitted by Ixodes scapularis ticks. The virus is thought to be maintained in environmental foci that are optimal for tick and vertebrate reservoirs, but details on DTV ecology are poorly understood. We investigated DTV tick infection rates and reservoir host abundance in a focus of consistent DTV activity in Maine, USA. Host and tick abundance, vegetation, and microclimate conditions were measured in three forest sites representing increasing invasive understory infestation. Sites were selected representing native understory, mixed vegetation with some invasive Japanese barberry (Berberis thunbergii), and a highly invasive site dominated by Japanese barberry. Japanese barberry in the mixed vegetation site averaged 1 m in height with space between plants, whereas the highly invasive site had impenetrable Japanese barberry over 1.5 m. The DTV infection rate was greater in the highly invasive site. Density of I. scapularis ticks were significantly lower in the native forest site, and no DTV was found. Another feature of the DTV focus was more stable humid microclimate throughout the year compared with the other sites and a nearby continuous section of forest, consistent with reports from Connecticut, USA. We conclude that invasive Japanese barberry stands provide favorable and consistent microclimate conditions to maintain high DTV infection rates annually among questing I. scapularis ticks. Understanding environmental and landscape features that support high infection rates could lead to the identification of high-risk habitats for contracting DTV.

Distribution and diversity of ticks determined by environmental factors in Ningxia, China

Ticks are important vectors of zoonotic pathogens, and represent an increasing threat for human and animal health. Considering the complex natural environments of Ningxia Hui Autonomous Region, China, we expect the diverse tick species in this region. Here, we conduct a field survey on parasitic and host-seeking ticks. A total of 10,419 ticks were collected, which belonged to nine species of four genera. There were significant differences in terms of vegetation index, altitude, and seven climatic factors among the four tick genera -Hyalomma, Dermacentor, Haemaphysalis, and Ixodes, except between Haemaphysalis and Ixodes, where no significant differences were observed in these factors. The ecological niche modelling revealed that the suitable habitats for Hyalomma asiaticum was in the northwest Ningxia, with annual ground surface temperature as the most important factor. The suitable area for Dermacentor nuttalli was in the southwest and eastern regions of Ningxia with elevation as the highest contribution. D. silvarum was best suited to the southern Ningxia also with elevation as the most important factor. The four tick species including Haemaphysalis longicornis, Hae. qinghaiensis, Hae. japonica, and Ixodes persulcatus were best suited to the southernmost Ningxia with annual precipitation as the main factors for Hae. longicornis and elevation for the other three ticks. The results of predicted potential distribution of different tick species provide a scientific basis for the prevention and control of ticks and tick-borne diseases in the region. Furthermore, the subsequent impacts of the Greening Program to regain forests and grasslands from former agricultural lands in Ningxia on tick population dynamics deserve further investigation.

Maximizing and sustaining the efficacy of tick tubes for management of Ixodes scapularis through optimized deployment strategies

The number of tick-borne disease cases continues to rise in the United States, with Lyme disease the most frequently reported vector-borne disease nationally. Practical and effective tick control tools and strategies are needed to reduce tick encounters and tick-borne disease risk. Tick management tubes have shown varying efficacy when used as part of a tick management plan. To evaluate factors contributing to the efficacy of tick management tubes, this study assessed changes in tick tube deployment on tick burden on wild-caught Peromyscus mice, a primary reservoir for the bacterium causing Lyme disease, in Pennsylvania from 2021 to 2023. Over 2 years, tick tubes were deployed starting at different times of the year, with cotton removal from the tubes assessed every 2 weeks from April to November and tick burden on wild-caught mice assessed every 2 months from April to October of each year. The effect of distance between tick management tubes was assessed in year 3 of this study, with mouse tick burden assessed pre- and post-treatment with tick tubes at varying intervals in a field setting. There was a significant reduction in mouse tick burden between treated and control transects, and pre- and post-treatment transects. Tick tube distance did not affect cotton removal or tick burden on mice. Still, cotton removal was highest in September-October, and amount removed increased the longer tick tubes were deployed in the field, highlighting the long-term benefits of using tick tubes as part of an integrated tick management plan. Future investigations to evaluate the impact of tick management tubes on tick nymph density and infection would be valuable for assessing the effectiveness of tick management tubes in reducing tick bite risk.

WITHDRAWN: Detection of Amblyomma maculatum and Rickettsia parkeri in prairies of Central Missouri

This article has been withdrawn: please see Elsevier Policy on Article Withdrawal (https://www.elsevier.com/about/policies/article-withdrawal). This article has been withdrawn at the request of the editor and publisher. The publisher regrets that an error occurred which led to the premature publication of this paper. This error bears no reflection on the article or its authors. The publisher apologizes to the authors and the readers for this unfortunate error.

A set of diagnostic tests for detection of active Babesia duncani infection

OBJECTIVES

Human babesiosis is an emerging and potentially fatal tick-borne disease caused by intraerythrocytic parasites of the Babesia genus. Among these, Babesia duncani is particularly notable for causing severe and life-threatening illness in humans. Accurate diagnosis and effective disease management hinge on the detection of active B. duncani infections. While molecular assays are available to detect the parasite in blood, a reliable method for identifying biomarkers of active infection remains elusive.

METHODS

We developed the first B. duncani antigen capture assays, targeting two immunodominant antigens, BdV234 and BdV38. These assays were validated using established in vitro and in vivo B. duncani infection models, and following drug treatment.

RESULTS

The assays demonstrated no cross-reactivity with other species such as B. microti, B. divergens, Babesia MO1, or Plasmodium falciparum, and can detect as few as 115 infected erythrocytes/µl of blood. Screening of 1731 blood samples from various biorepositories, including samples previously identified as Lyme and/or B. microti-positive, as well as new specimens from wild mice, revealed no evidence of B. duncani infection or cross-reactivity.

CONCLUSIONS

These assays hold significant promise for various applications, including point-of-care testing for the early detection of B. duncani in patients, field tests for screening reservoir hosts, and high-throughput screening of blood samples intended for transfusion.

An Integrated Approach to an Emerging Problem: Implementing a Whole Year of Camera Trap Survey in Evaluating the Impact of Wildlife on Tick Abundance

Tick-borne zoonoses are an emerging health issue. The expansion of ticks is mainly driven by climatic changes but also by new approaches to the management of the natural environment, increasing the abundance of vertebrate host species and thus the potential exposure to tick bites for both humans and companion animals. In this context, a holistic approach to studying ticks' ecology is required. In the present work, we shed light on the link between environmental tick abundance (global and specific of Ixodes ricinus nymphs, as the highest zoonotic threat) and the temporal occupancy of wildlife host species retrieved from camera traps (namely, wild ruminants, mesocarnivores and wild boar). We modelled this relationship by integrating abiotic factors relevant to tick survival, such as the vegetation cover and saturation deficit, and estimated the accuracy of prediction. To collect these data, we deployed camera traps in a peri-urban Natural Park in Northwest Italy to monitor wildlife for 1 whole year while collecting ticks in front of camera traps by dragging transects every 2 weeks. Overall, wildlife temporal occupancy showed an additive impact on tick abundance for species that are preferential hosts (deer and mesocarnivores) and a detractive impact for wild boar, which also presented a lower tick burden, particularly with regard to the tick species collected in the environment (mainly I. ricinus and Haemaphysalis punctata). Accuracy of prediction was higher for I. ricinus nymphs rather than the global model. Temporal fluctuations in the tick population were also highlighted. Wildlife temporal occupancy was not constant and varied between seasons according to feeding habits. In conclusion, we highlighted the utility of camera trap data to investigate tick ecology and acarological risk. This information is crucial in informing monitoring and prevention strategies to decrease the risk of tick bites in humans and thus zoonotic risk of tick-borne diseases.

Relating Wildlife Camera Trap Data to Tick Abundance: Testing the Relationship in Different Habitats

The increase in acarological risk of tick bites is significantly driven by profound changes in landscape, which alter the density and distribution of wildlife that support tick populations. As a result of habitat shifts and land abandonment, which create environments conducive to tick proliferation, the risk of disease transmission to humans and animals is increasing. In this context, it is important to explore tick ecology by applying a comprehensive methodology. In this study, we examined the relationship between wildlife temporal occupancy and tick abundance in two distinct regions: an alpine hunting district and a natural park in the Apennines. For each sampling point, we calculated wildlife temporal occupancy from camera trap pictures and estimated ticks' abundance from dragging transects in the area immediately surrounding camera traps. In modelling the relationship between those two variables, we included abiotic factors such as saturation deficit, normalized difference vegetation index, and altitude. Results show the importance of altitude and wildlife temporal occupancy (itself related to different habitat and land management characteristics) on the ecology of questing ticks. If employed in management decisions for natural environments, such information is useful to modulate the acarological risk and thus the risk of tick-borne pathogens' transmission.

Host-pathogen associations inferred from bloodmeal analyses of Ixodes scapularis ticks in a low biodiversity setting

Tick-borne pathogen emergence is dependent on the abundance and distribution of competent hosts in the environment. Ixodes scapularis ticks are generalist feeders, and their pathogen infection prevalence depends on their relative feeding on local competent and non-competent hosts. The ability to determine what host a larval life stage tick fed on can help predict infection prevalence, emergence, and spread of certain tick-borne pathogens and the risks posed to public health. Here, we use a newly developed genomic target-based technique to detect the source of larval bloodmeals by sampling questing nymphs from Block Island, RI, a small island with a depauperate mammalian community. We used previously designed specific assays to target all known hosts on this island and analyzed ticks for four human pathogenic tick-borne pathogens. We determined the highest proportion of larvae fed on avian species (42.34%), white-footed mice (36.94%), and white-tailed deer (20.72%) and occasionally fed on feral cats, rats, and voles, which are in low abundance on Block Island. Additionally, larvae that had fed on white-footed mice were significantly more likely to be infected with Borrelia burgdorferi and Babesia microti, while larvae that had fed on white-footed mice or white-tailed deer were significantly more likely to be infected with, respectively, mouse- and deer-associated genotypes of Anaplasma phagocytophilum. The ability to detect a nymph's larval host allows for a better understanding of tick feeding behavior, host distribution, pathogen prevalence, and zoonotic risks to humans, which can contribute to better tick management strategies.

IMPORTANCE

Tick-borne diseases, such as Lyme disease, babesiosis, and anaplasmosis, pose significant public health burdens. Tick bloodmeal analysis provides a noninvasive sampling method to evaluate tick-host associations and combined with a zoonotic pathogen assay, can generate crucial insights into the epidemiology and transmission of tick-borne diseases by identifying potential key maintenance hosts. We investigated the bloodmeals of questing Ixodes scapularis nymphs. We found that avian hosts, white-footed mice, and white-tailed deer fed the majority of larval ticks and differentially contributed to the prevalence of multiple tick-borne pathogens and pathogen genotypes in a low biodiversity island setting. Unraveling the intricate network of host-vector-pathogen interactions will contribute to improving wildlife management and conservation efforts, to developing targeted surveillance, and vector and host control efforts, ultimately reducing the incidence of tick-borne diseases and improving public health.

Lime for Lyme: Treatment of Leaf Litter with Dolomitic Lime Powder Impairs Activity of Immature Ixodes scapularis Ticks

Background: Tick-borne diseases are an emerging threat to public health throughout the temperate world, leading to a growing field of research aimed at developing and testing intervention strategies for reducing human-tick encounters or prevalence of infection in ticks. Various wide-spectrum chemical acaricides have proven effective for controlling tick populations, but many of these have potential deleterious side-effects on health and the environment. In addition to chemical acaricides, certain compounds such as diatomaceous earth have been shown to have physical acaricidal properties. We hypothesized that dolomitic lime (CaMg(CO3)2, a corrosive, desiccant mineral that is already used extensively in agricultural and forestry contexts to balance the pH of soils, may affect ticks' locomotory activity, habitat position, or survival and that this should manifest as a reduction in the number of questing ticks collected by dragging. Objective: This study aimed to formally assess this hypothesis in a controlled laboratory setting. Methods: We carried out a microcosm experiment, with one control and three treated microcosm trays, each replicating the natural substrate characterizing I. scapularis habitat in northeastern North America. Each tray was infested with 200 living larvae and 50 nymphs, and then treated with 0 (control), 50, 100, or 500 g/m2 of lime powder. Ticks were collected by microdragging 24 and 72 h postliming. Results: Efficacy of liming at reducing the number of collected questing ticks ranged from 87% to 100% for larvae and 0% to 69% for nymphs 24 h postliming and from 91% to 93% for larvae and -47% to 65% for nymphs 72 postliming. Conclusion: This study provides the first experimental evidence of the potential efficacy of liming for impairing activity of questing immature ticks. Given that lime is a low-cost material, that methods for widespread application in deciduous woodlands already exist, and that it has been documented as having a limited negative impact on the environment, further assessment of lime application as a public health risk reduction intervention for tick-borne diseases is warranted.

Spatio-temporal patterns of tick-borne disease diagnoses in Indiana, USA (2009-2018)

AIMS

Although tick-borne disease (TBD) incidence has increased in the United States (U.S.) in the past decade, new evidence suggests that notifiable diseases surveillance records may not accurately reflect the true magnitude of TBD diagnoses. Furthermore, while regional electronic health records (EHR) are readily accessible their potential use as a more stable and consistent source of TBD diagnoses data has remained largely unexplored.

METHODS AND RESULTS

In this study, we used EHR from a database of more than 100 hospitals, healthcare networks, and insurance providers in Indiana, U.S., to better understand incidence, spatio-temporal and demographic distribution of TBD Diagnoses from 2009-2018. Our results revealed that in Indiana, from 2009 to 2018, there were 5173 unique TBD Diagnoses across three diagnoses categories: Lyme disease (72.5%, n = 3751), Rickettsioses (12.0%, n = 623) and Other TBD Diagnoses (15.4%, n = 799). Using EHR, the average yearly Lyme disease diagnoses was more than double the cases obtained using notifiable disease surveillance data for the same period. Patients with a TBD Diagnoses were generally older (ages 45-59) and less racially diverse (96.3% white). Rickettsiosis diagnoses were reported more among male patients (55.2%), while Lyme disease diagnoses were higher among female patients (57.1%). Temporal data illustrated higher frequencies of diagnoses from May to July. Hot spot analysis identified a Lyme disease hot spot in northwest Indiana, while hotspots of Rickettsiosis and Other TBD Diagnoses category were identified in southwest Indiana. Extrapolated to the Indiana population, chi-squared (χ2) tests of independence revealed that the observed distribution of TBD diagnoses in our data was significantly different from the expected distribution in the Indiana population-based race, gender and age groups.

CONCLUSIONS

Our study findings demonstrate that in Indiana, EHR provide a stable data source for elucidating TBD disease burden and for monitoring spatio-temporal trends in TBD diagnoses.

No evidence of Bartonella infections in host-seeking Ixodes scapularis and Ixodes pacificus ticks in the United States

BACKGROUND

Bartonella spp. infect a variety of vertebrates throughout the world, with generally high prevalence. Several Bartonella spp. are known to cause diverse clinical manifestations in humans and have been recognized as emerging pathogens. These bacteria are mainly transmitted by blood-sucking arthropods, such as fleas and lice. The role of ticks in the transmission of Bartonella spp. is unclear.

METHODS

A recently developed quadruplex polymerase chain reaction (PCR) amplicon next-generation sequencing approach that targets Bartonella-specific fragments on gltA, ssrA, rpoB, and groEL was applied to test host-seeking Ixodes scapularis ticks (n = 1641; consisting of 886 nymphs and 755 adults) collected in 23 states of the eastern half of the United States and Ixodes pacificus ticks (n = 966; all nymphs) collected in California in the western United States for the presence of Bartonella DNA. These species were selected because they are common human biters and serve as vectors of pathogens causing the greatest number of vector-borne diseases in the United States.

RESULTS

No Bartonella DNA was detected in any of the ticks tested by any target.

CONCLUSIONS

Owing to the lack of Bartonella detection in a large number of host-seeking Ixodes spp. ticks tested across a broad geographical region, our results strongly suggest that I. scapularis and I. pacificus are unlikely to contribute more than minimally, if at all, to the transmission of Bartonella spp.

Tick-Borne Illnesses in Emergency and Wilderness Medicine

This review highlights the causative organisms, clinical features, diagnosis, and treatment of the most common tick-borne illnesses in the United States, including Lyme disease, Rocky Mountain spotted fever, anaplasmosis, ehrlichiosis, tularemia, Powassan virus, and alpha-gal syndrome. Tick bite prevention strategies and some basic tick removal recommendations are also provided.

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.

The Acari Hypothesis, IV: revisiting the role of hygiene in allergy

Allergy and its manifestations were first appreciated in the 1870 s. Today, the mechanism by which specific substances elicit allergic reactions remains poorly understood. This is problematic from a healthcare perspective because the prevalence of allergic disease and its societal costs are substantial. Regarding mechanistic understanding of allergy, a new proposal, The Acari Hypothesis, has been forwarded. The Hypothesis, borne from consideration of alpha-gal syndrome, postulates that acarians, i.e., mites and ticks, are operative agents of allergy. By way of their pathogenic payloads and salivary pattern recognition receptor(s), acarians potentiate in human hosts the generation of IgE against acarian dietary elements. Those elements account for most, if not all, known human allergens. Inasmuch as acarian-human interactions occur on human epithelial surfaces, it is to be expected factors that influence the presence and/or operation of acarians on those surfaces influence the expression of allergic diseases. In this report, it is proposed that two adaptations of catarrhine primates, i.e., Old World monkeys, apes and humans, evolved to deter acarian species: firstly, the expansion of eccrine glands across the entirety of body surface area, and, secondly, the secretion of sweat by those glands. Contemporary hygienic practices that reduce and/or disrupt the operation of eccrine glands are likely responsible for the increase in allergic disease seen today.

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.

Serosurveillance and the first detection of Bourbon virus RNA in a wildlife host

Bourbon virus (BRBV) is an emerging pathogen that can cause severe and fatal disease in humans. BRBV is vectored by Amblyomma americanum (lone star ticks), which are widely distributed across the central, southern, and eastern United States. Wildlife species are potentially important for the maintenance and transmission of BRBV, but little is known about which species are involved, and what other factors play a role in the exposure to BRBV. To assess the exposure risk to BRBV among wildlife in the St. Louis area, we collected sera from 98 individuals, representing 6 different mammalian species from two locations in St. Louis County: Tyson Research Center (TRC) and WildCare Park (WCP) from fall 2021 to spring 2023. The sera were used in a BRBV neutralization assay to detect neutralizing antibodies and RT-qPCR for viral RNA analysis. We also sampled and compared the abundance of A. americanum ticks at the two locations and modeled which factors influenced BRBV seropositivity across species. In TRC, we observed a high rate of seropositivity in raccoons (Procyon lotor, 23/25), and white-tailed deer (Odocoileus virginianus, 18/27), but a low rate in opossums (Didelphis virginiana, 1/18). Neutralizing antibodies were also detected in sampled TRC bobcats (Lynx rufus, 4/4), coyotes (Canis latrans, 3/3), and a red fox (Vulpes vulpes, 1/1). The virological analysis identified BRBV RNA in one of the coyote serum samples. In contrast to TRC, all sera screened from WCP were negative for BRBV-specific neutralizing antibodies, and significantly fewer ticks were collected at WCP (31) compared to TRC (2,316). Collectively, these findings suggest that BRBV circulates in multiple wildlife species in the St. Louis area and that tick density and host community composition may be important factors in BRBV ecology.

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.

Widespread Circulation of Tick-Borne Viruses in Virginia-Evidence of Exposure to Heartland, Bourbon, and Powassan Viruses in Wildlife and Livestock

Emerging tick-borne viruses such as Powassan virus (POWV), Bourbon virus (BRBV), and Heartland virus (HRTV), whilst rare, can cause severe health problems in humans. While limited clinical cases have been reported thus far in Virginia, the presence of tick-borne viruses poses a serious health threat, and the extent of their prevalence in Virginia is unknown. Here, we sought evidence of POWV, BRBV, and HRTV exposure in Virginia via a serological assessment of wildlife and livestock. Wildlife in Virginia were found to be seropositive against POWV (18%), BRBV (8%), and HRTV (5%), with western and northern regions of the state having a higher prevalence. Multiple wildlife species were shown to have been exposed to each virus examined. To a lesser extent, cattle also showed exposure to tick-borne viruses, with seroprevalences of 1%, 1.2%, and 8% detected in cattle against POWV, BRBV, and HRTV, respectively. Cross-reactivity against other known circulating mosquito-borne flaviviruses was ruled out. In conclusion, there is widespread exposure to tick-borne viruses in western and northern Virginia, with exposure to a diverse range of animal populations. Our study provides the first confirmation that HRTV is circulating in the Commonwealth. These findings strengthen the existing evidence of emerging tick-borne viruses in Virginia and highlight the need for public health vigilance to avoid tick bites.

A Set of Diagnostic Tests for Detection of Active Babesia duncani Infection

Human babesiosis is a rapidly emerging and potentially fatal tick-borne disease caused by intraerythrocytic apicomplexan parasites of the Babesia genus. Among the various species of Babesia that infect humans, B. duncani has been found to cause severe and life-threatening infections. Detection of active B. duncani infection is critical for accurate diagnosis and effective management of the disease. While molecular assays for the detection of B. duncani infection in blood are available, a reliable strategy to detect biomarkers of active infection has not yet been developed. Here, we report the development of the first B. duncani antigen capture assays that rely on the detection of two B. duncani -exported immunodominant antigens, BdV234 and BdV38. The assays were validated using blood samples from cultured parasites in human erythrocytes and B. duncani -infected laboratory mice at different parasitemia levels and following therapy. The assays display high specificity with no cross-reactivity with B. microti , B. divergens , Babesia MO1, or P. falciparum. The assay also demonstrates high sensitivity, detecting as low as 115 infected erythrocytes/µl of blood. Screening of 1,731 blood samples from diverse biorepositories, including previously identified Lyme and/or B. microti positive human samples and new specimens from field mice, showed no evidence of B. duncani infection in these samples. The assays could be useful in diverse diagnostic scenarios, including point-of-care testing for early B. duncani infection detection in patients, field tests for screening reservoir hosts, and high-throughput screening such as blood collected for transfusion.

Short summary

We developed two ELISA-based assays, BdACA38 and BdACA234, for detecting B. duncani , a potentially fatal tick-borne parasite causing human babesiosis. The assays target two immunodominant antigens, BdV234 and BdV38, demonstrating high specificity (no cross-reactivity with other Babesia species or Plasmodium falciparum ) and sensitivity (detecting as low as 115 infected erythrocytes/µl). The assays were validated using in vitro-cultured parasites and infected mice. Screening diverse blood samples showed no evidence of B. duncani active infection among 1,731 human and field mice blood samples collected from the north-eastern, midwestern, and western US. These assays offer potential in diverse diagnostic scenarios, including early patient detection, reservoir animal screening, and transfusion-transmitted babesiosis prevention.

Vaccine development: obligate intracellular bacteria new tools, old pathogens: the current state of vaccines against obligate intracellular bacteria

Obligate intracellular bacteria have remained those for which effective vaccines are unavailable, mostly because protection does not solely rely on an antibody response. Effective antibody-based vaccines, however, have been developed against extracellular bacteria pathogens or toxins. Additionally, obligate intracellular bacteria have evolved many mechanisms to subvert the immune response, making vaccine development complex. Much of what we know about protective immunity for these pathogens has been determined using infection-resolved cases and animal models that mimic disease. These studies have laid the groundwork for antigen discovery, which, combined with recent advances in vaccinology, should allow for the development of safe and efficacious vaccines. Successful vaccines against obligate intracellular bacteria should elicit potent T cell memory responses, in addition to humoral responses. Furthermore, they ought to be designed to specifically induce strong cytotoxic CD8+ T cell responses for protective immunity. This review will describe what we know about the potentially protective immune responses to this group of bacteria. Additionally, we will argue that the novel delivery platforms used during the Sars-CoV-2 pandemic should be excellent candidates to produce protective immunity once antigens are discovered. We will then look more specifically into the vaccine development for Rickettsiaceae, Coxiella burnetti, and Anaplasmataceae from infancy until today. We have not included Chlamydia trachomatis in this review because of the many vaccine related reviews that have been written in recent years.

Borreliella burgdorferi factor H-binding proteins are not required for serum resistance and infection in mammals

The causative agent of Lyme disease (LD), Borreliella burgdorferi, binds factor H (FH) and other complement regulatory proteins to its surface. B. burgdorferi B31 (type strain) encodes five FH-binding proteins (FHBPs): CspZ, CspA, and the OspE paralogs OspEBBN38, OspEBBL39, and OspEBBP38. This study assessed potential correlations between the production of individual FHBPs, FH-binding ability, and serum resistance using a panel of infectious B. burgdorferi clonal populations recovered from dogs. FHBP production was assessed in cultivated spirochetes and by antibody responses in naturally infected humans, dogs, and eastern coyotes (wild canids). FH binding specificity and sensitivity to dog and human serum were also assessed and compared. No correlation was observed between the production of individual FHBPs and FH binding with serum resistance, and CspA was determined to not be produced in animals. Notably, one or more clones isolated from dogs lacked CspZ or the OspE proteins (a finding confirmed by genome sequence determination) and did not bind FH derived from canines. The data presented do not support a correlation between FH binding and the production of individual FHBPs with serum resistance and infectivity. In addition, the limited number and polymorphic nature of cp32s in B. burgdorferi clone DRI85A that were identified through genome sequencing suggest no strict requirement for a defined set of these replicons for infectivity. This study reveals that the immune evasion mechanisms employed by B. burgdorferi are diverse, complex, and yet to be fully defined.

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.

Diversity of species and geographic distribution of tick-borne viruses in China

Introduction

Tick-borne pathogens especially viruses are continuously appearing worldwide, which have caused severe public health threats. Understanding the species, distribution and epidemiological trends of tick-borne viruses (TBVs) is essential for disease surveillance and control.

Methods

In this study, the data on TBVs and the distribution of ticks in China were collected from databases and literature. The geographic distribution of TBVs in China was mapped based on geographic locations of viruses where they were prevalent or they were detected in vector ticks. TBVs sequences were collected from The National Center for Biotechnology Information and used to structure the phylogenetic tree.

Results

Eighteen TBVs from eight genera of five families were prevalent in China. Five genera of ticks played an important role in the transmission of TBVs in China. According to phylogenetic analysis, some new viral genotypes, such as the Dabieshan tick virus (DTV) strain detected in Liaoning Province and the JMTV strain detected in Heilongjiang Province existed in China.

Discussion

TBVs were widely distributed but the specific ranges of viruses from different families still varied in China. Seven TBVs belonging to the genus Orthonairovirus of the family Nairoviridae such as Nairobi sheep disease virus (NSDV) clustered in the Xinjiang Uygur Autonomous Region (XUAR) and northeastern areas of China. All viruses of the family Phenuiviridae except Severe fever with thrombocytopenia syndrome virus (SFTSV) were novel viruses that appeared in the last few years, such as Guertu virus (GTV) and Tacheng tick virus 2 (TcTV-2). They were mainly distributed in the central plains of China. Jingmen tick virus (JMTV) was distributed in at least fourteen provinces and had been detected in more than ten species of tick such as Rhipicephalus microplus and Haemaphysalis longicornis, which had the widest distribution and the largest number of vector ticks among all TBVs. Parainfluenza virus 5 (PIV5) and Lymphatic choriomeningitis virus (LCMV) were two potential TBVs in Northeast China that could cause serious diseases in humans or animals. Ixodes persulcatus carried the highest number of TBVs, followed by Dermacentor nuttalli and H. longicornis. They could carry as many as ten TBVs. Three strains of Tick-borne encephalitis (TBEV) from Inner Mongolia Province clustered with ones from Russia, Japan and Heilongjiang Province, respectively. Several SFTSV strains from Zhejiang Province clustered with strains from Korea and Japan. Specific surveillance of dominant TBVs should be established in different areas in China.

Prompt diagnosis and appropriate treatment of Japanese spotted fever: A report of three cases

Background

Japanese Spotted Fever (JSF) is a Spotted Fever Group (SFG) rickettsiosis caused by Rickettsia japonica. More than 300 cases are diagnosed annually in Japan, and the number of reported cases has been increasing. Correct diagnoses depend on the triad of symptoms and signs, including fever, rash, and eschar, which can be seen at the site of vector bites. JSF is not life-threatening if treated appropriately without diagnostic delay but there are some fatal cases every year. This negligence leads to disseminated intravascular coagulation (DIC) and multiple organ failure (MOF), and poor prognoses, consequently. Prompt diagnosis of JSF is difficult when the aforementioned triad of signs and symptoms is not initially present.

Case report

This report describes three JSF cases: an 87-year-old woman with fever, shock, pancytopenia, DIC, and MOF; a 79-year-old man with fever and difficulty in movement; and a 78-year-old man with fever, general fatigue, and appetite loss. All patients had a rash and eschar, which led to prompt diagnosis and appropriate treatment immediately. All patients were treated without any complications.

Why should an emergency physician be aware of this?

As mentioned above, JFS can be fatal with delayed diagnoses and treatment initiations. The key for a prompt diagnosis is to recognize the triad of symptoms and signs, which are not often present initially, and it makes JSF diagnosis challenging. Repeated comprehensive physical examinations are essential for prompt diagnosis and improve prognosis of JSF.

Survey on tick infestation in stray dogs in localities of Malaysia

The close relationship between dogs and humans has led to concerns regarding the transmission of zoonotic pathogens through ectoparasites such as ticks. This study aimed to investigate the occurrence of ticks and the intensity on stray dogs with specific risk factors (size, sex, neutering status, body part). Additionally, identifying the predilection sites of ticks on stray dogs was crucial for developing an effective tick control program in Malaysia. A cross-sectional study was conducted among 64 stray dogs from Kelantan and Selangor States. These dogs were subjected to integumentary examinations, collecting 431 ticks comprising Rhipicephalus sanguineus s.l. "tropical lineage" and Haemaphysalis bispinosa from 53 infested dogs. The overall occurrence of tick infestation was 82.81% (53/64), with an average intensity of 8.13 ticks (range: 1-17) per stray dog. All the potential risk factors considered in this study showed no statistically significant result (P value >0.05). The head, ear, and neck were the most preferred attachment sites for ticks. These findings underscore the importance of implementing tick control programs for stray dogs, which serve as reservoirs of ticks and tick-borne pathogens for owned dogs and humans.