Identification of a novel pathogenic Borrelia species causing Lyme borreliosis with unusually high spirochaetaemia: a descriptive study

Prevalence of Lyme Disease and Relapsing Fever Borrelia spp. in Vectors, Animals, and Humans within a One Health Approach in Mediterranean Countries

The genus Borrelia has been divided into Borreliella spp., which can cause Lyme Disease (LD), and Borrelia spp., which can cause Relapsing Fever (RF). The distribution of genus Borrelia has broadened due to factors such as climate change, alterations in land use, and enhanced human and animal mobility. Consequently, there is an increasing necessity for a One Health strategy to identify the key components in the Borrelia transmission cycle by monitoring the human-animal-environment interactions. The aim of this study is to summarize all accessible data to increase our understanding and provide a comprehensive overview of Borrelia distribution in the Mediterranean region. Databases including PubMed, Google Scholar, and Google were searched to determine the presence of Borreliella and Borrelia spp. in vectors, animals, and humans in countries around the Mediterranean Sea. A total of 3026 were identified and screened and after exclusion of papers that did not fulfill the including criteria, 429 were used. After examination of the available literature, it was revealed that various species associated with LD and RF are prevalent in vectors, animals, and humans in Mediterranean countries and should be monitored in order to effectively manage and prevent potential infections.

Machine learning based DNA melt curve profiling enables automated novel genotype detection

Surveillance for genetic variation of microbial pathogens, both within and among species, plays an important role in informing research, diagnostic, prevention, and treatment activities for disease control. However, large-scale systematic screening for novel genotypes remains challenging in part due to technological limitations. Towards addressing this challenge, we present an advancement in universal microbial high resolution melting (HRM) analysis that is capable of accomplishing both known genotype identification and novel genotype detection. Specifically, this novel surveillance functionality is achieved through time-series modeling of sequence-defined HRM curves, which is uniquely enabled by the large-scale melt curve datasets generated using our high-throughput digital HRM platform. Taking the detection of bacterial genotypes as a model application, we demonstrate that our algorithms accomplish an overall classification accuracy over 99.7% and perform novelty detection with a sensitivity of 0.96, specificity of 0.96 and Youden index of 0.92. Since HRM-based DNA profiling is an inexpensive and rapid technique, our results add support for the feasibility of its use in surveillance applications.

BS, Raghuraman V, Rajyaguru U, Llamera KE, Andrew L, Anderson AS, Hovius JW, Liberator PA, Simon R, Hao L. Development of a sequence-based in silico OspA typing method for Borrelia burgdorferi sensu lato

Lyme disease (LD), caused by spirochete bacteria of the genus Borrelia burgdorferi sensu lato, remains the most common vector-borne disease in the northern hemisphere. Borrelia outer surface protein A (OspA) is an integral surface protein expressed during the tick cycle, and a validated vaccine target. There are at least 20 recognized Borrelia genospecies, that vary in OspA serotype. This study presents a new in silico sequence-based method for OspA typing using next-generation sequence data. Using a compiled database of over 400 Borrelia genomes encompassing the 4 most common disease-causing genospecies, we characterized OspA diversity in a manner that can accommodate existing and new OspA types and then defined boundaries for classification and assignment of OspA types based on the sequence similarity. To accommodate potential novel OspA types, we have developed a new nomenclature: OspA in silico type (IST). Beyond the ISTs that corresponded to existing OspA serotypes 1-8, we identified nine additional ISTs that cover new OspA variants in B. bavariensis (IST9-10), B. garinii (IST11-12), and other Borrelia genospecies (IST13-17). The IST typing scheme and associated OspA variants are available as part of the PubMLST Borrelia spp. database. Compared to traditional OspA serotyping methods, this new computational pipeline provides a more comprehensive and broadly applicable approach for characterization of OspA type and Borrelia genospecies to support vaccine development.

Reply to Shah, J.S.; Ramasamy, R. Target Antigens in Western and Line Immunoblots for Supporting the Diagnosis of Lyme Disease. Comment on "Porwancher et al. Immunoblot Criteria for Diagnosis of Lyme Disease: A Comparison of CDC Criteria to Alternative Interpretive Approaches. Pathogens 2023, 12, 1282"

We are writing in response to comments made by Shah and Ramasamy [...].

Emerging Tick-borne Infections in the Upper Midwest and Northeast United States Among Patients With Suspected Anaplasmosis

Background

Emerging tick-transmitted illnesses are increasingly recognized in the United States (US). To identify multiple potential tick-borne pathogens in patients from the Upper Midwest and Northeast US with suspected anaplasmosis, we used state-of-the-art methods (polymerase chain reaction [PCR] and paired serology) to test samples from patients in whom anaplasmosis had been excluded.

Methods

Five hundred sixty-eight patients without anaplasmosis had optimal samples available for confirmation of alternative tick-borne pathogens, including PCR and/or paired serology (acute-convalescent interval ≤42 days).

Results

Among 266 paired serology evaluations, for which the median acute-convalescent sampling interval was 28 (interquartile range, 21-33) days, we identified 35 acute/recent infections (24 [9%] Borrelia burgdorferi; 6 [2%] Ehrlichia chaffeensis/Ehrlichia muris subsp eauclairensis [EC/EME]; 3 [1%] spotted fever group rickettsioses [SFGR], and 2 [<1%] Babesia microti) in 33 (12%) patients. Two had concurrent or closely sequential infections (1 B burgdorferi and EC/EME, and 1 B burgdorferi and SFGR). Using multiplex PCR and reverse-transcription PCR, we identified 7 acute infections (5/334 [1%] Borrelia miyamotoi and 2/334 [1%] B microti) in 5 (1%) patients, including 2 with B microti-B miyamotoi coinfection, but no Borrelia mayonii, SFGR, Candidatus Anaplasma capra, Heartland virus, or Powassan virus infections. Thus, among 568 patients with ruled-out anaplasmosis, 38 (6.7%) had ≥1 agent of tick-borne illness identified, with 33 patients (35 infections) diagnosed by paired serology and 5 additional patients (7 infections) by PCR.

Conclusions

By identifying other tick-borne agents in patients in whom anaplasmosis had been excluded, we demonstrate that emerging tick-borne infections will be identified if specifically sought.

Screening Marine Microbial Metabolites as Promising Inhibitors of Borrelia garinii: A Structural Docking Approach towards Developing Novel Lyme Disease Treatment

Lyme disease caused by the Borrelia species is a growing health concern in many parts of the world. Current treatments for the disease may have side effects, and there is also a need for new therapies that can selectively target the bacteria. Pathogens responsible for Lyme disease include B. burgdorferi, B. afzelii, and B. garinii. In this study, we employed structural docking-based screening to identify potential lead-like inhibitors against the bacterium. We first identified the core essential genome fraction of the bacterium, using 37 strains. Later, we screened a library of lead-like marine microbial metabolites (n = 4730) against the arginine deiminase (ADI) protein of Borrelia garinii. This protein plays a crucial role in the survival of the bacteria, and inhibiting it can kill the bacterium. The prioritized lead compounds demonstrating favorable binding energies and interactions with the active site of ADI were then evaluated for their drug-like and pharmacokinetic parameters to assess their suitability for development as drugs. Results from molecular dynamics simulation (100 ns) and other scoring parameters suggest that the compound CMNPD18759 (common name: aureobasidin; IUPAC name: 2-[(4R,6R)-4,6-dihydroxydecanoyl]oxypropan-2-yl (3S,5R)-3,5-dihydroxydecanoate) holds promise as a potential drug candidate for the treatment of Lyme disease, caused by B. garinii. However, further experimental studies are needed to validate the efficacy and safety of this compound in vivo.

A tick saliva serpin, IxsS17 inhibits host innate immune system proteases and enhances host colonization by Lyme disease agent

Lyme disease (LD) caused by Borrelia burgdorferi is among the most important human vector borne diseases for which there is no effective prevention method. Identification of tick saliva transmission factors of the LD agent is needed before the highly advocated tick antigen-based vaccine could be developed. We previously reported the highly conserved Ixodes scapularis (Ixs) tick saliva serpin (S) 17 (IxsS17) was highly secreted by B. burgdorferi infected nymphs. Here, we show that IxsS17 promote tick feeding and enhances B. burgdorferi colonization of the host. We show that IxsS17 is not part of a redundant system, and its functional domain reactive center loop (RCL) is 100% conserved in all tick species. Yeast expressed recombinant (r) IxsS17 inhibits effector proteases of inflammation, blood clotting, and complement innate immune systems. Interestingly, differential precipitation analysis revealed novel functional insights that IxsS17 interacts with both effector proteases and regulatory protease inhibitors. For instance, rIxsS17 interacted with blood clotting proteases, fXII, fX, fXII, plasmin, and plasma kallikrein alongside blood clotting regulatory serpins (antithrombin III and heparin cofactor II). Similarly, rIxsS17 interacted with both complement system serine proteases, C1s, C2, and factor I and the regulatory serpin, plasma protease C1 inhibitor. Consistently, we validated that rIxsS17 dose dependently blocked deposition of the complement membrane attack complex via the lectin complement pathway and protected complement sensitive B. burgdorferi from complement-mediated killing. Likewise, co-inoculating C3H/HeN mice with rIxsS17 and B. burgdorferi significantly enhanced colonization of mouse heart and skin organs in a reverse dose dependent manner. Taken together, our data suggests an important role for IxsS17 in tick feeding and B. burgdorferi colonization of the host.

Human Tick-Borne Diseases and Advances in Anti-Tick Vaccine Approaches: A Comprehensive Review

This comprehensive review explores the field of anti-tick vaccines, addressing their significance in combating tick-borne diseases of public health concern. The main objectives are to provide a brief epidemiology of diseases affecting humans and a thorough understanding of tick biology, traditional tick control methods, the development and mechanisms of anti-tick vaccines, their efficacy in field applications, associated challenges, and future prospects. Tick-borne diseases (TBDs) pose a significant and escalating threat to global health and the livestock industries due to the widespread distribution of ticks and the multitude of pathogens they transmit. Traditional tick control methods, such as acaricides and repellents, have limitations, including environmental concerns and the emergence of tick resistance. Anti-tick vaccines offer a promising alternative by targeting specific tick proteins crucial for feeding and pathogen transmission. Developing vaccines with antigens based on these essential proteins is likely to disrupt these processes. Indeed, anti-tick vaccines have shown efficacy in laboratory and field trials successfully implemented in livestock, reducing the prevalence of TBDs. However, some challenges still remain, including vaccine efficacy on different hosts, polymorphisms in ticks of the same species, and the economic considerations of adopting large-scale vaccine strategies. Emerging technologies and approaches hold promise for improving anti-tick vaccine development and expanding their impact on public health and agriculture.

Developing a Prospective Gestational Lyme Disease Study

Lyme disease in pregnancy is understudied. The few available reports of Borrelia infection during pregnancy collecting clinical outcomes, with or without confirmed fetal infection both in utero and neonatal, are limited to case reports and small series. Population-based studies are not available. We propose a prospective study of Borrelia infection during pregnancy based in obstetrical practices in both endemic and nonendemic areas, with long term follow-up of pregnancy outcomes and development assessment of offspring infected or exposed to Borrelia in utero using current serological, microscopic, culture, and molecular techniques. In addition to detection of Borrelia burgdorferi sensu stricto, additional Borrelia species and other pathogens known to be transmitted by ticks will be tested. Serial biospecimens including maternal and cord blood, maternal peripheral blood mononuclear cells and urine, and, when clinically indicated, amniotic fluid, chorionic villi, intrauterine cord blood, will be collected with clinical data, imaging, and for infections treatment medications. Offspring will be followed until age 5 years with annual developmental assessments to assess pregnancy outcomes. The study will require parallel development of a biorepository with strategies for management, data security and data sharing. A public-private partnership will be required to support the study.

Detection of Borrelia burgdorferi sensu lato species in host-seeking Ixodes species ticks in the United States

Lyme disease is the most commonly reported vector-borne disease in the United States and is transmitted by Ixodes scapularis in the eastern US and I. pacificus in the west. The causative agents, Borrelia burgdorferi sensu stricto (Bbss) and B. mayonii belong to the B. burgdorferi sensu lato (Bbsl) species complex. An additional eight species of Bbsl have been identified in Ixodes species ticks in the US, but their geographic distribution, vector associations, human encounter rates and pathogenicity in humans are poorly defined. To better understand the geographic distribution and vector associations of Bbsl spirochetes in frequent and infrequent human-biting Ixodes species ticks in the US, we previously screened 29,517 host-seeking I. scapularis or I. pacificus ticks and 692 ticks belonging to eight other Ixodes species for Borrelia spirochetes using a previously described tick testing algorithm that utilizes a combination of real-time PCR and Sanger sequencing for Borrelia species identification. The assay was designed to detect known human pathogens spread by Ixodes species ticks, but it was not optimized to detect Bbsl co-infections. To determine if such co-infections were overlooked particularly in ticks infected with Bbss, we retested and analyzed a subsample of 845 Borrelia infected ticks using a next generation sequencing multiplex PCR amplicon sequencing (MPAS) assay that can identify Borrelia species and Bbsl co-infections. The assay also includes targets that can molecularly confirm identifications of Ixodes species ticks to better inform pathogen-vector associations. We show that Bbss is the most prevalent species in I. scapularis and I. pacificus; other Bbsl species were rarely detected in I. scapularis and the only Bbsl co-infections identified in I. scapularis were with Bbss and B. mayonii. We detected B. andersonii in I. dentatus in the Mid-Atlantic and Upper Midwest regions, B. kurtenbachii in I. scapularis in the Upper Midwest, B. bissettiae in I. pacificus and I. spinipalpis in the Northwest, and B. carolinensis in I. affinis in the Mid-Atlantic and Southeast, and B. lanei in I. spinipalpis in the Northwest. Twelve of 62 (19.4%) Borrelia-infected I. affinis from the Mid-Atlantic region were co-infected with Bbss and B. carolinensis. Our data support the notion that Bbsl species are maintained in largely independent enzootic cycles, with occasional spill-over resulting in multiple Bbsl species detected in Ixodes species ticks.

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.

Ixodes scapularis nymph saliva protein blocks host inflammation and complement-mediated killing of Lyme disease agent, Borrelia burgdorferi

Tick serine protease inhibitors (serpins) play crucial roles in tick feeding and pathogen transmission. We demonstrate that Ixodes scapularis (Ixs) nymph tick saliva serpin (S) 41 (IxsS41), secreted by Borrelia burgdorferi (Bb)-infected ticks at high abundance, is involved in regulating tick evasion of host innate immunity and promoting host colonization by Bb. Recombinant (r) proteins were expressed in Pichia pastoris, and substrate hydrolysis assays were used to determine. Ex vivo (complement and hemostasis function related) and in vivo (paw edema and effect on Bb colonization of C3H/HeN mice organs) assays were conducted to validate function. We demonstrate that rIxsS41 inhibits chymase and cathepsin G, pro-inflammatory proteases that are released by mast cells and neutrophils, the first immune cells at the tick feeding site. Importantly, stoichiometry of inhibition analysis revealed that 2.2 and 2.8 molecules of rIxsS41 are needed to 100% inhibit 1 molecule of chymase and cathepsin G, respectively, suggesting that findings here are likely events at the tick feeding site. Furthermore, chymase-mediated paw edema, induced by the mast cell degranulator, compound 48/80 (C48/80), was blocked by rIxsS41. Likewise, rIxsS41 reduced membrane attack complex (MAC) deposition via the alternative and lectin complement activation pathways and dose-dependently protected Bb from complement killing. Additionally, co-inoculating C3H/HeN mice with Bb together with rIxsS41 or with a mixture (rIxsS41 and C48/80). Findings in this study suggest that IxsS41 markedly contributes to tick feeding and host colonization by Bb. Therefore, we conclude that IxsS41 is a potential candidate for an anti-tick vaccine to prevent transmission of the Lyme disease agent.

The influence of physiological and pathological perturbations on blood-brain barrier function

The blood-brain barrier (BBB) is located at the interface between the vascular system and the brain parenchyma, and is responsible for communication with systemic circulation and peripheral tissues. During life, the BBB can be subjected to a wide range of perturbations or stresses that may be endogenous or exogenous, pathological or therapeutic, or intended or unintended. The risk factors for many diseases of the brain are multifactorial and involve perturbations that may occur simultaneously (e.g., two-hit model for Alzheimer's disease) and result in different outcomes. Therefore, it is important to understand the influence of individual perturbations on BBB function in isolation. Here we review the effects of eight perturbations: mechanical forces, temperature, electromagnetic radiation, hypoxia, endogenous factors, exogenous factors, chemical factors, and pathogens. While some perturbations may result in acute or chronic BBB disruption, many are also exploited for diagnostic or therapeutic purposes. The resultant outcome on BBB function depends on the dose (or magnitude) and duration of the perturbation. Homeostasis may be restored by self-repair, for example, via processes such as proliferation of affected cells or angiogenesis to create new vasculature. Transient or sustained BBB dysfunction may result in acute or pathological symptoms, for example, microhemorrhages or hypoperfusion. In more extreme cases, perturbations may lead to cytotoxicity and cell death, for example, through exposure to cytotoxic plaques.

Direct Detection of Lyme Borrelia: Recent Advancement and Use of Aptamer Technology

Borrelia burgdorferi sensu lato (B. burgdorferi s.l.), which is predominantly spread by ticks, is the cause of Lyme disease (LD), also known as Lyme borreliosis, one of the zoonotic diseases affecting people. In recent years, LD has become more prevalent worldwide, even in countries with no prior records. Currently, Lyme Borrelia detection is achieved through nucleic acid amplification, antigen detection, microscopy, and in vitro culture. Nevertheless, these methods lack sensitivity in the early phase of the disease and, thus, are unable to confirm active infection. This review briefly discusses the existing direct detection methods of LD. Furthermore, this review also introduces the use of aptamer technology integrated with biosensor platforms to detect the Borrelia antigen. This aptamer technology could be explored using other biosensor platforms targeting whole Borrelia cells or specific molecules to enhance Borrelia detection in the future.

From Tick to Test: A Comprehensive Review of Tick-Borne Disease Diagnostics and Surveillance Methods in the United States

Tick-borne diseases (TBDs) have become a significant public health concern in the United States over the past few decades. The increasing incidence and geographical spread of these diseases have prompted the implementation of robust surveillance systems to monitor their prevalence, distribution, and impact on human health. This comprehensive review describes key disease features with the geographical distribution of all known tick-borne pathogens in the United States, along with examining disease surveillance efforts, focusing on strategies, challenges, and advancements. Surveillance methods include passive and active surveillance, laboratory-based surveillance, sentinel surveillance, and a One Health approach. Key surveillance systems, such as the National Notifiable Diseases Surveillance System (NNDSS), TickNET, and the Tick-Borne Disease Laboratory Network (TBDLN), are discussed. Data collection and reporting challenges, such as underreporting and misdiagnosis, are highlighted. The review addresses challenges, including lack of standardization, surveillance in non-human hosts, and data integration. Innovations encompass molecular techniques, syndromic surveillance, and tick surveillance programs. Implications for public health cover prevention strategies, early detection, treatment, and public education. Future directions emphasize enhanced surveillance networks, integrated vector management, research priorities, and policy implications. This review enhances understanding of TBD surveillance, aiding in informed decision-making for effective disease prevention and control. By understanding the current surveillance landscape, public health officials, researchers, and policymakers can make informed decisions to mitigate the burden of (TBDs).

Recombinant protein immunoblots for differential diagnosis of tick-borne relapsing fever and Lyme disease

Lyme disease (LD) is caused by a group of tick-borne bacteria of the genus Borrelia termed Lyme disease Borreliae (LDB). The detection of serum antibodies to specific LDB antigens is widely used to support diagnosis of LD. Recent findings highlight a need for serological tests that can differentiate LD from tick-borne relapsing fever (TBRF) caused by a separate group of Borrelia species termed relapsing fever Borreliae. This is because LD and TBRF share some clinical symptoms and can occur in overlapping locations. The development of serological tests for TBRF is at an early stage compared with LD. This article reviews the application of line immunoblots (IBs), where recombinant proteins applied as lines on nitrocellulose membrane strips are used to detect antibodies in patient sera, for the diagnosis and differentiation of LD and TBRF.

Safety and immunogenicity of a novel multivalent OspA-based vaccine candidate against Lyme borreliosis: a randomised, phase 1 study in healthy adults

BACKGROUND

Lyme borreliosis, potentially associated with serious long-term complications, is caused by the species complex Borrelia burgdorferi sensu lato. We investigated a novel Lyme borreliosis vaccine candidate (VLA15) targeting the six most common outer surface protein A (OspA) serotypes 1-6 to prevent infection with pathogenic Borrelia spp prevalent in Europe and North America.

METHODS

This was a partially randomised, observer-masked, phase 1 study in healthy adults older than 18 years to younger than 40 years (n=179) done in trial sites in Belgium and the USA. Following a non-randomised run-in phase, a sealed envelope randomisation method was applied with a 1:1:1:1:1:1 ratio; three dose concentrations of VLA15 (12 μg, 48 μg, and 90 μg) were administered by intramuscular injection on days 1, 29, and 57. The primary outcome was safety (frequency of adverse events up to day 85) assessed in participants who received at least one vaccination. Immunogenicity was a secondary outcome. The trial is registered with ClinicalTrials.gov, NCT03010228, and is complete.

FINDINGS

Between Jan 23, 2017 and Jan 16, 2019, of 254 participants screened for eligibility, 179 were randomly assigned into six groups: alum-adjuvanted 12 μg (n=29), 48 μg (n=31), or 90 μg (n=31) and non-adjuvanted 12 μg (n=29 participants), 48 μg (n=29), or 90 μg (n=30). VLA15 was safe and well tolerated and the majority of adverse events were mild or moderate. Overall, adverse events were more frequent in the 48 μg and 90 μg groups (range 28-30 participants [94-97%]) when compared with the 12 μg group (25 [86%] participants, 95% CI 69·4-94·5) for adjuvanted and non-adjuvanted groups. Common local reactions were tenderness (151 [84%] participants; 356 events, 95% CI 78·3-89·4) and injection site pain (120 [67%]; 224 events, 59·9-73·5); most frequent systemic reactions were headache (80 [45%]; 112 events, 37·6-52·0), excessive fatigue (45 [25%]; 56 events, 19·4-32·0), and myalgia (45 [25%]; 57 events, 19·4-32·0). A similar safety and tolerability profile was observed between adjuvanted and non-adjuvanted formulations. The majority of solicited adverse events were mild or moderate. VLA15 was immunogenic for all OspA serotypes with higher immune responses induced in the adjuvanted higher dose groups (geometric mean titre range 90 μg with alum 61·3 U/mL-321·7 U/mL vs 23·8 U/mL-111·5 U/mL at 90 μg without alum).

INTERPRETATION

This novel multivalent vaccine candidate against Lyme borreliosis was safe and immunogenic and paves the way to further clinical development.

FUNDING

Valneva Austria.

Analysis of macerated ticks using Boolean logic gating colorimetric isothermal nucleic acid assays for Lyme Borrelia and Ixodes scapularis ticks

Lyme disease, one of the most common tickborne diseases, has been rapidly spreading in parallel with the expansion of the range of its tick vector. Better tick surveillance efforts are needed to accurately estimate disease risk and to guide public health and clinical management. We have developed two multiplex loop-mediated isothermal amplification (LAMP) reactions coupled with oligonucleotide strand displacement (OSD) probes to identify the tick host, Ixodes scapularis, and the Lyme disease pathogen, Borrelia burgdorferi, they carry. In each multiplex LAMP-OSD assay the co-presence of two target sequences is computed at the DNA level by linking the two corresponding amplicons and detecting the co-product on colorimetric lateral flow dipsticks. In tests with synthetic DNA, the co-presence of as few as four copies of input DNA could be detected, without producing spurious signals. Most importantly, though, the LAMP-OSD assay is amenable to being carried out directly with macerated tick samples, without any sample preparation. In such field conditions, assays performed robustly and demonstrated 97-100% sensitivity and 100% specificity with both field-collected and lab-raised artificially infected ticks. Such easy-to-use, arthropod and pathogen-specific assays would be well suited to field and near patient use without relying on complex instrumentation or infrastructure.

Multiomics Reveals Symbionts, Pathogens, and Tissue-Specific Microbiome of Blacklegged Ticks (Ixodes scapularis) from a Lyme Disease Hot Spot in Southeastern Ontario, Canada

Ticks in the family Ixodidae are important vectors of zoonoses, including Lyme disease (LD), which is caused by spirochete bacteria from the Borreliella (Borrelia) burgdorferi sensu lato complex. The blacklegged tick (Ixodes scapularis) continues to expand across Canada, creating hot spots of elevated LD risk at the leading edge of its expanding range. Current efforts to understand the risk of pathogen transmission associated with I. scapularis in Canada focus primarily on targeted screens, while natural variation in the tick microbiome remains poorly understood. Using multiomics consisting of 16S metabarcoding and ribosome-depleted, whole-shotgun RNA transcriptome sequencing, we examined the microbial communities associated with adult I. scapularis (n = 32), sampled from four tissue types (whole tick, salivary glands, midgut, and viscera) and three geographical locations within a LD hot spot near Kingston, Ontario, Canada. The communities consisted of both endosymbiotic and known or potentially pathogenic microbes, including RNA viruses, bacteria, and a Babesia sp. intracellular parasite. We show that β-diversity is significantly higher between the bacterial communities of individual tick salivary glands and midguts than that of whole ticks. Linear discriminant analysis effect size (LEfSe) determined that the three potentially pathogenic bacteria detected by V4 16S rRNA sequencing also differed among dissected tissues only, including a Borrelia strain from the B. burgdorferi sensu lato complex, Borrelia miyamotoi, and Anaplasma phagocytophilum. Importantly, we find coinfection of I. scapularis by multiple microbes, in contrast to diagnostic protocols for LD, which typically focus on infection from a single pathogen of interest (B. burgdorferi sensu stricto). IMPORTANCE As a vector of human health concern, blacklegged ticks (Ixodes scapularis) transmit pathogens that cause tick-borne diseases (TBDs), including Lyme disease (LD). Several hot spots of elevated LD risk have emerged across Canada as I. scapularis expands its range. Focusing on a hot spot in southeastern Ontario, we used high-throughput sequencing to characterize the microbiome of whole ticks and dissected salivary glands and midguts. Compared with whole ticks, salivary glands and midguts were more diverse and associated with distinct bacterial communities that are less dominated by Rickettsia endosymbiont bacteria and are enriched for pathogenic bacteria, including a B. burgdorferi sensu lato-associated Borrelia sp., Borrelia miyamotoi, and Anaplasma phagocytophilum. We also found evidence of coinfection of I. scapularis by multiple pathogens. Overall, our study highlights the challenges and opportunities associated with the surveillance of the microbiome of I. scapularis for pathogen detection using metabarcoding and metatranscriptome approaches.

Lyme Borreliosis in Dogs: Background, Epidemiology, Diagnostics, Treatment and Prevention

Lyme borreliosis (LB) is a multisystemic tick-borne disease that can affect many organs and have various clinical manifestations in dogs. We attempted to summarise various aspects of Lyme disease: i. e., pathogenesis, epidemiology, benefits and risks of diagnostic approaches, treatment options, and prevention in dogs. Several diagnostic bottlenecks for LB in dogs and humans are compared. Because the occurrence of LB in both humans and dogs is closely related, monitoring its prevalence in dogs as sentinel animals is an excellent aid in assessing the risk of Lyme disease in a given geographic area. Although clinical symptoms in humans help clinicians diagnose LB, they are ineffective in dogs because canines rarely exhibit LB symptoms. Despite significant differences in sensitivity and specificity, sero-logical two-step detection of antibodies against Borrelia spp. (ELISA and Western blot) is the most commonly used method in humans and dogs. The limitations of the assay highlight the need for further research to develop new clinical markers and more accurate diagnostic tests. Due to the lack of a specific all-encompassing LB test, a definitive diagnosis of LB remains a difficult and time-consuming process in human and veterinary medicine. Understanding the disease prevalence and diagnostics, as well as preventing its spread with effective and timely treatment, are fundamental principles of good disease management.

Detection and genetic characterization of a putative novel Borrelia genospecies in Ixodes apronophorus / Ixodes persulcatus / Ixodes trianguliceps sympatric areas in Western Siberia

Four genospecies from the Borrelia burgdorferi sensu lato complex were detected in Ixodes persulcatus and Ixodes pavlovskyi ticks from Siberia and genetically characterized. The presence of Borrelia spp. in Ixodes apronophorus and Ixodes trianguliceps ticks found in Asia has never been studied. In this study, genetic diversity of B. burgdorferi s.l. was investigated in three I. persulcatus / I. trianguliceps / I. apronophorus sympatric habitats in Western Siberia. Three groups of samples were examined: (i) ticks that were taken from rodents and molted in a laboratory; (ii) non-molted ticks collected from rodents; (iii) specimens from small mammals. Expectedly, Borrelia afzelii and Borrelia bavariensis were detected in I. persulcatus and in small mammals from the studied locations. Borrelia bavariensis was first found in molted I. apronophorus and I. trianguliceps. Identical genovariants of B. bavariensis were found in I. apronophorus, I. trianguliceps, and I. persulcatus. In addition, a new Borrelia genovariant was discovered in non-molted and molted I. apronophorus and non-molted I. persulcatus and I. trianguliceps, as well as in small mammals. This new genovariant was genetically characterized using MLST and single locus sequence analysis, which indicated that the new Borrelia genovariant significantly differs from all known Borrelia species. We propose the name "Candidatus Borrelia sibirica" for this putative new species.

An Overview of Anthropogenic Actions as Drivers for Emerging and Re-Emerging Zoonotic Diseases

Population growth and industrialization have led to a race for greater food and supply productivity. As a result, the occupation and population of forest areas, contact with wildlife and their respective parasites and vectors, the trafficking and consumption of wildlife, the pollution of water sources, and the accumulation of waste occur more frequently. Concurrently, the agricultural and livestock production for human consumption has accelerated, often in a disorderly way, leading to the deforestation of areas that are essential for the planet's climatic and ecological balance. The effects of human actions on other ecosystems such as the marine ecosystem cause equally serious damage, such as the pollution of this habitat, and the reduction of the supply of fish and other animals, causing the coastal population to move to the continent. The sum of these factors leads to an increase in the demands such as housing, basic sanitation, and medical assistance, making these populations underserved and vulnerable to the effects of global warming and to the emergence of emerging and re-emerging diseases. In this article, we discuss the anthropic actions such as climate changes, urbanization, deforestation, the trafficking and eating of wild animals, as well as unsustainable agricultural intensification which are drivers for emerging and re-emerging of zoonotic pathogens such as viral (Ebola virus, hantaviruses, Hendravirus, Nipah virus, rabies, and severe acute respiratory syndrome coronavirus disease-2), bacterial (leptospirosis, Lyme borreliosis, and tuberculosis), parasitic (leishmaniasis) and fungal pathogens, which pose a substantial threat to the global community. Finally, we shed light on the urgent demand for the implementation of the One Health concept as a collaborative global approach to raise awareness and educate people about the science behind and the battle against zoonotic pathogens to mitigate the threat for both humans and animals.

Transmission Cycle of Tick-Borne Infections and Co-Infections, Animal Models and Diseases

Tick-borne pathogens such as species of Borrelia, Babesia, Anaplasma, Rickettsia, and Ehrlichia are widespread in the United States and Europe among wildlife, in passerines as well as in domestic and farm animals. Transmission of these pathogens occurs by infected ticks during their blood meal, carnivorism, and through animal bites in wildlife, whereas humans can become infected either by an infected tick bite, through blood transfusion and in some cases, congenitally. The reservoir hosts play an important role in maintaining pathogens in nature and facilitate transmission of individual pathogens or of multiple pathogens simultaneously to humans through ticks. Tick-borne co-infections were first reported in the 1980s in white-footed mice, the most prominent reservoir host for causative organisms in the United States, and they are becoming a major concern for public health now. Various animal infection models have been used extensively to better understand pathogenesis of tick-borne pathogens and to reveal the interaction among pathogens co-existing in the same host. In this review, we focus on the prevalence of these pathogens in different reservoir hosts, animal models used to investigate their pathogenesis and host responses they trigger to understand diseases in humans. We also documented the prevalence of these pathogens as correlating with the infected ticks’ surveillance studies. The association of tick-borne co-infections with other topics such as pathogens virulence factors, host immune responses as they relate to diseases severity, identification of vaccine candidates, and disease economic impact are also briefly addressed here.

The Spectrum of Erythema Migrans in Early Lyme Disease: Can We Improve Its Recognition?

Background and objective Diagnosis of early Lyme disease (LD) often relies on clinical recognition of the skin lesion, erythema migrans (EM), a diagnostic sign of disease when laboratory testing is insensitive. Because EM can present in morphologically distinct forms, its recognition by clinicians can be challenging. This study aimed to characterize the clinical spectrum of lesions in patients presenting with suspected early LD in an ambulatory care setting to identify features that might help clinicians to be better prepared to recognize EM lesions. Methods Images of lesions from 69 participants suspected to have early LD were retrospectively evaluated by a dermatologist and a family practitioner with expertise in early LD. Reviewers made determinations on the diagnoses and morphological features of lesions. Agreement between reviewers and associations among lesion types and participant demographics, symptomology, and laboratory evidence of infection were examined using the kappa statistic and contingency tables, respectively. Results Challenges in diagnosing EM were evident in our study: initial concordance between reviewers was moderate [kappa statistic (95% CI): 0.45 (0.245 - 0.657)]. The final classification included 35 lesions (51%) that were agreed to be EM; 23 lesions (30%) were considered to be possible early EM or tick bite reactions, and 11 (16%) were thought not to be EM, but rather other diagnoses, including ringworm, allergic contact dermatitis, and mosquito bites. Only two lesions (6%) were observed with a classic bull's eye or ring-within-a-ring pattern. Most EM lesions were uniform (51%), pink (74%), oval lesions (63%), with well-demarcated borders (92%). Early EM or tick bite reactions were typically <5 cm in size (74%), red (52%), round lesions (61%), with a punctum present (100%). Lesions thought not to be EM also tended to be pink or red (64%), round (55%), or uniform (45%) lesions, but also had raised (25%) or irregular borders (33%), which were not commonly observed in the reviewer-classified EM or tick bite reaction lesions. Participants with lesions classified as EM reported that they had the lesions for more days (p = 0.043) and reported more symptoms (p = 0.017) than participants with other lesions. Only 14 (20%) participants overall had positive laboratory evidence for LD; these included 13 (37%) of the participants with EM-classified lesions. Conclusions EM commonly occurs in forms that are not the classic bull's eye. Patients often present with lesions that may represent the very early stage of EM or tick bite reactions, and most patients will test negative on currently available laboratory tests, challenging clinicians in making an LD diagnosis or treatment decisions. Additional studies to further characterize the morphological features of EM and how variation in skin lesions may be perceived among clinicians would be helpful for developing guidelines on improving clinician recognition of EM.

A novel laboratory method to simulate climatic stress with successful application to experiments with medically relevant ticks

Ticks are the most important vectors of zoonotic disease-causing pathogens in North America and Europe. Many tick species are expanding their geographic range. Although correlational evidence suggests that climate change is driving the range expansion of ticks, experimental evidence is necessary to develop a mechanistic understanding of ticks’ response to a range of climatic conditions. Previous experiments used simulated microclimates, but these protocols require hazardous salts or expensive laboratory equipment to manipulate humidity. We developed a novel, safe, stable, convenient, and economical method to isolate individual ticks and manipulate their microclimates. The protocol involves placing individual ticks in plastic tubes, and placing six tubes along with a commercial two-way humidity control pack in an airtight container. We successfully used this method to investigate how humidity affects survival and host-seeking (questing) behavior of three tick species: the lone star tick (Amblyomma americanum), American dog tick (Dermacentor variabilis), and black-legged tick (Ixodes scapularis). We placed 72 adult females of each species individually into plastic tubes and separated them into three experimental relative humidity (RH) treatments representing distinct climates: 32% RH, 58% RH, and 84% RH. We assessed the survival and questing behavior of each tick for 30 days. In all three species, survivorship significantly declined in drier conditions. Questing height was negatively associated with RH in Amblyomma, positively associated with RH in Dermacentor, and not associated with RH in Ixodes. The frequency of questing behavior increased significantly with drier conditions for Dermacentor but not for Amblyomma or Ixodes. This report demonstrates an effective method for assessing the viability and host-seeking behavior of tick vectors of zoonotic diseases under different climatic conditions.

Large-Scale Sequencing of Borreliaceae for the Construction of Pan-Genomic-Based Diagnostics

The acceleration of climate change has been associated with an alarming increase in the prevalence and geographic range of tick-borne diseases (TBD), many of which have severe and long-lasting effects-particularly when treatment is delayed principally due to inadequate diagnostics and lack of physician suspicion. Moreover, there is a paucity of treatment options for many TBDs that are complicated by diagnostic limitations for correctly identifying the offending pathogens. This review will focus on the biology, disease pathology, and detection methodologies used for the Borreliaceae family which includes the Lyme disease agent Borreliella burgdorferi. Previous work revealed that Borreliaceae genomes differ from most bacteria in that they are composed of large numbers of replicons, both linear and circular, with the main chromosome being the linear with telomeric-like termini. While these findings are novel, additional gene-specific analyses of each class of these multiple replicons are needed to better understand their respective roles in metabolism and pathogenesis of these enigmatic spirochetes. Historically, such studies were challenging due to a dearth of both analytic tools and a sufficient number of high-fidelity genomes among the various taxa within this family as a whole to provide for discriminative and functional genomic studies. Recent advances in long-read whole-genome sequencing, comparative genomics, and machine-learning have provided the tools to better understand the fundamental biology and phylogeny of these genomically-complex pathogens while also providing the data for the development of improved diagnostics and therapeutics.

When to Think About Other Borreliae:: Hard Tick Relapsing Fever (Borrelia miyamotoi), Borrelia mayonii, and Beyond

In North America, several hard tick-transmitted Borrelia species other than Borrelia burgdorferi cause human disease, including Borrelia miyamotoi, Borrelia mayonii, and possibly Borrelia bissettii. Due to overlapping clinical syndromes, nonspecific tickborne disease (TBD) testing strategies, and shared treatment approaches, infections with these lesser known Borrelia are likely under-reported. In this article, we describe the epidemiology, clinical manifestations, diagnosis, and treatment of these less common Borrelia pathogens.

Early Lyme Disease (Erythema Migrans) and Its Mimics (Southern Tick-Associated Rash Illness and Tick-Associated Rash Illness)

Erythema migrans, an expanding erythematous skin lesion that develops days to weeks following an Ixodes species tick bite, is the most common clinical manifestation of Lyme disease. Presentations in the United States differ somewhat from that in Europe, presumably because of the different etiologic agents. Diagnosis is based on the appearance of the skin lesion, rather than on laboratory testing. After treatment with an appropriate oral antibiotic for 10 to 14 days, the prognosis is excellent. Two conditions that cause a similar skin lesion following a tick bite, but are of unknown cause, are Southern tick-associated rash illness in the United States and tick-associated rash illness in Japan.

Diagnostic Testing for Lyme Disease

Standard 2-tier testing (STTT), incorporating a screening enzyme immunoassay (EIA) or an immunofluorescence assay (IFA) that reflexes to IgM and IgG immunoblots, has been the primary diagnostic test for Lyme disease since 1995. In 2019, the Food and Drug Administration approved a modified 2-tier test strategy using 2 EIAs: offering a faster, less expensive, and more sensitive assay compared with STTT. New technologies examine early immune responses to Borrelia burgdorferi have the potential to diagnose Lyme disease in the first weeks of infection when existing serologic testing is not recommended due to low sensitivity.

Potential quantitative effect of a laboratory-based approach to Lyme disease surveillance in high-incidence states

Historically, public health surveillance for Lyme disease has required clinical follow-up on positive laboratory reports for the purpose of case classification. In areas with sustained high incidence of the disease, this resource-intensive activity yields a limited benefit to public health practice. A range of burden-reducing strategies have been implemented in many states, creating inconsistencies that limit the ability to decipher trends. Laboratory-based surveillance, or surveillance based solely on positive laboratory reports without follow-up for clinical information on positive laboratory reports, emerged as a feasible alternative to improve standardization in already high-incidence areas. To inform expectations of a laboratory-based surveillance model, we conducted a retrospective analysis of Lyme disease data collected during 2012-2018 from 10 high-incidence states. The number of individuals with laboratory evidence of infection ranged from 1302 to 20,994 per state and year. On average, 55% of those were ultimately classified as confirmed or probable cases (range: 29%-86%). Among all individuals with positive laboratory evidence, 18% (range: 2%-37%) were determined to be 'not a case' upon investigation and 23% (range: 2%-52%) were classified as suspect cases due to lack of associated clinical information and thus were not reported to the Centers for Disease Control and Prevention (CDC). The number of reported cases under a laboratory-based approach to surveillance in high-incidence states using recommended two-tier testing algorithms is likely to be, on average, 1.2 times higher (range: 0.6-1.8 times) than what was reported to CDC during 2012-2018. A laboratory-based surveillance approach for high-incidence states will improve standardization and reduce burden on public health systems, allowing public health resources to focus on prevention messaging, exploration of novel prevention strategies and alternative data sources to yield information on the epidemiology of Lyme disease.

Past, present, and future of Lyme disease vaccines: antigen engineering approaches and mechanistic insights

Introduction: Transmitted by ticks, Lyme disease is the most common vector-borne disease in the Northern hemisphere. Despite the geographical expansion of human Lyme disease cases, no effective preventive strategies are currently available. Developing an efficacious and safe vaccine is therefore urgently needed. Efforts have previously been taken to identify vaccine targets in the causative pathogen (Borrelia burgdorferi sensu lato) and arthropod vector (Ixodes spp.). However, progress was impeded due to a lack of consumer confidence caused by the myth of undesired off-target responses, low immune responses, a limited breadth of immune reactivity, as well as by the complexities of the vaccine process development.Area covered: In this review, we summarize the antigen engineering approaches that have been applied to overcome those challenges and the underlying mechanisms that can be exploited to improve both safety and efficacy of future Lyme disease vaccines.Expert opinion: Over the past two decades, several new genetically redesigned Lyme disease vaccine candidates have shown success in both preclinical and clinical settings and built a solid foundation for further development. These studies have greatly informed the protective mechanisms of reducing Lyme disease burdens and ending the endemic of this disease.

Characterization of Immunological Responses to Borrelia Immunogenic Protein A (BipA), a Species-Specific Antigen for North American Tick-Borne Relapsing Fever

Tick-borne relapsing fever (TBRF) is a neglected vector-borne bacterial disease distributed worldwide. Borrelia turicatae, Borrelia parkeri, and Borrelia hermsii are three argasid-borne TBRF species previously implicated in human disease in North America. TBRF is likely underdiagnosed due to its nonspecific symptoms and poorly developed diagnostic tests. Studies suggest that the Borrelia immunogenic protein A (BipA) is specific to TBRF Borrelia but heterogenic between species. In this study, we hypothesized that antibody responses generated to BipA are specific to the North American TBRF species infecting a given animal. To test this, we characterized the expression and localization of native BipA in North American species of TBRF Borrelia. We also infected mice by needle inoculation or tick bite with B. turicatae, B. hermsii, or B. parkeri and evaluated serum sample reactivity to recombinant BipA (rBipA) that was produced from each species. Furthermore, serum samples from nonhuman primates and domestic dogs experimentally infected with B. turicatae were assessed. Lastly, we tested human Lyme disease (LD) serum samples to determine potential cross-reactivity to rBipA generated from B. turicatae, B. parkeri, and B. hermsii. Our findings indicate that rBipA has the potential to distinguish between infections of LD- and TBRF-causing spirochetes and that antibody responses were more robust toward the Borrelia species causing infection. This work further supports that rBipA can likely distinguish between B. turicatae, B. hermsii, and B. parkeri infections in mice, canines, and nonhuman primates. IMPORTANCEBorrelia species transmitted by soft or hard ticks cause tick-borne relapsing fever (TBRF). This is a debilitating disease distributed worldwide but is likely underdiagnosed or misdiagnosed as Lyme disease due to poorly developed diagnostic tests. Borrelia turicatae, Borrelia parkeri, and Borrelia hermsii are three TBRF species previously implicated in human disease in North America. Commonly used diagnostic methods do not identify the species causing infection. In this study, we evaluated the potential of recombinant Borrelia immunogenic protein A (rBipA) as a diagnostic antigen capable of distinguishing between infections of TBRF Borrelia species. We show that serum from mice, canines, and nonhuman primates infected with B. turicatae, B. parkeri, or B. hermsii react more strongly to the rBipA from the species causing infection. Furthermore, sera from Lyme disease patients failed to cross-react with our rBipA proteins, indicating the potential to use rBipA as a species-specific diagnostic antigen for TBRF.

Abundance of Ixodes ricinus Ticks (Acari: Ixodidae) and the Diversity of Borrelia Species in Northeastern Poland

Monitoring the abundance of ticks and the prevalence of pathogens in ticks is an important activity in assessing the risk of tick-borne diseases and helps to develop preventive measures. This study aimed to estimate the density of Ixodes ricinus, the prevalence of Borrelia species, and their diversity in northeastern Poland. The overall mean I. ricinus density was 9.7 ticks/100 m². There were no differences between years, subregions, or habitats of study. The Borrelia infection rate was higher in females (22.6%) and males (14.3%) than in nymphs 5.5% (MIR). The most infected ticks came from the eastern subregion (10.1%) where the incidence of borreliosis among the inhabitants was over 20% higher than in the other subregions. In the infected ticks, B. afzelii (38.3%) and B. garinii (34.5%) were predominant. B. bavariensis was confirmed in I. ricinus in Poland for the first time. The most polymorphic was B. garinii. B. miyamotoi (belonged to the European type) was identified as a mono-infection in 0.9% of ticks and in 1.5% as a co-infection with B. afzelii and with B. garinii. Besides the risk of borreliosis and co-infections with different Borrelia species, physicians should also be aware of B. miyamotoi infections among patients.

Lyme Carditis: From Pathophysiology to Clinical Management

Cardiac involvement is a rare but relevant manifestation of Lyme disease that frequently presents as atrioventricular block (AVB). Immune-mediated injury has been implicated in the pathogenesis of Lyme carditis due to possible cross-reaction between Borrelia burgdorferi antigens and cardiac epitopes. The degree of the AVB can fluctuate rapidly, with two-thirds of patients progressing to complete AVB. Thus, continuous heart rhythm monitoring is essential, and a temporary pacemaker may be necessary. Routinely permanent pacemaker implantation, however, is contraindicated because of the frequent transient nature of the condition. Antibiotic therapy should be initiated as soon as the clinical suspicion of Lyme carditis arises to reduce the duration of the disease and minimize the risk of complications. Diagnosis is challenging and is based on geographical epidemiology, clinical history, signs and symptoms, serological testing, ECG and echocardiographic findings, and exclusion of other pathologies. This paper aims to explain the pathophysiological basis of Lyme carditis, describe its clinical features, and delineate the treatment principles.

Atypical Borrelia garinii infection in an immunocompromised patient mimicking high grade lymphoma

We report an atypical Borrelia garinii infection in an immunocompromised patient. It was first suspected as a transformation of follicular lymphoma into high-grade lymphoma. Spirochetes were directly observed on a peripheral blood smear and the diagnosis was confirmed using molecular methods. The clinical presentation and the diagnosis are unique and contrast with the cases described in the literature in immunocompromised patients.

Predictive Model of Lyme Disease Epidemic Process Using Machine Learning Approach

Lyme disease is the most prevalent tick-borne disease in Eastern Europe. This study focuses on the development of a machine learning model based on a neural network for predicting the dynamics of the Lyme disease epidemic process. A retrospective analysis of the Lyme disease cases reported in the Kharkiv region, East Ukraine, between 2010 and 2017 was performed. To develop the neural network model of the Lyme disease epidemic process, a multilayered neural network was used, and the backpropagation algorithm or the generalized delta rule was used for its learning. The adequacy of the constructed forecast was tested on real statistical data on the incidence of Lyme disease. The learning of the model took 22.14 s, and the mean absolute percentage error is 3.79%. A software package for prediction of the Lyme disease incidence on the basis of machine learning has been developed. Results of the simulation have shown an unstable epidemiological situation of Lyme disease, which requires preventive measures at both the population level and individual protection. Forecasting is of particular importance in the conditions of hostilities that are currently taking place in Ukraine, including endemic territories.

Prevalence of Borrelia burgdorferi in Ixodidae Tick around Asia: A Systematic Review and Meta-Analysis

Lyme disease (LD) is a common arthropod-borne inflammatory disorder prevalent in the northern hemisphere. LD is caused by a spirochete named Borrelia burgdorferi s.l., which is transmitted to humans by ticks. Climate, environment, and other factors affect land use; recreational-behavior changes affect human contact with infected ticks. Studies in Europe and North America have looked at these aspects, but studies in Asia have not. We searched databases to identify all relevant abstracts published until March 2021. A meta-analysis was undertaken using the standard methods and procedures established by the Cochrane Collaboration. Ninety-one articles were included in our meta-analysis. The literature search identified data from nine countries (China, Japan, Malaysia, Mongolia, Pakistan, Russia Siberia region, South Korea, Thailand and Turkey). Furthermore, 53,003 ticks from six genera (Amblyomma, Dermacentor, Haemaphysalis, Hyalomma, Ixodes and Rhipicephalus) were inspected for infection with B. burgdorferi. The pooled prevalence was 11.1% (95% CI = 8.3–14.2%). Among the nine countries, China had the most studies (56) and Malaysia had the highest infection rate (46.2%). Most infected ticks were from the genera Ixodes and Haemaphysalis. Ticks of the genus Ixodes had the highest infection rate (16.9%). Obvious heterogeneity was noted in our meta-analysis. We analyzed the heterogeneity with regard to countries, genera, time points, and detection methods. This study suggests that Ixodes, Haemaphysalis and Dermacentor may be the most common tike of B. burgdorferi-positive in Asia. The highest proportion of ticks infected by B. burgdorferi were from the genus Ixodes. This meta-analysis is the first attempt to explain the B. burgdorferi infection of hard-body ticks in Asia. The infection rate for each country and infection rate of different tick genera were analyzed: there were large differences between them. The literature is concentrates mainly on East Asia, and data are limited. Our study can provide a reference for a more comprehensive and in-depth investigation of ticks in Asia infected by B. burgdorferi spirochetes.

Case Report: The First Borrelia yangtzensis Infection in a Human in Korea

Borrelia yangtzensis has been identified in rodents and ticks in China and Japan. A 57-year-old woman with bite mark was diagnosed with B. yangtzensis infection via molecular and serological testing. Here, we report the first case of human infection caused by B. yangtzensis in Korea.

Novel Applications of Metagenomics for Detection of Tickborne Pathogens

Background

Tick populations have expanded in many parts of the globe, bringing with them an enhanced appreciation and discovery of novel tickborne pathogens, as well an increased in reported human cases of tickborne disease. Targeted and unbiased (shotgun) clinical metagenomic sequencing tests are increasingly used for detection of known and emerging infectious agents and have recently been employed for detection of tickborne pathogens.

Content

This review describes the types of metagenomic sequencing assays used for detection of emerging tickborne pathogens and reviews the recent literature on this topic. Important diagnostic and interpretative challenges are also covered.

Summary

Metagenomic analysis has emerged as a powerful tool for detection, discovery, characterization, and classification of tickborne pathogens. Shotgun metagenomics is especially promising because it allows for detection of all tickborne bacteria, viruses, and parasites in a single specimen. Despite the potential advantages, there are several important challenges, including high cost, complexity of testing and interpretation, and slow turnaround time. No doubt, these challenges will diminish with increased use and advances in the field.

Prediction of Novel Drug Targets and Vaccine Candidates against Human Lice (Insecta), Acari (Arachnida), and Their Associated Pathogens

The emergence of drug-resistant lice, acari, and their associated pathogens (APs) is associated with economic losses; thus, it is essential to find new appropriate therapeutic approaches. In the present study, a subtractive proteomics approach was used to predict suitable therapeutics against these vectors and their infectious agents. We found 9701 proteins in the lice (Pediculus humanus var. corporis) and acari (Ixodes scapularis, Leptotrombidium deliense), and 4822 proteins in the proteomes of their APs (Babesia microti, Borreliella mayonii, Borrelia miyamotoi, Borrelia recurrentis, Rickettsia prowazekii, Orientia tsutsugamushi str. Boryong) that were non-homologous to host proteins. Among these non-homologous proteins, 365 proteins of lice and acari, and 630 proteins of APs, were predicted as essential proteins. Twelve unique essential proteins were predicted to be involved in four unique metabolic pathways of lice and acari, and 103 unique proteins were found to be involved in 75 unique metabolic pathways of APs. The sub cellular localization analysis of 115 unique essential proteins of lice and acari and their APs revealed that 61 proteins were cytoplasmic, 42 as membrane-bound proteins and 12 proteins with multiple localization. The druggability analysis of the identified 73 cytoplasmic and multiple localization essential proteins revealed 22 druggable targets and 51 novel drug targets that participate in unique pathways of lice and acari and their APs. Further, the predicted 42 membrane bound proteins could be potential vaccine candidates. Screening of useful inhibitors against these novel targets may result in finding novel compounds efficient for the control of these parasites.

Seasonality of Acute Lyme Disease in Children

Due to the life cycle of its vector, Lyme disease has known seasonal variation. However, investigations focused on children have been limited. Our objective was to evaluate the seasonality of pediatric Lyme disease in three endemic regions in the United States. We enrolled children presenting to one of eight Pedi Lyme Net participating emergency departments. Cases were classified based on presenting symptoms: early (single erythema migrans (EM) lesion), early-disseminated (multiple EM lesions, headache, cranial neuropathy, or carditis), or late (arthritis). We defined a case of Lyme disease by the presence of an EM lesion or a positive two-tier Lyme disease serology. To measure seasonal variability, we estimated Fourier regression models to capture cyclical patterns in Lyme disease incidence. While most children with early or early-disseminated Lyme disease presented during the summer months, children with Lyme arthritis presented throughout the year. Clinicians should consider Lyme disease when evaluating children with acute arthritis throughout the year.

Integrated Tick Management in South Central Wisconsin: Impact of Invasive Vegetation Removal and Host-Targeted Acaricides on the Density of Questing Ixodes scapularis (Acari: Ixodidae) Nymphs

As tick-borne disease incidence increases and pathogens expand into new areas, the need for effective tick management strategies is paramount. In this 5-yr study (2014-2018) conducted in south central Wisconsin, we assessed whether an integrated tick management approach, deployed during peak tick activity (May-August), was more effective at reducing black-legged ticks (Ixodes scapularis Say (Ixodida: Ixodidae)), than individual interventions. Using a factorial design, invasive vegetation removal (Amur honeysuckle, Lonicera maackii Ruprecht (Dipsacales: Caprifoliaceae) and common buckthorn, Rhamnus cathartica Linnaeus (Rosales: Rhamnaceae)) was coupled with deployments of permethrin-treated cotton nesting materials (tick tubes) that target the white-footed mouse (Peromyscus leucopus Rafinesque (Rodentia: Cricetidae)). Results show that the probability of encountering a larval tick by drag sampling was unaffected by treatments at the cumulative 5-yr level. However, vegetation removal significantly reduced larval encounters in 2014, 2015, and 2018, by 33%, 57%, and 61% respectively, and reduced the density of questing nymphal (DON) ticks by 45% in 2015 compared to controls. Despite the limited effect on DON, vegetation removal significantly reduced the cumulative 5-yr density of Borrelia burgdorferi sensu stricto infected nymphs (DIN) (70%) compared to controls as a result of decreased nymphal infection prevalence. Sites treated with tick tubes had lower DIN (66%) and DON (54%) across the study and nymphs were reduced every year following the initial year of deployment compared to controls. Combining treatments did not further reduce DIN or DONs. We conclude that long-term integration of tick tubes with invasive vegetation removal does not provide additional benefit over individual treatments alone.

Borreliae Part 1: Borrelia Lyme Group and Echidna-Reptile Group

Simple Summary

Borreliae are spirochaetes, which represent a heterogeneous phylum within bacteria. Spirochaetes are indeed distinguished from other bacteria for their spiral shape, which also characterizes Borreliae. This review describes briefly the organization of the phylum Spirocheteales with a digression about its pathogenicity and historical information about bacteria isolation and characterization. Among spirochaetes, Borrelia genus is here divided into three groups, namely the Lyme group (LG), the Echidna-Reptile group (REPG) and the Relapsing Fever group (RFG). Borreliae Part 1 deals with Lyme group and Echidna-Reptile group Borreliae, while the subject of Borreliae Part 2 is Relapsing Fever group and unclassified Borreliae. Lyme group Borreliae is organized here in sections describing ecology, namely tick vectors and animal hosts, epidemiology, microbiology, and Borrelia genome organization and antigen characterization. Furthermore, the main clinical manifestations in Lyme borreliosis are also described. Although included in the Lyme group due to their particular clinical features, Borrelia causing Baggio Yoshinari syndrome and Borrelia mayonii are described in dedicated paragraphs. The Borrelia Echidna-Reptile group has been recently characterized including spirochaetes that apparently are not pathogenic to humans, but infect reptiles and amphibians. The paragraph dedicated to this group of Borreliae describes their vectors, hosts, geographical distribution and their characteristics.

Abstract

Borreliae are divided into three groups, namely the Lyme group (LG), the Echidna-Reptile group (REPG) and the Relapsing Fever group (RFG). Currently, only Borrelia of the Lyme and RF groups (not all) cause infection in humans. Borreliae of the Echidna-Reptile group represent a new monophyletic group of spirochaetes, which infect amphibians and reptiles. In addition to a general description of the phylum Spirochaetales, including a brief historical digression on spirochaetosis, in the present review Borreliae of Lyme and Echidna-Reptile groups are described, discussing the ecology with vectors and hosts as well as microbiological features and molecular characterization. Furthermore, differences between LG and RFG are discussed with respect to the clinical manifestations. In humans, LG Borreliae are organotropic and cause erythema migrans in the early phase of the disease, while RFG Borreliae give high spirochaetemia with fever, without the development of erythema migrans. With respect of LG Borreliae, recently Borrelia mayonii, with intermediate characteristics between LG and RFG, has been identified. As part of the LG, it gives erythema migrans but also high spirochaetemia with fever. Hard ticks are vectors for both LG and REPG groups, but in LG they are mostly Ixodes sp. ticks, while in REPG vectors do not belong to that genus.

Metabolic Response in Patients With Post-treatment Lyme Disease Symptoms/Syndrome

BACKGROUND

Post-treatment Lyme disease symptoms/syndrome (PTLDS) occurs in approximately 10% of patients with Lyme disease following antibiotic treatment. Biomarkers or specific clinical symptoms to identify patients with PTLDS do not currently exist and the PTLDS classification is based on the report of persistent, subjective symptoms for ≥6 months following antibiotic treatment for Lyme disease.

METHODS

Untargeted liquid chromatography-mass spectrometry metabolomics was used to determine longitudinal metabolic responses and biosignatures in PTLDS and clinically cured non-PTLDS Lyme patients. Evaluation of biosignatures included (1) defining altered classes of metabolites, (2) elastic net regularization to define metabolites that most strongly defined PTLDS and non-PTLDS patients at different time points, (3) changes in the longitudinal abundance of metabolites, and (4) linear discriminant analysis to evaluate robustness in a second patient cohort.

RESULTS

This study determined that observable metabolic differences exist between PTLDS and non-PTLDS patients at multiple time points. The metabolites with differential abundance included those from glycerophospholipid, bile acid, and acylcarnitine metabolism. Distinct longitudinal patterns of metabolite abundance indicated a greater metabolic variability in PTLDS versus non-PTLDS patients. Small numbers of metabolites (6 to 40) could be used to define PTLDS versus non-PTLDS patients at defined time points, and the findings were validated in a second cohort of PTLDS and non-PTLDS patients.

CONCLUSIONS

These data provide evidence that an objective metabolite-based measurement can distinguish patients with PTLDS and help understand the underlying biochemistry of PTLDS.

Ticks and their epidemiological role in Slovakia: from the past till present

In Slovakia, 22 tick species have been found to occur to date. Among them, Ixodes ricinus, Dermacentor reticulatus, D. marginatus and marginally Haemaphysalis concinna, H. inermis and H. punctata have been identified as the species of public health relevance. Ticks in Slovakia were found to harbour and transmit zoonotic and/or potentially zoonotic agents such as tick-borne encephalitis virus (TBEV), spirochaetes of the Borrelia burgdorferi sensu lato (s.l.) complex, the relapsing fever sprirochaete Borrelia miyamotoi, bacteria belonging to the orders Rickettsiales (Rickettsia spp., Anaplasma phagocytophilum, Neoehrlichia mikurensis), Legionellales (Coxiella burnetii), and Thiotrichales (Francisella tularensis), and Babesia spp. parasites (order Piroplasmida). Ixodes ricinus is the principal vector of the largest variety of microorganisms including viruses, bacteria and piroplasms. TBEV, B. burgdorferi s.l., rickettsiae of the spotted fever group, C. burnetii and F. tularensis have been found to cause serious diseases in humans, whereas B. miyamotoi, A. phagocytophilum, N. mikurensis, Babesia microti, and B. venatorum pose lower or potential risk to humans. Distribution of TBEV has a focal character. During the last few decades, new tick-borne encephalitis (TBE) foci and their spread to new areas have been registered and TBE incidence rates have increased. Moreover, Slovakia reports the highest rates of alimentary TBE infections among the European countries. Lyme borreliosis (LB) spirochaetes are spread throughout the distribution range of I. ricinus. Incidence rates of LB have shown a slightly increasing trend since 2010. Only a few sporadic cases of human rickettsiosis, anaplasmosis and babesiosis have been confirmed thus far in Slovakia. The latest large outbreaks of Q fever and tularaemia were recorded in 1993 and 1967, respectively. Since then, a few human cases of Q fever have been reported almost each year. Changes in the epidemiological characteristics and clinical forms of tularaemia have been observed during the last few decades. Global changes and development of modern molecular tools led to the discovery and identification of emerging or new tick-borne microorganisms and symbionts with unknown zoonotic potential. In this review, we provide a historical overview of research on ticks and tick-borne pathogens in Slovakia with the most important milestones and recent findings, and outline future directions in the investigation of ticks as ectoparasites and vectors of zoonotic agents and in the study of tick-borne diseases.

Linear Cryogel Arrays: On the Fast Track for Borreliosis Detection

The detection of IgG/IgM antibodies is a crucial tool for the diagnosis of infectious diseases as they give specific information such as the stage of infection or when it approximately occurred. In this work, a linear cryogel array (LCA) technology is described for the detection of IgG and IgM antibodies, indicative of a borreliosis infection in human sera. The LCA consists of a transparent capillary filled with functionalized cryogel compartments. For the generation of these cryogel arrays, solutions containing a photo-copolymer and the appropriate antigens are sucked into a surface-modified glass capillary. The solution compartments are separated from each other through air pockets. After freezing the solutions, a photo-induced cross-linking process is performed, through which the solutions are transformed into cryogel compartments, covalently attached to the capillary walls. We show that the LCA technology allows the simultaneous detection of IgG and IgM antibodies via a sandwich immunoassay in sera from Borrelia-infected patients within 1 h for sample sizes of only 12 μL. A study with sera from 42 patients conducted with the LCAs and referenced - depending on the source of the sera - to a commercial line immunoassay and a chemiluminescent immunoassay, which are currently widely used for Lyme disease screening, demonstrates the diagnostic potential of the approach.