Pathogen transmission in relation to duration of attachment by Ixodes scapularis ticks

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.

Assessment of the speed of transmission of Ehrlichia canis, Anaplasma phagocytophilum, and Borrelia burgdorferi sensu stricto by infected ticks through an in vitro experimental model

BACKGROUND

Canine vector-borne diseases (CVBDs) have significant clinical and public health implications.

METHODS

This experimental study used a validated continuous-flow in vitro feeding system (CFIFS) to investigate the speed of transmission (SOT) of three tick-borne pathogens (TBPs): Ehrlichia canis by laboratory-infected Rhipicephalus sanguineus (18.3% infection rate), Anaplasma phagocytophilum by laboratory-infected Ixodes ricinus (56%), and Borrelia burgdorferi sensu stricto (s.s.) by laboratory-infected I. ricinus (76%). Three experiments were conducted, one per pathogen/tick model. A total of 58-60 ticks were used per feeding system. Four to six replicates were obtained per experiment. All ticks were laboratory-reared. The tick infections were performed by feeding the nymphal stages on infected hosts.

RESULTS

All ticks began to attach and feed 3 h after being introduced to the feeding system. At the maximum attachment, 89.7% of R. sanguineus were attached at 57 h, with 4-30% attachment at 51 h for I. ricinus infected with A. phagocytophilum, and 6.3-47.9% at 48 h for I. ricinus infected with B. burgdorferi s.s. Polymerase chain reaction (PCR) tests were used to detect the presence of pathogens from blood samples collected every 3 h. Swab samples from the inner face of the feeding membrane were also collected and tested every 6 h during the B. burgdorferi s.s.

STUDY

In this experimental in vitro design, after the first tick attachments were observed, E. canis exhibited SOT of 3-6 h, A. phagocytophilum of 12-15 h, and B. burgdorferi of 42-45 h in blood but only 3-6 h on inner membrane swabs.

CONCLUSIONS

The findings of this in vitro study highlight the transmission time of some TBPs, confirming previous data obtained in vitro or in vivo, by using the same design for all tick/pathogen models. This is a way to estimate the possibility of using acaricidal drugs to block pathogen transmission based on the SOT and the speed of kill of these compounds.

Powassan Virus Encephalitis in Pediatric Patients

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

Early embryonic development in the tick Ixodes scapularis suggests syncytial organization and cellularization before blastoderm formation

Ixodes ticks are the most important vectors of arthropod-borne diseases in the United States, Canada, and Europe. Ixodes scapularis is the major vector that transmits the causative agent of Lyme disease in the eastern United States and can transmit up to six additional pathogens. In recent years, many advances have been made in building the toolkit for I. scapularis research, including genomic resources, transcriptomes, and forward and reverse genetics techniques. However, an understanding of the early embryonic development of this species is still lacking. In this study, we attempted to fill this knowledge gap and to further the efforts of functional genomics tools development. We developed a staging system consisting of 16 (0-15) stages describing unique morphologies and used wheat germ agglutinin staining and fluorescent dye injections to confirm cell membrane formation. These results provide an opportunity to identify an ideal time window for tick transgenics and deepen our understanding of the events during embryo development.

The ability of an oral combination of afoxolaner, moxidectin and pyrantel to protect dogs from Borrelia burgdorferi infections transmitted by Ixodes scapularis

BACKGROUND

Two studies were conducted to determine whether treatment with NexGard® Plus (NP), a combination of afoxolaner, moxidectin, and pyrantel, prevents transmission of Borrelia burgdorferi to dogs by naturally infected Ixodes scapularis.

METHODS

For each study, 20 dogs were randomly assigned to two groups (n = 10/group): NP and negative control. Twenty-eight days post-treatment, each dog was infested with approximately 50 I. scapularis that had a 60% B. burgdorferi infection rate in study 1 and a 38.5% infection rate in study 2. Five days post-infestation, ticks were counted and removed. The B. burgdorferi-specific C6 antibody was tested for using the SNAP® 4Dx® test (IDEXX) and the Lyme Quant C6 test with serum collected before treatment and infestation and 21, 35, 49, 63, and 75 days post-infestation. Skin biopsies were collected 76 days post-infestation and quantitative polymerase chain reaction (qPCR) conducted to detect B. burgdorferi DNA.

RESULTS

On the day of count and removal, no ticks were found on treated dogs, while control dogs had an average of 25.1 ticks in study 1 and 19.6 ticks in study 2, for efficacy of 100% (P ≤ 0.0001). All dogs were seronegative before infestation. The first dog in the control groups became seropositive 21 days post-infestation in study 1 and 35 days post-infestation in study 2 by the SNAP 4Dx test and by 21 days post-infestation by the Lyme Quant C6 test in both studies. Ten of 10 dogs in the control group in both studies seroconverted by the end of the study. None of the skin biopsies from treated dogs were positive for B. burgdorferi DNA, while at least three of the four skin biopsies from each of the control dogs tested positive at the end of the studies. No clinical signs of Lyme disease were detected in any of the dogs.

CONCLUSIONS

The results of these studies indicate that NexGard® Plus administered at a dose close to the minimum recommended dose of 2.5 mg/kg afoxolaner is effective 28 days after a single treatment in the prevention of B. burgdorferi transmission from naturally infected I. scapularis ticks to dogs.

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.

Comparison of the initial and residual speed of Amblyomma americanum kill on dogs treated with a single dose of Bravecto® Chew (25 mg/kg fluralaner) or Simparica TRIO® (1.2 mg/kg sarolaner, 24 µg/kg moxidectin, 5 mg/kg pyrantel)

BACKGROUND

To manage tick infestations and reduce tick-borne pathogen transmission risk to dogs, compliant administration of a fast-acting ectoparasiticide is necessary. Isoxazoline-containing ectoparasiticide products provide systemic whole-body coverage; however, differences in tick kill have been observed between products and these differences may be more pronounced when controlling common dose-limiting tick species such as Amblyomma americanum.

METHODS

Dogs were ranked by tick carrying capacity, randomly allocated to one of three treatment groups, and administered Bravecto® Chews (minimum 25 mg/kg fluralaner), Simparica TRIO® (minimum 1.2 mg/kg sarolaner, 24 µg/kg moxidectin, 5 mg/kg pyrantel), or no treatment. Dogs were infested with approximately 50 unfed adult (25 female, 25 male) A. americanum on days -2, 21, 28, and 35. Live tick counts were performed at 8, 12, 24, 48, and 72 h post-treatment (day 0) and post-infestation on days 21, 28, and 35. At each tick count timepoint, product efficacy was determined by comparing geometric mean live tick counts for each product-treated group to the untreated group and a linear mixed model was used for between-group comparisons.

RESULTS

Compared with untreated dogs, significant control of existing A. americanum infestations began by 8 h post-treatment (81.6%) and reached 98.0% control by 12-h for Bravecto®-treated dogs. In comparison, significant control for Simparica TRIO®-treated dogs began by 24 h post-treatment (97.7%). When reinfested on day 21, A. americanum infestations were controlled more quickly for Bravecto® compared with Simparica TRIO®-treated dogs at 12 h (efficacy 95.3% versus 25.5%, P < 0.001) and 24 h (efficacy 99.7% versus 70.9%, P < 0.001) post-infestation. Similarly, when reinfested on day 28, faster A. americanum control occurred for Bravecto® compared with Simparica TRIO®-treated dogs at 12 h (efficacy 87.9% versus 18.3%, P < 0.001) and at 24 h (99.2% versus 59.3%, P < 0.001) post-infestation. Finally, when reinfested on day 35, time to ≥ 90% efficacy was achieved by 48 h for Bravecto®-treated dogs compared with 72 h post-infestation for Simparica TRIO®-treated dogs. Both products performed within label indications and no treatment-related adverse reactions occurred during the study.

CONCLUSIONS

Amblyomma americanum infestations are controlled more quickly immediately upon treatment and at 21, 28, and 35 days post-treatment for Bravecto® compared with Simparica TRIO®-treated dogs.

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.

Phase separation and ageing of glycine-rich protein from tick adhesive

Hard ticks feed on their host for multiple days. To ensure firm attachment, they secrete a protein-rich saliva that eventually forms a solid cement cone. The underlying mechanism of this liquid-to-solid transition is currently not understood. This study focuses on the phase transitions of a disordered glycine-rich protein (GRP) found in tick saliva. We show that GRP undergoes liquid-liquid phase separation via simple coacervation to form biomolecular condensates in salty environments. Cation-π and π-π interactions mediated by periodically placed arginine and aromatic amino-acid residues are the primary driving forces that promote phase separation. Interestingly, GRP condensates exhibit ageing by undergoing liquid-to-gel transition over time and exhibit adhesive properties, similar to the naturally occurring cement cone. Finally, we provide evidence for protein-rich condensates in natural tick saliva. Our findings provide a starting point to gain further insights into the bioadhesion of ticks, to develop novel tick control strategies, and towards achieving biomedical applications such as tissue sealants.

2024 American Heart Association and American Red Cross Guidelines for First Aid

Codeveloped by the American Heart Association and the American Red Cross, these guidelines represent the first comprehensive update of first aid treatment recommendations since 2010. Incorporating the results of structured evidence reviews from the International Liaison Committee on Resuscitation, these guidelines cover first aid treatment for critical and common medical, traumatic, environmental, and toxicological conditions. This update emphasizes the continuous evolution of evidence evaluation and the necessity of adapting educational strategies to local needs and diverse community demographics. Existing guidelines remain relevant unless specifically updated in this publication. Key topics that are new, are substantially revised, or have significant new literature include opioid overdose, bleeding control, open chest wounds, spinal motion restriction, hypothermia, frostbite, presyncope, anaphylaxis, snakebite, oxygen administration, and the use of pulse oximetry in first aid, with the inclusion of pediatric-specific guidance as warranted.

Prevalence of Babesia microti Co-Infection with Other Tick-Borne Pathogens in Pennsylvania

Babesia microti is a protozoan that infects red blood cells, causing hemolytic anemia and flu-like symptoms in humans. Understanding co-infections is crucial for the better diagnosis, treatment, and management of tick-borne diseases. This study examined the prevalence of Babesia microti co-infection with other prevalent tick-borne pathogens in Pennsylvania. The dataset acquired from the Dr. Jane Huffman Wildlife Genetics Institute included passive surveillance data from Ixodes spp. from 2021 to 2023. Submitted ticks were screened for tick-borne pathogens using species-specific TaqMan qPCR. Of the 793 B. microti-positive ticks pulled for analysis, 65.0% were co-infected with other pathogens (n = 516). Notably, 60.9% of the B. microti-positive ticks were co-infected with Borrelia burgdorferi, 10.2% with Anaplasma phagocytophilum Ap-ha, and 7.5% carried a triple co-infection with B. burgdorferi and A. phagocytophilum Ap-ha. The rates of B. microti infection and its co-infections are on the rise, with patterns observed in Pennsylvania and other regions of the USA. While other studies have collected both nymphal and adult ticks to screen for co-infections in Pennsylvania, our study stood out as a unique contribution to the field by focusing exclusively on B. microti-positive ticks. The continued monitoring of tick-borne co-infections is vital to prevent misdiagnosis and ensure effective treatment regimens.

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

Background

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

Methods

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

Results

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

Conclusion

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

Powassan Virus Encephalitis after Tick Bite, Manitoba, Canada

A case of Powassan encephalitis occurred in Manitoba, Canada, after the bite of a black-legged tick. Awareness of this emerging tickborne illness is needed because the number of vector tick species is growing. No specific treatment options exist, and cases with illness and death are high. Prevention is crucial.

Fipronil prevents transmission of Lyme disease spirochetes

Lyme disease, a tick-borne illness caused by Borrelia spirochetes, poses a significant threat to public health. While acaricides effectively control ticks on pets and livestock, their impact on pathogen transmission is often unclear. This study investigated the acaricidal efficacy of fipronil against Ixodes ricinus ticks and its potential to block Borrelia afzelii transmission. Initially, we employed the ex vivo membrane blood-feeding system to assess the dose–response acaricidal activity of ivermectin, fipronil and its metabolite fipronil sulfone, when supplemented in the blood meal throughout tick feeding. To obtain the temporal resolution of their acaricidal activity, ticks were allowed to initiate blood feeding on an artificial membrane before being exposed to a 1-time topical application of these acaricides. Fipronil demonstrated superior speed of acaricidal activity, with onset of tick moribundity within a few hours, prompting its selection for further in vivo testing with Borrelia-infected ticks. The I. ricinus nymphs infected with B. afzelii were topically treated with fipronil shortly after attachment to mice. Four weeks post-feeding, the skin and internal organs were examined for the presence of Borrelia. No spirochetes were detected in any organ of mice exposed to fipronil-treated ticks, while 9 out of 10 control mice, exposed to non-treated infectious ticks, displayed Borrelia infection. The in vitro co-culture experiments confirmed that fipronil had no direct effect on Borrelia viability, indicating a tick-directed effect. Overall, these results underline the potential of fipronil as a valuable tool for tick control strategies and suggest a concept for acaricide-mediated Borrelia-transmission blockers.

Assessment of Knowledge, Attitudes, and Practices Toward Ticks and Tickborne Disease among Healthcare Professionals Working in Schools in New York and Maryland

Healthcare Professionals Working in Schools (HPWS) are responsible for providing health services to students and play a role in providing education to prevent illnesses, including tickborne diseases (TBD). Providing TBD education to children has been shown to increase prevention behaviors and knowledge of TBD symptoms, but little is known regarding the current state of TBD awareness among HPWS. In spring 2019 we conducted a cross-sectional knowledge, attitudes, and practices (KAP) survey of HPWS in two states with a high incidence of Lyme disease (LD) to inform design of TBD prevention programs. The survey queried general knowledge of TBDs, school practices regarding TBDs, and availability of TBD resources. Overall, higher confidence, experience, risk perception, prior training on TBD, and more years employed as a HPWS were independently associated with knowledge of LD transmission, symptoms, and correct tick removal practices. State and local health departments should consider prioritizing engagement with HPWS to provide educational opportunities about tickborne diseases.

Comparative speed of kill provided by lotilaner (Credelio™), sarolaner (Simparica Trio™), and afoxolaner (NexGard™) to control Amblyomma americanum infestations on dogs

BACKGROUND

Canine acaricides with rapid onset and sustained activity can reduce pathogen transmission risk and enhance pet owner experience. This randomized, complete block design, investigator-masked study compared the speed of kill of Amblyomma americanum provided by three monthly-use isoxazoline-containing products.

METHODS

Eight randomized beagles per group were treated (day 0), per label, with sarolaner (combined with moxidectin and pyrantel, Simparica Trio™), afoxolaner (NexGard™), or lotilaner (Credelio™), or remained untreated. Infestations with 50 adult A. americanum were conducted on days - 7, - 2, 21, and 28, and tick counts were performed on day - 5 (for blocking), and at 4, 8, 12, 24, 48, and 72 h following treatment and subsequent infestations. Efficacy calculations were based on geometric mean live tick counts. A linear mixed model was used for between-group comparisons.

RESULTS

On day 0, only lotilaner significantly reduced an A. americanum infestation by 12 h (43.3%; P = 0.002). Efficacy of lotilaner and afoxolaner at 24 h post-treatment was 95.3% and 97.6%, respectively, both significantly different from sarolaner (74%) (P = 0.002, P < 0.001, respectively). On day 21, at 12 h postinfestation, lotilaner efficacy (59.6%) was significantly different from sarolaner (0.0%) (P < 0.001) and afoxolaner (6.3%) (P < 0.001). At 24 h, lotilaner efficacy (97.4%) was significantly different (P < 0.001) from sarolaner and afoxolaner (13.6% and 14.9%, respectively). On day 28, at 12 h postinfestation, lotilaner efficacy (47.8%) was significantly different from sarolaner (17.1%) (P = 0.020) and afoxolaner (9.0%) (P = 0.006). At 24 h, lotilaner efficacy (92.3%) was significantly different from sarolaner 4.9% (P < 0.001) and afoxolaner (0.0%) (P < 0.001). Speed of kill for sarolaner and afoxolaner, but not lotilaner, significantly declined over the study period. Following reinfestation on day 28, neither sarolaner nor afoxolaner reached 90% efficacy by 48 h. By 72 h, sarolaner efficacy was 97.4% and afoxolaner efficacy was 86.3%. Only lotilaner achieved ≥ 90% efficacy by 24 h post-treatment and 24 h postinfestation on days 21 and 28. Time to ≥ 90% efficacy following new infestations consistently occurred 24-48 h earlier for lotilaner compared with sarolaner or afoxolaner.

CONCLUSIONS

Credelio (lotilaner) has a more rapid onset of acaricidal activity against A. americanum than Simparica Trio (sarolaner-moxidectin-pyrantel) and NexGard (afoxolaner). Only lotilaner's speed of tick kill is sustained throughout the dosing period.

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.

Climate crisis risks to elderly health: strategies for effective promotion and response

The climate crisis significantly impacts the health and well-being of older adults, both directly and indirectly. This issue is of growing concern in Canada due to the country's rapidly accelerating warming trend and expanding elderly population. This article serves a threefold purpose: (i) outlining the impacts of the climate crisis on older adults, (ii) providing a descriptive review of existing policies with a specific focus on the Canadian context, and (iii) promoting actionable recommendations. Our review reveals the application of current strategies, including early warning systems, enhanced infrastructure, sustainable urban planning, healthcare access, social support systems, and community engagement, in enhancing resilience and reducing health consequences among older adults. Within the Canadian context, we then emphasize the importance of establishing robust risk metrics and evaluation methods to prepare for and manage the impacts of the climate crisis efficiently. We underscore the value of vulnerability mapping, utilizing geographic information to identify regions where older adults are most at risk. This allows for targeted interventions and resource allocation. We recommend employing a root cause analysis approach to tailor risk response strategies, along with a focus on promoting awareness, readiness, physician training, and fostering collaboration and benchmarking. These suggestions aim to enhance disaster risk management for the well-being and resilience of older adults in the face of the climate crisis.

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.

Coinfection of Babesia and Borrelia in the Tick Ixodes ricinus-A Neglected Public Health Issue in Europe?

Ixodes ricinus nymphs and adults removed from humans, and larvae and nymphs from birds, have been analysed for infection with Babesia species and Borrelia species previously in separately published studies. Here, we use the same data set to explore the coinfection pattern of Babesia and Borrelia species in the ticks. We also provide an overview of the ecology and potential public health importance in Sweden of I. ricinus infected both with zoonotic Babesia and Borrelia species. Among 1952 nymphs and adult ticks removed from humans, 3.1% were PCR-positive for Babesia spp. Of these Babesia-positive ticks, 43% were simultaneously Borrelia-positive. Among 1046 immatures of I. ricinus removed from birds, 2.5% were Babesia-positive, of which 38% were coinfected with Borrelia species. This study shows that in I. ricinus infesting humans or birds in Sweden, potentially zoonotic Babesia protozoa sometimes co-occur with human-pathogenic Borrelia spp. Diagnostic tests for Babesia spp. infection are rarely performed in Europe, and the medical significance of this pathogen in Europe could be underestimated.

Zoonotic Bacterial Infections Triggering Cytokine Storm Syndrome

Zoonotic infections can result in life-threatening complications that can manifest with hemophagocytic lymphohistiocytosis (HLH)/cytokine storm syndrome (CSS). Bacteria constitute the largest group of zoonotic infection-related HLH cases. The growing list of zoonotic bacterial infections associated with HLH/CSS include Brucella spp., Rickettsia spp., Ehrlichia, Coxiella burnetii, Mycobacterium spp., and Bartonella spp. Patients most commonly present with fever, cytopenias, hepatosplenomegaly, myalgias, and less frequently with rash, jaundice, and lymphadenopathy.

Assessing the Influence of Climate Change and Environmental Factors on the Top Tick-Borne Diseases in the United States: A Systematic Review

In the United States (US), tick-borne diseases (TBDs) have more than doubled in the past fifteen years and are a major contributor to the overall burden of vector-borne diseases. The most common TBDs in the US-Lyme disease, rickettsioses (including Rocky Mountain spotted fever), and anaplasmosis-have gradually shifted in recent years, resulting in increased morbidity and mortality. In this systematic review, we examined climate change and other environmental factors that have influenced the epidemiology of these TBDs in the US while highlighting the opportunities for a One Health approach to mitigating their impact. We searched Medline Plus, PUBMED, and Google Scholar for studies focused on these three TBDs in the US from January 2018 to August 2023. Data selection and extraction were completed using Covidence, and the risk of bias was assessed with the ROBINS-I tool. The review included 84 papers covering multiple states across the US. We found that climate, seasonality and temporality, and land use are important environmental factors that impact the epidemiology and patterns of TBDs. The emerging trends, influenced by environmental factors, emphasize the need for region-specific research to aid in the prediction and prevention of TBDs.

High levels of alpha-gal with large variation in the salivary glands of lone star ticks fed on human blood

Tick bites, associated with the secretion of tick saliva containing the xenoglycan galactose-alpha-1, 3-galactose (alpha-gal or aGal), are recognized as the causal factors of alpha-Gal syndrome (AGS; or red meat allergy) in humans. AGS occurs after the increased production of IgE antibodies against aGal, which is found in most mammalian cells, except for the Old World monkey and humans. The aGal sensitization event has been linked to an initial tick bite, followed by consumption of red meat containing the aGal glycan, which triggers the onset of the allergic response resulting in urticaria, anaphylaxis, or even death. In North America, the lone star tick, Amblyomma americanum, has been identified as the main culprit for AGS. However, only a subset of the human population exposed to lone star tick bites develops AGS. This suggests the presence of unidentified variables associated with the sensitization event. To evaluate the quantitative variations of the aGal in ticks, we evaluated the differences in aGal levels in different strains of A. americanum ticks partially fed on different blood sources using an artificial feeding system and animal hosts. We found significantly higher aGal levels in the female ticks fed on human blood than those fed on the blood of other mammals with large variations among different tick populations and individuals. We propose that host-specific genetic components in the A. americanum ticks are involved in the production of high aGal epitope in the tick saliva, which provides a part of the explanation for the variables associated with the AGS sensitization event of the tick bite.

Vaccines against tick-borne diseases: a big step forward?

Ticks and tick-borne diseases are on the rise due to socioecosystemic changes and climate modification and are affecting human and animal health. Few vaccines are available. Two recent articles from Matias et al. and Pine et al. used mRNA technology to explore tick and pathogen proteins as vaccine candidates.

Comparison of the initial and residual speed of Ixodes scapularis kill on dogs treated with a single dose of Bravecto® Chew (25 mg/kg fluralaner) or Simparica TRIO® (1.2 mg/kg sarolaner, 24 µg/kg moxidectin, 5 mg/kg pyrantel)

BACKGROUND

Compliant ectoparasiticide product use is a comprehensive way to control ticks and reduce the risk of tick-borne pathogen transmission to dogs. Because the systemically acting isoxazoline ectoparasiticides require tick attachment for drug delivery, fast speed of kill is essential to minimize tick-borne pathogen transmission risk.

METHODS

Dogs of satisfactory tick-carrying capacity were randomly allocated to treatment groups and administered, per label instructions, Bravecto® Chews (minimum 25 mg/kg fluralaner), Simparica TRIO® (minimum 1.2 mg/kg sarolaner, 24 µg/kg moxidectin, 5 mg/kg pyrantel), or no treatment. Dogs were infested with approximately 50 unfed adult (35 female, 15 male) Ixodes scapularis on Day -2, 21 and 28. Live tick counts were performed at 4, 8, 12 and 24 h post-treatment (Day 0) and post-infestation on Day 21 and 28. Tick control efficacy was determined by comparing live tick means for each product-treated group to the untreated control group and each other at all time points using a linear mixed model. The percent of dogs free of live ticks was analyzed using the Fisher's exact test for treatment group comparison.

RESULTS

The untreated control group maintained adequate tick infestations throughout the study. Using geometric means, an existing I. scapularis infestation was controlled by 99.7% and 93.0% 12 h post-treatment and by 100% and 99.5% 24 h post-treatment, for Bravecto® and Simparica TRIO®-treated dogs, respectively. Ixodes scapularis infestations were controlled more quickly for Bravecto®- compared to Simparica TRIO®-treated dogs on Day 21 at 8 h (efficacy 74.0% vs. 0.0%, p = 0.003) and 12 h (efficacy 99.2% vs. 39.4%, p < 0.001) post-infestation and Day 28 at 8 h (efficacy 92.2% vs. 0.0%, p < 0.001) and 12 h (efficacy 99.6% vs. 27.7%, p < 0.001) post-infestation. On Day 28 post-treatment, the efficacy of Bravecto® and Simparica TRIO® to control a new I. scapularis infestation was 100% and 96.6%, respectively, by 24 h post-infestation. Of product-treated dogs, 100% of Bravecto®-treated dogs were free of live ticks by 24 h post-treatment or post-infestation. No treatment-related adverse reactions occurred during the study.

CONCLUSIONS

Ixodes scapularis infestations are controlled more quickly 21 and 28 days post-treatment for dogs administered a single dose of Bravecto® compared to dogs administered a single dose of Simparica TRIO®.

Powassan Virus Infections: A Systematic Review of Published Cases

BACKGROUND

Powassan virus is an emerging neurotropic arbovirus transmitted by the tick Ixodes scapularis. This systematic review was conducted to aggregate data on its clinical manifestations, diagnostic findings, and complications.

METHODS

PubMed was searched until August 2023 using the term "Powassan", to identify all published cases of Powassan virus infections, as per PRISMA guidelines.

RESULTS

Among the 380 abstracts identified, 45 studies describing 84 cases (70 adult, 14 pediatric) were included. Cases were reported from the USA and Canada. Complications included paralysis in 44.1% of adult and 42.6% of pediatric cases, cognitive deficits in 33.3% of adult and 25% of pediatric cases, while the mortality rate was 19.1% and 7.1% in the adult and pediatric populations, respectively. Correlation analysis revealed an association between mortality and age (r = 0.264, p = 0.029), development of paralysis (r = 0.252, p = 0.041), or respiratory distress or failure (r = 0.328, p = 0.006). Factors associated with persistent neurological deficits were development of ataxia (r = 0.383, p = 0.006), paralysis (r = 0.278, p = 0.048), speech disorder (r = 0.319, p = 0.022), and cranial nerve involvement (r = 0.322, p = 0.017). Other significant correlations included those between speech disorders and ataxia (r = 0.526, p < 0.001), and between paralysis and respiratory distress or failure (r = 0.349, p = 0.003).

CONCLUSION

Powassan virus infections have significant morbidity and mortality and should be suspected in cases of encephalitis and possible tick exposure. PROSPERO registration number: CRD42023395991.

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.

Cross-alteration of murine skin and tick microbiome concomitant with pathogen transmission after Ixodes ricinus bite

BACKGROUND

Ticks are major vectors of diseases affecting humans such as Lyme disease or domestic animals such as anaplasmosis. Cross-alteration of the vertebrate host skin microbiome and the tick microbiome may be essential during the process of tick feeding and for the mechanism of pathogen transmission. However, it has been poorly investigated.

METHODS

We used mice bitten by field-collected ticks (nymphs and adult ticks) in different experimental conditions to investigate, by 16S rRNA gene metabarcoding, the impact of blood feeding on both the mouse skin microbiome and the tick microbiome. We also investigated by PCR and 16S rRNA gene metabarcoding, the diversity of microorganisms transmitted to the host during the process of tick bite at the skin interface and the dissemination of the pathogen in host tissues (blood, heart, and spleen).

RESULTS

Most of the commensal bacteria present in the skin of control mice were replaced during the blood-feeding process by bacteria originating from the ticks. The microbiome of the ticks was also impacted by the blood feeding. Several pathogens including tick-borne pathogens (Borrelia/Borreliella, Anaplasma, Neoehrlichia, Rickettsia) and opportunistic bacteria (Williamsia) were transmitted to the skin microbiome and some of them disseminated to the blood or spleen of the mice. In the different experiments of this study, skin microbiome alteration and Borrelia/Borreliella transmission were different depending on the tick stages (nymphs or adult female ticks).

CONCLUSIONS

Host skin microbiome at the bite site was deeply impacted by the tick bite, to an extent which suggests a role in the tick feeding, in the pathogen transmission, and a potentially important impact on the skin physiopathology. The diversified taxonomic profiles of the tick microbiome were also modified by the blood feeding. Video Abstract.

What a Tick Can Tell a Doctor: Using the Human-Biting Tick in the Clinical Management of Tick-Borne Disease

With expanding concern about ticks, there is a general sense of uncertainty about the diagnosis and treatment of tick-borne diseases. The diagnosis process is often based on clinical judgment in conjunction with laboratory testing and can be pathogen specific. Treatments may require disease-dependent approaches, and co-infections complicate or increase the severity of the clinical picture. Measuring exposure indices in the tick has become popular among providers and their patients, though this practice is not universally understood, and certain public health agencies have voiced concerns regarding interpretation and rigor of testing. As many providers subscribe to or recommend these services to aid in pretest risk and exposure assessments, this work sought to clarify the role of pathogen testing human-biting ticks as a complement to the diagnostic pipeline and raises points that must be addressed through future research and interdisciplinary conversation. Future work is needed to develop quality control oversight for tick testing laboratories. Studies on the integration of tick testing with human cases to see how these services affect health outcomes are also needed. Alongside these, improvements in the quality and availability of diagnostics are of critical importance.

Tick extracellular vesicles in host skin immunity and pathogen transmission

Ticks can transmit a variety of human pathogens, including intracellular and extracellular bacteria, viruses, and protozoan parasites. Historically, their saliva has been of immense interest due to its anticoagulant, anti-inflammatory, and anesthetic properties. Only recently, it was discovered that tick saliva contains extracellular vesicles (EVs). Briefly, it has been observed that proteins associated with EVs are important for multiple tick-borne intracellular microbial lifestyles. The impact of tick EVs on viral and intracellular bacterial pathogen transmission from the tick to the mammalian host has been shown experimentally. Additionally, tick EVs interact with the mammalian skin immune system at the bite site. The interplay between tick EVs, the transmission of pathogens, and the host skin immune system affords opportunities for future research.

Deer management generally reduces densities of nymphal Ixodes scapularis, but not prevalence of infection with Borrelia burgdorferi sensu stricto

Human Lyme disease-primarily caused by the bacterium Borrelia burgdorferi sensu stricto (s.s.) in North America-is the most common vector-borne disease in the United States. Research on risk mitigation strategies during the last three decades has emphasized methods to reduce densities of the primary vector in eastern North America, the blacklegged tick (Ixodes scapularis). Controlling white-tailed deer populations has been considered a potential method for reducing tick densities, as white-tailed deer are important hosts for blacklegged tick reproduction. However, the feasibility and efficacy of white-tailed deer management to impact acarological risk of encountering infected ticks (namely, density of host-seeking infected nymphs; DIN) is unclear. We investigated the effect of white-tailed deer density and management on the density of host-seeking nymphs and B. burgdorferi s.s. infection prevalence using surveillance data from eight national parks and park regions in the eastern United States from 2014-2022. We found that deer density was significantly positively correlated with the density of nymphs (nymph density increased by 49% with a 1 standard deviation increase in deer density) but was not strongly correlated with the prevalence of B. burgdorferi s.s. infection in nymphal ticks. Further, while white-tailed deer reduction efforts were followed by a decrease in the density of I. scapularis nymphs in parks, deer removal had variable effects on B. burgdorferi s.s. infection prevalence, with some parks experiencing slight declines and others slight increases in prevalence. Our findings suggest that managing white-tailed deer densities alone may not be effective in reducing DIN in all situations but may be a useful tool when implemented in integrated management regimes.

Frequency of Positive Polymerase Chain Reaction (PCR) Testing for Borrelia burgdorferi on Whole Blood Samples That Tested Positive for Babesia microti by PCR from an Endemic Area for Both Infections in New York State

Because both Babesia microti and Borrelia burgdorferi can be transmitted by the bite of a single coinfected Ixodes scapularis tick, an attempt was made to determine the frequency with which whole blood samples that tested positive for B. microti infection by polymerase chain reaction (PCR) would also test positive by PCR for B. burgdorferi infection. Over a 7-year period from 2013 to 2019, 119 different patients tested positive for B. microti infection by PCR on at least one blood sample. Among the 118 patients with a positive B. microti PCR blood sample that could also be tested by a qualitative PCR for B. burgdorferi, only one patient tested positive (0.85%, 95% CI 0.02 to 4.6%). Routine PCR testing of every B. microti PCR-positive blood specimen to detect B. burgdorferi coinfection appears to have a low yield, even in a highly endemic geographic area for both of these infections.

EVIDENCE OF PROTOZOAN AND BACTERIAL INFECTION AND CO-INFECTION AND PARTIAL BLOOD FEEDING IN THE INVASIVE TICK HAEMAPHYSALIS LONGICORNIS IN PENNSYLVANIA

The Asian longhorned tick, Haemaphysalis longicornis, an invasive tick species in the United States, has been found actively host-seeking while infected with several human pathogens. Recent work has recovered large numbers of partially engorged, host-seeking H. longicornis, which together with infection findings raises the question of whether such ticks can reattach to a host and transmit pathogens while taking additional bloodmeals. Here we conducted molecular blood meal analysis in tandem with pathogen screening of partially engorged, host-seeking H. longicornis to identify feeding sources and more inclusively characterize acarological risk. Active, statewide surveillance in Pennsylvania from 2020 to 2021 resulted in the recovery of 22/1,425 (1.5%) partially engorged, host-seeking nymphal and 5/163 (3.1%) female H. longicornis. Pathogen testing of engorged nymphs detected 2 specimens positive for Borrelia burgdorferi sensu lato, 2 for Babesia microti, and 1 co-infected with Bo. burgdorferi s.l. and Ba. microti. No female specimens tested positive for pathogens. Conventional PCR blood meal analysis of H. longicornis nymphs detected avian and mammalian hosts in 3 and 18 specimens, respectively. Mammalian blood was detected in all H. longicornis female specimens. Only 2 H. longicornis nymphs produced viable sequencing results and were determined to have fed on black-crowned night heron, Nycticorax nycticorax. These data are the first to molecularly confirm H. longicornis partial blood meals from vertebrate hosts and Ba. microti infection and co-infection with Bo. burgdorferi s.l. in host-seeking specimens in the United States, and the data help characterize important determinants indirectly affecting vectorial capacity. Repeated blood meals within a life stage by pathogen-infected ticks suggest that an understanding of the vector potential of invasive H. longicornis populations may be incomplete without data on their natural host-seeking behaviors and blood-feeding patterns in nature.

Human-Biting Ixodes scapularis Submissions to a Crowd-Funded Tick Testing Program Correlate with the Incidence of Rare Tick-Borne Disease: A Seven-Year Retrospective Study of Anaplasmosis and Babesiosis in Massachusetts

Tick-borne zoonoses pose a serious burden to global public health. To understand the distribution and determinants of these diseases, the many entangled environment-vector-host interactions which influence risk must be considered. Previous studies have evaluated how passive tick testing surveillance measures connect with the incidence of human Lyme disease. The present study sought to extend this to babesiosis and anaplasmosis, two rare tick-borne diseases. Human cases reported to the Massachusetts Department of Health and submissions to TickReport tick testing services between 2015 and 2021 were retrospectively analyzed. Moderate-to-strong town-level correlations using Spearman's Rho (ρ) were established between Ixodes scapularis submissions (total, infected, adult, and nymphal) and human disease. Aggregated ρ values ranged from 0.708 to 0.830 for anaplasmosis and 0.552 to 0.684 for babesiosis. Point observations maintained similar patterns but were slightly weaker, with mild year-to-year variation. The seasonality of tick submissions and demographics of bite victims also correlated well with reported disease. Future studies should assess how this information may best complement human disease reporting and entomological surveys as proxies for Lyme disease incidence in intervention studies, and how it may be used to better understand the dynamics of human-tick encounters.

Passive Surveillance of Human-Biting Ixodes scapularis Ticks in Massachusetts from 2015-2019

This study aimed to analyze human-biting Ixodes scapularis ticks submitted to TickReport tick testing service from 2015-2019 in Massachusetts to (1) examine possible patterns of pathogen-positive adult and nymphal ticks over time and (2) explore how socioeconomic factors can influence tick submissions. A passive surveillance data set of ticks and tick-borne pathogens was conducted over 5 years (2015-2019) in Massachusetts. The percentages of four tick-borne pathogens: Borrelia burgdorferi, Anaplasma phagocytophilum, Babesia microti, and Borrelia miyamotoi were determined by Massachusetts county and by month and year. Regression models were used to examine the association between zip-code-level socioeconomic factors and submissions. A total of 13,598 I. scapularis ticks were submitted to TickReport from Massachusetts residents. The infection rate of B. burgdorferi, A. phagocytophilum, and B. microti was 39%, 8%, and 7% in adult ticks; 23%, 6%, and 5% in nymphal ticks, respectively. A relatively higher level of education was associated with high tick submission. Passive surveillance of human-biting ticks and associated pathogens is important for monitoring tick-borne diseases, detecting areas with potentially high risks, and providing public information. Socioeconomic factors should be considered to produce more generalizable passive surveillance data and to target potentially underserved areas.

Evolution of Tick Vaccinology Highlights Changes in Paradigms in This Research Area

Ticks and tick-borne diseases affect human and animal health worldwide. Although some tick-protective antigens have been identified and characterized, further research is needed for the development and application of effective anti-tick vaccines, which currently are unavailable for human protection. To study the trends and gaps in anti-tick vaccine approaches, herein we used scientometric analysis to evaluate several aspects of tick vaccinology. Co-authorship and citations networks pointed out two main research fronts, one focused on the laboratory protocols driving the recognition of candidate antigens and the other devoted to field experiments of protection against ticks. The analysis demonstrated the prominence of research in European countries on the topic. The scientometric approach allowed the recognition of isolated teams working casually on the topic, the lack of cooperation between middle- and low-income countries, and the need for sustained and integrated research. Most important, we identified a considerable lack of new candidates for vaccine development, as well as the participation of African and Asian countries. These results provide significant insights obtained from bibliographical analysis, suggest the strength and weaknesses in this field of research, and highlight new directions to advance in the development of effective vaccines for the control of tick infestations and tick-borne pathogens.

Human attachment site preferences of ticks parasitizing in New York

Ticks transmit several arthropod-borne pathogens in New York State. The primary human-biting ticks in this region are Ixodes scapularis, Amblyomma americanum, and Dermacentor variabilis. Body regions where tick bites human vary depending on the tick species and life stage, and clothing worn by the host. A community tick submission system was used to acquire information about bite-site location prior to pathogen testing to understand species and life stage-specific body-segment preferences. These data resulted in the identification of species-specific preferences for location, with D. variabilis preferentially biting the head and neck and A. americanum preferring the thighs, groin, and abdomen. Ixodes scapularis was found across the body, although it showed a significant life stage difference with adults preferring the head, midsection, and groin, while nymphs/larvae preferred the extremities. Infection with Borrelia burgdorferi resulted in a significant change in attachment site. This provides an assessment of which body region ticks of the most common species in New York are likely to be found.

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.

Tick species infesting humans in the United States

The data for human tick encounters in the United States (US) presented in this paper were compiled with the goals of: (i) presenting quantitative data across the full range of native or recently established human biting ixodid (hard) and argasid (soft) tick species with regards to their frequency of infesting humans, based on published records of ticks collected while biting humans or crawling on clothing or skin; and (ii) providing a guide to publications on human tick encounters. Summary data are presented in table format, and the detailed data these summaries were based on are included in a set of Supplementary Tables. To date, totals of 36 ixodid species (234,722 specimens) and 13 argasid species (230 specimens) have been recorded in the published literature to infest humans in the US. Nationally, the top five ixodid species recorded from humans were the blacklegged tick, Ixodes scapularis (n=158,008 specimens); the lone star tick, Amblyomma americanum (n=36,004); the American dog tick, Dermacentor variabilis (n=26,624); the western blacklegged tick, Ixodes pacificus (n=4,158); and the Rocky Mountain wood tick, Dermacentor andersoni (n=3,518). Additional species with more than 250 ticks recorded from humans included Ixodes cookei (n=2,494); the Pacific Coast tick, Dermacentor occidentalis (n=809); the brown dog tick, Rhipicephalus sanguineus sensu lato (n=714); the winter tick, Dermacentor albipictus (n=465); and the Gulf Coast tick, Amblyomma maculatum (n=335). The spinose ear tick, Otobius megnini (n=69), and the pajaroello tick, Ornithodoros coriaceus (n=55) were the argasid species most commonly recorded from humans. Additional information presented for each of the 49 tick species include a breakdown of life stages recorded from humans, broad geographical distribution in the US, host preference, and associated human pathogens or medical conditions. The paper also provides a history of publications on human tick encounters in the US, with tables outlining publications containing quantitative data on human tick encounters as well as other notable publications on human-tick interactions. Data limitations are discussed. Researchers and public health professionals in possession of unpublished human tick encounter data are strongly encouraged to publish this information in peer-reviewed scientific journals. In future papers, it would be beneficial if data consistently were broken down by tick species and life stage as well as host species and ticks found biting versus crawling on clothing or skin.

Immunization of guinea pigs with cement extract induces resistance against Ixodes scapularis ticks

As hematophagous parasites, many tick species are important vectors of medical and veterinary disease agents. Proteins found in tick saliva and midgut have been used with some success in immunizations of animal hosts against feeding ticks, and whole saliva has been used effectively in this capacity against Ixodes scapularis, the primary vector of tickborne pathogens in the United States. Tick saliva is a complex substance containing hundreds of proteins, and the identification of specific protective antigens is ongoing. We performed a series of experiments immunizing guinea pigs with extracts prepared from midgut or attachment cement collected from adult female I. scapularis followed by challenge with nymphs of the same species. Midgut extract did not induce protective immunity, while immunization with cement extract resulted in partial protection of hosts as evidenced by premature tick detachment and 34-41% reduction in tick engorgement weights. Proteomic characterization of I. scapularis cement was performed, demonstrating that the cement extract was compositionally different from tick saliva, and vitellogenin-like lipoproteins were the most abundant proteins in cement extract (>40%). Cement was also heavily enriched with lysozymes and defensins, including those originating from both the mammalian host as well as ticks. These results demonstrate that I. scapularis cement contains immunogenic components capable of stimulating host resistance against tick feeding. Because the cement is present at the tick-host interface for an extended period of time during the feeding process, these antigens present auspicious candidates for further evaluation and potential inclusion in an anti-tick vaccine.

Tick-Borne Pathogens in Questing Blacklegged Ticks (Acari: Ixodidae) From Pike County, Pennsylvania

Active surveillance was conducted by collecting questing ticks from vegetation through a 2-yr survey in Pike County, Pennsylvania. Over a thousand blacklegged ticks (Ixodes scapularis Say) and American dog ticks (Dermacentor variabilis Say) were collected. A single specimen of the following species was collected: lone star tick (Amblyomma americanum L.), rabbit tick (Haemaphysalis leporispalustris Packard), and an Asian longhorned tick (Haemaphysalis longicornis Neumann). This study represents the largest county-wide study in Pennsylvania, surveying 988 questing I. scapularis adult and nymphs. Molecular detection of five distinct tick-borne pathogens was screened through real-time PCR at a single tick resolution. Respectively, the overall 2-yr adult and nymph prevalence were highest with Borrelia burgdorferi (Spirochaetales: Spirochaetacceae) (45.99%, 18.94%), Anaplasma phagocytophilum (Rickettsiales: Anaplasmataceae) (12.29%, 7.95%) where the variant-ha (8.29%, 3.03%) was overall more prevalent than the variant-v1 (2.49%, 4.17%), Babesia microti (Piroplasmida: Babesiidae) (4.97%, 5.30%), Borrelia miyamotoi (Spirochaetales: Spirochaetaceae) (1.38%, 1.89%), and Powassan virus lineage II [POWV]/deer tick virus (DTV) (2.07%, 0.76%). Adult and nymph coinfection prevalence of B. burgdorferi and B. microti (3.03%, 4.97%) and adult coinfection of B. burgdorferi and A. phagocytophilum or A. phagocytophilum and B. microti were significantly higher than the independent infection rate expected naturally. This study highlights the urgency to conduct diverse surveillance studies with large sample sizes to better understand the human risk for tick-borne diseases within small geographical areas.

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.

Molecular detection of spotted fever group rickettsiae in hedgehogs (Erinaceus amurensis) and hedgehog-attached ticks in Xuyi County, Southeast China

Tick-borne diseases like Rickettsia, Anaplasma and Ehrlichia are widespread infectious zoonoses that threaten the health of both humans and animals worldwide. Ticks and their hosts, such as hedgehogs, can play a crucial role in transmitting tick-borne diseases and the cycle of Rickettsia. To investigate the presence and identity of Rickettsia in hedgehogs and hedgehog-attached ticks in Xuyi County, Southeast China, 114 ticks were collected from 45 hedgehogs captured totally. Via morphological and molecular methods, all these ticks were identified as two species: Haemaphysalis flava (110/114, 96.5%) and Haemaphysalis longicornis (4/114, 3.5%). Rickettsia spp. were genotypically characterized by PCR targeting rrs, gltA, ompA, ompB, and sca4 gene fragments. The prevalence of spotted fever group rickettsiae (SFGR) infection found in hedgehogs and ticks was 17.8% (8/45) and 78.1% (89/114), respectively. Phylogenetic analyses demonstrated that those Rickettsia spp. belong to two species: Rickettsia heilongjiangensis (R. heilongjiangensis XY-1) and a potential new species, Candidatus Rickettsia xuyiensis XY-2. The present study gave the first evidence of R. heilongjiangensis and Candidatus R. xuyiensis in ticks and hedgehogs of Southeast China. Our findings suggest that hedgehogs might be involved in the natural transmission cycle of Rickettsia species.

Human Granulocytic Anaplasmosis-A Systematic Review of Published Cases

Anaplasma phagocytophilum is an emerging, Gram-negative, obligate intracellular pathogen that is transmitted by a tick vector. Human infection ranges from asymptomatic to severe disease that can present with pancytopenia, multiorgan failure, and death. The aim of this systematic review is to analyze case reports and case series reported over the last two decades in peer-reviewed journals indexed in the Medline/PubMed database according to the PRISMA guidelines. We found 110 unique patients from 88 case reports and series. The most common mode of transmission was tick bite (60.9%), followed by blood transfusion (8.2%). Infection was acquired by blood transfusion in nearly half (42%) of the immunocompromised patients. Most patients reported fever (90%), followed by constitutional (59%) and gastrointestinal symptoms (56%). Rash was present in 17% of patients, much higher than in previous studies. Thrombocytopenia was the most common laboratory abnormality (76%) followed by elevated aspartate aminotransferase (AST) (46%). The diagnosis was most commonly established using whole-blood polymerase chain reaction (PCR) in 76% of patients. Coinfection rate was 9.1% and Borrelia burgdorferi was most commonly isolated in seven patients (6.4%). Doxycycline was used to treat 70% of patients but was only used as an empiric treatment in one-third of patients (33.6%). The overall mortality rate was 5.7%, and one patient died from trauma unrelated to HGA. The mortality rates among immunocompetent and immunocompromised patients were 4.2% (n = 4/95) and 18.2% (n = 2/11), respectively. Four of the six patients who died (66.6%) received appropriate antibiotic therapy. Among these, doxycycline was delayed by more than 48 h in two patients.

Personal protection measures to prevent tick bites in the United States: Knowledge gaps, challenges, and opportunities

Personal protection measures to prevent human tick encounters from resulting in bites are widely recommended as the first line of defense against health impacts associated with ticks. This includes using repellents, wearing untreated or permethrin-treated protective clothing, and conducting tick checks after coming inside, aided by removing outdoor clothing articles and running them in a dryer on high heat (to kill undetected ticks) and taking a shower/bath (to aid in detecting ticks on the skin). These measures have the benefit of incurring no or low cost, but they need to be used consistently to be most effective. In this paper, I review the level of use (acceptability combined with behavior) of the above-mentioned personal protection measures and their effectiveness to prevent tick bites and tick-borne disease. Studies on the level of use of personal protection measures to prevent tick bites have used different recruitment strategies, focused on different types of respondent populations, employed variable phrasings of survey questions relating to a given personal protection measure, and presented results based on variable frequencies of taking action. This complicates the synthesis of the findings, but the studies collectively indicate that members of the public commonly take action to prevent tick bites, most frequently by wearing untreated protective clothing or conducting tick checks (done routinely by 30 to 70% of respondents in most studies of the public), followed by showering/bathing after being outdoors or using repellents on skin/clothing (15 to 40% range), and with permethrin-treated clothing being the least frequently used tick bite prevention method (<5 to 20% range). A suite of experimental studies have shown that applying repellents or permethrin to coveralls or uniform-style clothing can result in decreased numbers of tick bites, but similar studies are lacking for members of the public wearing summer-weight clothing during normal daily activities. Moreover, a set of case-control and cross-sectional studies have explored associations between use of different personal protection measures to prevent tick bites and Lyme disease or other tick-borne infections. The results are mixed for each personal protection measure, with some studies indicating that regular use of the measure is associated with a reduction in tick-borne disease while other studies found no similar protective effect. One possible interpretation is that these personal protection measures can protect against tick-borne infection but the information gathered to date has not been sufficiently detailed to clarify the circumstances under which protection is achieved, especially with regards to frequency of use, parts of the body being protected, and use of combinations of two or more potentially protective measures. In conclusion, personal protection measures to prevent tick bites are used by the public and merit further study to better understand how they need to be used to have the greatest public health impact.

Entomological risk of African tick-bite fever (Rickettsia africae infection) in Eswatini

BACKGROUND

Rickettsia africae is a tick-borne bacterium that causes African tick-bite fever (ATBF) in humans. In southern Africa, the tick Amblyomma hebraeum serves as the primary vector and reservoir for R. africae and transmits the bacterium during any life stage. Previous research has shown that even when malaria has been dramatically reduced, unexplained acute febrile illnesses persist and may be explained by the serological evidence of rickettsiae in humans.

METHODOLOGY/PRINCIPAL FINDINGS

We collected 12,711 questing Amblyomma larvae across multiple land use types in a savanna landscape in Eswatini. Our results show that host-seeking Amblyomma larvae are abundant across both space and time, with no significant difference in density by land use or season. We investigated the entomological risk (density of infected larvae) of ATBF from A. hebraeum larvae by testing over 1,600 individual larvae for the presence of R. africae using a novel multiplex qPCR assay. We found an infection prevalence of 64.9% (95% CI: 62.1-67.6%) with no land use type significantly impacting prevalence during the dry season of 2018. The mean density of infected larvae was 57.3 individuals per 100m2 (95% CI: 49-65 individuals per 100m2).

CONCLUSIONS

Collectively, our results demonstrate R. africae infected A. hebraeum larvae, the most common tick species and life stage to bite humans in southern Africa, are ubiquitous in the savanna landscape of this region. Increased awareness of rickettsial diseases is warranted for policymakers, scientists, clinicians, and patients. Early detection of disease via increased clinician awareness and rapid diagnostics will improve patient outcomes for travelers and residents of this region.

Integrative Alternative Tactics for Ixodid Control

Simple Summary

Hard ticks are important for economic and health reasons, and control has mainly relied upon use of synthetic acaricides. Contemporary development of resistance and concerns relating to health and environmental safety have elicited exploration into alternative tactics for hard tick management. Some examples of alternative tactics involve biological control, desiccant dusts, growth regulators, vaccines, cultural methods, and ingested medications.

Abstract

Ixodids (hard ticks), ectoparasitic arthropods that vector the causal agents of many serious diseases of humans, domestic animals, and wildlife, have become increasingly difficult to control because of the development of resistance against commonly applied synthetic chemical-based acaricides. Resistance has prompted searches for alternative, nonconventional control tactics that can be used as part of integrated ixodid management strategies and for mitigating resistance to conventional acaricides. The quest for alternative control tactics has involved research on various techniques, each influenced by many factors, that have achieved different degrees of success. Alternative approaches include cultural practices, ingested and injected medications, biological control, animal- and plant-based substances, growth regulators, and inert desiccant dusts. Research on biological control of ixodids has mainly focused on predators, parasitoid wasps, infective nematodes, and pathogenic bacteria and fungi. Studies on animal-based substances have been relatively limited, but research on botanicals has been extensive, including whole plant, extract, and essential oil effects on ixodid mortality, behavior, and reproduction. The inert dusts kaolin, silica gel, perlite, and diatomaceous earth are lethal to ixodids, and they are impervious to environmental degradation, unlike chemical-based toxins, remaining effective until physically removed.

Crowdsourced Tick Image-Informed Updates to U.S. County Records of Three Medically Important Tick Species

Burgeoning cases of tick-borne disease present a significant public health problem in the United States. Passive tick surveillance gained traction as an effective way to collect epidemiologic data, and in particular, photograph-based tick surveillance can complement in-hand tick specimen identification to amass distribution data and related encounter demographics. We compared the Federal Information Processing Standards (FIPS) code of tick photos submitted to a free public identification service (TickSpotters) from 2014 to 2019 to published nationwide county reports for three tick species of medical concern: Ixodes scapularis Say (Ixodida: Ixodidae), Ixodes pacificus Cooley and Kohls (Ixodida: Ixodidae), and Amblyomma americanum Linneaus (Ixodida: Ixodidae). We tallied the number of TickSpotters submissions for each tick species according to "Reported" or "Established" criteria per county, and found that TickSpotters submissions represented more than half of the reported counties of documented occurrence, and potentially identified hundreds of new counties with the occurrence of these species. We detected the largest number of new county reports of I. scapularis presence in Michigan, North Carolina, and Texas. Tick image submissions revealed potentially nine new counties of occurrence for I. pacificus, and we documented the largest increase in new county reports of A. americanum in Kentucky, Illinois, Indiana, and Ohio. These findings demonstrate the utility of crowdsourced photograph-based tick surveillance as a complement to other tick surveillance strategies in documenting tick distributions on a nationwide scale, its potential for identifying new foci, and its ability to highlight at-risk localities that might benefit from tick-bite prevention education.