Search

A promising alternative approach to conventional vector and rodent control practices is the use of a bait containing a rodenticide and acaricide in controlling vectors and pathogen reservoirs concurrently. In the United States, Lyme disease continues to be the most prevalent vector-borne disease with approximately 500,000 Lyme disease cases estimated each year. Previous research has demonstrated the usefulness of a low dose fipronil bait in controlling Ixodes scapularis larvae feeding on white-footed mice. However, considering white-footed mice can be an unwanted species because of their association with tick-borne disease and hantaviruses, a combination rodent and tick bait (RTB) might provide a useful alternative to encourage additional community participation in integrated tick management (ITM) efforts. The purpose of this research was to evaluate the use of RTB (0.025 % warfarin, 0.005 % fipronil) in controlling white-footed mice and I. scapularis larvae. Studies were designed in part based on Environmental Protection Agency (EPA) guidelines. A laboratory choice test was conducted to evaluate the use of RTB in controlling white-footed mice over 15-day exposure when they were exposed to an alternative diet. Mice were observed every day for mortality and signs of warfarin toxicity. A simulated field test was conducted to evaluate the use of RTB, presented in the presence of an alternative diet, in controlling I. scapularis parasitizing white-footed mice over 4-day exposure. Mice were fitted with capsules and manually infested with I. scapularis larvae. The inside of each capsule was observed to evaluate tick attachment. Replete larvae detaching from each mouse were collected. Blood was collected from all treatment group mice via cardiac puncture to determine the fipronil sulfone concentration in plasma for each animal. Results indicated that RTB would be adequately consumed in the presence of an alternative diet under laboratory and simulated field conditions. Treatment with RTB resulted in 100 % mortality of white-footed mice during 15-day exposure and prevented 100 % larvae from feeding to repletion during 4-day exposure. All mice succumbing to RTB showed signs of warfarin toxicity. All mice parasitized with ticks that were exposed to RTB had fipronil sulfone detectable in plasma, with even the lowest concentration detected (8.1 parts per billion) controlling 100 % parasitizing I. scapularis larvae. The results suggest that RTB could be a useful means of rodent and tick control for use in ITM programs., (Copyright © 2024 The Author(s). Published by Elsevier GmbH.. All rights reserved.)

Lyme disease has expanded into the Great Plains of the USA. To investigate local enzootic transmission, small mammals were trapped in two forested tracts in northeastern North Dakota during 2012 and 2013. Peromyscus mice and southern red-backed voles, Myodes gapperi, comprised over 90% of all mammals captured. One site was dominated by Peromyscus (79% of 100 mammals captured). At the other site, M. gapperi (59% of 107 mammals captured) was more abundant than Peromyscus (36%). Immature stages of two tick species parasitized small mammals: Dermacentor variabilis and Ixodes scapularis. Larval I. scapularis ectoparasitism was significantly higher on Peromyscus (81% infested; 3.7 larvae per infested mouse) than M. gapperi (47% infested; 2.6 larvae per infested vole) whereas larval and nymphal D. variabilis ectoparasitism were highest on M. gapperi. Over 45% of infested rodents were concurrently infested with both tick species. Testing engorged I. scapularis larvae from Peromyscus (n = 66) and M. gapperi (n = 20) yielded xenopositivity prevalence for Borrelia burgdorferi sensu lato (s.l.) in these rodents of 6% and 5%, respectively. Progeny of field collected M. gapperi were used to determine host infectivity for a local isolate of B. burgdorferi sensu stricto (s.s.). Five M. gapperi were injected with spirochetes, infested with pathogen-free I. scapularis larvae on days 10, 20, and 40 after infection, and engorged larvae molted to nymphs. Subsamples of nymphs were tested by PCR for B. burgdorferi s. s. DNA and yielded infection rates of 56% (n = 100 nymphs tested), 75% (n = 8) and 64% (n = 31), respectively. The remaining infected nymphs were fed on BALB/c Mus musculus mice and 7 d later, mice were euthanized, and tissues were cultured for B. burgdorferi s.s. Nymphs successfully transmitted spirochetes to 13 of 18 (72%) mice that were exposed to 1-5 infected ticks. Theoretical reservoir potentials - i.e., ability to generate B. burgdorferi infected nymphs - were compared between Peromyscus and M. gapperi. At one site, Peromyscus accounted for nearly all Borrelia-infected nymphs produced (reservoir potential value of 0.935). At the other site, the reservoir potentials for Peromyscus (0.566) and M. gapperi (0.434) were comparable. The difference was attributed to differences in the relative abundance of voles versus mice between sites and the higher level of ectoparasitism by larval I. scapularis on Peromyscus versus M. gapperi at both sites. The southern red-backed vole, M. gapperi, contributes to the enzootic maintenance of Lyme disease spirochetes in North Dakota and possibly other areas where this rodent species is abundant., Competing Interests: Declaration of competing interest The authors declare that they have no competing financial interests or personal relationships that could influence the work reported in this paper., (Copyright © 2024 The Authors. Published by Elsevier GmbH.. All rights reserved.)

Ixodes scapularis, the black-legged tick, is a major arthropod vector that transmits the causative agents of Lyme disease and several other pathogens of human significance. The tick midgut is the main tissue involved in blood acquisition and digestion and the first organ to have contact with pathogens ingested through the blood meal. Gene expression in the midgut before, during, and after a blood meal may vary in response to the physiological changes due to blood feeding. A systems biology approach based on RNA and protein sequencing was used to gain insight into the changes in tick midgut transcripts and proteins during blood ingestion (unfed and partially fed) and digestion (1-, 2-, 7-, and 14 days post detachment from the host) by the Ixodes scapularis female ticks. A total of 2,726 differentially expressed transcripts, and 449 proteins were identified across the time points. Genes involved in detoxification of xenobiotics, proteases, protease inhibitors, metabolism, and immunity were differentially expressed in response to blood feeding. Similarly, proteins corresponding to the same groups were also differentially expressed. Nine genes from major gene categories were chosen as potential vaccine candidates, and, using RNA interference, the effect of these gene knockdowns on tick biology was investigated. Knockdown of these genes had variable negative impacts on tick physiology, such as the inability to engorge fully and to produce eggs and increased mortality. These and additional gene targets provide opportunities to explore novel tick control strategies., Competing Interests: Declaration of competing interest The authors have declared no competing interests., (Copyright © 2024 The Author(s). Published by Elsevier GmbH.. All rights reserved.)

The burden of tick-borne diseases continues to increase in the United States. Tick surveillance has been implemented to monitor changes in the distribution and prevalence of human disease-causing pathogens in ticks that frequently bite humans. Such efforts require accurate identification of ticks to species and highly sensitive and specific assays that can detect and differentiate pathogens from genetically similar microbes in ticks that have not been demonstrated to be pathogenic in humans. We describe a modification to a next generation sequencing pathogen detection assay that includes a target that accurately identifies Ixodes ticks to species. We show that the replacement of internal control primers used to ensure assay performance with primers that also act as an internal control and can additionally differentiate tick species, retains high sensitivity and specificity, improves efficiency, and reduces costs by eliminating the need to run separate assays to screen for pathogens and for tick identification., Competing Interests: Declaration of competing interest none., (Copyright © 2024. Published by Elsevier GmbH.)

Ixodes scapularis ticks are vectors of infectious agents that cause illness in humans, including Lyme disease. Recent years have seen a surge in tick-borne diseases (TBD) resulting in a high demand for tick management products. Plants offer a valuable source of active compounds for the development of novel, eco-friendly tick control products, reducing potential risks to human and animal health. Essential oils (EOs) have emerged as potential acaricides and repellents against ticks providing an alternative to synthetic chemicals and aiding in the prevention of TBD by lowering the risk of tick bites. We investigated the acaricidal activity of EOs from lemongrass (Cymbopogon citratus), geranium (Pelargonium x asperum), savory thyme (Thymus saturejoides), and white thyme (Thymus zygis) on I. scapularis. The interactions (i.e., synergistic, antagonistic, or additive) of their binary mixtures were also evaluated. EO samples were analyzed via gas chromatography-mass spectrometry to determine their chemical composition. The adult immersion test was used to determine the lethal concentration (LC 50 ) of each EO alone and in mixtures. Quantitative assessment of synergistic, additive, or antagonistic effect of the binary mixtures was performed by calculating the combination index. Strong acaricidal activity was recorded for savory thyme and white thyme EOs, with LC 50 values of 28.0 and 11.0 μg/μL, respectively. The LC 50 of lemongrass and geranium EOs were 49.0 and 39.7 μg/μL, respectively. Among the tested EOs, savory thyme and white thyme had a strong acaricidal effect on I. scapularis, which might be linked to the presence of carvacrol (26.05 % ± 0.38) and thymol (53.6 % ± 2.31), main components present in savory thyme and white thyme EOs, respectively. The tick killing efficacy of lemongrass and geranium EOs was lower when mixed than when used separately (LC 50 of 65.3 µg/µL). The same happened with savory thyme and white thyme EOs, except at 9.75 µg/µL where they had a synergistic effect (LC 50 of 58.3 µg/µL). Lemongrass and savory thyme EOs had a synergistic effect at low concentrations, and an antagonistic effect at higher concentrations (LC 50 of 95.4 µg/µL). Lemongrass and white thyme EOs had a synergistic effect against ticks from 15 to 120 µg/µL (LC 50 of 18.5 µg/µL) similar to white thyme EO. Geranium and savory thyme EOs had an antagonistic effect at all concentrations, with an LC 50 of 66.8 µg/µL. Geranium and white thyme EOs also had an antagonistic effect, except at 12.7 µg/µL where they had a synergistic effect (LC 50 of 66.8 µg/µL). The interaction observed when combining selected essential oils suggests promising potential for developing acaricidal formulations aimed at controlling ticks and curbing the transmission of tick-borne disease agents., Competing Interests: Declaration of interests The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Authors. Published by Elsevier GmbH.. All rights reserved.)

Borrelia burgdorferi is a tick-borne spirochete that causes Lyme disease in humans. The host immune system controls the abundance of the spirochete in the host tissues. Recent work with immunocompetent Mus musculus mice strain C3H/HeJ found that males had a higher tissue infection prevalence and spirochete load compared to females. The purpose of this study was to determine whether host sex and acquired immunity interact to influence the prevalence and abundance of spirochetes in the tissues of the commonly used mouse strain C57BL/6. Wildtype (WT) mice and their SCID counterparts (C57BL/6) were experimentally infected with B. burgdorferi via tick bite. Ear biopsies were sampled at weeks 4, 8, and 12 post-infection (PI) and five tissues (left ear, ventral skin, heart, tibiotarsal joint of left hind leg, and liver) were collected at necropsy (16 weeks PI). The mean spirochete load in the tissues of the SCID mice was 260.4x higher compared to the WT mice. In WT mice, the infection prevalence in the ventral skin was significantly higher in males (40.0 %) compared to females (0.0 %), and the spirochete load in the rear tibiotarsal joint was significantly higher (4.3x) in males compared to females. In SCID mice, the spirochete load in the ventral skin was 200.0x higher in males compared to females, but there were no significant sex-specific difference in spirochete load in the other tissues (left ear, heart, tibiotarsal joint, or liver). Thus, the absence of acquired immunity greatly amplified the spirochete load in the ventral skin of male mice. It is important to note that the observed sex-specific differences in laboratory mice cannot be extrapolated to humans. Future studies should investigate the mechanisms underlying the male bias in the abundance of B. burgdorferi in the mouse skin., Competing Interests: Declaration of competing interests The authors declare that they have no conflicts of interest., (Copyright © 2024. Published by Elsevier GmbH.)

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

Guinea pigs repeatedly exposed to Ixodes scapularis develop acquired resistance to the ticks (ATR). The molecular mechanisms of ATR have not been fully elucidated, and partially involves immune responses to proteins in tick saliva. In this study, we examined the metabolome of sera of guinea pigs during the development of ATR. Induction of components of the tyrosine metabolic pathway, including hydroxyphenyllactic acid (HPLA), were associated with ATR. We therefore administered HPLA to mice, an animal that does not develop ATR, and exposed the animals to I. scapularis. We also administered nitisinone, a known inhibitor of tyrosine degradation, to another group of mice. The mortality of I. scapularis that fed on mice given HPLA or nitisinone was 26 % and 72 % respectively, compared with 2 % mortality among ticks that fed on control animals. These data indicate that tick bites alter the guinea pig metabolome, and that the tyrosine metabolism pathway can potentially be targeted for I. scapularis control., Competing Interests: Declaration of Competing Interest Authors declare that they have no competing interests., (Copyright © 2023 The Author(s). Published by Elsevier GmbH.. All rights reserved.)

Ixodes scapularis (the blacklegged tick) was considered a species of no medical concern until the mid-1970s. By that time, the tick's geographic distribution was thought to be mainly in the southeastern United States (US), with additional localized populations along the Eastern Seaboard north to southern Massachusetts and in the Upper Midwest. Since 1975, I. scapularis has been implicated as a vector of seven human pathogens and is now widely distributed across the eastern US up to the border with Canada. Geographic expansion of tick-borne diseases associated with I. scapularis (e.g., Lyme disease, anaplasmosis, and babesiosis) is attributed to an expanding range of the tick. However, due to changes in tick surveillance efforts over time, it is difficult to differentiate between range expansion and increased recognition of already established tick populations. We provide a history of the documented occurrence of I. scapularis in the US from its description in 1821 to present, emphasizing studies that provide evidence of expansion of the geographic distribution of the tick. Deforestation and decimation of the white-tailed deer (Odocoileus virginianus), the primary reproductive host for I. scapularis adults, during the 1800s presumably led to the tick disappearing from large areas of the eastern US where it previously had been established. Subsequent reforestation and deer population recovery, together with recent climate warming, contributed to I. scapularis proliferating in and spreading from refugia where it had persisted into the early 1900s. From documented tick collection records, it appears I. scapularis was present in numerous locations in the southern part of the eastern US in the early 1900s, whereas in the north it likely was limited to a small number of refugia sites during that time period. There is clear evidence for established populations of I. scapularis in coastal New York and Massachusetts by 1950, and in northwestern Wisconsin by the late 1960s. While recognizing that surveillance for I. scapularis increased dramatically from the 1980s onward, we describe multiple instances of clearly documented expansion of the tick's geographic distribution in the Northeast, Upper Midwest, and Ohio Valley regions from the 1980s to present. Spread and local population increase of I. scapularis, together with documentation of Borrelia burgdorferi sensu stricto in host-seeking ticks, was universally followed by increases in Lyme disease cases in these areas. Southward expansion of northern populations of I. scapularis, for which the host questing behavior of the nymphal stage leads to substantially higher risk of human bites compared with southern populations, into Virginia and North Carolina also was followed by rising numbers of Lyme disease cases. Ongoing surveillance of ticks and tick-borne pathogens is essential to provide the data needed for studies that seek to evaluate the relative roles of land cover, tick hosts, and climate in explaining and predicting geographic expansion of ticks and tick-borne diseases., (Published by Elsevier GmbH.)

Tick-borne diseases continue to threaten human health across the United States. Both active and passive tick surveillance can complement human case surveillance, providing spatio-temporal information on when and where humans are at risk for encounters with ticks and tick-borne pathogens. However, little work has been done to assess the concordance of the acarological risk metrics from each surveillance method. We used data on Ixodes scapularis and its associated human pathogens from Connecticut (2019-2021) collected through active collections (drag sampling) or passive submissions from the public to compare county estimates of tick and pathogen presence, infection prevalence, and tick abundance by life stage. Between the surveillance strategies, we found complete agreement in estimates of tick and pathogen presence, high concordance in infection prevalence estimates for Anaplasma phagocytophilum, Borrelia burgdorferi sensu stricto, and Babesia microti, but no consistent relationships between actively and passively derived estimates of tick abundance or abundance of infected ticks by life stage. We also compared nymphal metrics (i.e., pathogen prevalence in nymphs, nymphal abundance, and abundance of infected nymphs) with reported incidence of Lyme disease, anaplasmosis, and babesiosis, but did not find any consistent relationships with any of these metrics. The small spatial and temporal scale for which we had consistently collected active and passive data limited our ability to find significant relationships. Findings are likely to differ if examined across a broader spatial or temporal coverage with greater variation in acarological and epidemiological outcomes. Our results indicate similar outcomes between some actively and passively derived tick surveillance metrics (tick and pathogen presence, pathogen prevalence), but comparisons were variable for abundance estimates., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Published by Elsevier GmbH.)

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., Competing Interests: Declaration of Competing Interest The authors declare no conflicts of interest., (Copyright © 2023. Published by Elsevier GmbH.)

While the topical acaricidal treatment of rodent pathogen reservoirs has been readily explored over the past several decades, oral systemic acaricidal treatment is only recently gaining traction as an alternative approach to the management of ticks and tick-borne pathogens. Recent laboratory tests have shown promise in the effectiveness of this systemic strategy against the blacklegged tick (Ixodes scapularis) and a Canadian field evaluation was recently published, but no recent field data from the United States yet exist. With this research, we sought to field deploy a commercially available fipronil-laced bait (Kaput® Flea Control Bait, Scimetrics LLC., Wellington, CO, USA; 0.005% fipronil; Environmental Protection Agency Reg. No. 72500-28), in an alternate use targeting white-footed mice (Peromyscus leucopus) to determine bait acceptance and potential impacts to juvenile I. scapularis burdens. Bait was readily accepted by wild P. leucopus and other rodent reservoirs. An ad libitum distribution strategy as well as placing smaller volumes of fipronil-laced bait within individual Sherman traps both resulted in significant reductions (57-94%) in juvenile I. scapularis burdens as compared to control over two years. The oral delivery of systemic acaricides shows promise in reduction of I. scapularis burdens on P. leucopus and should be further explored to determine effectiveness on host-seeking tick abundances, associated pathogen infection, and potentially incorporated into integrated tick management programs., (Copyright © 2023 The Authors. Published by Elsevier GmbH.. All rights reserved.)

The geographic range of the blacklegged tick, Ixodes scapularis, is expanding northward from the United States into southern Canada, and studies suggest that the lone star tick, Amblyomma americanum, will follow suit. These tick species are vectors for many zoonotic pathogens, and their northward range expansion presents a serious threat to public health. Climate change (particularly increasing temperature) has been identified as an important driver permitting northward range expansion of blacklegged ticks, but the impacts of host movement, which is essential to tick dispersal into new climatically suitable regions, have received limited investigation. Here, a mechanistic movement model was applied to landscapes of eastern North America to explore 1) relationships between multiple ecological drivers and the speed of the northward invasion of blacklegged ticks infected with the causative agent of Lyme disease, Borrelia burgdorferi sensu stricto, and 2) its capacity to simulate the northward range expansion of infected blacklegged ticks and uninfected lone star ticks under theoretical scenarios of increasing temperature. Our results suggest that the attraction of migratory birds (long-distance tick dispersal hosts) to resource-rich areas during their spring migration and the mate-finding Allee effect in tick population dynamics are key drivers for the spread of infected blacklegged ticks. The modeled increases in temperature extended the climatically suitable areas of Canada for infected blacklegged ticks and uninfected lone star ticks towards higher latitudes by up to 31% and 1%, respectively, and with an average predicted speed of the range expansion reaching 61 km/year and 23 km/year, respectively. Differences in the projected spatial distribution patterns of these tick species were due to differences in climate envelopes of tick populations, as well as the availability and attractiveness of suitable habitats for migratory birds. Our results indicate that the northward invasion process of lone star ticks is primarily driven by local dispersal of resident terrestrial hosts, whereas that of blacklegged ticks is governed by long-distance migratory bird dispersal. The results also suggest that mechanistic movement models provide a powerful approach for predicting tick-borne disease risk patterns under complex scenarios of climate, socioeconomic and land use/land cover changes., Competing Interests: Declaration of Competing Interest None., (Crown Copyright © 2023. Published by Elsevier GmbH. All rights reserved.)

Tick-borne disease poses a growing public health burden in the United States and understanding the patterns of presence and density of infected vector ticks is key to developing and implementing effective public health management strategies. Citizen science has emerged as a highly effective means to generate data sets on the geographical distribution of tick species. But to date, nearly all citizen science studies of ticks are 'passive surveillance' programs in which researchers accept reports of ticks, together with either physical specimens or digital images, found opportunistically on people, pets, and livestock from community members for species identification and in some cases also tick-borne pathogen detection. These studies are limited because data are not collected systematically, making comparisons among locations and over time challenging, and introducing considerable reporting bias. In this study, we engaged citizen scientists in 'active surveillance' of host-seeking ticks, training volunteers to actively collect ticks on their woodland properties in an emergent region of tick-borne disease in the state of Maine, USA. We developed volunteer recruitment strategies, materials to train volunteers in data collection methods, field data collection protocols based on techniques used by professional scientists, and a variety of incentives to promote volunteer retention and satisfaction with their experiences, and we communicated research findings to participants. A total of 125 volunteers in 2020 and 181 volunteers in 2021 collected 7,246 ticks in southern and coastal Maine, including the American dog tick (Dermacentor variabilis, 4,023 specimens), the blacklegged tick (Ixodes scapularis, 3,092 specimens), and the rabbit tick (Haemaphysalis leporispalustris, 102 specimens). We demonstrated the feasibility of citizen scientists collecting ticks using active surveillance methods and found that volunteers were motivated to participate largely by their interest in the scientific problem and a desire to learn about ticks on their properties., Competing Interests: Declaration of Competing Interests The authors declare no competing interests., (Copyright © 2023 The Author(s). Published by Elsevier GmbH.. All rights reserved.)

Forest thinning is a management tool used in the New Jersey Pinelands and elsewhere to improve forest health and resilience, mitigate wildfire risk, and manage for wildlife. Forest thinning leads to warmer drier microclimates, which have been shown in both field and laboratory studies to reduce tick survival and reproduction. To directly assess the effects of forest thinning on the abundance and diversity of ticks and on the prevalence of tick-borne human pathogens, we sampled ticks weekly from March to November 2021 at three replicated pairs of thinned and unthinned forest sites composed primarily of pitch-pine, shortleaf pine, and various oak species. We characterized microclimate in the understory and forest floor at each sampling plot by deploying multiple data loggers to monitor temperature and relative humidity throughout the study period. As expected, we found that thinned plots were significantly drier and warmer than unthinned plots. We also found that average questing tick abundance was 92% lower in thinned as compared with unthinned plots. Of the three main tick species collected in unthinned plots (Amblyomma americanum, Ixodes scapularis, and Dermacentor albipictus) only A. americanum and a single I. scapularis were collected in thinned plots. Prevalence of Ehrlichia species in A. americanum did not differ between treatments, and the sole I. scapularis collected in a thinned plot was infected with Borrelia burgdorferi sensu lato. However, the significant and much lower tick abundance in thinned plots indicates a lower risk of human-tick encounters. Our results add to the growing evidence that landscape and forest management can reduce local tick abundance, thereby reducing tick-borne disease risk., Competing Interests: Declaration of Competing Interest none, (Copyright © 2022. Published by Elsevier GmbH.)

Climatic and land use changes have contributed to substantial changes in the abundance, distribution, and activity patterns of ticks in Canada, which have led to an increased risk of tick bites and tick-borne pathogen exposure for companion animals. The objectives of this study were to describe current spatial and temporal patterns of Ixodes spp. on companion animals in Canada and explore the association between tick bites and dog and cat demographic factors. Ticks were collected for one year (April 2019 - March 2020) from 94 veterinary clinics. Included with each submission was a short questionnaire containing owner-reported information on travel history, date of removal and suspected location of tick acquisition, and animal-specific demographic factors. Ticks were identified morphologically using a stereomicroscope, standard keys, and through PCR analyses. Mixed effect multivariable logistic regression models were built to explore the association between an Ixodes scapularis bite and animal demographic factors; veterinary clinic was included as a random effect. Approximately 2300 submissions were received from clinics across Canada, totalling 4425 ticks. The most common Ixodes spp. was I. scapularis (n = 2168), followed by Ixodes pacificus (n = 172) and Ixodes cookei (n = 155). Ixodes scapularis were well distributed in regions across central and eastern Canada. Ixodes cookei was found in eastern Canada, with the greatest numbers from Quebec and New Brunswick. Ixodes pacificus submissions were restricted to British Columbia. Across eastern Canada, dogs of the herding, mixed breed (large and small), sporting, working, terrier, and toy breed groups, and spayed cats were all found to have higher odds of acquiring I. scapularis, compared to other tick species. For the dog model, significant interactions were found between predictor variables age and sex. Regional information on tick distribution, seasonality, and risk factors for acquisition contribute to evidence-based veterinary practices for tick and tick-borne disease control in Canada., (Copyright © 2022 The Author(s). Published by Elsevier GmbH.. All rights reserved.)

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., (Copyright © 2022 The Authors. Published by Elsevier GmbH.. All rights reserved.)

Lyme disease, caused primarily in North America by the bacterium Borrelia burgdorferi sensu stricto, is the most frequently reported vector-borne disease in North America and its geographic extent is increasing in all directions from foci in the northeastern and north central United States. Several southeastern states, including Virginia and North Carolina, have experienced large increases in Lyme disease incidence in the past two decades, with the biggest changes in incidence occurring in the western portion of each state. We tested the hypothesis that B. burgdorferi s.s. was present in western Virginia and North Carolina Peromyscus leucopus populations prior to the recent emergence of Lyme disease. Specifically, we examined archived P. leucopus museum specimens, sampled between 1900 and 2000, for B. burgdorferi s.s. DNA. After confirming viability of DNA extracted from ear punch biopsies from P. leucopus study skins collected between 1945 and 2000 in 19 Virginia counties and 17 North Carolina counties, we used qPCR of two species-specific loci to test for the presence of B. burgdorferi s.s. DNA. Ten mice, all collected from the Eastern Shore of Virginia in 1989, tested positive for presence of B. burgdorferi; all of the remaining 344 specimens were B. burgdorferi-negative. Our results suggest that B. burgdorferi s.s was not common in western Virginia or North Carolina prior to the emergence of Lyme disease cases in the past two decades. Rather, the emergence of Lyme disease in this region has likely been driven by the relatively recent expansion of B. burgdorferi s.s. in southward-moving ticks and reservoir hosts in the mountainous counties of these two states., (Copyright © 2022. Published by Elsevier GmbH.)

Lyme disease is an emerging public health threat in Ontario, Canada due to ongoing range expansion of the tick vector, Ixodes scapularis. Tick density is an important predictor of human Lyme disease risk and is typically measured using active tick surveillance via drag sampling, which is time and resource-intensive. New cost-effective tools are needed to augment current surveillance activities. Our objective was to evaluate the ability of a maximum entropy (Maxent) species distribution model to predict I. scapularis density in three regions of Ontario - Ottawa, Kingston, and southern Ontario - in order to determine its utility in predicting the public health risk of Lyme disease. Ticks were collected via drag sampling at 60 sites across the three regions. Model-predicted habitat suitability was calculated from a previously constructed Maxent model as the mean predicted habitat suitability within a 1-km radius of each site. Spearman's correlation coefficient was used to quantify the continuous relationship between model-predicted habitat suitability and tick density, and negative binomial regression was used to quantify the relationship between tick density and model-predicated habitat suitability. Spearman's correlation coefficients for the full study area, Kingston region, and Ottawa region were 0.517, 0.707, and 0.537, respectively, indicating a moderate positive relationship and ability of the model to predict tick density. Regression analysis further demonstrated a significant positive association between tick density and model-predicted habitat suitability (p< 0.001). Using a dichotomized measure of model-predicted habitat suitability, the incidence rate ratio - the ratio of ticks per m 2 in sites predicted to have a 'suitable' habitat compared to those predicted to have 'not suitable' habitat - was 33.95, indicating that tick density was significantly higher at sites situated in areas with predicted suitable habitat. Given that tick density is an important component of Lyme disease risk, the ability to predict high tick density locations using the Maxent model may make it a cost-effective tool for identifying geographic areas that pose elevated public health risk of Lyme disease., (Copyright © 2022. Published by Elsevier GmbH.)

Borrelia miyamotoi is a relapsing fever spirochete carried by Ixodes spp. ticks throughout the northern hemisphere. The pathogen is acquired either transovarially (vertically) or horizontally through blood-feeding and passed transtadially across life stages. Despite these complementary modes of transmission, infection prevalence of ticks with B. miyamotoi is typically low (<5%) in natural settings and the relative contributions of the two transmission modes have not been studied extensively. Horizontal transmission of B. miyamotoi (strain CT13-2396 or wild type strain) was initiated using infected Ixodes scapularis larvae or nymphs to expose rodents, which included both the immunocompetent CD-1 laboratory mouse (Mus musculus) and a natural reservoir host, the white-footed mouse (Peromyscus. leucopus), to simulate natural enzootic transmission. Transovarial transmission was evaluated using I. scapularis exposed to B. miyamotoi as either larvae or nymphs feeding on immunocompromised SCID mice (M. musculus) and subsequently fed as females on New Zealand white rabbits. Larvae from infected females were qPCR-tested individually to assess transovarial transmission rates. Tissue tropism of B. miyamotoi in infected ticks was demonstrated using in situ hybridization. Between 1 and 12% of ticks were positive (post-molt) for B. miyamotoi after feeding on groups of CD-1 mice or P. leucopus with evidence of infection, indicating that horizontal transmission was inefficient, regardless of whether infected larvae or nymphs were used to challenge the mice. Transovarial transmission occurred in 7 of 10 egg clutches from infected females. Filial infection prevalence in larvae ranged from 3 to 100% (median 71%). Both larval infection prevalence and spirochete load were highly correlated with maternal spirochete load. Spirochetes were disseminated throughout the tissues of all three stages of unfed ticks, including the salivary glands and female ovarian tissue. The results indicate that while multiple transmission routes contribute to enzootic maintenance of B. miyamotoi, transovarial transmission is likely to be the primary source of infected ticks and therefore risk assessment and tick control strategies should target adult female ticks., (Copyright © 2022. Published by Elsevier GmbH.)

Cases of anomalous morphologies in the blacklegged tick, Ixodes scapularis, have been reported in both field-collected and human-biting specimen in the Northeastern and Midwestern United States, complicating the identification of this medically important tick species. We herein describe four cases of morphological anomalies in I. scapularis females exhibiting nanism and abnormally small genital apertures. We also report a female I. scapularis displaying slight asymmetry in the lower abdomen oriented toward the right side and an abnormal anal groove completely enclosing the anus. The identity of each specimen was confirmed using taxonomic keys, high resolution light and scanning electron microscopy imaging, and DNA sequencing of the 18S rRNA gene. All specimens described in this study were found parasitizing human hosts and were submitted to the Connecticut Agricultural Experiment Station-Tick Testing Laboratory in 2021 for species identification and pathogen screening. Here, we also discuss recent reports of teratological abnormalities in I. scapularis as well as likely causes for such deformities and potential implications., (Copyright © 2022. Published by Elsevier GmbH.)

Lyme disease is the most common tick-borne illness in the United States and is becoming more prevalent each year. It is transmitted to humans and animals through the bites of Ixodes scapularis ticks infected with Borrelia burgdorferi in the eastern United States, I. pacificus in the western U.S, and I. ricinus in Europe and Asia. In Kentucky, where Lyme disease is non-endemic, the number of reported human cases in 2010 totaled five. In 2019, that number had increased by over 300%. Identifying the distribution of I. scapularis populations infected with B. burgdorferi is important data for effective prevention strategies and an important first step in monitoring disease spread. In collaboration with the Kentucky Department for Public Health, we performed surveillance for I. scapularis throughout the state of Kentucky using both active and passive surveillance methods. Diagnostic testing for the identification of B. burgdorferi (sensu stricto) was also conducted. We identified 457 I. scapularis ticks from March 2019 to December 2020 from 32 counties in Kentucky. B. burgdorferi was detected in I. scapularis populations collected from 14 different counties. These results add to the little data that exists in Kentucky on I. scapularis and B. burgdorferi distribution., (Copyright © 2021 Elsevier GmbH. All rights reserved.)

The geographic range of the blacklegged tick, Ixodes scapularis, and its associated human pathogens have expanded substantially over the past 20 years putting an increasing number of persons at risk for tick-borne diseases, particularly in the upper midwestern and northeastern United States. Prevention and diagnosis of tick-borne diseases rely on an accurate understanding by the public and health care providers of when and where persons may be exposed to infected ticks. While tracking changes in the distribution of ticks and tick-borne pathogens provides fundamental information on risk for tick-borne diseases, metrics that incorporate prevalence of infection in ticks better characterize acarological risk. However, assessments of infection prevalence are more labor intensive and costly than simple measurements of tick or pathogen presence. Our objective was to examine whether data derived from repeated sampling at longitudinal sites substantially influences public health recommendations for Lyme disease and anaplasmosis prevention, or if more constrained sampling is sufficient. Here, we summarize inter-annual variability in prevalence of the agents of Lyme disease (Borrelia burgdorferi s.s.) and anaplasmosis (Anaplasma phagocytophilum) in host-seeking I. scapularis nymphs and adults at 28 longitudinal sampling sites in the Upper Midwestern US (Michigan, Minnesota, and Wisconsin). Infection prevalence was highly variable among sites and among years within sites. We conclude that monitoring infection prevalence in ticks aids in describing coarse acarological risk trends, but setting a fixed prevalence threshold for prevention or diagnostic decisions is not feasible given the observed variability and lack of temporal trends. Reducing repeated sampling of the same sites had minimal impact on regional (Upper Midwest) estimates of average infection prevalence; this information should be useful in allocating scarce public health resources for tick and tick-borne pathogen surveillance, prevention, and control activities., (Copyright © 2021. Published by Elsevier GmbH.)

The tick vector of Lyme disease, Ixodes scapularis, is currently expanding its geographical distribution northward into southern Canada driving emergence of Lyme disease in the region. Despite large-scale studies that attributed different factors such as climate change and changes in land use to the geographical expansion of the tick, a comprehensive understanding of local patterns of tick abundance is still lacking in that region. Using a newly endemic periurban nature park located in Quebec (Canada) as a model, we explored intra-habitat patterns in tick distribution and their relationship with biotic and abiotic factors. We verified the hypotheses that (1) there is spatial heterogeneity in tick densities at the scale of the park and (2) these patterns can be explained by host availability, habitat characteristics and microclimatic conditions. During tick activity season in three consecutive years, tick, deer, rodent and bird abundance, as well as habitat characteristics and microclimatic conditions, were estimated at thirty-two sites. Patterns of tick distribution and abundance were investigated by spatial analysis. Generalised additive mixed models were constructed for each developmental stage of the tick and the relative importance of significant drivers on tick abundance were derived from final models. We found fine-scale spatial heterogeneity in densities of all tick stages across the park, with interannual variability in the location of hotspots. For all stages, the local density was related to the density of the previous stage in the previous season, in keeping with the tick's life cycle. Adult tick density was highest where drainage was moderate (neither waterlogged nor dry). Microclimatic conditions influenced the densities of immature ticks, through the effects of weather at the time of tick sampling (ambient temperature and relative humidity) and of the seasonal microclimate at the site level (degree-days and number of tick adverse moisture events). Seasonal phenology patterns were generally consistent with expected curves for the region, with exceptions in some years that may be attributable to founder events. This study highlights fine scale patterns of tick population dynamics thus providing fundamental knowledge in Lyme disease ecology and information applicable to the development of well-targeted prevention and control strategies for public natural areas affected by this growing problem in southern Canada., (Copyright © 2021. Published by Elsevier GmbH.)

This study assessed the duration of tick attachment necessary for a successful transmission of Anaplasma phagocytophilum by an infected I. scapularis nymph. Individual nymphs were placed upon BALB/c mice and allowed to feed for predetermined time intervals of 4 to 72 h. Ticks removed from mice at predetermined intervals were tested by PCR for verification of infection and evaluation of the bacterial load. The success of pathogen transmission to mice was assessed by blood-PCR at 7, 14 and 21 days postinfestation, and IFA at 21 days postinfestation. Anaplasma phagocytophilum infection was documented in 10-30 % of mice, from which ticks were removed within the first 20 h of feeding. However, transmission success was ≥70% if ticks remained attached for 36 h or longer. Notably, none of the PCR-positive mice that were exposed to infected ticks for 4 to 8 h and only half of PCR-positive mice exposed for 24 h developed antibodies within 3 weeks postinfestation. On the other hand, all mice with detectable bacteremia after being infested for 36 h seroconverted. This suggests that although some of the ticks removed prior to 24 h of attachment succeed in injecting a small amount of A. phagocytophilum, this amount is insufficient for stimulating humoral immunity and perhaps for establishing disseminated infection in BALB/c mice. Although A. phagocytophilum may be present in salivary glands of unfed I. scapularis nymphs, the amount of A. phagocytophilum initially contained in saliva appears insufficient to cause sustainable infection in a host. Replication and, maybe, reactivation of the agent for 12-24 h in a feeding tick is required before a mouse can be consistently infected., (Copyright © 2021. Published by Elsevier GmbH.)

Deer management (e.g., reduction) has been proposed as a tool to reduce the acarological risk of Lyme disease. There have been few opportunities to investigate Ixodes scapularis (blacklegged tick) and Borrelia burgdorferi sensu stricto dynamics in the absence of white-tailed deer (Odocoileus virginianus) in midwestern North America. A pair of islands in Lake Michigan presented a unique opportunity to study the role of alternative hosts for the adult stage of the blacklegged tick for maintaining a tick population as a deer herd exists on North Manitou Island but not on South Manitou Island, where coyotes (Canis latrans) and hares (Lepus americanus) are the dominant medium mammals. Additionally, we were able to investigate the maintenance of I. scapularis and B. burgdorferi in small mammal communities on both islands, which were dominated by eastern chipmunks (Tamias striatus). From 2011 to 2015, we surveyed both islands for blacklegged ticks by drag cloth sampling, bird mist netting, and small and medium-sized mammal trapping. We assayed questing ticks, on-host ticks, and mammal biopsies for the Lyme disease pathogen, B. burgdorferi. We detected all three life stages of the blacklegged tick on both islands. Of the medium mammals sampled, no snowshoe hares (Lepus americanus, 0/23) were parasitized by adult blacklegged ticks, but 2/2 coyotes (Canis latrans) sampled on South Manitou Island in 2014 were parasitized by adult blacklegged ticks, suggesting that coyotes played a role in maintaining the tick population in the absence of deer. We also detected I. scapularis ticks on passerine birds from both islands, providing support that birds contribute to maintaining as well as introducing blacklegged ticks and B. burgdorferi to the islands. We observed higher questing adult and nymphal tick densities, and higher B. burgdorferi infection prevalence in small mammals and in adult ticks on the island with deer as compared to the deer-free island. On the islands, we also found that 25% more chipmunks were tick-infested than mice, fed more larvae and nymphs relative to their proportional abundance compared to mice, and thus may play a larger role compared to mice in the maintenance of B. burgdorferi. Our investigation demonstrated that alternative hosts could maintain a local population of blacklegged ticks and an enzootic cycle of the Lyme disease bacterium in the absence of white-tailed deer. Thus, alternative adult blacklegged tick hosts should be considered when investigating deer-targeted management tools for reducing tick-borne disease risk, especially when the alternative host community may be abundant and diverse., (Copyright © 2021. Published by Elsevier GmbH.)

Over the past three decades, citizens of Maine in the northeastern United States have experienced increasing blacklegged tick (Ixodes scapularis) abundance and rising incidence of Lyme and other tick-borne diseases. White-tailed deer (Odocoileus virginianus) overabundance has been considered one cause of the high incidence of tick-borne diseases on offshore islands of New England. Most of Maine's 15 offshore, unbridged island communities have a history of concern about ticks, Lyme disease, and white-tailed deer overabundance, but have been challenged to keep deer numbers down through hunting or culls. This history has led to perennial, often divisive community debates about whether and how to reduce the size of their deer herds. In 2016 we conducted a convenience sample survey of year-round and summer residents of Maine's offshore islands to quantify the level of concern about Lyme disease, and assess the motivations and level of support for deer herd reduction. Among respondents, 84 % agreed Lyme disease was a problem on their island and 61 % supported deer herd reduction. Agreement that Lyme disease was a problem was associated with having acquired tick-borne disease as well as with tick bites without disease. Respondents ranked deer overabundance as a top cause of tick abundance and tick-borne disease and supported deer herd reduction as an approach to reduce the risk of Lyme disease. Other problems associated with deer overabundance (vehicle collisions, damage to landscaping, and damage to forests) also motivated support for deer reduction. Approval of doe permits, an expanded archery season, and sharpshooting as reduction methods was greater than an expanded firearms season. Respondents felt responsibility for tick control fell to the town for the most part, and recognized that multiple factors have contributed to the tick problem in Maine, not just deer., (Copyright © 2020 Elsevier GmbH. All rights reserved.)

Measures of acarological risk of exposure to Ixodes scapularis-borne disease agents typically focus on nymphs; however, the relapsing fever group spirochete Borrelia miyamotoi can be passed transovarially, and I. scapularis larvae are capable of transmitting B. miyamotoi to their hosts. To quantify the larval contribution to acarological risk, relative to nymphs and adults, we collected questing I. scapularis for 3 yr at Fort McCoy, Wisconsin (WI, n = 23,367 ticks), and Cape Cod, Massachusetts (MA, n = 4190) in the United States. Borrelia miyamotoi infection prevalence was estimated for I. scapularis larvae, nymphs, females, and males, respectively, as 0.88, 2.05, 0.63, and 1.22 % from the WI site and 0.33, 2.32, 2.83, and 2.11 % from the MA site. Densities of B. miyamotoi-infected ticks (DIT, per 1000 m 2 ) were estimated for larvae, nymphs, females, and males, respectively, as 0.36, 0.14, 0.01, and 0.03 from the WI site and 0.05, 0.06, 0.03, and 0.02 from the MA site. Thus, although larval infection prevalence with B. miyamotoi was significantly lower than that of nymphs and similar to that of adults, because of their higher abundance, the larval contribution to the overall DIT was similar to that of nymphs and trended towards a greater contribution than adults. Assuming homogenous contact rates with humans, these results suggest that eco-epidemiological investigations of B. miyamotoi disease in North America should include larvae. A fuller appreciation of the epidemiological implications of these results, therefore, requires an examination of the heterogeneity in contact rates with humans among life stages., (Copyright © 2020 Elsevier GmbH. All rights reserved.)

Ticks deposit salivary proteins into the skin during a bite to mediate acquisition of a blood meal. Acquired resistance to tick bites has been demonstrated to prevent Borrelia burgdorferi sensu lato (s.l.) transmission. However, the mechanism of resistance, as well as the protective antigens, have remained elusive. To address these unknowns, we utilized a guinea pig model of tick resistance and a mouse model of permissiveness. Guinea pigs developed immunity after multiple Ixodes scapularis tick infestations, characterized by rapid tick detachment and impaired feeding. In comparison, mice tolerated at least 6 infestations with no significant impact on feeding. We analyzed the bite sites by RNA-sequencing and histology, identifying several inflammatory pathways in tick immune animals, such as FcεRI signaling and complement activation, and activation of coagulation pathways that could impair local blood flow. Together, these results identify important pathways altered during tick rejection and potential tick proteins that could serve as vaccine candidates., (Copyright © 2020 Elsevier GmbH. All rights reserved.)

Ticks and tick-borne diseases are on the rise world-wide and vaccines to prevent transmission of tick-borne diseases is an urgent public health need. Tick transmission of pathogens to the mammalian host occurs during tick feeding. Therefore, it is reasoned that vaccine targeting of tick proteins essential for feeding would thwart tick feeding and consequently prevent pathogen transmission. The phenomenon of acquired tick-immunity, wherein, repeated tick infestations of non-natural hosts results in the development of host immune responses detrimental to tick feeding has served as a robust paradigm in the pursuit of tick salivary antigens that may be vaccine targeted. While several salivary antigens have been identified, immunity elicited against these antigens have only provided modest tick rejection. This has raised the possibility that acquired tick-immunity is directed against tick components other than tick salivary antigens. Using Ixodes scapularis, the blacklegged tick, that vectors several human pathogens, we demonstrate that immunity directed against tick salivary glycoproteins is indeed sufficient to recapitulate the phenomenon of tick-resistance. These observations emphasize the utility of tick salivary glycoproteins as viable vaccine targets to thwart tick feeding and direct our search for anti-tick vaccine candidates., (Copyright © 2020 Elsevier GmbH. All rights reserved.)

Ticks are obligate hematophagous arthropods and must tolerate starvation during off-host periods. Macroautophagy (hereafter autophagy) is a well-conserved self-eating mechanism of cell survival and is essential for recycling cellular contents during periods of starvation, stress, and injury in organisms. Although the genome sequence of Ixodes scapularis (Say) is available, the characteristics and functions of autophagy-related gene families remain largely unknown. To advance our understanding of autophagy in I. scapularis, we used comprehensive genomic approaches to identify Atg genes. Homologues of 14 Atg genes were identified, and their protein motif compositions were predicted. Phylogenetic analysis indicated that ATGs in I. scapularis were evolutionarily closely related to their homologues in Haemaphysalis longicornis and Rhipicephalus microplus ticks. Expression patterns of Atg genes differed across tick developmental stages. Immunofluorescence results by monodansylcadaverine (MDC) staining indicated that autophagy was activated after amino acid starvation treatments in I. scapularis embryo-derived cell lines ISE6 and IDE8. Subsequently, the expression of key Atg genes involved in autophagy pathway in both cell lines were examined. In ISE6 cells, the expression levels of three Atg genes (Atg4B, Atg6 and Atg8A) increased significantly after amino acid starvation; similarly, four Atg genes (Atg4A, Atg4B, Atg6 and Atg8B) were upregulated in IDE8 cells in response to starvation. In parallel, the MDC and lysotracker staining results indicated that autophagy was triggered after amino acid starvation treatments in R. microplus embryo-derived cell line BME26. Our observations showed that Atg family genes are highly conserved in ticks and function in autophagy pathway induced by amino acid starvation. These results also provide valuable insight for further autophagy-related research as a new strategy for blocking the transmission of tick-borne pathogens., Competing Interests: Declaration of Competing Interest The authors declare no conflict of interest., (Copyright © 2020 The Authors. Published by Elsevier GmbH.. All rights reserved.)

Recent studies have highlighted the occurrence and distribution of Ixodes scapularis ticks infected with Borrelia burgdorferi sensu stricto (s.s.) around the city of Ottawa, Ontario, Canada, and the need for strategies to mitigate the risk of human exposure and infection. We conducted a field study from July to October 2018 to examine the effectiveness of ecotonal woodchip borders as an environmental control method to suppress the density of host-seeking ticks along recreational trails in Ottawa. We used an experimental design with ten 100-m trail replicates randomized to intervention or control groups, and monitored questing tick density at weekly intervals in mid-summer and early fall. We compared questing tick density between woodchip-treated and untreated trails using a mixed-effects Poisson regression model. Of the 138 I. scapularis ticks collected, there were 86 adult and nymphal ticks, 37 (43 %) of which were positive for B. burgdorferi s.s. A total of 58 Haemaphysalis leporispalustris were also collected. Mean combined adult and nymphal I. scapularis density was 1.15 (1.40 standard deviation; SD) per 100 m in the control group compared to 0.28 (0.56 SD) per 100 m in the intervention group, reflecting a 75 % reduction in questing tick density on trail replicates treated with woodchip borders (p < 0.001). An effect of the intervention was observed in both sampling periods. This study indicates that woodchip borders may be an effective strategy to suppress questing tick density along trail margins where recreational trail users are more active, thereby reducing the likelihood of tick encounters., (Copyright © 2019 The Authors. Published by Elsevier GmbH.. All rights reserved.)

As tick-borne diseases continue to emerge across the United States, there is need for a better understanding of the tick and pathogen communities in the southern states and of habitat features that influence transmission risk. We surveyed questing and on-host ticks in pine-dominated forests with various fire management regimes in the Sam Houston National Forest, a popular recreation area near Houston, Texas. Four linear transects were established- two with a history of controlled burns, and two unburned. Systematic drag sampling yielded 112 ticks from two species, Ixodes scapularis (n=73) and Amblyomma americanum (n=39), with an additional 106 questing ticks collected opportunistically from drag cloth operators. There was a significant difference in systematically-collected questing tick density between unburned (15 and 18 ticks/1000 m 2 ) and burned (2 and 4 ticks/1000 m 2 ) transects. We captured 106 rodents and found 74 ticks on the rodents, predominantly Dermacentor variabilis. One unburned transect had significantly more ticks per mammal than any of the other three transects. DNA of Rickettsia species was detected in 146/292 on and off-host ticks, including the 'Rickettsial endosymbiont of I. scapularis' and Rickettsia amblyommatis, which are of uncertain pathogenicity to humans. Borrelia lonestari was detected in one A. americanum, while Borrelia burgdorferi sensu stricto, the agent of Lyme disease, was not detected in any tick samples. Neither Borrelia nor Rickettsia spp. were detected in any of the mammal ear biopsies (n=64) or blood samples (n=100) tested via PCR. This study documents a high prevalence in ticks of Rickettsia spp. thought to be endosymbionts, a low prevalence of relapsing fever group Borrelia in ticks, and a lack of detection of Lyme disease-group Borrelia in both ticks and mammals in an east Texas forested recreation area. Additionally, we observed low questing tick density in areas with a history of controlled burns. These results expand knowledge of tick-borne disease ecology in east Texas which can aid in directing future investigative, modeling, and management efforts., (Copyright © 2019 The Authors. Published by Elsevier GmbH.. All rights reserved.)

The invasive, human-biting Asian longhorned tick, Haemaphysalis longicornis, was detected in New Jersey in the eastern United States in August of 2017 and by November of 2018 this tick had been recorded from 45 counties across 9 states, primarily along the Eastern Seaboard. The establishment of H. longicornis in the United States has raised the questions of how commonly it will bite humans and which native pathogens may naturally infect this tick. There also is a need for experimental vector competence studies with native pathogens to determine if H. longicornis can acquire a given pathogen while feeding, pass it transstadially, and then transmit the pathogen in the next life stage. In this experimental study, we evaluated the vector competence of a population of H. longicornis originating from the United States (New York) for a native isolate (B31) of the Lyme disease spirochete, Borrelia burgdorferi sensu stricto (s.s.). In agreement with a previous experimental study on the vector competence of H. longicornis for Borrelia garinii, we found that uninfected H. longicornis larvae could acquire B. burgdorferi s.s. while feeding on infected Mus musculus mice (infection prevalence >50% in freshly fed larvae) but that the infection was lost during the molt to the nymphal stage. None of 520 tested molted nymphs were found to be infected, indicating that transstadial passage of B. burgdorferi s.s. is absent or rare in H. longicornis; and based on the potential error associated with the number of nymphs testing negative in this study, we estimate that the upper 95% limit for infection prevalence was 0.73%. An Ixodes scapularis process control showed both effective acquisition of B. burgdorferi s.s. from infected mice by uninfected larvae and transstadial passage to the nymphal stage (infection prevalence of 80-82% for both freshly fed larvae and molted nymphs). We also observed that although H. longicornis larvae could be compelled to feed on mice by placing the ticks within feeding capsules, attachment and feeding success was minimal (<0.5%) when larvae were placed freely on the fur of the mice. We conclude that H. longicornis is unlikely to contribute more than minimally, if at all, to transmission of Lyme disease spirochetes in the United States., (Published by Elsevier GmbH.)

Ixodes scapularis is the primary vector of Lyme disease spirochetes in eastern and central North America, and local densities of this tick can affect human disease risk. We sampled larvae and nymphs from sites in Massachusetts and Wisconsin, USA, using flag/drag devices and by collecting ticks from hosts, and measured environmental variables to evaluate the environmental factors that affect local distribution and abundance of I. scapularis. Our sites were all forested areas with known I. scapularis populations. Environmental variables included those associated with weather (e.g., temperature and relative humidity), vegetation characteristics (at canopy, shrub, and ground levels), and host abundance (small and medium-sized mammals and reptiles). The numbers of larvae on animals at a given site and season showed a logarithmic relationship to the numbers in flag/drag samples, suggesting limitation in the numbers on host animals. The numbers of nymphs on animals showed no relationship to the numbers in flag/drag samples. These results suggest that only a small proportion of larvae and nymphs found hosts because in neither stage did the numbers of host-seeking ticks decline with increased numbers on hosts. Canopy cover was predictive of larval and nymphal numbers in flag/drag samples, but not of numbers on hosts. Numbers of small and medium-sized mammal hosts the previous year were generally not predictive of the current year's tick numbers, except that mouse abundance predicted log numbers of nymphs on all hosts the following year. Some measures of larval abundance were predictive of nymphal numbers the following year. The mean number of larvae per mouse was well predicted by measures of overall larval abundance (based on flag/drag samples and samples from all hosts), and some environmental factors contributed significantly to the model. In contrast, the mean numbers of nymphs per mouse were not well predicted by environmental variables, only by overall nymphal abundance on hosts. Therefore, larvae respond differently than nymphs to environmental factors. Furthermore, flag/drag samples provide different information about nymphal numbers than do samples from hosts. Flag/drag samples can provide information about human risk of acquiring nymph-borne pathogens because they provide information on the densities of ticks that might encounter humans, but to understand the epizootiology of tick-borne agents both flag/drag and host infestation data are needed., (Copyright © 2019. Published by Elsevier GmbH.)

Cases of morphological anomalies in the blacklegged tick, Ixodes scapularis (Acari: Ixodidae), have recently been reported from the Northeastern and upper Midwestern United States, potentially complicating identification of this important vector of human disease-causing pathogens. We hereby report a case of a morphological anomaly in I. scapularis, biting a human host residing in Norwich, Connecticut. Using a dichotomous morphological key, high-resolution and scanning electron microscopy images, as well as DNA sequencing, the tick was identified as an adult female I. scapularis with three legs on the left side of the abdomen versus four on the right side, which we believe is the first case of ectromely in an adult I. scapularis. Using diagnostic genes in polymerase chain reaction, the specimen tested positive for Borrelia burgdorferi sensu lato and Anaplasma phagocytophilum, the causative agents for Lyme disease and anaplasmosis, respectively, and also showed evidence of a rickettsial endosymbiont. Here we discuss recent reports of morphological anomalies in I. scapularis, and emphasize the significance of additional studies of teratology in this important tick species and its potential implications., (Copyright © 2019 Elsevier GmbH. All rights reserved.)

Ixodes scapularis is responsible for the transmission of a variety of pathogens in North America, including Borrelia burgdorferi sensu stricto, Anaplasma phagocytophilum and Babesia microti. Songbirds have previously been described as agents of tick dispersal, and a combination of empirical data and modeling efforts have implicated songbirds in the range expansion of I. scapularis northward into Canada during spring bird migration. The role of fall bird migration has received comparatively less attention, particularly at a continental scale. The aim of the current research was to use a novel individual-based modeling approach (IBM) to investigate the role of southward migrating songbirds in the dispersal of I. scapularis within the continental United States. The IBM used in this research explicitly models dispersal by two extensively studied migrating songbird species, wood thrush Hylocichla mustelina and ovenbird Seiurus aurocapillus. Our IBM predicts the annual dispersal of more than four million ticks by H. mustelina and S. aurocapillus, notably into areas as far west as the Dakotas, and as far south as Central Alabama. Predicted dispersal locations include areas where the southern phenotype of I. scapularis dominates, suggestive of a possible mechanism for previously described unidirectional gene flow from north to south. In addition, the model demonstrates that three species-specific songbird traits - breeding range, migration timing, and propensity for tick attachment - each play a major role in the relative magnitude of tick dispersal by different songbird species. The pattern of I. scapularis dispersal predicted by this model suggests that migrating songbirds may have contributed to the range expansion of the tick historically, and may continue to do so presently and into the future, particularly as climate changes the geographic areas that are suitable for I. scapularis. Ultimately, widespread tick dispersal by migrating songbirds likely increases the human risk of Lyme disease and other tick-borne diseases in the United States., (Copyright © 2019 Elsevier GmbH. All rights reserved.)

Lyme disease is the most prevalent vector-borne disease in the United States. Ixodes scapularis, commonly referred to as the blacklegged tick, is the primary vector of Lyme disease spirochetes, Borrelia burgdorferi sensu lato (s.l.), in the eastern United States. Connecticut has pervasive populations of I. scapularis and remains a hotspot for Lyme disease. A primary aim of this study was to determine if passively collected data on human-biting I. scapularis ticks in Connecticut could serve as a useful proxy for Lyme disease incidence based on the cases reported by the Connecticut Department of Public Health (CDPH). Data for human-biting I. scapularis ticks submitted to the Tick Testing Laboratory at the Connecticut Agricultural Experiment Station (CAES-TTL), and tested for infection with B. burgdorferi s.l., were used to estimate the rate of submitted nymphs, nymphal infection prevalence, and the rate of submitted infected nymphs. We assessed spatiotemporal patterns in tick-based measures and Lyme disease incidence with generalized linear and spatial models. In conjunction with land cover and household income data, we used generalized linear mixed effects models to examine the association between tick-based risk estimates and Lyme disease incidence. Between 2007 and 2017, the CAES-TTL received 26,116 I. scapularis tick submissions and the CDPH reported 23,423 Lyme disease cases. The rate of submitted nymphs, nymphal infection prevalence, the rate of submitted infected nymphs, and Lyme disease incidence all decreased over time during this eleven-year period. The rate of submitted nymphs, the rate of submitted infected nymphs, and Lyme disease incidence were spatially correlated, but nymphal infection prevalence was not. Using a mixed modeling approach to predict Lyme disease incidence and account for spatiotemporal structuring of the data, we found the best fitting tested model included a strong, positive association with the rate of submitted infected nymphs and a negative association with the percent of developed land for each county. We show that within counties, submissions of B. burgdorferi s.l. infected nymphs were strongly and positively associated with inter-annual variation in reported Lyme disease cases. Tick-based passive surveillance programs may be useful in providing independent measures of entomological risk, particularly in settings where Lyme disease case reporting practices change substantially over time., (Copyright © 2019 Elsevier GmbH. All rights reserved.)

We employed high throughput sequencing to survey the microbiomes of Ixodes scapularis collected in New York and Connecticut. We examined 197 individual I. scapularis adults and pools from 132 adults and 197 nymphs. We detected Borrelia burgdorferi sensu stricto in 56.3% of individual ticks, Anaplasma phagocytophilum in 10.6%, Borrelia miyamotoi in 5%, Babesia microti in 7.6%, and Powassan virus in 3.6%. We did not detect Borrelia mayonii, Ehrlichia muris eauclairensis, Bartonella spp. or pathogenic Babesia species other than B. microti. The most abundant bacterium (65%), and only rickettsial species identified, was the endosymbiont Rickettsia buchneri. A filarial nematode was found in 13.7% of adult ticks. Fourteen viruses were detected including South Bay virus (22%) and blacklegged tick phlebovirus 1 and 2 (73%). This study provides insight into the microbial diversity of I. scapularis in New York State and Connecticut., (Copyright © 2019 The Authors. Published by Elsevier GmbH.. All rights reserved.)

Anaplasma phagocytophilum, the agent of human anaplasmosis, is an obligate intracellular bacterium that uses multiple survival strategies to persist in Ixodes scapularis ticks. Our previous study showed that A. phagocytophilum efficiently induced the tyrosine phosphorylation of several Ixodes proteins that includes extended phosphorylation of actin at tyrosine residue Y178. In order to identify the tyrosine kinase responsible for the A. phagocytophilum induced tyrosine phosphorylation of proteins, we combed the I. scapularis genome and identified a non-receptor Src tyrosine kinase ortholog. I. scapularis Src kinase showed high degree of amino acid sequence conservation with Dsrc from Drosophila melanogaster. We noted that at different developmental stages of I. scapularis ticks, larvae expressed significantly higher levels of src transcripts in comparison to the other stages. We found that A. phagocytophilum significantly reduced Src levels in unfed nymphs and in nymphs while blood feeding (48 h during feeding) in comparison to the levels noted to relative uninfected controls. However, A. phagocytophilum increased Src levels in fully engorged larvae and nymphs (48 h post feeding) and in vitro tick cells in comparison to the relative uninfected controls. Inhibition of Src kinase expression and activity by treatment with src-dsRNA or Src-inhibitor, respectively, significantly reduced A. phagocytophilum loads in ticks and tick cells. Overall, our study provides evidence for the important role of I. scapularis Src kinase in facilitating A. phagocytophilum colonization and survival in the arthropod vector., (Copyright © 2019 Elsevier GmbH. All rights reserved.)

Tick microbiomes may play an important role in pathogen transmission. However, the drivers of microbiome variation are poorly understood, and this limitation has impeded mechanistic understanding of the functions of microbial communities for pathogen acquisition. The goal of this research was to characterize the role of the blood meal host in structuring the microbiome of Ixodes scapularis, the primary vector of Lyme disease in the eastern United States, and to determine if ticks that fed from different host species harbor distinct bacterial communities. We performed high-throughput 16S rDNA amplicon sequencing on I. scapularis nymphs that fed as larvae from known wildlife hosts: raccoon, Virginia opossum, striped skunk, red squirrel or gray squirrel. Using Analysis of Similarity, we found significant differences in the abundance-weighted Unifrac distance matrix among ticks fed from different host species (p =  0.048) and a highly significant difference in the weighted and unweighted Unifrac matrices for individuals within species (p <  0.01). This finding of associations between the blood meal host and I. scapularis microbiome demonstrates that the blood meal host may be a driver of microbiome variation that should be accounted for in studies of pathogen acquisition by ticks., (Copyright © 2019 Elsevier GmbH. All rights reserved.)

Most people who contract Lyme borreliosis in the eastern United States (US) acquire infection from the bite of the nymphal life stage of the vector tick Ixodes scapularis, which is present in all eastern states. Yet <5% of Lyme borreliosis cases are reported from outside the north-central and northeastern US. Geographical differences in nymphal questing (i.e., host-seeking behavior) may be epidemiologically important in explaining this latitudinal gradient in Lyme borreliosis incidence. Using field enclosures and a 'common garden' experimental design at two field sites, we directly tested this hypothesis by observing above-litter questing of laboratory-raised nymphal I. scapularis whose parents were collected from 15 locations (= origins) across the species' range. Relative to southern nymphs from origins considered to be of low acarologic risk, northern nymphs from high-risk origins were eight times as likely to quest on or above the surface of the leaf litter. This regional variation in vector behavior (specifically, the propensity of southern nymphs to remain under leaf litter) was highly correlated with Lyme borreliosis incidence in nymphs' counties of origin. We conclude that nymphal host-seeking behavior is a key factor contributing to the low incidence of Lyme borreliosis in southern states. Expansion of northern I. scapularis populations could lead to increased incidence in southern states of Lyme borreliosis and other diseases vectored by this tick, if the 'northern' host-seeking behavior of immigrant nymphs is retained. Systematic surveillance for I. scapularis nymphs questing above the leaf litter in southern states will help predict future geographic change in I. scapularis-borne disease risk., (Copyright © 2019 Elsevier GmbH. All rights reserved.)

Cervid babesiosis, caused by the protozoan hemoparasite Babesia odocoilei and transmitted by the blacklegged tick Ixodes scapularis, is an emerging disease of Canadian cervids. This pathogen has not yet been described in humans. Data are lacking on the role of migratory birds in the adventitious spread of Ba. odocoilei-infected ticks, as well as on the infection status of I. scapularis in environments used by susceptible wildlife hosts. Following a high-mortality outbreak of cervid babesiosis at the Toronto Zoo [TZ], the present study was initiated to investigate Ba. odocoilei and other tick-borne pathogens of veterinary and public health importance (Borrelia burgdorferi sensu stricto (s.s.), Anaplasma phagocytophilum, Borrelia miyamotoi, and Babesia microti) in I. scapularis at three sites in southern Ontario, Canada. Blanket dragging for questing ticks yielded I. scapularis from the three sites evaluated: TZ, Point Pelee National Park, and Long Point Bird Observatory [LPBO]. Babesia odocoilei was identified in I. scapularis collected by dragging at the TZ and at LPBO. Borrelia burgdorferi s.s. was identified in I. scapularis at all three sites. Anaplasma phagocytophilum was identified in I. scapularis collected from the TZ. During the springs of 2016 and 2017, 1102 northward-migrating birds were examined for ticks at LPBO. One or more I. scapularis were found on 3.2% of birds (n = 595) in 2016, and 6.7% (n = 507) of birds in 2017. Overall, across both years, 0.2% and 0.5% of birds carried one or more I. scapularis ticks that tested PCR-positive for Ba. odocoilei and Bo. burgdorferi s.s., respectively. These data indicate that Ba. odocoilei-positive I. scapularis are found in southern Ontario, and suggest that bird-borne ticks have the potential to contribute to range expansion of both Ba. odocoilei and Bo. burgdorferi s.s. in Canada., (Copyright © 2019 Elsevier GmbH. All rights reserved.)

Borrelia miyamotoi is a relapsing fever spirochete transmitted by ticks in the Ixodes ricinus complex. In the eastern United States, B. miyamotoi is transmitted by I. scapularis, which also vectors several other pathogens including B. burgdorferi sensu stricto. In contrast to Lyme borreliae, B. miyamotoi can be transmitted vertically from infected female ticks to their progeny. Therefore, in addition to nymphs and adults, larvae can vector B. miyamotoi to wildlife and human hosts. Two widely varying filial infection prevalence (FIP) estimates - 6% and 73% - have been reported previously from two vertically infected larval clutches; to our knowledge, no other estimates of FIP or transovarial transmission (TOT) rates for B. miyamotoi have been described in the literature. Thus, we investigated TOT and FIP of larval clutches derived from engorged females collected from hunter-harvested white-tailed deer in 2015 (n = 664) and 2016 (n = 599) from Maine, New Hampshire, Tennessee, and Wisconsin. After engorged females oviposited in the lab, they (n = 492) were tested for B. miyamotoi infection by PCR. Subsequently, from each clutch produced by an infected female, larval pools, as well as 100 individual eggs or larvae, were tested. The TOT rate of the 11 infected females was 90.9% (95% CI; 57.1-99.5%) and the mean FIP of the resulting larval clutches was 84.4% (95% CI; 68.1-100%). Even though the overall observed vertical transmission rate (the product of TOT and FIP; 76.7%, 95% CI; 44.6-93.3%) was high, additional horizontal transmission may be required for enzootic maintenance of B. miyamotoi based on the results of a previously published deterministic model. Further investigation of TOT and FIP variability and the underlying mechanisms, both in nature and the laboratory, will be needed to resolve this question. Meanwhile, studies quantifying the acarological risk of Borrelia miyamotoi disease need to consider not only nymphs and adults, but larval I. scapularis as well., (Copyright © 2019 Elsevier GmbH. All rights reserved.)

An inverse relationship between biodiversity and human health has been termed the 'dilution effect' paradigm. In the case of tick-borne infections such as Lyme disease, the key assumption is that Borrelia burgdorferi sensu lato abundance is increased by the loss of less competent (dilution) hosts as biodiversity declines. White-tailed deer play a dual role in the pathogen cycle, as key reproductive hosts for adult ticks and incompetent hosts for the pathogen. While the role of deer as hosts of adult ticks is well established, the extent to which deer also feed immature ticks and reduce the proportion infected is unknown because of logistic constraints in measuring this empirically. We estimated the proportion of larvae that fed on deer in an extremely species-poor community on Block Island, RI, where tick nymphal infection prevalence was found to be lower than expected. In 2014, we measured the density, larval tick burdens, and realized reservoir competence of small mammal and bird hosts on Block Island, RI. In 2015, we measured the infection prevalence of host-seeking Ixodes scapularis nymphs resulting from larvae fed on available hosts in 2014. We back-estimated the proportion of larvae expected to have fed on deer in 2014 (the only unknown parameter) to result in the nymphal infection prevalence observed in 2015. Back-estimation predicted that 29% of larval ticks must have fed on deer to yield the observed 30% nymphal infection prevalence. In comparison, the proportion of larvae feeding on mice was 44% and 27% on birds. Our study identified an influential role of deer in reducing nymphal tick infection prevalence and a potential role as dilution hosts if the reduction in nymphal infection prevalence outweighs the role of deer as tick population amplifiers. Because both deer and competent hosts may increase in anthropogenic, fragmented habitats, the links between fragmentation, biodiversity, and Lyme disease risk may be complex and difficult to predict. Furthermore, a nonlinear relationship between deer abundance and Lyme disease risk would reduce the efficacy of deer population reduction efforts to control Lyme disease., (Copyright © 2018 The Authors. Published by Elsevier GmbH.. All rights reserved.)

Ixodes scapularis vectors several pathogens including Borrelia burgdorferi, the agent of Lyme disease. Nymphal and larval stages, and the pathogens transmitted by I. scapularis are maintained in a zoonotic cycle involving rodent reservoir hosts, predominantly Peromyscus leucopus. Humans are not reservoir hosts, however, accidental encounters of infected ticks with humans, results in pathogen transmission to the human host. Laboratory models of non-reservoir hosts such as guinea pigs develop a strong immune response to tick salivary proteins and reject ticks upon repeated tick infestations. Anecdotal and scientific evidence suggests that humans that get frequent tick bites might also develop resistance to ticks. Mus musculus, the laboratory model of natural host, does not develop resistance to I. scapularis upon repeated tick infestations. Addressing this dichotomy in vector-host interaction, we present data that suggest that the salivary transcriptome and proteome composition is different in mouse and guinea pig-fed I. scapularis, and that these differences might contribute to differences in host immune responses. These findings reveal a new insight into vector-host interactions and offer a functional paradigm to better understand the phenomenon of acquired tick-resistance., (Copyright © 2018 Elsevier GmbH. All rights reserved.)

The hard tick-borne relapsing fever spirochete, Borrelia miyamotoi, has recently gained attention as a cause of human illness, but fundamental aspects of its enzootic maintenance are still poorly understood. Challenges to experimental studies with B. miyamotoi-infected vector ticks include low prevalence of infection in field-collected ticks and seemingly inefficient horizontal transmission from infected immunocompetent rodents to feeding ticks. To reliably produce large numbers of B. miyamotoi-infected ticks in support of experimental studies, we developed an animal model where immunocompromised Mus musculus SCID mice were used as a source of B. miyamotoi-infection for larval and nymphal Ixodes scapularis ticks. Following needle inoculation with 1 × 10 5 spirochetes, the SCID mice developed a high spirochetemia (greater than 1 × 10 7 copies of B. miyamotoi purB per mL of blood) that persisted for at least 30 d after inoculation. In comparison, immunocompetent M. musculus CD-1 mice developed transient infections, detectable for only 2-8 d within the first 16 d after needle inoculation, with a brief, lower peak spirochetemia (8.5 × 10 4 - 5.6 × 10 5 purB copies per mL of blood). All larval or nymphal ticks fed on infected SCID mice acquired B. miyamotoi, but frequent loss of infection during the molt led to the proportion infected ticks of the resulting nymphal or adult stages declining to 22-29%. The ticks that remained infected after the molt had well-disseminated infections which then persisted through successive life stages, including transmission to larval offspring., (Published by Elsevier GmbH.)

The growing risk of transmission of tick-borne zoonotic pathogens to humans in Ontario, Canada, warrants investigations into regional tick distribution, tick burdens of local peridomestic animals, and prevalence of tick-borne pathogens. The objectives of this study were to investigate the geographic distribution and magnitude of tick infestations in opportunistically sampled mammalian wildlife and companion animals (i.e., dogs) in southern Ontario and to test these ticks for evidence of zoonotic tick-borne pathogens. Ticks collected from wildlife carcasses, live-trapped wildlife and companion animals (2015-2016), as well as wildlife diagnostic cases (2011-2013), were identified to species and life stage. Ixodes scapularis ticks were tested by real-time PCR for Anaplasma phagocytophilum, Babesia microti, Borrelia miyamotoi and Borrelia burgdorferi sensu stricto (s.s.). Amblyomma americanum ticks were tested for Ehrlichia chaffeensis. A total of 1687 ticks of six species were collected from 334 animals, including 224 raccoons (n = 1381 ticks) and 50 dogs (n = 67 ticks). The most common tick species collected from parasitized raccoons were Ixodes texanus (n = 666 ticks) and Dermacentor variabilis (n = 600 ticks), which were removed from 58.5% (median: 2 ticks; range: 1-36) and 49.1% (median: 2 ticks; range: 1-64) of raccoons, respectively. Of I. scapularis tested, 9.3% (4/43) were positive for Bo. burgdorferi s.s. and 2.3% (1/43) for A. phagocytophilum. These results reveal that numerous tick species parasitize common, peridomestic wildlife and that at least two zoonotic, tick-borne pathogens circulate in southern Ontario. Host-tick vector-pathogen dynamics should continue to be monitored in the face of global climate change, landscape alterations and expanding human populations., (Crown Copyright © 2018. Published by Elsevier GmbH. All rights reserved.)

The relapsing fever spirochete, Borrelia miyamotoi, is increasingly recognized as a cause of human illness (hard tick-borne relapsing fever) in the United States. We previously demonstrated that single nymphs of the blacklegged tick, Ixodes scapularis, can transmit B. miyamotoi to experimental hosts. However, two recent epidemiological studies from the Northeastern United States indicate that human cases of hard tick-borne relapsing fever peak during late summer, after the spring peak for nymphal tick activity but coincident with the peak seasonal activity period of larval ticks in the Northeast. These epidemiological findings, together with evidence that B. miyamotoi can be passed from infected I. scapularis females to their offspring, suggest that bites by transovarially-infected larval ticks can be an important source of human infection. To demonstrate experimentally that transovarially-infected larval I. scapularis ticks can transmit B. miyamotoi, outbred Mus musculus CD1 mice were exposed to 1 or 2 potentially infected larvae. Individual fed larvae and mouse blood taken 10 d after larvae attached were tested for presence of B. miyamotoi DNA, and mice also were examined for seroreactivity to B. miyamotoi 8 wk after tick feeding. We documented B. miyamotoi DNA in blood from 13 (57%) of 23 mice exposed to a single transovarially-infected larva and in 5 (83%) of 6 mice exposed to two infected larvae feeding simultaneously. All 18 positive mice also demonstrated seroreactivity to B. miyamotoi. Of the 11 remaining mice without detectable B. miyamotoi DNA in their blood 10 d after infected larvae attached, 7 (64%) had evidence of spirochete exposure by serology 8 wk later. Because public health messaging for risk of exposure to Lyme disease spirochetes focuses on nymphal and female I. scapularis ticks, our finding that transovarially-infected larvae effectively transmit B. miyamotoi should lead to refined tick-bite prevention messages., (Published by Elsevier GmbH.)

Human granulocytic anaplasmosis (HGA) is an emerging disease in Canada because of range expansion by the arthropod vector, Ixodes scapularis. These ticks carry the Ap-ha variant of Anaplasma phagocytophilum (Ap-ha), which has been implicated in causing HGA, and the Ap-variant 1, which is not associated with human infection. We report the detection of 13 genotypes of the ankyrin (ankA) gene among 76 infected blacklegged ticks. Haplotype network and phylogenetic analyses revealed that the ankA genotypes corresponding to the Ap-ha variant did not form a monophyletic assemblage. They formed two distinct clades (Clades I and III), one of which was genetically more similar in nucleotide and amino acid sequences to genotypes of Ap-variant 1 that comprised Clade II. Additional work is needed to explore the evolutionary history of A. phagocytophilum in North America, and to determine if there are differences in pathogenicity or clinical symptoms associated with the two divergent groups of the Ap-ha variant given the significant differences in ankA amino acid sequence., (Crown Copyright © 2018. Published by Elsevier GmbH. All rights reserved.)