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As the primary vector of Lyme disease spirochetes and several other medically significant pathogens, Ixodes scapularis presents a threat to public health in the United States. The incidence of Lyme disease is growing rapidly in upper midwestern states, particularly Michigan, Minnesota, and Wisconsin. The probability of a tick bite, acarological risk, is affected by the phenology of host-seeking I. scapularis. Phenology has been well-studied in northeastern states, but not in the Upper Midwest. We conducted biweekly drag sampling across 4 woodland sites in Minnesota between April and November from 2015 to 2017. The majority of ticks collected were I. scapularis (82%). Adults were active throughout our entire 8-month collection season, with sporadic activity during the summer, larger peaks in activity observed in April, and less consistent and lower peaks observed in October. Nymphs were most active from May through August, with continuing low-level activity in October, and peak activity most commonly observed in June. The observed nymphal peak corresponded with the typical peak in reported human Lyme disease and anaplasmosis cases. These findings are consistent with previous studies from the Upper Midwest and highlight a risk of human exposure to I. scapularis at least from April through November. This information may aid in communicating the seasonality of acarological risk for those living in Minnesota and other upper midwestern states as well as being relevant to the assessment of the ecoepidemiology of Lyme disease and the modeling of transmission dynamics.

Lyme disease is the most commonly reported vector-borne disease in the United States, and the number of cases reported each year continues to rise. The complex nature of the relationships between the pathogen (Borrelia burgdorferi sensu stricto), the tick vector (Ixodes scapularis Say), multiple vertebrate hosts, and numerous environmental factors creates challenges for understanding and predicting tick population and pathogen transmission dynamics. LYMESIM is a mechanistic model developed in the late 1990s to simulate the life-history of I. scapularis and transmission dynamics of B. burgdorferi s.s. Here we present LYMESIM 2.0, a modernized version of LYMESIM, that includes several modifications to enhance the biological realism of the model and to generate outcomes that are more readily measured under field conditions. The model is tested for three geographically distinct locations in New York, Minnesota, and Virginia. Model-simulated timing and densities of questing nymphs, infected nymphs, and abundances of nymphs feeding on hosts are consistent with field observations and reports for these locations. Sensitivity analysis highlighted the importance of temperature in host finding for the density of nymphs, the importance of transmission from small mammals to ticks on the density of infected nymphs, and temperature-related tick survival for both density of nymphs and infected nymphs. A key challenge for accurate modeling of these metrics is the need for regionally representative inputs for host populations and their fluctuations. LYMESIM 2.0 is a useful public health tool that downstream can be used to evaluate tick control interventions and can be adapted for other ticks and pathogens.

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.

Introduction: The prevalence of Francisella tularensis in Minnesota ticks is unknown. Ticks collected at seven sites were tested to determine the infection prevalence of F. tularensis in D...

Tick-borne diseases, due to a diversity of bacterial pathogens, represent a significant and increasing public health threat throughout the Northern Hemisphere. A high-throughput 16S V1-V2 rRNA gene-based metagenomics assay was developed and evaluated using13,000 residual samples from patients suspected of having tick-borne illness and1,000 controls. Taxonomic predictions for tick-borne bacteria were exceptionally accurate, as independently validated by secondary testing. Overall, 881 specimens were positive for bacterial tick-borne agents. Twelve tick-borne bacterial species were detected, including two novel pathogens, representing a 100% increase in the number of tick-borne bacteria identified compared to what was possible by initial PCR testing. In three blood specimens, two tick-borne bacteria were simultaneously detected. Seven bacteria, not known to be tick transmitted, were also confirmed to be unique to samples from persons suspected of having tick-borne illness. These results indicate that 16S V1-V2 metagenomics can greatly simplify diagnosis and accelerate the discovery of bacterial tick-borne pathogens.

Ixodes scapularis is the vector of at least seven human pathogens in Minnesota, two of which are known to cause Lyme disease (Borrelia burgdorferi sensu stricto and Borrelia mayonii). In Minnesota, the statewide incidence of Lyme disease and other I. scapularis-borne diseases and the geographic extent over which cases have been reported have both increased substantially over the last two decades. These changes correspond with an expanding distribution of I. scapularis over a similar time frame. Because the risk of exposure to I. scapularis-borne pathogens is likely related to the number of ticks encountered, we developed an acarological risk model predicting the density of host-seeking I. scapularis nymphs (DON) in Minnesota. The model was informed by sampling 81 sites located in 42 counties in Minnesota. Two main foci were predicted by the model to support elevated densities of host-seeking I. scapularis nymphs, which included the seven-county Minneapolis-St. Paul metropolitan area and counties in northern Minnesota, including Lake of the Woods and Koochiching counties. There was substantial heterogeneity observed in predicted DON across the state at the county scale; however, counties classified as high risk for I. scapularis-borne diseases and counties with known established populations of I. scapularis had the highest proportion of the county predicted as suitable for host-seeking nymphs (≥ 0.13 nymphs/100 m2). The model provides insight into areas of potential I. scapularis population expansion and identifies focal areas of predicted suitable habitat within counties where the incidence of I. scapularis-borne diseases has been historically low.

BACKGROUND: Tick-transmitted Borrelia species fall into two heterogeneous bacterial complexes comprised of multiple species, the relapsing fever (RF) group and the Borrelia burgdorferi sensu lato group, which are the causative agents of Lyme borreliosis (LB), the most common tickborne disease in the northern hemisphere. Geographic expansion of human LB in the United States and discovery of emerging Borrelia pathogens underscores the importance of surveillance for disease causing Borrelia. METHODS: De-identified clinical specimens, submitted by providers throughout the United States, for patients suspected of LB, anaplasmosis, ehrlichiosis, or babesiosis, were screened using a Borrelia genus level TaqMan PCR. Borrelia species and sequence types (STs) were characterized by multi-locus sequence typing (MLST) utilizing next generation sequencing. RESULTS: Among the 7,292 tested specimens tested, five different Borrelia species were identified: two causing LB, B. burgdorferi (n=25) and B. mayonii (n=9), and three RF borreliae, B. hermsii (n=1), B. miyamotoi (n=8), and Candidatus B. johnsonii (n=1), a species previously detected only in the bat tick, Carios kelleyi. ST diversity was greatest for B. burgdorferi positive specimens, with new STs identified primarily among synovial fluids. CONCLUSION: These results demonstrate broad PCR screening followed by MLST is a powerful surveillance tool for uncovering the spectrum of Borrelia species causing human disease, improving understanding of their geographic distribution, and investigating the correlation between B. burgdorferi STs and joint involvement. Detection of Candidatus B. johnsonii in a patient with suspected tickborne disease suggests this species may be a previously undetected cause of illness in humans with exposure to bat ticks.

Ixodes scapularis Say, the black-legged tick, is the primary vector in the eastern United States of several pathogens causing human diseases including Lyme disease, anaplasmosis, and babesiosis. Over the past two decades, I. scapularis -borne diseases have increased in incidence as well as geographic distribution. Lyme disease exists in two major foci in the United States, one encompassing northeastern states and the other in the Upper Midwest. Minnesota represents a state with an appreciable increase in counties reporting I. scapularis -borne illnesses, suggesting geographic expansion of vector populations in recent years. Recent tick distribution records support this assumption. Here, we used those records to create a fine resolution, subcounty-level distribution model for I. scapularis using variable response curves in addition to tests of variable importance. The model identified 19% of Minnesota as potentially suitable for establishment of the tick and indicated with high accuracy (AUC = 0.863) that the distribution is driven by land cover type, summer precipitation, maximum summer temperatures, and annual temperature variation. We provide updated records of established populations near the northwestern species range limit and present a model that increases our understanding of the potential distribution of I. scapularis in Minnesota.

Tularemia is a rare but often serious infectious disease caused by Francisella tularensis, a bacterium with an extremely low infectious dose and the ability to cause illness through several routes including arthropod bites, contact with infected animals and exposure to contaminated water, food or soil. Tularemia is found throughout the northern hemisphere, and cases have occurred in all U.S. states except Hawaii. Thirteen cases have been reported to the Minnesota Department of Health since 1994, including 3 in 2016. This article presents the 2016 cases as well as data on all the reported cases. Clinicians should consider tularemia in patients with a compatible clinical illness and exposure history, particularly those who present with acute fever and regional lymphadenopathy. Treatment should be initiated early in highly suspect cases, without waiting for laboratory results.

In the north-central United States, the blacklegged tick (Ixodes scapularis) is currently known to vector seven human pathogens. These include five bacteria (Borrelia burgdorferi sensu stricto, Borrelia mayonii, Borrelia miyamotoi, Anaplasma phagocytophilum, Ehrlichia muris eauclairensis), one protozoan (Babesia microti) and one virus (Powassan). We sought to assess the prevalence and distribution of these pathogens in host-seeking nymphs collected throughout Minnesota, a state on the northwestern edge of the tick's expanding range, where reported cases of I. scapularis-borne diseases have increased in incidence and geographic range over the past decade. Among the 1240 host-seeking I. scapularis nymphs that we screened from 64 sites, we detected all seven pathogens at varying frequencies. Borrelia burgdorferi s.s. was the most prevalent and geographically widespread, found in 25.24% of all nymphs tested. Anaplasma phagocytophilum and Babesia microti were also geographically widespread, but they were less prevalent than Bo. burgdorferi s.s. (detected in 6.29% and 4.68% of ticks, respectively). Spatial clusters of sites with high prevalence for these three pathogens were identified in the north-central region of the state. Prevalence was less than 1.29% for each of the remaining pathogens. Two or more pathogens were detected in 90 nymphs (7.26%); coinfections with Bo. burgdorferi s.s. and either A. phagocytophilum (51 nymphs, 4.11%) or Ba. microti (43 nymphs, 3.47%) were the most common combinations. The distribution and density of infected ticks mirrors the distribution of notifiable tick-borne diseases in Minnesota and provides information on the distribution and prevalence of recently described human pathogens.

Hard ticks of the order Ixodidae serve as vectors for numerous human pathogens, including the causative agent of Lyme DiseaseBorrelia burgdorferi. Tick-associated microbes can influence pathogen colonization, offering the potential to inhibit disease transmission through engineering of the tick microbiota. Here, we investigate whetherB. burgdorferiencounters abundant bacteria within the midgut of wild adultIxodes scapularis, its primary vector. Through the use of controlled sequencing methods and confocal microscopy, we find that the majority of field-collected adultI. scapularisharbor limited internal microbial communities that are dominated by endosymbionts. A minority ofI. scapularisticks harbor abundant midgut bacteria and lackB. burgdorferi. We find that the lack of a stable resident midgut microbiota is not restricted toI. scapularissince extension of our studies toI. pacificus, Amblyomma maculatum, andDermacentorspp showed similar patterns. Finally, bioinformatic examination of theB. burgdorferigenome revealed the absence of genes encoding known interbacterial interaction pathways, a feature unique to theBorreliagenus within the phylumSpirochaetes. Our results suggest that reduced selective pressure from limited microbial populations within ticks may have facilitated the evolutionary loss of genes encoding interbacterial competition pathways fromBorrelia.

The distribution of I. scapularis, the tick vector of the bacteria that cause Lyme disease, has been expanding over the last two decades in the north-central United States in parallel with increasing incidence of human cases of Lyme disease in that region. However, assessments of residential risk for exposure to ticks are lacking from this region. Here, we measured the density of host-seeking I. scapularis nymphs in two suburban and two rural public recreational sites located in Washington County, Minnesota as well as in nearby residential properties. We sought to compare tick densities across land use types and to identify environmental factors that might impact nymphal density. We also assessed the prevalence of infection in the collected ticks with Lyme disease spirochetes (Borrelia burgdorferi sensu stricto, B. mayonii), and other I. scapularis-borne pathogens including B. miyamotoi, Babesia microti and Anaplasma phagocytophilum. Similar to studies from the eastern United States, on residential properties, I. scapularis nymphal densities were highest in the ecotonal areas between the forest edge and the lawn. Residences with the highest densities of nymphs were more likely to have a higher percentage of forest cover, log piles, and signs of deer on their property. In recreational areas, we found the highest nymphal densities both in the wooded areas next to trails as well as on mowed trails. Among the 303 host-seeking I. scapularis nymphs tested for pathogens, B. burgdorferi sensu stricto, A. phagocytophilum and B. miyamotoi were detected in 42 (13.8%), 14 (4.6%), and 2 (0.6%) nymphs, respectively.

Lyme borreliosis (LB) is a multisystem disease caused by spirochetes in the Borrelia burgdorferisensu lato (Bbsl) genospecies complex. We previously described a novel Bbsl genospecies (type strain MN14-1420T) that causes LB among patients with exposures to ticks in the upper midwestern USA. Patients infected with the novel Bbsl genospecies demonstrated higher levels of spirochetemia and somewhat differing clinical symptoms as compared with those infected with other Bbsl genospecies. The organism was detected from human specimens using PCR, microscopy, serology and culture. The taxonomic status was determined using an eight-housekeeping-gene (uvrA, rplB, recG, pyrG, pepX, clpX, clpA and nifS) multi-locus sequence analysis (MLSA) and comparison of 16S rRNA gene, flaB, rrf-rrl, ospC and oppA2 nucleotide sequences. Using a system threshold of 98.3 % similarity for delineation of Bbsl genospecies by MLSA, we demonstrated that the novel species is a member of the Bbsl genospecies complex, most closely related to B. burgdorferisensu stricto (94.7-94.9 % similarity). This same species was identified in Ixodes scapularis ticks collected in Minnesota and Wisconsin. This novel species, Borrelia mayonii sp. nov, is formally described here. The type strain, MN14-1420, is available through the Deutsche Sammlung von Mikroorganismen und Zelkulturen GmbH (DSM 102811) and the American Type Culture Collection (ATCC BAA-2743).

Summary Background Lyme borreliosis is the most common tick-borne disease in the northern hemisphere. It is a multisystem disease caused by Borrelia burgdorferi sensu lato genospecies and characterised by tissue localisation and low spirochaetaemia. In this study we aimed to describe a novel Borrelia species causing Lyme borreliosis in the USA. Methods At the Mayo clinic, from 2003 to 2014, we tested routine clinical diagnostic specimens from patients in the USA with PCR targeting the oppA1 gene of B burgdorferi sensu lato. We identified positive specimens with an atypical PCR result (melting temperature outside of the expected range) by sequencing, microscopy, or culture. We collected Ixodes scapularis ticks from regions of suspected patient tick exposure and tested them by oppA1 PCR. Findings 100 545 specimens were submitted by physicians for routine PCR from Jan 1, 2003 to Sept 30, 2014. From these samples, six clinical specimens (five blood, one synovial fluid) yielded an atypical oppA1 PCR product, but no atypical results were detected before 2012. Five of the six patients with atypical PCR results had presented with fever, four had diffuse or focal rash, three had symptoms suggestive of neurological inclusion, and two were admitted to hospital. The sixth patient presented with knee pain and swelling. Motile spirochaetes were seen in blood samples from one patient and cultured from blood samples from two patients. Among the five blood specimens, the median oppA1 copy number was 180 times higher than that in 13 specimens that tested positive for B burgdorferi sensu stricto during the same time period. Multigene sequencing identified the spirochaete as a novel B burgdorferi sensu lato genospecies. This same genospecies was detected in ticks collected at a probable patient exposure site. Interpretation We describe a new pathogenic Borrelia burgdorferi sensu lato genospecies (candidatus Borrelia mayonii ) in the upper midwestern USA, which causes Lyme borreliosis with unusually high spirochaetaemia. Clinicians should be aware of this new B burgdorferi sensu lato genospecies, its distinct clinical features, and the usefulness of oppA1 PCR for diagnosis. Funding US Centers for Disease Control and Prevention Epidemiology and Laboratory Capacity for Infectious Diseases (ELC) Cooperative Agreement and Mayo Clinic Small Grant programme.

On June 27, 2016, the Minnesota Department of Health (MDH) Public Health Laboratory (PHL) was notified of a suspected Francisella tularensis isolate cultured at a hospital laboratory. The isolate was confirmed as F. tularensis type B at MDH PHL by reverse transcription-polymerase chain reaction, culture, and direct fluorescent antibody testing. Francisella tularensis subspecies tularensis (type A) and holarctica (type B) bacteria are the causative agents of tularemia.