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Lyme disease risk areas have increased across Canada in recent decades with the ongoing range expansion of Ixodes scapularis and Borrelia burgdorferi. Different methodologies are used by federal and provincial governments to determine local Lyme disease risk, which can make comparisons between regions challenging. In this study, seven Canadian Lyme disease risk classification methodologies were compared with each other to highlight the strengths and limitations of how each definition measured I. scapularis and B. burgdorferi risk. Each methodology was applied to active surveillance data from Ontario, and per cent agreement and kappa statistics were calculated. The methodologies varied in their measurements of the risk of exposure to I. scapularis and B. burgdorferi based on their use of active surveillance techniques, multiple types of collected surveillance data and laboratory confirmation of B. burgdorferi. Most initial Lyme disease risk site classifications were maintained over time. Kappa and per cent agreement statistics highlighted large differences between 8 of the 15 methodology pairings, indicating the presence of inconsistencies between most methodologies. Accurate, consistent surveillance and assessment of the spread of I. scapularis and its pathogens will aid with communicating Lyme disease risk to the public and preventing tick‐borne pathogen transmission. [ABSTRACT FROM AUTHOR]

Range expansion of the vector tick species, Ixodes scapularis, has been detected in Ontario over the last two decades. This has led to elevated risk of exposure to Borrelia burgdorferi, the bacterium that causes Lyme disease. Previous research using passive surveillance data suggests that I. scapularis populations establish before the establishment of B. burgdorferi transmission cycles, with a delay of ∼5 years. The objectives of this research were to examine spatial and temporal patterns of I. scapularis and its pathogens from 2017 to 2019 in southwestern, eastern, and central Ontario, and to explore patterns of B. burgdorferi invasion. Over the 3-year study period, drag sampling was conducted at 48 sites across Ontario. I. scapularis ticks were tested for B. burgdorferi, Borrelia miyamotoi, Anaplasma phagocytophilum, and Babesia species, including Babesia microti and Babesia odocoilei, and Powassan virus. I. scapularis was detected at 30 sites overall, 22 of which had no history of previous tick detection. B. burgdorferi was detected at nine sites, eight of which tested positive for the first time during this study and five of which had B. burgdorferi detected concurrently with initial tick detection. Tick and pathogen hotspots were identified in eastern Ontario in 2017 and 2018, respectively. These findings provide additional evidence on the range expansion and population establishment of I. scapularis in Ontario and help generate hypotheses on the invasion of B. burgdorferi in Ontario. Ongoing public health surveillance is critical to monitor changes in I. scapularis and its pathogens in Ontario. [ABSTRACT FROM AUTHOR]

The blacklegged tick, Ixodes scapularis, is established in several regions of Ontario, Canada, and continues to spread into new geographic areas across the province at a rapid rate. This poses a significant public health risk since I. scapularis transmits the Lyme disease-causing bacterium, Borrelia burgdorferi, and other pathogens of potential public health concern. The objective of this study was to develop species distribution models for I. scapularis and B. burgdorferi to predict and compare the potential distributions of the tick vector and the Lyme disease pathogen as well as the ecological factors most important for species establishment. Ticks were collected via tick dragging at 120 sites across southern, central, and eastern Ontario between 2015 and 2018 and tested for tick-borne pathogens. A maximum entropy (Maxent) approach was used to model the potential distributions of I. scapularis and B. burgdorferi. Two independent datasets derived from tick dragging at 25 new sites in 2019 and ticks submitted by the public to local health units between 2015 and 2017 were used to validate the predictive accuracy of the models. The model for I. scapularis showed high suitability for blacklegged ticks in eastern Ontario and some regions along the shorelines of the Great Lakes, and moderate suitability near Algonquin Provincial Park and the Georgian Bay with good predictive accuracy (tick dragging 2019: AUC = 0.898; ticks from public: AUC = 0.727). The model for B. burgdorferi showed a similar predicted distribution but was more constrained to eastern Ontario, particularly between Ottawa and Kingston, and along Lake Ontario, with similarly good predictive accuracy (tick dragging 2019: AUC = 0.958; ticks from public: AUC = 0.863. The ecological variables most important for predicting the distributions of I. scapularis and B. burgdorferi included elevation, distance to deciduous and coniferous forest, proportions of agricultural land, water, and infrastructure, mean summer/spring temperature, and cumulative annual degree days above 0°C. Our study presents a novel application of species distribution modelling for I. scapularis and B. burgdorferi in Ontario, Canada, and provides an up to date projection of their potential distributions for public health knowledge users. [ABSTRACT FROM AUTHOR]

Abstract 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. [ABSTRACT FROM AUTHOR]

Tick dragging is an important tool used by public health for Ixodes scapularis surveillance to identify Lyme disease risk areas in Ontario, Canada. Concerns have been raised on the repeatability of tick dragging due to fluctuations that occur in the tick population in response to micro- and macroclimatic variations. Our objective was to assess the repeatability of tick dragging over a short timescale by examining three outcome measures: presence/absence of ticks, tick abundance, and likelihood of tick establishment based on an indicator developed by Clow et al. (2018). We conducted tick dragging twice per site within a 1-month period at a total of 15 sites in eastern and southern Ontario. Ixodes scapularis were detected at 11 sites. The outcome of presence/absence was consistent at 13 of 15 sites. Abundance was highly variable, changing between each visit at sites where ticks were detected. The likelihood level was consistent at 13 of 15 sites. Based on the kappa statistic, there was substantial agreement between measurements for the presence/absence and the likelihood levels. Our results indicate that both presence/absence and likelihood levels provide more consistent outcomes for tick dragging than tick abundance alone; however, applying the dragging data to the likelihood indicator provides additional information about the potential risk associated with I. scapularis establishment in the area. [ABSTRACT FROM AUTHOR]

The emergence of the vector Ixodes scapularis in Ontario, Canada poses a significant public health risk. Both passive and active surveillance approaches have been employed by public health professionals (i.e., government employees) to monitor for the range expansion of this tick. Field surveillance using drag sampling for questing ticks is a recognized and effective method to identify reproducing tick populations. The degree of effort (i.e., number of visits per site) can enhance the sensitivity and specificity of surveillance, but increased effort conflicts with the cost to public health for field surveillance. Here we developed an indicator to determine the likelihood of I. scapularis establishment based on field sampling results. Field data from two established populations of I. scapularis in Ontario were incorporated with previous analyses of surveillance data to create the indicator, which is in the form of a scoring system. The life stage(s) collected, overall abundance and past surveillance findings from a site are all considered and a level is assigned for the likelihood of I. scapularis establishment based on current field sampling results. The likelihood levels are non-zero (i.e., no I. scapularis detected, but risk still present due to adventitious ticks), low, medium or high, and recommendations for future surveillance and public health measures are provided. The indicator was validated against field sampling results from five other established sites in the province and correctly categorized all five areas as high likelihood of establishment. The indicator was also applied to field sampling results from 36 sites of unknown status that were visited twice during the period of 2014–2016. There was substantial agreement of levels between measurements, as calculated using a weighted kappa. The indicator can assist public health professionals with the interpretation of field sampling results and direct their efforts for ongoing surveillance and public health interventions for I. scapularis-borne diseases, including Lyme disease. [ABSTRACT FROM AUTHOR]

The microbiota of hard ticks has been an area of growing interest due to the potential role that the broader microbial community may play in pathogen carriage and transmission. In the last two decades, Ontario, Canada has experienced rapid changes in the risk of tick-borne disease, primarily due to the range expansion of Ixodes scapularis . Another human-biter, Dermacentor variabilis , is a longstanding resident of the province, but currently poses minimal risk of pathogen transmission. To examine the microbiota of these two species, we collected adult and nymphal I. scapularis and D. variabilis from the eastern and southern regions of the province via tick dragging, and conducted next generation sequencing of 19 samples (composed of 45 ticks) via Illumina MiSeq. A total of 1400469 sequences were detected (median 69118/sample; range 23350–155227). The most abundant families of bacteria were unclassified Clostridiales and Ruminococcaceae for both I. scapularis and D. variabilis . No significant differences in the relative abundances of any phylum, class, order, family or genus were detected between locations (east vs south), sex, life stage or tick species. There were no differences in community membership or structure based on unifrac and AMOVA analyses. Female and male ticks had lower microbial diversity when compared to nymphs, based on the Simpson’s index and Shannon evenness index. The findings of our study differ from previous studies of these tick species conducted in other geographic areas, and highlight the potential role geography and related ecological factors may have in shaping the tick microbiota. [ABSTRACT FROM AUTHOR]

The invasion of the blacklegged tick, Ixodes scapularis into Ontario, Canada poses a significant risk to public health because it is a vector for numerous pathogens, including Borrelia burgdorferi sensu stricto, the causative agent of Lyme disease. Baseline field sampling in 2014 and 2015 detected I. scapularis and B. burgdorferi at sites across southern, eastern and central Ontario, including a hot spot in eastern Ontario. A “speed of spread” model for I. scapularis developed by Leighton and colleagues (2012) estimated that the tick’s range was expanding northward at 46 km/year. In 2016, we revisited a subset of sites sampled in 2014 and 2015 to understand the changing nature of risk, and assess whether the rate of tick invasion is consistent with the speed of spread estimate. Ticks were collected via tick dragging at 17 out of 36 sites, 5 of which were new sites for I. scapularis. Samples were positive for B. burgdorferi at 8 sites. No other I. scapularis-borne pathogens were detected. Centrographic statistics revealed an increase in the dispersion of I. scapularis positive sites in eastern Ontario. Field data for each site were then compared to the model’s predicted year of establishment for each census subdivision. Our findings illustrate that the range expansion of I. scapularis and the emergence of B. burgdorferi is ongoing, and provide short timescale evidence of the processes associated with I. scapularis spread. The range front appears to be moving at a rate of ~46 km/year, with colonization of the tick behind this range front occurring at a slower and heterogeneous rate. Assessment of site-level ecological factors did not provide any insight into the underlying processes that may be influencing the colonization of I. scapularis in specific areas. Ongoing field sampling is needed to monitor this dynamic process. This study highlights the current geographic risk associated with Lyme disease, which can be used to target public health interventions to the areas of greatest risk. [ABSTRACT FROM AUTHOR]

In northeastern North America, the blacklegged tick, Ixodes scapularis , is the vector of numerous tick-borne pathogens, including the agent of Lyme disease, Borrelia burgdorferi sensu stricto. Since 1990, there has been a rapid spread of I. scapularis northward into the province of Ontario, Canada. Climate change has been implicated as one of the driving factors for the spread of this vector. Other ecological factors also influence survival of I. scapularis populations and may facilitate invasion. The objective of this study was to identify local abiotic and biotic factors of significance for the invasion of I. scapularis in Ontario. The presence of ticks was determined by drag sampling at 154 sites in southern, eastern and central Ontario from May to October in 2014 and 2015. At each site, data on site aspect, forest cover, understory density and composition, soil moisture and composition, and the depth of litter layer were collected. Cumulative degree days above zero °C, total precipitation and elevation were attributed to each site using a geographic information system. A mixed multi-variable logistic regression model was created to assess the impact of the ecological factors on the presence of I. scapularis . In total, I. scapularis was found at 29 sites (18.8%) across the study area. The density of the understory, the presence of shrubs and the interaction of these two ecological factors were statistically significant, as well as longitude and cumulative degree days above zero. Our findings illustrate that local ecological factors are of importance for the invasion of I. scapularis into Ontario, and may be used to enhance local public health interventions and current predictive models and risk maps for I. scapularis . [ABSTRACT FROM AUTHOR]

Over the past two decades, the northward spread of Ixodes scapularis across Ontario, Canada, has accelerated and the risk of Lyme disease has increased. Active surveillance is a recognized and effective method for detecting reproducing populations of I. scapularis. In this study, we conducted field sampling consistent with an active surveillance approach from May to October 2014 at 104 sites in central, eastern, and southern Ontario to determine the current distribution of I. scapularis and other tick species, and enhance our understanding of the geographic risk associated with Borrelia burgdorferi and other tick-borne pathogens of public health significance in this region. I. scapularis was present at 20 of the 104 sites visited. Individuals of the tick species Dermacentor variabilis, Haemaphysalis leporispalustris, and Ixodes dentatus were also collected. I. scapularis was positive by PCR for B. burgdorferi at five sites. These sites formed a significant spatial cluster in eastern Ontario. No ticks were PCR positive for Borrelia miyamotoi, Anaplasma phagocytophilum, and Babesia microti. This study provides an up-to-date picture of the distribution of I. scapularis and other tick species, and the risk of B. burgdorferi and other pathogens of public health significance in central, eastern, and southern Ontario. This information may allow for more effective surveillance efforts and public health interventions for Lyme disease and other tick-borne diseases in this region. [ABSTRACT FROM AUTHOR]

• The Maxent model has a moderate ability to predict blacklegged tick density across the study region, with good predictive ability in a region with long-established tick populations. • When model-predicted habitat suitability is dichotomized, the model-predicted "suitable" habitat is strongly associated with higher tick density. • The model predicts the upper limit of tick density, suggesting that areas predicted to have high model-predicted habitat suitability may experience increasing tick abundance in the future. • The Maxent model may allow for limited active surveillance resources to be targeted to areas most likely to experience increasing LD risk. 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 m2 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. [ABSTRACT FROM AUTHOR]

In the Thousand Islands region of eastern Ontario, Canada, Lyme disease is emerging as a serious health risk. The factors that influence Lyme disease risk, as measured by the number of blacklegged tick (Ixodes scapularis) vectors infected with Borrelia burgdorferi, are complex and vary across eastern North America. Despite study sites in the Thousand Islands being in close geographic proximity, host communities differed and both the abundance of ticks and the prevalence of B. burgdorferi infection in them varied among sites. Using this archipelago in a natural experiment, we examined the relative importance of various biotic and abiotic factors, including air temperature, vegetation, and host communities on Lyme disease risk in this zone of recent invasion. Deer abundance and temperature at ground level were positively associated with tick abundance, whereas the number of ticks in the environment, the prevalence of B. burgdorferi infection, and the number of infected nymphs all decreased with increasing distance from the United States, the presumed source of this new endemic population of ticks. Higher species richness was associated with a lower number of infected nymphs. However, the relative abundance of Peromyscus leucopus was an important factor in modulating the effects of species richness such that high biodiversity did not always reduce the number of nymphs or the prevalence of B. burgdorferi infection. Our study is one of the first to consider the interaction between the relative abundance of small mammal hosts and species richness in the analysis of the effects of biodiversity on disease risk, providing validation for theoretical models showing both dilution and amplification effects. Insights into the B. burgdorferi transmission cycle in this zone of recent invasion will also help in devising management strategies as this important vector-borne disease expands its range in North America. [ABSTRACT FROM AUTHOR]

Blacklegged ticks ( Ixodes scapularis) are vectors for several important human diseases, including Lyme disease, human granulocytic anaplasmosis (HGA), and human babesiosis, caused by Borrelia burgdorferi, Anaplasma phagocytophilum, and Babesia microti, respectively. The continued northward range expansion of blacklegged ticks and associated pathogens is an increasing public health concern in Canada. The Thousand Islands region of eastern Ontario has recently been identified as a new endemic area for Lyme disease in Canada, but the occurrence of other pathogens in ticks in this area has not been fully described. Our objectives were to determine the prevalence of A. phagocytophilum and B. microti in small mammals and questing ticks in the Thousand Islands area and identify the strains of A. phagocytophilum circulating in ticks in the area. Serum and larval ticks were collected from trapped small mammals, and questing ticks were collected via drag sampling from up to 12 island and mainland sites in 2006, 2009, and 2010. A. phagocytophilum was identified by PCR in 3.4% (47/1388) ticks from eight of 12 sites; the prevalence ranged from 8.9% in 2006 to 3% in 2009. All 365 ticks tested for B. microti were negative. Antibodies to A. phagocytophilum were detected in 2.8% (17/611) of white-footed mice ( Peromyscus leucopus) at two of 11 sites in 2006, 2009, or 2010. All 34 A. phagocytophilum-positive ticks submitted for strain identification using single-nucleotide polymorphism genotyping assays targeting the 16S rRNA gene were identified as a variant strain (Ap variant-1), which is not commonly associated with human disease. Our findings suggest that people are at low risk of contracting HGA or human babesiosis due to locally acquired tick bites in the Thousand Islands area. However, continued surveillance is warranted as these pathogens continue to expand their ranges in North America. [ABSTRACT FROM AUTHOR]