Background:The range expansion of ticks transmitting zoonotic diseases in Canada poses challenges for public health surveillance. Active monitoring of where tick populations are emerging helps inform public health responses, but is resource intensive and logistically complex. Crowdsourced data may provide a cost-effective approach to augment surveillance. In this study, we assessed the value of crowdsourced data from eTick, a platform whereby the public submits tick photographs for expert identification. Objective:We aimed to (1) characterize spatial patterns of eTick submissions and identify socioecological factors associated with their occurrence and frequency, and (2) assess the ability of indicators derived from eTick to predict census subdivisions (CSDs) with established tick populations. Methods:We conducted a retrospective ecological assessment (2020-2023) for the effectiveness of crowdsourced data to detect established blacklegged tick (Ixodes scapularis) populations in Quebec, Canada. First, we applied a spatial scan approach to assess significantly high submission rates in human- and animal-origin data separately. Then, using zero-inflated regression models, we assessed socioecological factors associated with the occurrence and counts of tick submissions. Next, we used logistic regression models to assess the value of using eTick surveillance data to predict the presence of established tick populations, as documented by active surveillance. Finally, we calculated thresholds for eTick submissions to maximize sensitivity, specificity, or a balance of both metrics for detecting established tick populations, and developed scenarios to interpret linear predictors of submission counts across different socioecological contexts. Results:No clusters in submissions were detected for human and animal-origin data. However, high concentrations of ticks found on humans corresponded with areas reporting a high risk of Lyme disease. Tick submissions of animal origin extended beyond endemic areas, highlighting their complementary surveillance value. Zero-inflated models identified socioeconomic, climatic, and land cover factors significantly associated with submission rates. Logistic regression models, including significant socioecological factors, performed best to identify CSDs with established tick populations. Predictive performance was similar for ticks from humans (area under the curve [AUC] 0.86), animals (AUC 0.83), and all submissions combined (AUC 0.85). Using the best model adjusted for population size, median income, median age, and cumulative degree days above 0 °C, an optimal threshold of 3.32 crowdsourced tick submissions allowed the detection of CSDs with established tick populations while maximizing sensitivity and specificity (both 0.76). Conclusions:This work introduces a framework for analyzing crowdsourced surveillance data by correcting for participation bias and benchmarking against active surveillance. Unlike approaches relying on traditional or unadjusted data, it incorporates socioecological factors associated with reporting. We show that crowdsourced data can yield reliable inferences about vector distributions and provide a methodological approach that could be applied across species and regions. Applied to eTick, it supports integration into surveillance systems to improve early detection, targeting interventions, and cost-effective monitoring of emerging risks by public health.

Climate change is driving the expansion of various tick species in North America. In this context, it is essential to ensure that vector populations can be effectively detected and monitored in both emerging and endemic regions. The objective of this study was to characterize the methods used for sampling questing hard ticks of the family Ixodidae and synthesize current knowledge on their effectiveness. A scoping review was conducted and 56 studies published before October 2024 were included in the analysis. Overall, 63% of the studies were conducted in North America and 9% in Europe. The majority of the studies concerned Ixodes spp. (63%). Most studies on Ixodes spp. and Dermacentor spp. examined cloth-based methods such as dragging, flagging, and sweeping, while CO₂ traps were most frequently studied for Amblyomma spp. Only seven studies quantified the proportion of the estimated tick population sampled using collection methods. Overall, a single dragging passage was estimated to capture only a small proportion of the questing nymph population, approximately 6% (5.9–6.3%). Several technical, environmental, and climatic factors may influence sampling effectiveness, including temperature, sampling period, and cloth type. Methodological variability across studies limited comparability and hindered the establishment of standardized guidelines. Nevertheless, we can conclude that no single collection method emerged as a gold standard, and that a combination of methods may be required. Based on these findings, we provide evidence-based recommendations for the selection of tick sampling methods based on different objectives, tick genus, life stage, and environmental and climatic factors.

Human granulocytic anaplasmosis (HGA) is a tick-borne disease emerging in North America, caused by the zoonotic variant Ap-ha (human active) of the bacterium Anaplasma phagocytophilum. This research aimed to understand the reservoir competency of small mammals for Ap-ha in the province of Québec, Canada. To achieve this aim, wild small mammals were sampled from June to August in 2022 and 2023 and tested for Ap and its variants (Ap-ha, Ap-v1) using qPCR targeting the msp2 and 16S genes. In total, 547 small mammals from nine different taxa were live captured across two years. Nearly half (48.2 %) of small mammals carried at least one Ixodes scapularis tick larva and 29.3 % carried at least one I. scapularis nymph. The odds of Ap infection were three times higher in eastern chipmunks (OR = 2.98, p < 0.05) and five times lower in red squirrels (OR = 0.21, p < 0.01) when compared to Peromyscus spp. mice. When infected, Peromyscus mice and eastern chipmunks transmitted the infection on average to 6.8 % (CI95: 24.9–48.7) and 52.9 % (CI95: 16.7–89.1) of feeding larvae, respectively. An Ap variant could be identified in 90 % (109/121) of infected small mammals, all of which were the Ap-ha strain. In conclusion, eastern chipmunks and Peromyscus mice should be considered as reservoir hosts contributing to the transmission and emergence of anaplasmosis in Canada. This study also confirms the circulation of the Ap-ha variant within host and tick communities in Southeastern Canada.

Deer keds (Lipoptena cervi), an introduced European species, are expanding their geographic range in North America. We document their first recorded presence in Québec, Canada, map their distribution, and highlight the detection of pathogens of potential public health relevance. In the Estrie region of southern Québec, 47 deer keds (L. cervi) were collected from 14 (5.5%) of 254 harvested white-tailed deer (Odocoileus virginianus). Borrelia spp. and Anaplasma phagocytophilum were detected in the body of 1/44 and 8/44 L. cervi specimens, respectively. A statistically significant spatial cluster of white-tailed deer infested by L. cervi was found in southern Estrie using the Bernoulli-based spatial scan statistic.

Climate change is reshaping Arctic ecosystems, heightening the risk of vector-borne diseases caused by pathogens such as California serogroup (CSG) viruses, including Jamestown Canyon virus (JCV) and Snowshoe Hare virus (SSHV). Despite their emerging public health threat, data on Arctic mosquito populations and CSG virus prevalence remain limited. To address this gap, we conducted a 3-yr mosquito surveillance program at 8 sites across northern Canada and the United States, engaging local community members in mosquito collection through a standardized protocol using a butterfly net. From 4,038 sampled mosquitoes, we identified 18 species-17 of which were from the genus Aedes Meigen, 1818. We also reported new distribution records for Aedes euedes Howard, Dyar, & Knab, 1913, Aedes implicatus Vockeroth, 1954, and Aedes spencerii (Theobald, 1901). JCV was detected in 10 mosquito species across 7 sites, while SSHV was detected in just one species at a single site. Notably, JCV was found in Ae. euedes, Aedes impiger (Walker, 1948), and Aedes pionips Dyar, 1919 for the first time in North America. JCV was detected in Cambridge Bay, Nunavut, where only 3 Arctic mosquito species were present, none of which are recognized as potential JCV vectors. This finding raises the possibility of undocumented vector species or a previously unrecognized transmission role for Arctic mosquitoes. The broad distribution of JCV across species and locations suggests widespread enzootic transmission, underscoring the need to reassess the potential of Arctic mosquitoes as disease vectors in a rapidly changing climate.

The small Indian mongoose (Urva auropunctata) is a non-native invasive species throughout the Caribbean and the primary terrestrial wildlife rabies reservoir on 4 islands in the region. In the 1970s and 1980s, island-wide attempts to control and eliminate mongoose rabies through culling or poisoning in Cuba and Grenada proved unsuccessful. On some islands, localized population reduction of mongooses is used to mitigate predation on endangered species or to reduce the nuisance and frequency of interactions with humans. However, the short- and medium-term demographic responses of mongooses to local population reduction and the impacts for infectious disease transmission remain unexplored. We conducted an experimental removal of mongooses across a 0.42-km2 area of dry forest in St. Kitts. Employing capture-mark-recapture techniques, we quantified the demographic and behavioral responses of mongooses within the study area. We collected individual-level data using an automated radio-telemetry system, monitoring the daily presence of 19 collared mongooses for 7 months before and up to 7 weeks after experimental removals. The mongoose population density rebounded to pre-removal levels within 7 weeks of the removal, primarily because of the influx of reproductively active females. The proportion of juveniles increased from 1-3% before removals to 14% at 7 weeks after removals yet returned to baseline levels at 6 months after removals. The local immigration of mongooses to the site was evident through changes in capture per unit effort, observed as early as the first week after removals. Tagged mongooses that frequented the study area during the pre-removal period increased their daily presence for 5-30 days after removals. Our results indicate that a localized and intensive mongoose removal program targeting a high-density population has short-term but not long-term residual impacts to the population. Further investigation into contact rates among mongooses and space use among resident and immigrating individuals is essential to advance our understanding of the impacts of localized removals on short- and long-term mongoose population disease dynamics.

Lyme disease (LD) is a threat to public health in southern regions of Canada. In response, we used a One Health approach to design an integrated intervention in a high-incidence LD community in southern Québec aiming to increase preventive behaviours in the population and reduce the density of Borrelia burgdorferi-infected Ixodes scapularis ticks in the environment. The environmental component involved distributing fluralaner baits to rodents around residential properties and public trails from 2019 to 2023. Effectiveness was measured by changes in the density of questing nymphs (DON) and the prevalence of B. burgdorferi-infected nymphs (NIP). Treated areas were compared to areas located between 0 and 250 m from treatment locations and to untreated areas located >250 m away. The DON was reduced by 39 % (95 % confidence interval [95 % CI] = 1 - 62 %) in treated areas when compared to untreated areas in 2021 and 2022. Over this same period, in areas between 0 and 250 m, the DON was lower when closer to bait stations (P = 0.001). The treatment significantly reduced the NIP in treated area in 2020 (Odds ratio [OR] = 0.87 [95 % CI 0.08 - 0.98]), 2021 (OR = 0.85 [95 % CI 0.26 - 0.97], and 2022 (OR = 0.88 [95 % CI 0.12 - 0.98]), and in areas between 0 and 250 m in 2020 (OR = 0.87 [0.08 - 0.98]) and 2021 (OR = 0.84 [95 % CI 0.25 - 0.97]). This study confirms the potential of rodent-targeted fluralaner baiting for reducing the density of infected questing nymphs in peri‑urban environments.

Ixodes scapularis ticks are the primary vector of Lyme disease (LD) in North America, and their range has expanded into southeastern and southcentral Canada with climate change. This study presents a comprehensive machine learning (ML) framework to estimate the probability of blacklegged tick population establishment as measured using active tick surveillance data. Environmental predictor variables were derived from Earth observation (EO) data at multiple spatial scales to assess their individual contributions in the prediction models. Among the tested ML algorithms, XGBoost emerged as the top-performing model, achieving high sensitivity (0.83) and specificity (0.71) in predicting population establishment. Performance was optimized when using predictor variables derived from a 1 km radius around surveillance sites. Top predictors included cumulative annual degree-days above 0°C and maximum temperature of warmest month, reflecting the importance of temperature in enabling tick survival and reproduction. Additional predictor variables of high importance included silty soil (lower clay content) with slightly higher than average SOC and pH, and land cover types that contained broadleaf forests (percent mixed forest, percent broadleaf) and less urban areas. By integrating ML with open access EO data, this study demonstrates that accurate, easily updatable risk maps can be produced to support public health management of LD, and more broadly, the growing threat of tick-borne diseases in a changing climate.

Zoonotic diseases, particularly those originating in wildlife, pose significant public health and economic risks. Rabies, a viral zoonosis with near-100% case fatality in humans, is a prime example of such a threat, especially in regions like North America where wildlife-such as raccoons-serve as key reservoirs. This study assesses the economic efficiency of Ontario, Canada's raccoon rabies control program, which combines oral rabies vaccination (ORV), trap-vaccinate-release (TVR), and surveillance strategies. Using a spatial agent-based epidemiological model, the study estimates the benefits and costs of intervention compared to a no-intervention scenario over the period 2015-2025. Benefits were quantified as avoided public health costs, including post-exposure prophylaxis (PEP), animal testing (AT), and human exposure investigations (INVT), and converted to 2023 CAD. Results show that the intervention prevented significant economic losses, with benefit-cost ratios ranging from 1.5 to 14.16 depending on assumed rates of intervention necessity, confirming the program's cost-effectiveness. This analysis not only supports continued investment in wildlife rabies control but also provides a scalable economic framework for other zoonotic disease management programs utilizing a One Health approach.

Predators in food webs are valuable sentinel species for zoonotic and multi-host pathogens such as Toxoplasma gondii. This protozoan parasite is ubiquitous in warm-blooded vertebrates, and can have serious adverse effects in immunocompromised hosts and foetuses. In northern ecosystems, T. gondii is disproportionately prevalent in Inuit people and wildlife, in part due to multiple routes of transmission. We combined data on T. gondii infection in foxes from Nunavik (northern Québec, Canada) with stable isotope data tracking trophic relationships between foxes and several of their main prey species. Red (Vulpes vulpes) and Arctic fox (Vulpes lagopus) carcasses were collected by local trappers from 2015 to 2019. We used magnetic capture PCR to detect DNA of T. gondii in heart and brain tissues, and enzyme-linked immunosorbent assay to detect antibodies in blood. By linking infection status with diet composition, we showed that infected foxes had a higher probability of consuming aquatic prey and migratory geese, suggesting that these may be important sources of T. gondii transmission in the Arctic. This use of stable isotopes to reveal parasite transmission pathways can be applied more broadly to other foodborne pathogens, and provides evidence to assess and mitigate potential human and animal health risks associated with T. gondii in northern ecosystems.

Abstract The development of interventions targeting reservoirs of Borrelia burgdorferi sensu stricto with acaricide to reduce the density of infected ticks faces numerous challenges imposed by ecological and operational limits. In this study, the pharmacokinetics, efficacy and toxicology of fluralaner were investigated in Mus musculus and Peromyscus leucopus mice, the main reservoir of B. burgdorferi in North America. Fluralaner showed rapid distribution and elimination, leading to fast plasma concentration (Cp) depletion in the first hours after administration followed by a slow elimination rate for several weeks, resulting in a long terminal half-life. Efficacy fell below 100% while Cp (± standard deviation) decreased from 196 ± 54 to 119 ± 62 ng/mL. These experimental results were then used in simulations of fluralaner treatment for a duration equivalent to the active period of Ixodes scapularis larvae and nymphs. Simulations showed that doses as low as 10 mg/kg have the potential to protect P. leucopus against infestation for a full I. scapularis active season if administered at least once every 7 days. This study shows that investigating the pharmacology of candidate acaricides in combination with pharmacokinetic simulations can provide important information to support the development of effective interventions targeting ecological reservoirs of Lyme disease. It therefore represents a critical step that may help surpass limits inherent to the development of these interventions.

Background: Tick-borne diseases are an emerging threat to public health throughout the temperate world, leading to a growing field of research aimed at developing and testing intervention strategies for reducing human-tick encounters or prevalence of infection in ticks. Various wide-spectrum chemical acaricides have proven effective for controlling tick populations, but many of these have potential deleterious side-effects on health and the environment. In addition to chemical acaricides, certain compounds such as diatomaceous earth have been shown to have physical acaricidal properties. We hypothesized that dolomitic lime (CaMg(CO3)2, a corrosive, desiccant mineral that is already used extensively in agricultural and forestry contexts to balance the pH of soils, may affect ticks' locomotory activity, habitat position, or survival and that this should manifest as a reduction in the number of questing ticks collected by dragging. Objective: This study aimed to formally assess this hypothesis in a controlled laboratory setting. Methods: We carried out a microcosm experiment, with one control and three treated microcosm trays, each replicating the natural substrate characterizing I. scapularis habitat in northeastern North America. Each tray was infested with 200 living larvae and 50 nymphs, and then treated with 0 (control), 50, 100, or 500 g/m2 of lime powder. Ticks were collected by microdragging 24 and 72 h postliming. Results: Efficacy of liming at reducing the number of collected questing ticks ranged from 87% to 100% for larvae and 0% to 69% for nymphs 24 h postliming and from 91% to 93% for larvae and -47% to 65% for nymphs 72 postliming. Conclusion: This study provides the first experimental evidence of the potential efficacy of liming for impairing activity of questing immature ticks. Given that lime is a low-cost material, that methods for widespread application in deciduous woodlands already exist, and that it has been documented as having a limited negative impact on the environment, further assessment of lime application as a public health risk reduction intervention for tick-borne diseases is warranted.

Abstract Arctic ecosystems face increasing risks from vector-borne diseases due to climate-driven shifts in disease patterns and vector distribution. However, species identification challenges impact vector-borne disease surveillance, necessitates accurate identification. Aedes species are predominant among Arctic mosquitoes and pose health risks, with some species potentially carrying Jamestown Canyon and Snowshoe hare viruses. However, identifying Aedes species is challenging, especially under Arctic conditions and with complex adult traits. This study assessed the suitability of DNA barcoding (COI and ITS2 regions) and morphological characteristics for the identification of Arctic black-legged Aedes. It also aimed to evaluate the reliability of publicly available sequences. Our analysis focused on Aedes impiger, Aedes nigripes, and two species from the Punctor subgroup – Aedes hexodontus and Aedes punctor. In our study, the COI barcoding region distinguished Ae. impiger and Ae. nigripes but not within the species of the Punctor subgroup. In addition, the ITS2 barcoding region did not differentiate the species. When we evaluated GenBank and BOLD sequences, we found issues of under-representation and misidentifications, particularly within the Punctor subgroup. Based on these results, we recommend addressing identification difficulties, particularly within the Punctor subgroup, and advocate for more comprehensive morphological and molecular identification strategies. Integrating morphology and DNA barcoding holds promise for robust disease surveillance in Arctic regions, yet challenges persist, especially in complex species groups like the Punctor subgroup. Tackling these issues is pivotal to ensuring accurate vector status determination and reliable disease risk assessments in a rapidly changing Arctic ecosystem.

Abstract Introduction The increased burden of climate-sensitive infectious diseases (CSIDs) within the circumpolar region, one of the many impacts of climate change, is impacting human, animal and ecosystem health. An integrated One Health approach to surveillance of CSIDs has been promoted by the scientific community as a prerequisite to enhance preparedness and response. Up to now, little is known about how the One Health approach has been implemented in surveillance systems for CSIDs in the Arctic and surrounding regions. Objectives The objectives of this study were to map surveillance activities currently implemented in the Canadian Arctic and subarctic for the 16 CSID identified by the Arctic Council, to describe how One Health has been operationalized in these activities, and to explore the integration and leadership of Indigenous partners in current surveillance systems. Method We performed the mapping in three steps: a rapid review of the scientific literature, a review of the grey literature and an online questionnaire sent to key stakeholders involved in CSID surveillance in the Canadian Arctic and subarctic regions. Results and conclusions We identified 37 scientific peer-reviewed and 58 grey literature records. We mapped (1) surveillance of mandatory notifiable diseases at the federal, provincial or territorial levels not specific to the Arctic and subarctic regions, and (2) non-mandatory surveillance programs specific to the Arctic and subarctic regions. We described programs targeting either a single disease, human populations or wildlife. In most programs, there was no explicit mention of the integration of the One Health approach, and little information was available on collaboration efforts between sectors. Programs involved Indigenous communities at various levels, ranging from very low communication to community members, to high involvement and leadership in program management. Improvement in current CSID surveillance activities in Canada should include enhancing information accessibility, ensuring geographic representation, fostering sustainability in implementation of One Health strategies, and stronger involvement of Indigenous communities in the leadership of surveillance systems. An internationally harmonised approach across the Arctic and subarctic regions for all CSIDs has the potential to unify circumpolar surveillance efforts, save resources, and ultimately better inform public health authorities on the actions to prioritize in the context of climate change.

Ixodes scapularis and Ixodes pacificus are vectors of a range of pathogens of public health significance in North America. These ticks transmit pathogens to and from wild animal reservoir host species, but also bite humans and expose them to the pathogens. We describe the geographical and temporal distribution of the pathogen Babesia odocoilei, the causative agent of cervid babesiosis. Ixodes spp. ticks collected through active and passive surveillance were submitted to the National Microbiology Laboratory of the Public Health Agency of Canada for analysis of the presence of B. odocoilei from 2018 to 2021. Generalized linear models were constructed to evaluate the temporal change of B. odocoilei prevalence across Canada. Babesia odocoilei-positive I. scapularis are widespread across south-central and eastern regions of Canada, with an overall prevalence of 12.0 % in both nymphs (CI 95 % : 11.4-12.6) and adults (CI 95 % : 11.9-12.1) collected in passive surveillance and 13.2 % (CI 95 % : 12.9-13.5) and 10.0 % (CI 95 % : 9.8-10.2) in nymphs and adult, respectively, collected in active surveillance. A single I. pacificus tick tested positive in active surveillance out of 29 ticks collected in British Columbia, while no B odocoilei-positive I. scapularis were found in passive surveillance among the 11 adult ticks tested. Although B. odocoilei infection prevalence of adult I. scapularis was significantly higher in 2019 (14.1 %) than in 2018 (7.4 %), it remained stable from 2019 to 2021, suggesting that this pathogen may already be well established in endemic tick populations. The results provided in this article represent, to date, the most comprehensive picture of B. odocoilei distribution and prevalence in ticks in Canada and highlight the interest of maintaining One Health surveillance approaches to give added insight into disease transmission cycles for less well-characterized microorganisms.

The environmental risk of Lyme disease, defined by the density of Ixodes scapularis ticks and their prevalence of Borrelia burgdorferi infection, is increasing across the Ottawa, Ontario region, making this a unique location to explore the factors associated with environmental risk along a residential-woodland gradient. In this study, we collected I. scapularis ticks and trapped Peromyscus spp. mice, tested both for tick-borne pathogens, and monitored the intensity of foraging activity by deer in residential, woodland, and residential-woodland interface zones of four neighbourhoods. We constructed mixed-effect models to test for site-specific characteristics associated with densities of questing nymphal and adult ticks and the infection prevalence of nymphal and adult ticks. Compared to residential zones, we found a strong increasing gradient in tick density from interface to woodland zones, with 4 and 15 times as many nymphal ticks, respectively. Infection prevalence of nymphs and adults together was 15 to 24 times greater in non-residential zone habitats. Ecological site characteristics, including soil moisture, leaf litter depth, and understory density, were associated with variations in nymphal density and their infection prevalence. Our results suggest that high environmental risk bordering residential areas poses a concern for human-tick encounters, highlighting the need for targeted disease prevention.

In the Arctic, rabies is endemic in the Arctic fox (Vulpes lagopus), posing a significant and ongoing health risk for people and domestic animals. The mechanisms by which rabies is maintained within the low-density fox populations in the Arctic remain unclear. In this study, we developed a spatially explicit individual-based stochastic epidemiological model and performed an uncertainty analysis to better understand Arctic fox rabies dynamics. Rabies persisted in 25.68% of model simulations, with several variables having significant impact on rabies persistence: probability of rabies transmission, spatial and temporal distribution food resources, mean litter size and variability of rabies incubation periods. Where rabies is endemic, we identified 5 key parameters for rabies dynamics: spatiotemporal resource distribution, probability of birth for adult females, mean and standard deviation of litter size, and incubation period of rabies. Our study demonstrates that Arctic rabies can persist in its primary host under conditions consistent with existing empirical data in the literature and showed the important role played by the spatial and temporal distribution of resources. Finally, our results suggest that the ecological impacts of rapid climate warming could decrease the overall persistence of rabies in the Arctic and the associated health risk in Arctic communities.