Ticks and Tick-borne Diseases

Spatio-temporal scales have a clear influence on microbial community distribution and diversity and are thus essential to consider to identify and study the dynamics of microorganisms. The invasive tick species Hyalomma marginatum has recently become established in southern France. It carries pathogens of medical and veterinary interest including the Crimean-Congo hemorrhagic fever virus, Rickettsia aeschlimannii, Theileria equi and Anaplasma phagocytophilum among others. While the pathogenic communities of H. marginatum were identified and their spatial distribution characterised, their temporal dynamics are still unknown. We performed a monthly H. marginatum tick collection from February to September 2022 in a sentinel site in southern France in order to study their presence and temporal dynamics. On the 281 ticks analysed, we detected pathogens included R. aeschlimannii, A. phagocytophilum and T. equi with infection rates reaching 47.0%, 4.6% and 11.0% respectively. Overall, 14.6% of ticks were infected with at least Theileria or Anaplasma, with monthly fluctuations ranging from 2.9% to 28.6%. Strong temporal patterns were observed for each of the detected pathogens, particularly for R. aeschlimannii whose infection rates drastically increased at the beginning of summer, correlated with the monthly mean temperatures in the sentinel site. Based on these results, we hypothesized that R. aeschlimannii might be a secondary symbiont of H. marginatum that could play a role into stress response to temperature. The analysis of monthly and seasonal fluctuations in H. marginatum-borne pathogens allowed us to conclude that the risk of infection is present throughout H. marginatum activity period, but particularly in summer. HighlightsO_LIStrong monthly fluctuations of pathogen infection rates were observed especially for Rickettsia aeschlimannii, currently identified as a human pathogen whose pathogenic status in humans and its symbiotic status in H. marginatum are both questioned. C_LIO_LIThe increase in temperature is correlated with the increase in Rickettsia aeschlimannii infection rates, providing clues about its potential function as a symbiont in H. marginatum. C_LIO_LITicks are recurrently infected with at least one other pathogen belonging to Theileria or Anaplasma genera with monthly fluctuations ranging from 2.9% to 28.6%. C_LIO_LIThe monthly dynamics of H. marginatum-borne pathogens are important to consider to assess the risk posed by this tick. C_LI Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=81 SRC="FIGDIR/small/589770v1_ufig1.gif" ALT="Figure 1"> View larger version (24K): org.highwire.dtl.DTLVardef@b703d5org.highwire.dtl.DTLVardef@15cc273org.highwire.dtl.DTLVardef@e238d4org.highwire.dtl.DTLVardef@ebe1_HPS_FORMAT_FIGEXP M_FIG C_FIG

Hyalomma marginatum is a common ectoparasitic tick of ungulates, lagomorphs, insectivores, ground-foraging birds, observed in Corsica for decades, but whose permanent establishment in mainland France is very recent. This species is known to be one of the main vectors of the Crimean-Congo Hemorrhagic Fever virus, but also of various parasitic, bacterial or viral pathogens. In this study, we investigated the molecular infection rates of numerous tick-borne pathogens in H. marginatum ticks mainly sampled on horses, and occasionally on other animal species, from the French Mediterranean rim and Corsica between 2016 and 2020. In total, 1, 195 DNA and RNA purified from individual ticks or pools of ticks were screened for 26 microbial genera or species (viruses, bacteria and parasites), using a high-throughput microfluidic real-time PCR system (BioMark dynamic array system, Standard Biotools). For individual ticks and pooled ones, respectively, the most prevalent tick-borne microorganisms were Francisella-like endosymbionts at 97.0% and 96.8%, followed by Rickettsia aeschlimannii (76.4% and 96.4%), Theileria spp. and Theileria equi (3,5% and 0%; 1,9% and 5,8%), Anaplasma phagocytophilum (3.7% and 6.7%), and West Nile virus (0.1% and 0.4%). Babesia occultans (0.9%), Ehrlichia minasensis (0.3%), and Coxiella-like endosymbionts (0.1%) were only detected in individual ticks. Our study provides an overview of the diversity of microorganisms and tick-borne pathogens detected in the invasive tick H. marginatum in Corsica and the continental departments of the Mediterranean rim. Our study opens up new research perspectives on the epidemiology of tick-borne pathogens carried by H. marginatum and on the associated public and veterinary health risks.

Hyalomma marginatum is an invasive tick species recently established in mainland southern France. This tick is known to host a diverse range of human and animal pathogens such as Rickettsia aeschlimannii, Theileria equi, Anaplasma phagocytophilum, Anaplasma marginale, Ehrlichia minasensis, Crimean-Congo hemorrhagic fever and West Nile virus. While information about the dynamics of these pathogens is crucial to assess disease risk and develop effective monitoring strategies, few data on the spatial dynamics of these pathogens are currently available. We thus collected ticks in 27 sites in the Occitanie region to characterize spatial patterns of H. marginatum- borne pathogens. Several pathogens have been detected: Theileria equi (9.2%), Theileria orientalis (0.2%), Anaplasma phagocytophilum (1.6%), Anaplasma marginale (0.8%) and Rickettsia aeschlimannii (87.3%). Interestingly, we found a spatial clustered distribution for the pathogen R. aeschlimannii between two geographically isolated areas with infection rates and bacterial loads significantly lower in Herault/Gard departments (infection rate 78.6% in average) compared to Aude/Pyrenees-Orientales departments (infection rate 92.3% in average). At a smaller scale, R. aeschlimannii infection rates varied from one site to another, ranging from 29% to 100%. Overall, such high infection rates (87.3% in average) and the effective maternal transmission of R. aeschlimannii might suggest a role as a tick symbiont in H. marginatum. Moreover, currently identified as a human pathogen, such results also question about its pathogenic status in humans given the low number of human cases. Further studies are thus needed to understand both the status and the role of R. aeschlimannii in H. marginatum ticks. IMPORTANCETicks are obligatory hematophagous arthropods which transmit pathogens of medical and veterinary importance. Their infections cause serious health issues in humans and considerable economic loss in domestic animals. Information about the presence of pathogens in ticks and their dynamics is crucial to assess disease risk for public and animal health. Analysing tick-borne pathogens in ticks collected in 27 sites in the regions Occitanie, our results highlight clear spatial patterns in the Hyalomma marginatum-borne pathogen distribution and strengthen the postulate that it is essential to develop effective monitoring strategies and consider the spatial scale to better characterize the circulation of tick-borne pathogens.

We assessed the temporal and spatial distribution of Borrelia burgdorferi, Borrelia miyamotoi, Babesia microti, and Anaplasma phagocytophilum among human-biting Ixodes scapularis ticks in Massachusetts using ticks submitted to the TickReport pathogen passive surveillance program. From January 2015 to December 2017, Ixodes scapularis was the most frequently submitted tick species (n=7462). B. burgdorferi prevalence increased in ticks during the study period in adults and nymphs (37.1-39.1% in adults, 19.0%-23.9% in nymphs). The proportion of B. microti infected ticks increased from 5.7% to 8.1% in adult ticks but remained constant in nymphs (5.4-5.6%). Stable or decreasing annual prevalence of B. miyamotoi (2.2 - 2.2% in adults, 1.0-1.9% in nymphs) and A.phagocytophilum (7.6-7.2% in adults, 5.0-4.0% in nymphs) were detected. Coinfections were observed and included all pathogen combinations. Ticks were submitted year-round and had stable infection rates. The temporal pattern of B. burgdorferi- positive nymphs aligned with reported cases of Lyme disease, as did positive B. microti nymphs and babesiosis. A similar situation is seen with B. miyamotoi with an insignificant fall peak in cases. Anaplasmosis demonstrated a significant bimodal distribution with reported cases peaking in the spring and fall. This pattern is similar to that of A. phagocytophilum-infected adult ticks. B. microti infected nymphs were significantly predictive of town-level babesiosis incidence and A. phagocytophilum infected adults were significantly predictive of town-level anaplasmosis incidence in a spatially adjusted negative binomial model. Unlike field collection studies, the high number of ticks submitted provides a high-resolution picture of pathogen prevalence and provides data relevant to human health at the town level. Through temporal and geographic analyses we demonstrate concordance between our passive surveillance tick pathogen data and state reports of tickborne disease.

Piroplasms, which include the agents of cattle fever and human and dog babesiosis, are a diverse group of blood parasites of significant veterinary and medical importance. The invasive Asian longhorned tick, Haemaphysalis longicornis, is a known vector of piroplasms in its native range in east Asia and invasive range in Australasia. In the US state of Virginia, H. longicornis has been associated with Theileria orientalis Ikeda outbreaks that caused cattle mortality. We examined 667 H. longicornis collected in 2021 from three sites in New Brunswick, New Jersey, the US state where established populations of this species were first detected in 2017. We used primers targeting the 18S small subunit rRNA and the cytochrome b oxidase loci and unveiled the presence of DNA from an unidentified Theileria species (in 1 nymph) and Theileria cervi type F (1 adult, 5 nymphs). In addition, we sequenced a 130 bp fragment of the cytochrome oxidase b locus from Odocoileus virginianus, the white-tailed deer, in a partially engorged questing H. longicornis, supporting the association of this tick species with deer. We also detected DNA from an undescribed Babesia sensu stricto ( true Babesia, 2 adults, 2 nymphs) as well as Babesia sp. Coco (1 adult, 1 nymph). Finally, we detected DNA from Babesia microti S837 (1 adult, 4 nymphs). Babesia microti S837 has been sequenced from striped skunks, Mephitis mephitis, and is closely related to the human pathogen B. microti US-type. The five parasites we are associating with H. longicornis represent a diverse assemblage spanning three clades in the piroplasm phylogeny, two undescribed, raising concerns of transmission amplification of veterinary pathogens as well as spillover of pathogens from wildlife to humans.

Feline cytauxzoonosis is an emerging tick-borne disease in Europe. While infections have been reported in different European countries, the tick vector remains unknown. This study investigated 665 ticks collected in 2019 (n= 160), 2022 (n= 7) and 2024 (n= 658) in a Cytauxzoon spp. hotspot region in central Switzerland (62 ticks from cats; 603 ticks from vegetation). Ticks were morphologically characterized, pooled by origin and life-stage, screened for Cytauxzoon spp. 18S rRNA by qPCR and conventional PCR and positive samples confirmed by sequencing. All ticks belonged to Ixodes ricinus (50 males, 83 females, 532 nymphs). Four tick pools from 2019 tested Cytauxzoon spp. positive: one pool of 4 non-engorged male ticks from cats and three pools of 5-6 nymphs each from vegetation. All ticks collected in 2022 and 2024 tested negative. Amplification of the almost full-length (1535 bp, 1 pool) or partial (219-140 bp, 3 pools) 18S rRNA gene revealed a sequence identify of 98.6-100% with Cytauxzoon spp. previously detected in cats from this area. The detection of Cytauxzoon spp. in questing Ixodes ricinus nymphs suggests a potential role of this tick species in the parasites transmission cycle in Central Europe and raises the possibility of transovarial transmission. Mitochondrial gene sequencing was unsuccessful, but the detected Cytauxzoon spp. likely represent Cytauxzoon europaeus. Discrepancies between qPCR and conventional PCR results point to possible amplification of tick endosymbionts, highlighting the importance of confirmatory sequencing particularly when testing tick-derived DNA. In conclusion, this is the first report of Cytauxzoon spp. in questing I. ricinus ticks in Europe. Our findings underscore the need for further research to confirm vector competence and clarify transmission dynamics.

Ixodid tick species such as Ixodes ovatus and Haemaphysalis flava are essential vectors of tick-borne diseases in Japan. In this study, we investigated the population genetic structures and gene flow of I. ovatus and H. flava as affected by the tick host mobility. We hypothesized that I. ovatus and H. flava may have differences in their genetic structure due to the low mobility of small rodent hosts of I. ovatus at the immature stage in contrast to the mediated dispersal of avian hosts for immature H. flava. We collected 307 adult I. ovatus and 220 adult H. flava from 29 and 17 locations across Niigata Prefecture, Japan. We investigated the genetic structure at two mitochondrial loci (cox1, 16S rRNA gene). For I. ovatus, pairwise FST and analysis of molecular variance (AMOVA) analyses of cox1 sequences indicated significant genetic variation among populations. Both cox1 and 16S rRNA markers showed non-significant genetic variation among locations for H. flava. The Bayesian tree and haplotype network of cox1 marker for I. ovatus samples in Niigata Prefecture found 3 genetic groups wherein most haplotypes in group 2 were distributed in low altitudinal areas. When we added cox1 sequences of I. ovatus from China to the phylogenetic analysis, three genetic groups (China 1, China 2, and Niigata and Hokkaido, Japan) were formed in the tree suggesting the potential for cryptic species in the genetic group in Japan. Our results support our hypothesis and suggest that the host preference of ticks at the immature stage may influence the genetic structure and gene flow of the ticks. This information is vital in understanding the tick-host interactions in the field to better understand the tick-borne disease transmission and in designing an effective tick control program.

A detailed understanding of the human antibody response to Outer surface protein C (OspC) of Borrelellia burgdorferi has important implications for Lyme disease diagnostics and vaccines. In this report, a total of 13 peptides encompassing eight reported OspC linear B cell epitopes from OspC types A, B and K, including the conserved C-terminus (residues 193-210: peptide C10), were evaluated by multiplex immunoassay (MIA) for IgG reactivity with [~]700 human serum samples confirmed positive in a two-tiered Lyme disease diagnostic assay and [~]160 post-treatment Lyme disease (PTLD) serum samples. The VlsE C6-17 peptide was included as a positive control. Diagnostic serum IgG reacted with 11 of the 13 OspC-derived peptides, significantly more than controls, with the C10 peptide being the most reactive. In the PTLD serum samples, two OspC peptides including C10 were significantly more reactive than controls. Spearmans rank correlation matrices and hierarchical clustering indicated a strong correlation between C10 and VlsE C6-17 peptide reactivity but little demonstrable association between C10 and the other OspC peptides or recombinant OspC. OspC peptide reactivities (excluding C10) were strongly correlated with each other and were disproportionately influenced by a subset of pan-reactive samples. In the PTLD cohort, C10 clustered with the other OspC-derived peptides and was distinct from OspC and VlsE C6-17. The asynchronous serologic response to OspC, C10, and the OspC-derived peptides reveals the complexity of B cell responses to B. burgdorferi and confounds simple interpretation of antibody profiles associated with Lyme disease. IMPORTANCELyme disease is an emerging tick-borne infection caused by the spirochete, Borreliella burgdorferi. In humans, antibodies against spirochetal outer surface lipoproteins are proposed to play a role in disease resolution and in protection against reinfection. Some of those same antibodies also serve as diagnostic indicators of an active or history of Lyme disease. In this study, we sought to validate reported antibody binding sites on Outer surface protein C (OspC), a known target of both protective and diagnostic antibodies.

We analysed the geographic risk of Lyme borreliosis taking into account the biogeography of tick vectors and carrier hosts, together with environmental and anthropogenic factors. Four pathogeographical scenarios were set in order to represent the contribution of vectors and hosts in the spatial zoonotic risk. For that propose, we built distribution models based on the occurrence of Lyme borreliosis cases in humans and ixodid vectors. Besides Ixodes species, we considered other ixodid ticks with potential to be vectors. These models were combined through fuzzy logic operators, according to the criteria stablished in each scenario. Finally, the transmission risk model for Lyme borreliosis which best fitted its global distribution was selected. The risk model selected considered ixodid vectors and mammal carriers as explanatory variables together with environment and anthropogenic factors. Ixodes species contributed to explain the geographical risk of Lyme borreliosis to larger extent than other ixodid ticks. The risk model described regions with Lyme borreliosis transmission risk where its presence is still uncertain, such as northern Africa and inland areas of western USA. Likewise, our model indicated favourable conditions for the presence of human cases in northern latitudes beyond its endemic distribution. Applying this multi-scenario methodology approach have led us to a risk model, in which the diversity of ixodid vectors and carrier hosts might modify the spatial risk without a geographical limitation.

BackgroundIxodes ricinus ticks act as vectors for numerous pathogens that present substantial health threats. Additionally, they harbour vertically transmitted symbionts, some of which have been linked to diseases. The difficulty of isolating and cultivating these symbionts has hampered our understanding of their biological role, their potential to cause disease, and their modes of transmission. To expand our understanding on the tick symbiont Midichloria mitochondrii and on Rickettsia helvetica, which has been linked to disease in humans, we utilized deep sequencing on sixteen individual adult female ticks collected from coastal dune and forested areas in the Netherlands. ResultsBy employing a combination of second and third-generation sequencing techniques, we successfully reconstructed the complete genomes of M. mitochondrii from eleven individuals, R. helvetica from eight individuals and the mitochondrial genome from all ticks. Additionally, we visualised the location of R. helvetica in tick organs and constructed genome-scale metabolic models (GEMs) of both symbionts to study their environmental dependencies. Our analysis revealed a strong cophylogeny between M. mitochondrii and mitochondrial genomes, suggesting frequent maternal transmission. In contrast, the absence of cophylogeny between R. helvetica and the mitochondrial genomes, coupled with its presence in the receptaculum seminis of I. ricinus females, raises the possibility of paternal transmission of R. helvetica. Notably, the genetic diversity of R. helvetica was found to be very low, except for the rickA virulence gene, where the presence of up to thirteen insertions of a33nt-long repeat led to significant variability. However, this variation could not account for the differences in infection prevalence observed across eight distinct locations in the Netherlands. ConclusionsBy employing deep sequencing, it becomes feasible to extract complete genomes and genetic data of symbionts directly from their host organisms. This methodology serves as a robust means to gain fresh insights into their interactions. Our observations, which suggest paternal transmission of R. helvetica, a relatively unexplored mode of transmission in ticks, require validation through experimental investigations. The genetic variations identified in the rickA virulence gene of R. helvetica have the potential to influence the infectivity and transmission dynamics of R. helvetica

Ornithodoros turicata is a vector of relapsing fever (RF) spirochetes in North America and transmits Borrelia turicatae to a variety of vertebrate hosts. The remarkably long lifespan of O. turicata and its ability to maintain spirochetes horizontally (between life stages) and vertically to progeny promotes the perpetuation of B. turicatae in nature. Nevertheless, the reproductive biology of O. turicata is poorly understood. In this report, we collected ticks from a park within a neighborhood of Austin, Texas. They were reared to adulthood and male ticks were individually housed with females. We observed autogenous reproduction by the ticks and further investigated vertical transmission of B. turicatae by quantifying filial infection rates in a cohort of progeny ticks. These results indicate that O. turicata transovarially transmits B. turicatae during autogenous reproduction and further signify the tick as a natural reservoir of the spirochetes. ImportancePrevious research has implicated Ornithodoros ticks, including Ornithodoros turicata, as long-term reservoirs of relapsing fever (RF) spirochetes. Considering the ticks long lifespan and their efficiency in maintaining and transferring spirochetes within the population, the infection could persist in a given enzootic focus for decades. However, little is known about the relative importance of horizontal and vertical transmission routes in the persistence and evolution of RF Borrelia. Our observations on the reproductive biology of O. turicata in the absence of vertebrate hosts indicate an additional mechanism by which B. turicata can be maintained in the environment. This work establishes the foundation for studying O. turicata reproduction and spirochete-vector interactions, which will aid in devising control measures for Ornithodoros ticks and RF spirochetes.

Surveillance studies were implemented in Sinaloa, Mexico to determine the circulation of tick-borne relapsing fever spirochetes. Argasid ticks were collected from a human dwelling in the village of Camayeca and spirochetes were isolated. Genomic analysis indicated that Borrelia turicatae is a threat to those living in resource limited settings. Article Summary LineWe report the collection of argasid ticks from a peridomestic setting in Mexico and the isolation of Borrelia turicatae; increased surveillance efforts are needed on this overlooked vector-borne pathogen.

Tick-borne flaviviruses and Borrelia spp. are globally spread pathogens of zoonotic potential that are maintained by a transmission cycle at the interface between ticks and vertebrate hosts, mainly wild animals. Aside data on pathogen burden in ticks, information on the status of various hosts relative to infection could be critical. We reviewed how those infections have been studied in wildlife species in the field to discuss how collected data provided relevant epidemiological information and identify needs for further studies. The literature was screened for populational studies on direct or antibody detection for tick-borne Borrelia spp. and flaviviruses in animals, in the wild. Overall, Borrelia spp. were more studied (73% of case studies, representing 297 host species) than flaviviruses (27% of case studies, representing 114 host species). Studies on both Borrelia spp. and flaviviruses focused mainly on the same species, namely bank vole and yellow-necked mouse. Most studies were order-specific and cross-sectional, reporting prevalence at various locations, but with little insight into the underlying epidemiological dynamics. Species with potential to act as reservoir hosts were overlooked, notably passerine birds. We highlight the necessity of collecting both demographics and infection data in wildlife studies, and to consider communities of species, to better estimate zoonotic risk potential in the One Health context.

BackgroundUnderstanding the geographic distribution of Rickettsia montanensis infections in Dermacentor variabilis is important for tick-borne disease management in the United States, as both a tick-borne agent of interest and a potential confounder in surveillance of other rickettsial diseases. Two previous studies modeled niche suitability for D. variabilis with and without R. montanensis, from 2002-2012, indicating that the D. variabilis niche overestimates the infected niche. This study updates these, adding data since 2012. MethodsNewer surveillance and testing data were used to update Species Distribution Models (SDMs) of D. variabilis, and R. montanensis infected D. variabilis, in the United States. Using random forest (RF) models, found to perform best in previous work, we updated the SDMs and compared them with prior results. Warrens I niche overlap metric was used to compare between predicted suitability for all ticks and pathogen positive niche models across datasets. ResultsWarrens I indicated <2% change in predicted niche, and there was no change in order of importance of environmental predictors, for D. variabilis or R. montanensis positive niche. The updated D. variabilis niche model overpredicted suitability compared to the updated R. montanensis positive niche in key peripheral parts of the range, but slightly underpredicted through the northern and midwestern parts of the range. This reinforces previous findings of a more constrained pathogen-positive niche than predicted by D. variabilis records alone. ConclusionsThe consistency of predicted niche suitability for D. variabilis in the United States, with the addition of nearly a decade of new data, corroborates this is a species with generalist habitat requirements. Yet a slight shift in updated niche distribution, even of low suitability, included more southern areas, pointing to a need for continued and extended monitoring and surveillance. This further underscores the importance of revisiting vector and vector-borne disease distribution maps.

Crimean-Congo Haemorrhagic Fever (CCHF) is a tick-borne zoonosis with significant public health implications due to its expanding geographic distribution and potential for severe outcomes in humans. This study represents the first serological survey conducted in mainland France to detect antibodies against the Crimean-Congo Haemorrhagic Fever Virus (CCHFV) in domestic and wild fauna, providing critical insights into the viruss circulation. We analyzed 8,609 cattle sera and 2,182 wildlife sera collected across the French Mediterranean region from 2008 to 2022, using enzyme-linked immunosorbent assays (ELISA) and pseudo-plaque reduction neutralization tests (PPRNT) for antibody detection and confirmation. Seropositivity was detected in both cattle (2.04%) and wildlife (2.25%), with higher rates observed in specific regions such as Pyrenees-Orientales and Hautes-Pyrenees. These findings reveal spatial clusters of CCHFV circulation and suggest the existence of enzootic transmission cycles involving local tick vectors and animal hosts. Our multivariate analysis identified key factors influencing seropositivity, including animal age, habitat characteristics, and potential wildlife interactions. The presence of natural open habitats and coniferous forests was significantly associated with higher seropositivity in cattle, while sex and geographical variability played a role in wildlife seroprevalence. These findings highlight the importance of environmental and anthropogenic factors in shaping the dynamics of CCHFV transmission. This study demonstrates that CCHFV is actively circulating in parts of mainland France, emphasizing the need for enhanced surveillance and integrated approaches to monitor zoonotic pathogens. It also raises questions about the role of additional tick vectors, such as Hyalomma lusitanicum, in the transmission cycle. These results contribute to a better understanding of CCHF epidemiology and offer valuable guidance for public health strategies to mitigate the risks associated with this emerging disease. Author SummaryCrimean-Congo Haemorrhagic Fever (CCHF) is a severe disease spread by ticks that affects humans and animals. Although the disease is largely distributed in parts of Europe, Africa, and Asia, its presence in France has been uncertain. My study investigated whether the virus causing this disease is circulating in southern mainland France by testing blood samples from domestic animals, like cattle, and wild animals, such as deer and wild boars, for signs of previous infection. I found evidence of the virus in several regions, particularly in the Pyrenees-Orientales, Hautes-Pyrenees and Alpes-maritimes, suggesting that the virus is indeed circulating among animals and ticks in some parts of mainland France. By studying where infected animals were found and considering factors such as age, habitat, and environmental conditions, I identified that older animals seem to have been more often exposed to the virus, as well as animals frequenting open environments favorable to ticks. These findings are important because they show that the disease could potentially spread to new areas and affect human populations. My work highlights the need for ongoing monitoring of ticks and animals for CCHFV epidemiological surveillance and the protection of public health.

BackgroundLyme disease is caused by Borrelia burgdorferisensulato (BBSL) which is usually found in wild and domestic mammals worldwide. Human cases of B. burgdorferi infections have been identified in China, but little direct surveillance of potential rodent reservoirs has been performed in Yunnan Province, Southwestern China. Yunnan Province is a tropical area with a diverse topographic range and sustains a high biodiversity of small mammals that could potentially play an important role in the transmission of a variety of B. burgdorferigenospecies.\n\nMethods3659 small mammals were captured in 159 sample siteslocated 23 countries inYunnan Province and screened for BBSL infection by nested PCR based on 5S-23S rRNA intergenic spacer gene of BBSL.Univariate and multivariate forward stepwise logistic regression analysis was used to access the association between infections and related risk factors.\n\nResultsInfection with BBSL was confirmed in 3.99%(146/3659) of small mammals. Significant differences in prevalence rates of BBSL were observed at varying landscape types and altitudes.Small mammals in forested areas had higher prevalence rates than other landscape types as did small mammals found at altitudes greater than 2500 meters. The 5S-23S rRNA intergenic spacergene revealed that there were 5 genotype of BBSL, including B. afzelii, B. burgdorferisensustricto, B.japonica, B.gariniiand B.valaisiana, which demonstrate the genetic diversity and regional distribution.\n\nConclusionsThere exists a wide distribution and genetic diversity of endemic BBSL in Southwestern China, warranting further investigations and monitoring of clinical disease in individuals presenting with symptoms of Lyme disease in these areas.\n\nAuthor summaryLyme disease is caused by Borrelia burgdorferi sensu lato (BBSL) which is usually found in wild and domestic mammals worldwide. Human cases of Borrelia burgdorferi sensu lato infections have been identified in China, but little direct surveillance of potential rodent reservoirs has been performed in Southwestern China. This study documents potential small mammal reservoir hosts collected from a large of sample sites from different landscape types and altitudes, with PCR and sequencing identifying the wide distribution and genetic diversity of endemic Borrelia burgdorferi sensu lato in Southwestern China. This was the first report that B. japonica was detected in Apodemus draco and Niviventer excelsior in China. This study adds to body of literature on Borrelia burgdorferi sensu lato in China. This work will provide insight regarding small mammals to target for surveillance and we access the association between gender, developmental stage of rodents, environmental landscape and altitude to better prevent human exposure.

Ixodiphagus hookeri (Hymenoptera: Encyrtidae) is a highly specialized koinobiont endoparasitoid of hard ticks (Acari: Ixodidae). While it is considered a prime target for biological control of ticks, longitudinal data on natural parasitisation of tick populations is scarce, consequently leading to a lack of understanding regarding the effects of global warming on wasp populations and factors impacting natural parasitisation rates of ticks. To fill in these gaps, we present a longitudinal time series on natural I. hookeri parasitisation of Ixodes ricinus from the northernmost limits of their occurrence. In total, 2,111 I. ricinus nymphs collected between 2014-2021 from Seili Island in southwestern Finland were screened for I. hookeri DNA utilizing an in-house qPCR assay. Samples had previously been screened for several tick-borne pathogens and larval blood meal sources. Generalized linear mixed models were fitted to determine factors influencing the probability of parasitisation of questing nymphs, whether parasitisation influences tick densities, and if differences in parasitisation can be identified between early (May to mid-July) and late (mid-July to October) season. Log odds ratios were calculated to assess parasitisation-pathogen and parasitisation-host associations. An artificial tick feeding system was used to feed nymphs collected from the island. An increase in I. hookeri parasitisation was observed on the island between 2014-2021. The overall parasitisation prevalence was 8.2 %, with year and study site specific values ranging from 0 to 38 %. Larvae densities, July mean temperatures and parasitisation rates at t-1 were observed to increase probability of parasitisation. Parasitisation was more likely if the nymphs had fed on deer as larvae or carried Babesia spp. protozoa, and less likely if they carried Borrelia spp. Twelve wasps emerged from an artificially fed nymph, immediately starting oviposition and expiring within seven days. We present here the longest time series of natural I. hookeri parasitisation of I. ricinus ticks. An increasing trend in parasitisation was observed, indicating increases in the wasp population likely linked to global warming. Our results regarding associations between parasitisation and tick-borne pathogens - and directly linking parasitisation events to deer - support findings from previous research, which have indicated that parasitisation of ticks is more likely to occur on large host animals than on small hosts or ticks questing on the ground. The results suggest that larvae may be more important parasitisation targets for the wasps than previously accredited.

In Europe, Lyme borreliosis is the most common vector-borne human disease, caused mainly by Borrelia afzelii and Borrelia garinii, two species of the Borrelia burgdorferi sensu lato (Bbsl) complex transmitted by the tick Ixodes ricinus. Accurately assessing the spatial risk of human exposure to these pathogens is essential for efficient public health surveillance. However conventional monitoring often struggles to produce geographically explicit, large-scale data that capture the heterogeneity of human exposure and its drivers. Focusing on continental France, we leveraged data from the French CiTIQUE citizen science programme to analyse spatial variation of Bbsl infection in georeferenced human-biting I. ricinus ticks and to model the relationship between Bbsl distribution and environmental, ecological, and anthropogenic factors. From 2017-2019, 1,891 ticks were analysed, of which 15% tested positive for Bbsl. The most prevalent genospecies were B. afzelii (7.2%) and B. garinii (4.2%). Infection rates varied spatially, with distinct distribution patterns across pathogen groups. Tick habitat suitability was the most consistent predictor for overall Bbsl infection probability, genospecies-specific models revealed the importance of their respective reservoir hosts: B. afzelii occurrence was positively associated with rodent species richness, whereas B. garinii was associated with Turdidae species and showed potential traces of a dilution effect due to rodents. Our findings demonstrate the value of citizen science for complementing formal surveillance and provide the first geographically explicit, large-scale insights into Bbsl eco-epidemiology in France. This scalable approach offers an adaptable framework for monitoring vector-borne disease risk and guiding public health strategies. ImportanceLyme borreliosis, caused by Borrelia burgdorferi sensu lato, is the most common human vector-borne disease in Europe. Accurate assessment of spatial exposure risk is essential for effective public health surveillance and interventions. Using data from the French CiTIQUE citizen science program, we reveal pathogen-specific spatial patterns and identify the factors shaping them, at a geographic resolution not previously studied. Our findings demonstrate that citizen science can provide a scalable and adaptive framework for long-term surveillance of vector-borne disease risk, offering valuable insights to guide targeted prevention and control measures.

We detected Borrelia puertoricensis in migratory Mexican free-tailed bats sampled in Oklahoma during 2022 and 2023, representing only the second detection of this relapsing fever species in wild vertebrates. Although prevalence was low (0.79%), our findings suggest migratory bats could contribute to dispersal of tick-borne pathogens in North America.

Borrelia burgdorferi, a tick-vectored spirochete bacteria best known for causing Lyme disease, has been found to induce physiological and behavioural changes in its tick vector that can increase tick fitness and its ability to transmit the bacteria. The mechanism by which this bacterium modulates these changes remains unknown. Epigenetics plays a central role in transducing external and internal microbiome environmental influences to the organism, so we investigated DNA methylation and the expression of a key histone modification enzyme in Borrelia-infected and uninfected Ixodes scapularis ticks. DNA methylation of the pericentromeric tandem repeats family, Ixodes scapularis Repeats (ISR) were assessed by methylated-DNA immunoprecipitation (MeDIP) followed by qPCR of the ISR regions. DNA methylation of the ISR sequences was found. The different repeats had different levels of DNA methylation, however, these levels were not significantly affected by the presence or absence of B. burgdorferi. The epigenetic regulator euchromatic histone lysine methyltransferase 2 (EHMT2) is recognized as having a key role in modulating the organismal stress response to infections. To assess EHMT2 transcription in Borrelia-infected and uninfected ticks, real-time reverse transcriptase PCR was performed. Uninfected ticks had over 800X lower EHMT2 expression than infected ticks. This study is among the first to identify a gene that may be involved in producing epigenetic differences in ticks depending on infection status and lays the groundwork for future epigenetic studies of I. scapularis in response to B. burgdorferi as well as other pathogens that these ticks transmit.