The research, published in the journal Parasites & Vectors, was conducted by James C. Burtis, Erik Foster, and Rebecca J. Eisen of the CDC’s Division of Vector-Borne Diseases in Fort Collins, Colorado. Their central question was deceptively simple: across seven western states, which counties have environmental conditions suitable both for the bacterium to maintain itself in local wildlife cycles and for infected nymphs to climb up onto vegetation and wait for a host? That second condition matters enormously for human health. Nymphal ticks are tiny, roughly the size of a poppy seed, and their host-seeking behavior above the ground is what brings them into contact with people hiking, gardening, or working outdoors. A tick that never quests above vegetation poses far less risk of a bite.

To build their analysis, the team confronted the fundamental scarcity of western tick surveillance data. Systematic records documenting the densities of host-seeking, infected nymphs are limited in the region, in stark contrast to the eastern United States where such data underpin county-level risk maps. The researchers turned to the ArboNET Tick Module, a national database maintained by the CDC that aggregates tick surveillance submissions from public health partners. Because those records alone could not cover the full geographic extent of potential tick habitat, they supplemented the database with an exhaustive review of the published literature and public health records, collating county-level observations of host-seeking nymphs and separately compiling reports of B. burgdorferi sensu stricto infections detected in both nymphal and adult I. pacificus.

The compilation revealed a striking imbalance. Host-seeking I. pacificus nymphs had been recorded in 54 counties across the seven western states, while evidence of Bbss-infected I. pacificus existed in only 36 counties, all of them in California, Oregon, and Washington. That distinction is critical. A tick population can thrive in a county without the bacterium circulating among the wildlife that feed the ticks. Enzootic transmission, the sustained cycling of the spirochete between ticks and reservoir hosts such as small mammals and birds, requires a specific confluence of vector abundance, competent reservoir species, and favorable climate. Some counties may host abundant ticks but, for reasons of host community composition or microclimate, never sustain the pathogen.

With these records in hand, the researchers built separate habitat suitability models for the two phenomena: one predicting where host-seeking nymphs are likely to occur, and another predicting where Bbss-infected ticks of either stage have been or are likely to be found. The modeling approach drew on multiple algorithms rather than a single statistical technique, a strategy that guards against the idiosyncrasies of any one method. Crucially, the team set the suitability thresholds of all algorithms to achieve 90 percent sensitivity, meaning the models were deliberately tuned to flag nearly every county with a known record, even at the cost of including some counties where the tick or pathogen may ultimately be absent. In public health terms, this conservative choice favors caution: it is better to overestimate the map of potential risk than to tell residents of an affected county they are safe.

The final step was an overlay. By intersecting the suitable habitat for host-seeking nymphs with the suitable habitat for infected I. pacificus, the researchers identified counties where the environment plausibly supports the full combination of conditions that generate acarological risk: infected nymphs actively questing above vegetation. The resulting map told a geographically focused story. Suitable habitat for encountering Bbss-infected host-seeking nymphs clustered mostly in central and northern California and along the coastal corridors of Washington and Oregon. The pattern was markedly narrower than the overall footprint of the tick itself, confirming that I. pacificus occupies a far broader range than the Lyme disease transmission zones within it.

The numbers quantify that contrast vividly. An earlier modeling effort had classified 113 counties across the western states as suitable for I. pacificus. Yet the new analysis found only 76 counties characterized as suitable for detecting Bbss-infected host-seeking nymphs by at least one of the team’s models. In other words, more than a third of the counties that could host the tick lack evidence of conditions supporting the infected, questing nymphs that pose the greatest hazard to people. For residents and clinicians, this reframes the geography of concern: living in a county where western blacklegged ticks exist is not equivalent to living in a county where Lyme transmission cycles are plausible.

The study’s authors are careful about what their models can and cannot say. The suitability maps identify where infected, host-seeking nymphs are environmentally plausible, but they do not differentiate the magnitude of risk within or among counties. A county flagged as suitable might support low densities of infected nymphs while another supports densities orders of magnitude higher, and the binary classification cannot capture that gradient. Nor can the models replace direct measurement; density of infected nymphs, the metric most tightly linked to human case risk, requires labor-intensive field dragging and pathogen testing that surveillance programs in the West have struggled to sustain. What the models provide instead is a prioritization tool, a way to direct scarce surveillance resources toward the counties where field data would be most informative.

That prioritization is precisely how the authors frame the study’s practical payoff. As a next step toward improving acarological risk assessment in the western United States, the research highlights specific counties where enhanced tick surveillance is warranted. Field confirmation in modeled-suitable counties without existing records could verify the presence of infected questing nymphs, while surveillance in borderline counties could sharpen the thresholds of future models. The approach mirrors strategies used in the East, where layered surveillance and modeling have produced the county maps that clinicians and the public routinely consult. Bringing the West closer to that standard has been a long-standing goal of CDC vector-borne disease programs, and the intramurally funded study represents a substantial advance toward it.

For the public, the message embedded in the maps is one of informed vigilance rather than alarm. The core risk zones in central and northern coastal California and the Pacific Northwest coasts are places where outdoor recreation and residential development interleave with tick habitat, and where standard precautions remain essential: using repellents, performing tick checks after time outdoors, and promptly removing attached ticks. At the same time, the finding that infected questing nymphs are plausible in fewer counties than the tick’s total range offers reassurance to residents of inland and southern areas where the tick occurs but the pathogen apparently does not. As climate and land use continue to shift, the interplay between tick distributions and pathogen transmission will evolve, and models like these, anchored to surveillance and repeatedly updated, will be central to keeping western Lyme disease risk maps honest, current, and actionable.

Subject of Research: Habitat suitability modeling for Borrelia burgdorferi-infected western blacklegged tick nymphs in the western United States

Article Title: Identifying counties with suitable habitat for host-seeking Borrelia burgdorferi sensu stricto-infected Ixodes pacificus nymphs across seven states in the western United States

Article References: Burtis, J. C., Foster, E., & Eisen, R. J. (2026). Identifying counties with suitable habitat for host-seeking Borrelia burgdorferi sensu stricto-infected Ixodes pacificus nymphs across seven states in the western United States. Parasites & Vectors. https://doi.org/10.1186/s13071-026-07730-5

Image Credits: AI Generated

DOI: 10.1186/s13071-026-07730-5

Keywords: Lyme disease, Ixodes pacificus, Borrelia burgdorferi, tick surveillance, habitat suitability modeling, nymphal ticks, western United States, CDC, acarological risk, vector-borne disease, county-level mapping, Parasites & Vectors

The authors, led by Mark Ferguson and Joanne Garrett of the European Centre for Environment and Human Health, point out that the study of urban green spaces, climate change and vector-borne diseases are each mature and substantial research fields. The pairwise interactions among them are at least partly understood. What has been missing, they argue, is sustained attention to the intersection of all three domains simultaneously, precisely the place where the most consequential and least anticipated public health outcomes are likely to emerge. As cities race to plant trees, restore wetlands and build green corridors to cope with a warming climate, the question of who else benefits from that vegetation, and at what cost, has remained largely unexamined.

The health benefits of urban greenery are well documented and typically fall into three broad categories. Restoration covers processes such as stress recovery and mental restoration after cognitive fatigue. Capability building refers to green spaces’ role in facilitating physical activity, from jogging to children’s play. Protection from harms includes the cooling effect of vegetation during heatwaves and the capacity of parks and wetlands to manage stormwater and reduce flood risk. Interventions designed to capture these benefits now take many forms: green and blue infrastructure such as urban green corridors that encourage active travel, social programming including nature-based prescribing in clinical settings, and Nature-based Solutions that tackle multiple environmental, social and economic challenges at once, such as a wetland designed to improve water quality, provide recreation and boost biodiversity.

Into this largely benign picture, the authors introduce an uncomfortable cast of characters. The principal vector-borne diseases emerging in European urban areas include tick-borne infections such as Lyme disease and mosquito-borne infections such as dengue, chikungunya and Zika. Ticks infected with Borrelia, the bacterium responsible for Lyme disease, can travel into new areas on birds, moving from Lyme-endemic rural regions into cities and introducing the pathogen there. Urban green space design and management, including practices such as conservation grazing with livestock, may increase habitat suitability for ticks and their natural hosts, which include rodents, birds and deer. Those changes could facilitate the establishment of urban Lyme disease transmission cycles in places where they have historically been absent.

Mosquitoes present a parallel and arguably more alarming challenge. For diseases spread by invasive Aedes mosquitoes, such as dengue, Zika and chikungunya, the increased humidity and shelter provided by dense vegetation can create ideal resting sites. The same applies to the Culex mosquitoes that carry West Nile virus, which thrive in natural wetlands, container habitats and flooded areas. Coupled with the movement of infected migratory birds, these conditions could allow urban cycles of West Nile virus to become established. The economic stakes are considerable: while uncertainty surrounds future health care burdens under changing climates, the global historic costs of dengue, Zika and chikungunya have been estimated at a mean annual cost of 3.29 billion US dollars, and surveillance of disease-carrying vectors remains a major public health challenge associated with significant costs.

Climate change acts as an accelerant on every one of these dynamics. Beyond the direct health burden of heat and extreme weather, a warming world lengthens transmission seasons, expands the geographic range of vectors, and alters pathogen survival and replication rates. The evidence is already quantifiable. According to figures cited in the article from the 2025 Lancet Countdown report, climate change increased the transmission potential of dengue by Aedes albopictus and Aedes aegypti by 48.5 per cent and 11.6 per cent respectively between the decades of 1951 to 1960 and 2015 to 2024. Those are not projections of a distant future but measurements of a shift that has already occurred within living memory.

The climate is also reshaping how people actually use green spaces, which changes exposure patterns in ways that are difficult to predict. Vegetation growth conditions are shifting, with drought causing increased vegetation stress and forcing designers to rethink which species can survive and continue delivering cooling and other services. Human behaviour is adapting too. A study in Germany identified a temperature threshold of 30 degrees Celsius, above which park visits for activities such as jogging and playing with children declined sharply. A more recent study estimated that high temperature and humidity significantly reduce the recreational value of green spaces. Yet climate change may also push people to use parks during cooler periods of the day, in the mornings and at night, and during milder seasons, potentially shifting human-vector contact into hours and months when mosquitoes and ticks are most active.

It is at this behavioural intersection that the authors pose some of their most provocative questions. Will people still be jogging in green spaces if those spaces are hot, humid, or full of disease-carrying ticks and mosquitoes? Will more people picnic outdoors to escape overheated homes, increasing their vector exposure, particularly under trees where ticks might thrive? And, crucially, can urban green spaces be designed to deliver climate adaptation goals without simultaneously increasing vector presence or human-vector contact? What are the net public health outcomes when the substantial benefits of green spaces are weighed honestly against increased exposure risk? None of these questions currently has a confident answer, and the authors argue that this gap in knowledge is itself a policy risk.

The uncertainty extends deep into the tools that governments use to make decisions. Current limited understanding of the interactions and long-term feedbacks between climate change, biodiversity loss and gain, infection risk and ecosystem services makes it difficult for policymakers to evaluate the trade-offs and co-benefits of interventions aimed at climate adaptation, nature recovery and public health. Economic valuation in this context is only partial: certain health endpoints such as mortality risk are well studied, while the valuation of morbidity remains relatively underdeveloped. Assigning economic value to biodiversity loss or gain is difficult, and although some ecosystem services have been the focus of valuation studies, many cultural and spiritual dimensions of green space remain stubbornly hard to price. The authors call for research using integrated assessment models that link climate, ecological, epidemiological, behavioural and socioeconomic data to predict how environmental change and management interventions influence green space use, biodiversity, vector-borne disease risks and wider societal wellbeing. Systems-thinking approaches, which can capture dynamic processes, feedback loops and unintended consequences while simulating alternative policy and management scenarios, are also gaining visibility as a way to handle this complexity.

Because research takes time to translate into impact, and because empirical data can only reflect present or past states, the authors insist that action cannot wait for perfect evidence. Investments in green spaces are already being made, whether in creating new spaces in housing developments or transforming existing ones through planting and changed service provision. They therefore call for current planning and environmental policies that shape the design, management and development of urban green spaces to be amended now, accepting the unknowns. Concretely, they advocate balanced assessments of multiple risks alongside potential benefits, using Health Impact Assessment and the health components of Environmental Impact Assessment to ensure that green space interventions manage vector-borne disease risk while still creating opportunities for health promotion. They also call for a denser monitoring system of urban green spaces so that problems such as widespread tick infestation can be detected and mitigated swiftly, and they emphasise community participation in green space management to ensure inclusive designs and desired outcomes. The message is ultimately one of urgency rather than alarm: healthy, resilient and biodiverse ecosystems remain fundamental to human health, and the goal is not to abandon urban greening but to plan proactively, so that the parks of a hotter century deliver their benefits without quietly cultivating their costs.

Subject of Research: Interactions between urban green space management, climate change and vector-borne disease risk in public health decision-making

Article Title: Balancing urban green space benefits and vector-borne disease risk under climate change: Critical decision-making for 21st century public health

Article References: Ferguson, M., Garrett, J. K., Tschirren, B., Wheeler, B. W., Vaux, A. G. C., Guell, C., Medlock, J. M., Bonneaud, C., Taylor, T. J., & Huebner, G. M. (2026). Balancing urban green space benefits and vector-borne disease risk under climate change: Critical decision-making for 21st century public health. PLOS Climate, 5(9), e0001016. https://doi.org/10.1371/journal.pclm.0001016

Image Credits: AI Generated

DOI: 10.1371/journal.pclm.0001016

Keywords: urban green space, vector-borne disease, climate change, Lyme disease, dengue, ticks, mosquitoes, Nature-based Solutions, public health, Health Impact Assessment, biodiversity, urban planning

Methylglyoxal is a small, electrophilic ketoaldehyde produced as a byproduct of carbohydrate metabolism. In many organisms it arises when the flow of sugar phosphates through central metabolism becomes imbalanced, particularly when dihydroxyacetone phosphate accumulates. The enzyme methylglyoxal synthase, encoded by the mgsA gene, channels this intermediate into methylglyoxal rather than allowing it to continue down the glycolytic route. Once formed, methylglyoxal attacks nucleophilic side chains on amino acids, most notably lysine, arginine, and cysteine residues, forming covalent adducts known as advanced glycation end products. These modifications can distort protein structure, interfere with enzyme active sites, and disrupt protein-protein interactions. Because of this destructive chemistry, the accumulation of methylglyoxal has been described as carbonyl stress, a condition generally assumed to be harmful or outright lethal to microbial cells.

The research team set out to determine whether this pathway even operates in spirochetes, a group of spiral-shaped bacteria with distinctive genetics and metabolism. B. burgdorferi has an unusually reduced genome and depends almost entirely on its tick and mammalian hosts for nutrients, so the question of how it manages carbohydrate and phosphate balance is biologically important. The investigators identified several environmental signals that trigger carbonyl stress in the Lyme disease spirochete, including glycerol and peptides. Glycerol is particularly interesting because B. burgdorferi can use it as a carbon source during its tick phase, when blood is unavailable and the bacterium must survive on alternative substrates. Peptides, meanwhile, reflect the amino acid-rich environment the spirochete encounters in mammalian tissues and blood. The finding that both classes of nutrients feed into the carbonyl stress pathway suggests that methylglyoxal production is tied to the specific metabolic states the bacterium passes through during its enzootic cycle between tick and host.

Central to the study was the demonstration that methylglyoxal production and the resulting glycation of proteins depend on the product of the mgsA gene, designated bb0364 in the B. burgdorferi genome. When this gene’s function was removed, the spirochete no longer produced detectable methylglyoxal, and the characteristic protein adducts of advanced glycation disappeared. This genetic dependency establishes that the pathway is not an incidental chemical side reaction but a controlled enzymatic process. The researchers could therefore treat mgsA as a molecular switch, turning carbonyl stress on or off and observing the consequences for the bacterium’s physiology and its ability to infect animals.

One of the most consequential discoveries was phylogenetic. The carbonyl stress pathway proved to be active in Lyme disease spirochetes but absent in function from relapsing fever Borrelia species and from B. mayonii, another human pathogen in the Lyme disease group. Relapsing fever spirochetes are famous for achieving enormous densities in the bloodstream, cycling through antigenic variation to evade antibodies and producing recurrent febrile episodes. The fact that these blood-dwelling relatives lack an active methylglyoxal pathway, while the tissue-adapted Lyme disease spirochete retains one, hints at an evolutionary trade-off. The authors suggest that carbonyl stress may be selected against in spirochetes that reach high numbers in the blood, where the metabolic consequences of glycation could become intolerable at large population sizes.

To test whether methylglyoxal production matters during actual infection, the team turned to the tick-mouse model of Lyme disease, the standard experimental system for studying B. burgdorferi in its natural transmission context. Ticks infected with spirochetes were allowed to feed on mice, and the course of infection was followed through the mammalian host. The results provided evidence that the production of methylglyoxal and the glycation of proteins are not necessarily lethal to the spirochete, at least in this organism, contradicting the long-standing assumption that carbonyl stress is uniformly toxic. Bacteria carrying an intact pathway persisted through the infection cycle, indicating that B. burgdorferi can tolerate a level of self-inflicted protein damage that would cripple many other microbes. This tolerance raises the possibility that the pathway confers some benefit that offsets its biochemical costs.

The clearest hint of that benefit came from an elegant cross-species experiment. The researchers introduced the B. burgdorferi mgsA gene and its associated carbonyl stress pathway into B. hermsii, a relapsing fever spirochete that naturally lacks the system. When the engineered bacteria were used to infect mice, the peak level of spirochetemia during the relapse phase of infection dropped significantly compared with infections caused by unmodified B. hermsii. In other words, forcing a blood-dwelling spirochete to run the Lyme disease carbonyl stress pathway curtailed its ability to flood the bloodstream. This result supports the idea that methylglyoxal production imposes a cost on explosive growth in blood, and it explains why relapsing fever species, which depend on high-density blood infections for transmission, would have lost or never maintained this pathway.

Taken together, these findings define a previously unrecognized post-translational modification system in B. burgdorferi. Rather than relying solely on the phosphorylation, acetylation, and proteolytic processing that bacteria typically use to tune protein function, the Lyme disease spirochete appears to exploit direct chemical glycation by methylglyoxal as a regulatory layer. Because the pathway is triggered by glycerol and peptides, nutrients encountered at particular stages of the tick-mouse cycle, methylglyoxal-mediated modification could help the bacterium reprogram its proteome as it transitions between metabolically distinct environments. Proteins damaged by glycation might be preferentially degraded, redirected, or inactivated, allowing the spirochete to adjust its physiology in ways that standard transcriptional regulation alone cannot achieve.

The study also reframes how scientists think about carbonyl stress in microbial pathogenesis. For decades, methylglyoxal has been studied mainly as a threat that bacteria must detoxify through glyoxalase systems and related enzymes. The new work shows that at least one pathogen has integrated this reactive metabolite into its normal biology, tolerating the damage it causes and possibly using it to govern its lifestyle. The contrast between Lyme disease and relapsing fever spirochetes offers a natural experiment in evolutionary strategy: one pathogen persists at low densities in collagen-rich tissues for months or years, while the other races through the blood in massive waves. The presence of an active carbonyl stress pathway in the former and its apparent incompatibility with the latter suggests that methylglyoxal biology is entwined with the fundamental ecological strategies of these bacteria.

Future work will need to identify which B. burgdorferi proteins are glycated in vivo, how those modifications alter protein function, and whether the pathway influences the bacterium’s ability to establish persistence in joints, heart, and nervous system tissue. The findings also raise questions about whether carbonyl stress contributes to the chronic inflammatory environment characteristic of Lyme disease, since advanced glycation end products are known to interact with host immune receptors in other contexts. For now, the study stands as a vivid example of how a molecule once dismissed as metabolic waste can turn out to be a purposeful instrument of pathogen regulation, and it underscores how much remains to be learned from comparing closely related spirochetes that have evolved to occupy radically different niches within their hosts.

Subject of Research: Methylglyoxal-mediated carbonyl stress and protein glycation regulation in Lyme disease and relapsing fever spirochetes

Article Title: Metabolic regulation of the carbonyl stress pathway and methylglyoxal in Lyme disease and relapsing fever spirochetes

Article References: Drecktrah, D., Hall, L. S., Cheff, B., Richards, C., Raffel, S. J., Wulf, M., Bailey, I. T., Gherardini, F., & Samuels, D. S. (2026). Metabolic regulation of the carbonyl stress pathway and methylglyoxal in Lyme disease and relapsing fever spirochetes. PLOS Pathogens, 22(9), e1014657. https://doi.org/10.1371/journal.ppat.1014657

Image Credits: AI Generated

DOI: 10.1371/journal.ppat.1014657

Keywords: Lyme disease, Borrelia burgdorferi, methylglyoxal, carbonyl stress, advanced glycation end products, mgsA, spirochetes, relapsing fever, Borrelia hermsii, protein glycation, tick-mouse model, metabolic regulation

The research, led by Mariachiara Vardeu and Elena Ghiorzi of the University of Padua together with colleagues at the University of Pavia, was conceived around a central weakness in the existing literature: most tick microbiome studies choose a decontamination method by convention rather than by evidence. Ethanol washes, bleach treatments, and commercial DNA-degrading reagents all appear in published workflows, but until now there has been no direct, controlled comparison of how effectively each removes surface-associated bacteria while preserving the tick’s internal microbial community. Without such a benchmark, differences between laboratories could reflect cleaning chemistry as much as genuine biology, undermining efforts to compare microbiome data across studies, regions, or tick populations.

To build that benchmark, the team designed an elegant experimental trick. Rather than relying on the unknown and variable bacteria naturally present on wild-caught ticks, they deliberately contaminated adult Ixodes ricinus ticks and nymphs with a defined bacterial mock community of known composition. This meant that the researchers knew exactly which bacterial sequences represented surface contamination and could track, with precision, how much of that signal survived each cleaning treatment. Any mock-community reads remaining after decontamination were, by definition, residual surface contamination; any reduction in those reads measured the effectiveness of the protocol. It is a simple idea in principle, but one that transforms decontamination from a matter of faith into a measurable quantity.

The contaminated ticks were then subjected to five decontamination regimens: a wash in 70% ethanol, the traditional mainstay of tick microbiome studies; a 1% bleach treatment; DNA/RNA Zap, a commercial reagent that degrades nucleic acids on external surfaces; and two combination protocols in which a lysozyme pre-treatment, designed to weaken bacterial cell walls, was followed by either bleach or DNA/RNA Zap. Mock-inoculated ticks that received no decontamination served as controls. After cleaning, the researchers characterized the microbial communities using Oxford Nanopore full-length 16S rRNA gene sequencing, a platform that reads the entire bacterial barcoding gene rather than short fragments, providing higher taxonomic resolution for identifying which bacteria survived which treatment.

The results were striking in their clarity. Ethanol, the most widely used decontamination agent in the field, consistently showed the weakest effect, leaving substantial mock-community signal intact and suggesting that many published tick microbiome profiles built on ethanol-washed specimens may carry a meaningful contribution from surface bacteria. By contrast, both bleach and DNA/RNA Zap, whether applied alone or preceded by lysozyme, produced near-complete depletion of the mock-community reads. In other words, the two harsher chemical approaches came closest to erasing the experimental contamination signal, while the gentler ethanol wash barely dented it. Perhaps unexpectedly, the enzymatic lysozyme pre-treatment conferred no measurable advantage over bleach or DNA/RNA Zap used on their own, a finding that simplifies protocol design and removes an unnecessary step from future workflows.

Effectiveness at removing contaminants is only half the story, however. An ideal decontamination protocol must also preserve the tick’s genuine internal microbiota, including endosymbionts that play roles in tick nutrition and reproduction, and any pathogens the tick may harbor. To probe this dimension, the team compared sequencing results from tick legs, which are dominated by surface-associated microbes, with leg-free bodies, which contain the internal organs and their resident communities. This anatomical dissection revealed that Brevibacterium, a bacterial genus frequently reported in tick studies, was predominantly surface-associated in this system, raising the possibility that some taxa previously interpreted as tick symbionts may in fact be exoskeletal passengers. Meanwhile, the endosymbiont Candidatus Midichloria, a bacterium closely associated with Ixodes ticks, remained readily detectable in leg-free bodies even after decontamination, indicating that the effective treatments stripped the surface without erasing the tick’s true internal signature.

The preservation of pathogen signals was equally reassuring. In nymphs that had been experimentally infected with Borrelia, the causative agent of Lyme disease, Borrelia-associated sequences remained readily detectable following surface treatment. This matters enormously for disease surveillance, because ticks are routinely screened for Borrelia and other pathogens using molecular methods, and a decontamination protocol aggressive enough to destroy pathogen DNA would compromise those assays. The study’s findings suggest that bleach- and DNA/RNA Zap-based protocols occupy a valuable middle ground: strong enough to eliminate exoskeletal contamination, yet gentle enough to leave internal microbial and pathogen signals intact and quantifiable.

Beyond the head-to-head protocol comparison, the study also explored how decontamination choice shapes community-level diversity analyses, the statistical frameworks ecologists use to compare microbiomes across samples. These analyses suggested treatment-associated differences in the bacterial profiles recovered from the ticks, hinting that laboratories using different cleaning methods may not be sampling quite the same biological reality. The authors are careful to frame these diversity patterns as exploratory rather than definitive, but the implication is clear: decontamination is not a neutral technical detail but an active variable that can shift the apparent composition of a tick’s microbiome, potentially confounding meta-analyses that pool data from studies using different protocols.

The authors are equally candid about the limits of their benchmark. The mock-community approach, while powerful, was tested under controlled laboratory conditions with a defined and relatively simple surface community. Real ticks collected in the field carry more diverse and unevenly distributed microbial loads, and different tick species present different exoskeleton chemistries and sizes that could influence how reagents penetrate and perform. Validation using field-collected ticks, additional tick species, more complex surface-associated microbial communities, and independent laboratory settings will be required before the community can propose broader methodological standardization. The researchers also emphasize that the optimal decontamination strategy may depend on the biological compartment and microbial fraction of interest, meaning that a one-size-fits-all protocol may never exist.

Nevertheless, the study delivers an immediately actionable message for anyone working on tick microbiomes or tick-borne pathogen surveillance. Under the conditions tested, bleach and DNA/RNA Zap produced the strongest reduction in experimentally introduced surface bacteria while preserving dominant tick-associated taxa and pathogen sequences, whereas ethanol, the field’s default choice, performed worst. Lysozyme pre-treatment added nothing measurable. For a research community racing to understand how tick microbiomes influence vector competence and disease transmission across a changing European landscape, this quantitative framework arrives at an opportune moment. By making surface decontamination a benchmarked, comparable step rather than an unexamined habit, the Padua-led team has taken a meaningful step toward microbiome data that can be trusted, compared, and built upon, and toward a clearer picture of what really lives inside one of Europe’s most medically important arthropods.

Subject of Research: Benchmarking surface decontamination protocols for tick microbiome profiling using 16S rRNA sequencing

Article Title: Benchmarking surface decontamination methods for reliable Ixodes ricinus microbiome profiling

Article References: Vardeu, M., Ghiorzi, E., Bernabè, G., Bellato, M., Vezzi, A., Salata, C., Castagliuolo, I., & Lavezzo, E. (2026). Benchmarking surface decontamination methods for reliable Ixodes ricinus microbiome profiling. Parasites & Vectors. https://doi.org/10.1186/s13071-026-07726-1

Image Credits: AI Generated

DOI: 10.1186/s13071-026-07726-1

Keywords: Ixodes ricinus, tick microbiome, surface decontamination, 16S rRNA sequencing, Oxford Nanopore, mock community, Borrelia, Midichloria, Brevibacterium, Lyme disease, vector competence, Parasites & Vectors

The scale of the underlying field effort is remarkable. Between 2013 and 2025, members of the Hokkaido University Tick Hunting Team, joined by collaborators across the country, systematically dragged cloth flags through vegetation at 1,018 sites spanning 38 of Japan’s 47 prefectures. This flagging method, the standard technique for sampling host-seeking ticks, involves pulling a white cloth square across low vegetation so that questing ticks latch onto it. The surveys yielded a total of 22,416 individual ticks, representing the sixteen species that formed the basis of the modeling work. Because tick distribution data have historically been restricted to localized studies, this dataset provides an unusually broad and consistent foundation for predicting where each species can persist across the entire Japanese archipelago.

To transform field observations into predictive maps, the team employed the maximum entropy method, widely known as Maxent, a machine-learning approach that estimates the probability of species presence from occurrence records and environmental variables. The models incorporated three categories of predictors: climatic variables such as temperature and precipitation, topographic features such as elevation, and landscape variables describing land cover and habitat type. The resulting predictions were generated at a resolution of one square kilometer, fine enough to distinguish habitat suitability between neighboring valleys or forest patches. Model performance was robust across the sixteen species, giving the researchers confidence that the maps capture genuine ecological patterns rather than statistical noise.

Among all the environmental variables tested, one emerged with unexpected prominence: snow depth. For six of the sixteen tick species, snow depth contributed the largest share of explanatory power in the models. This finding carries real ecological weight. Deep, persistent snow insulates the ground layer where ticks overwinter, moderating the extreme cold that would otherwise kill them, but it also shapes the length of the active season and the structure of the vegetation communities ticks depend on. In a country that stretches from subtropical Okinawa to the frigid northern island of Hokkaido, snow depth turns out to be a fundamental determinant of where ticks can establish populations, and by extension, where the pathogens they carry can circulate.

The predicted suitable habitats showed striking interspecific variation, following both latitudinal and elevational gradients. Some species are confined to the cool, snowy north, while others thrive in the warmer south; some occupy lowland forests, others climb into mountain terrain. This diversity of distribution patterns matters because each tick species is a competent vector for a different set of pathogens. A map that lumps all ticks together would obscure precisely the spatial structure that determines which diseases threaten which communities. The new species-by-species approach reveals that patchwork in detail for the first time.

The most consequential step of the analysis went beyond mapping habitats and asked whether the predicted distributions actually explain where human cases of tick-borne disease occur. The researchers converted their one-kilometer probability maps into prefecture-level statistics, calculating for each of Japan’s prefectures the proportion of grid cells predicted to be occupied by each tick species. They then used regression analyses to test whether these occupancy proportions could account for the reported numbers of five notifiable tick-borne diseases: severe fever with thrombocytopenia syndrome, tick-borne encephalitis, Japanese spotted fever, Lyme disease, and relapsing fever. The answer was a clear yes, with significant correlations between the predicted area occupied by suspected vector species and the reported case counts for each disease.

The species-disease alignments were biologically coherent in ways that strengthen confidence in the results. For diseases with a predominantly northern distribution, such as Lyme disease, the predicted distributions of Ixodes pavlovskyi and Ixodes persulcatus aligned closely with reported case occurrence, and both species are known vectors of the Borrelia bacteria that cause the illness. At the opposite end of the map, Haemaphysalis flava emerged as the primary contributor to model performance for Japanese spotted fever and the secondary contributor for severe fever with thrombocytopenia syndrome, two diseases concentrated in southern and western Japan. Again, the correlated species are recognized vectors of the corresponding pathogens. In other words, the models did not merely find statistical associations; they recovered the known vector ecology of each disease from environmental data alone.

This external validation against disease surveillance data is what elevates the study from a biogeographic exercise to a practical public health tool. Species distribution models are often evaluated solely on their ability to reproduce the occurrence records used to build them, which risks circularity. By demonstrating that independently collected human disease reports track the predicted tick distributions, the researchers provided evidence that the maps capture something real about transmission risk on the ground. For public health authorities, this means the maps can serve as an early-warning layer, highlighting prefectures where environmental conditions favor vector species even before cases accumulate.

The implications extend beyond Japan’s borders. Climate change is expected to shift temperature and snowfall patterns across temperate Asia, and because snow depth proved to be such a powerful predictor, changes in snow cover could redraw the boundaries of tick habitat in the coming decades. Species currently confined to Hokkaido’s snowy forests might expand southward or upslope, carrying tick-borne encephalitis and other northern diseases into new territories. Conversely, warming could compress the suitable habitat of cold-adapted species. The modeling framework established in this study, with its one-kilometer resolution and multi-species coverage, provides a baseline against which such shifts can be measured and anticipated.

The study also demonstrates the value of sustained, collaborative fieldwork. Twelve years of surveys, involving dozens of students and researchers in the Hokkaido University Tick Hunting Team and partner laboratories from Kitasato University, the University of Tokyo, the University of Osaka, and beyond, produced the occurrence data that no amount of modeling ingenuity could substitute for. The authors note that the resulting maps, offering a nationwide overview of tick distributions, serve as basic information for anticipating the occurrence of tick-borne diseases in the region. For clinicians, the maps offer context for differential diagnosis when patients present with fever after outdoor exposure; for epidemiologists, they provide a spatial framework for surveillance prioritization; and for the public, they offer a clearer picture of the invisible landscape of risk that accompanies a walk through Japan’s forests and grasslands.

Subject of Research: Species distribution modeling of tick vectors and tick-borne disease occurrence in Japan

Article Title: Predicting the distribution of 16 tick species in Japan and its association with the occurrence of tick-borne diseases

Article References: Ito, M., Ohari, Y., Ohsugi, Y., Taya, Y., Hayashi, N., Ogata, S., Kusakisako, K., Qiu, Y., Nonaka, N., Mizuma, K., Torii, S., Kajihara, M., Hokkaido University Tick Hunting Team (HUT-HuT), Mimura, Y., Regilme, M. A. F., Thu, M. J., Kovba, A., Kwak, M., Teo, E., … Nakao, R. (2026). Predicting the distribution of 16 tick species in Japan and its association with the occurrence of tick-borne diseases. Parasites & Vectors. https://doi.org/10.1186/s13071-026-07717-2

Image Credits: AI Generated

DOI: 10.1186/s13071-026-07717-2

Keywords: ticks, species distribution modeling, Maxent, Japan, Lyme disease, severe fever with thrombocytopenia syndrome, Japanese spotted fever, tick-borne encephalitis, snow depth, vector ecology, public health, Ixodes

The logic behind the approach rests on the peculiar ecology of Lyme disease in the northeastern United States. The blacklegged tick, Ixodes scapularis, passes the bacterium Borrelia burgdorferi sensu stricto through its life stages, but the pathogen’s persistence in a given landscape depends heavily on one particular host: the white-footed mouse, Peromyscus leucopus. These abundant rodents serve as the principal natural reservoir of the spirochete, and larval ticks that feed on infected mice are far more likely to acquire the bacterium than larvae feeding on deer, birds, or other mammals. When those larvae molt into nymphs the following year, the infected nymphs become the primary threat to humans, delivering the bite that transmits Lyme disease in the vast majority of cases.

Interrupting the cycle at the mouse-tick interface has therefore long been an attractive target for researchers. Earlier laboratory and simulated field studies had already demonstrated that a bait containing just 0.005 percent fipronil could systemically control Ixodes scapularis ticks parasitizing treated white-footed mice. Fipronil, the same active ingredient found in some companion-animal flea and tick products, works systemically: after a mouse ingests the bait, the compound and its metabolites circulate in the animal’s blood, and ticks that attach and begin feeding are killed before they can complete their blood meal. The question the Connecticut study set out to answer was whether that laboratory promise would survive contact with real backyards, real weather, and real wildlife.

Between 2022 and 2024, the research team deployed reusable rodent bait stations on residential properties during the period when blacklegged ticks are active in their nymphal and larval stages, roughly May through August. The stations dispensed the fipronil-treated bait to free-ranging mice, and the team monitored consumption, replenishing bait as needed to keep the system running through each season. On average, each property received 4.9 kilograms of bait per year, which translates to approximately 247 milligrams of fipronil—a remarkably small total quantity of active ingredient distributed across an entire property over an entire season.

To confirm that the mice were actually being exposed to the compound, the researchers captured white-footed mice during the larval season each year on both treated and untreated control properties and analyzed their blood plasma. The results were striking: fipronil sulfone, a metabolite that serves as a marker of exposure, was detectable in 100 percent of plasma samples analyzed in both 2022 and 2023, and in 83.3 percent of samples in 2024. In other words, the bait stations were doing their job, delivering the active ingredient to the target animals with high consistency even under fully natural field conditions.

The effect on the ticks themselves was even more impressive. On treated properties, the number of larvae parasitizing captured mice fell by up to 84.2 percent compared with control properties, and the number of larvae that successfully engorged—those that managed to complete a blood meal, which is the critical step for both tick survival and pathogen acquisition—dropped by up to 92.5 percent. A larval tick that fails to engorge on a mouse not only fails to acquire Borrelia from that mouse; it also faces greatly reduced odds of surviving to molt into the next life stage. The bait, in effect, turned the most important host in the Lyme disease system into a lethal trap for its parasites.

The benefits extended to the pathogen as well. Molecular assays used to detect Borrelia burgdorferi infection in the captured mice showed that infection prevalence in white-footed mice on treated properties was significantly reduced by up to 34.1 percent relative to controls. That reduction matters because fewer infected mice means fewer larval ticks acquiring the spirochete, which in principle should mean fewer infected nymphs questing for human blood the following spring. The study thus demonstrated a measurable dent in the reservoir competence of the local mouse population, achieved not by reducing mouse numbers but by breaking the tick-mouse transmission loop.

The picture was more nuanced, however, when the researchers turned to the stage of the tick life cycle that matters most for human health. Drag sampling and flagging during the nymphal seasons were used to estimate the abundance of host-seeking nymphs on the properties, and molecular testing assessed how many of those nymphs carried Borrelia. While both nymph density and nymphal infection showed reductions on treated properties, neither difference reached statistical significance compared with the control sites. The authors suggest that the bait application rate during the larval season may need to be increased to push these downstream effects over the threshold of detectability—a reminder that intervening at one link of a complex transmission chain does not automatically translate into reduced risk at every other link.

That caveat aside, the study represents one of the most thorough field evaluations to date of a systemic acaricide bait aimed at the wildlife reservoir of Lyme disease. Its design—multi-year, property-level, with matched controls, bait-consumption monitoring, pharmacokinetic confirmation, and molecular pathogen testing on both rodents and questing ticks—addresses many of the weaknesses that have plagued earlier tick-control trials. The extremely low dose of active ingredient involved also raises the prospect of an environmentally targeted intervention: rather than broadcasting insecticides across vegetation, the treatment is delivered only to the small mammals that seek out the bait stations, and only in quantities measured in hundreds of milligrams per property per year.

The researchers, based at Genesis Laboratories in Colorado and the Connecticut Agricultural Experiment Station, were supported by a contract with the United States Centers for Disease Control and Prevention, and the work benefited from molecular detection assistance from CDC scientists. They emphasize that additional field studies are needed to confirm the findings and to explore what large-scale treatment across neighborhoods or landscapes might achieve, since tick populations on untreated properties can continually seed treated areas. Still, the core result stands: a bait box, a few hundred milligrams of fipronil, and the natural foraging behavior of white-footed mice were enough to strip the vast majority of larval ticks from the animals that sustain Lyme disease in the northeastern United States. As integrated tick management strategies evolve, the humble mouse bait station may prove to be one of the most quietly powerful tools in the fight against America’s most common vector-borne disease.

Subject of Research: Field efficacy of low-dose fipronil bait for controlling blacklegged ticks on white-footed mice and reducing Lyme disease transmission

Article Title: Efficacy of a low-dose fipronil bait in controlling blacklegged tick (Ixodes scapularis) larvae parasitizing white-footed mice (Peromyscus leucopus) under field conditions in the northeastern United States

Article References: Poché, D. M., Williams, S. C., Linske, M. A., & Poché, R. M. (2026). Efficacy of a low-dose fipronil bait in controlling blacklegged tick (Ixodes scapularis) larvae parasitizing white-footed mice (Peromyscus leucopus) under field conditions in the northeastern United States. Parasites & Vectors, 19(1), Article 423. https://doi.org/10.1186/s13071-026-07676-8

Image Credits: AI Generated

DOI: 10.1186/s13071-026-07676-8

Keywords: Lyme disease, Ixodes scapularis, Peromyscus leucopus, fipronil, tick control, Borrelia burgdorferi, vector-borne disease, systemic acaricide, bait stations, integrated tick management, Connecticut, public health

The research team, led by Dieter J. A. Heylen of the Evolutionary Ecology Group at the University of Antwerp, together with colleagues from the Luxembourg Institute of Health and certified bird ringers in Belgium, examined 284 redwings captured during late-autumn migration in 2022 and 2024. Both years were marked by unusually mild autumn conditions, a detail that proved central to interpreting the results. Of the birds sampled, 72.9 percent were infested with ticks, a rate the authors describe as the highest ever reported for this species anywhere in Europe. The overwhelming majority of the parasites collected were Ixodes ricinus, the castor bean tick whose blood-feeding stages are responsible for transmitting the majority of tick-borne infections to humans and domestic animals across the European continent.

The scale of pathogen carriage among those ticks was equally striking. The team screened 698 ticks removed from the migrating birds and found that 12.9 percent carried Borrelia bacteria. The infections were not confined to a single lineage. Genetic screening identified multiple genospecies of the Borrelia burgdorferi sensu lato complex, including strains associated with birds and others associated with mammals, alongside Borrelia miyamotoi, a relapsing-fever spirochete increasingly recognized as a human pathogen. Perhaps most telling, infected ticks were found on nearly one-third of the birds examined, meaning that a large proportion of the migrating population was effectively functioning as a long-distance courier service for viable, pathogen-laden parasites.

Extrapolating from their field measurements to the size of the European redwing population, the researchers estimate that tens of millions of Borrelia-infected ticks may be transported southward each autumn on the backs of these migrating thrushes. Ticks attached to birds can detach at stopover sites hundreds or thousands of kilometers from where they were acquired, seeding new locations with both the arthropods themselves and the pathogens they carry. Because migratory birds travel enormous distances in short periods, they represent one of the most efficient dispersal mechanisms available to ticks, whose own locomotion over a lifetime rarely exceeds a few meters. The study thus adds a seasonal dimension to what ecologists already understood about birds as tick vectors: the phenomenon does not stop when summer ends.

The timing of the infestations is what gives the work its conceptual force. Migratory birds calibrate the onset and pace of their journeys primarily by photoperiod, the changing length of daylight, which is an astronomical cue immune to year-to-year weather. Tick activity, by contrast, is governed largely by ambient temperature, since ticks are ectotherms whose questing behavior halts when conditions become cold. Historically, late-autumn temperatures across much of western and central Europe fell low enough to push ticks into dormancy well before the main passage of redwings, minimizing the overlap between the two biological calendars. The Belgium study, conducted during two exceptionally mild Novembers, documents what happens when that buffer disappears: host and parasite schedules collide, and the birds depart with an unintended cargo.

This divergence between climatically driven parasite activity and photoperiodically driven migration is a textbook example of a phenological mismatch, and the study’s authors argue that continued climate warming is likely to widen it in the parasites’ favor. Migration timing is comparatively stable, anchored to day length, while the tick activity season expands at both ends of the year as winters warm. Each increment of autumn warming therefore extends the period during which questing ticks can board migrating hosts. The consequence, according to the researchers, is a strengthening seasonal window for long-distance parasite dispersal, one that epidemiological models of Lyme disease risk have largely failed to incorporate because they treat late autumn as an epidemiological dead zone.

The age structure of the infestations added a further layer of biological insight. Birds in their first calendar year, that is, individuals hatched the same summer and undertaking their first migration, carried significantly higher tick loads than older birds. The authors suggest several non-exclusive explanations, including the inexperience of young birds in grooming and preening parasites effectively, behavioral differences in habitat use that bring first-year birds into closer contact with questing ticks, and possible physiological differences in skin characteristics that affect how readily ticks attach and feed. Whatever the mechanism, the pattern means that a disproportionate share of the dispersing parasite burden travels on the youngest cohort, the very individuals that make up the bulk of many migratory populations and that colonize wintering areas before returning north in spring.

The pathogens detected on these birds are of more than academic concern. Borrelia burgdorferi sensu lato encompasses the genospecies responsible for the great majority of Lyme borreliosis cases in Europe, an infection that can produce erythema migrans rashes, neurological complications, arthritis and cardiac involvement when untreated. Borrelia miyamotoi, though historically overshadowed by its Lyme-causing relatives, has been implicated in human cases of a relapsing-fever-like illness and, in immunocompromised patients, severe meningoencephalitis. The identification of both avian-associated and mammalian-associated genospecies on migrating redwings underscores the role of birds in maintaining and redistributing genetically diverse pathogen reservoirs, with consequences for the local disease ecology of every stopover and wintering ground along the flyway.

It is important to note that the study does not claim that migrating birds directly infect humans. Ticks feeding on birds do not transmit Borrelia to their hosts in ways that pose immediate public-health danger at the moment of capture. The risk pathway is indirect: infected ticks detach in new environments, and if those environments support the tick’s life cycle and suitable reservoir hosts, the parasites and their pathogens can establish locally. A southbound redwing that drops an infected larva or nymph in a French hedgerow, an Iberian woodland or a Mediterranean scrubland effectively introduces Borrelia genetic material into a new ecological arena, where subsequent feeding cycles on local wildlife can amplify and maintain the pathogen. The study’s contribution is to show that this introduction channel remains open deep into the season previously considered safe.

The work also carries a methodological message for disease surveillance. Monitoring programs for tick-borne pathogens in Europe typically concentrate their efforts on spring and early summer, when human exposure risk peaks and tick activity is maximal. The Belgian findings argue for extending surveillance into the late-autumn migration window, particularly during warm years, to capture a dispersal event of continental significance. With both sampling years of the study falling among the mildest autumns on record, and with climate projections pointing toward more frequent such conditions, the overlap between southbound migration and active, infected ticks may shift from an anomaly to a routine feature of the European disease landscape. What the redwings reveal, in effect, is that the geography and seasonality of Lyme disease risk are being quietly rewritten at altitude, one migrating thrush and one hitchhiking tick at a time.

Subject of Research: Late-autumn dispersal of Borrelia-infected ticks by southward-migrating redwings and its implications for Lyme disease epidemiology under climate warming

Article Title: Lyme beyond the season: late-autumn dissemination of infected ticks by southward migrating redwings (Turdus iliacus)

Article References: Heylen, D. J. A., Ledegen, I., Grimon, M., Reteng, P., Hübschen, J. M., & Krawczyk, A. I. (2026). Lyme beyond the season: late-autumn dissemination of infected ticks by southward migrating redwings (Turdus iliacus). Parasites & Vectors. https://doi.org/10.1186/s13071-026-07673-x

Image Credits: AI Generated

DOI: 10.1186/s13071-026-07673-x

Keywords: Lyme disease, redwing, Turdus iliacus, Ixodes ricinus, Borrelia, bird migration, tick-borne pathogens, phenological mismatch, climate change, parasite dispersal, Borrelia miyamotoi, seasonal surveillance