Rodriguez, K. S. | bioRxiv Science

bioRxiv2026

Comparison of tick surveillance approaches: Utilizing trailhead tick-check stations to support tick surveillance and community education

IntroductionWith rising tick-borne disease (TBD) cases and the geographical expansion of tick populations, the need for effective surveillance and public education regarding local risk is crucial. This study assessed the effectiveness of tick-check stations as a tool for tick surveillance, and their impact on community knowledge, attitude, and practices (KAP) related to ticks and TBD. MethodsTo assess the effectiveness of tick-check stations for surveillance, we evaluated station engagement and compared tick density estimates, species composition, and life-stage distributions with those obtained through concurrent active surveillance. In addition, we compared submission numbers and tick species and life stages to those collected through a mail-in submission system conducted by the Colorado Department of Public Health and Environment (CDPHE). To quantify feasibility, we estimated effort per tick and compared effort across simulated sampling scenarios. Finally, in-person surveys were conducted at trailheads to assess baseline tick KAP and to evaluate differences between sites with and without tick-check stations ResultsEngagement with tick-check stations was sustained throughout the study. Temporal tick densities estimated from tick-check station submissions were correlated with density estimates from active surveillance (R = 0.534), and species composition and life-stage distributions did not significantly differ between methods. Tick-check stations required less effort per tick than active surveillance when sampling sites were nearby or tick densities were low, whereas sites that were farther away or had higher tick densities required less effort per tick under a hybrid surveillance approach. When asked to list tick-borne pathogens in Colorado, 47% of survey participants who had read tick-check station signage identified Rocky Mountain spotted fever compared with 20% of participants in the control group (p = 0.007; odds ratio). Notably, a low proportion of survey participants (24%) reported performing tick-checks to prevent tick bites. ConclusionTick-check stations can provide tick density estimates comparable to active surveillance while requiring less effort in many scenarios, particularly in low-density settings. Our findings also highlight opportunities for targeted outreach to address gaps in TBD knowledge. As both a surveillance and educational tool, tick-check stations offer a sustainable approach for expanding tick monitoring in resource-limited settings.

ecology↗

bioRxiv2026

Resistance to Pyrethroids in Aedes aegypti: Insights into Transcriptomic Response to Different Insecticide Concentrations Transcriptomic responses of Aedes aegypti to insecticide concentrations

Insecticide spraying is a common strategy for controlling dengue outbreaks, but its effectiveness is compromised by the development of resistance in mosquito populations. In this study, we subjected a strain of Aedes aegypti known for its exceptional ability to develop resistance to controlled permethrin and lambda-cyhalothrin insecticides pressure using two different concentrations. We analyzed resistance mechanisms that are enhanced at each concentration and used RNA sequencing to identify transcripts specifically associated with these exposure levels. Our objective was to uncover the molecular mechanisms triggered by different insecticide concentrations and to distinguish responses between type I and type II pyrethroids, which differ in chemical structure. Our results showed that kdr mutations confer only moderate levels of resistance, as do detoxifying enzymes. For lambda-cyhalothrin, we identified genes involved in the electron transport chain, mitochondrial function, and overall responses to oxidative stress. tRNA transcripts were also upregulated, along with mitochondrial and stress-response transcripts, suggesting a metabolic shift, particularly toward maintaining homeostasis under oxidative stress. These changes point to mechanisms that sustain resistance to this type II insecticide beyond direct detoxification in this population. On the contrary, permethrin induced marked overexpression of cuticle genes, CYP450 genes (especially CYP4), and Odorant Binding Proteins. These expression patterns, together with metabolic enzymes, point to detoxification, reduced penetration, or even sequestration of insecticide, all of which intensify with increasing concentrations. This overregulation of genes suggests an integrated response complemented by classical metabolic detoxification and accompanied by overregulation of mitochondrial complexes. We showed that despite the shared mode of action of the insecticides permethrin and lambda-cyhalothrin, they elicit distinct responses in this Ae. aegypti population. We also showed that the transcriptomic response depends on insecticide concentration and may modulate insecticide tolerance. This article advances understanding of the complexity of pyrethroid resistance in Aedes aegypti and underscores the importance of considering both the insecticide type and the concentration used in vector control programs. Author summaryAedes aegypti mosquitoes transmit dengue and other arboviruses, being a major public health problem in tropical regions like Colombia, where control relies on pyrethroid insecticide spraying. Based on reports of inconsistent results in the field due to different effects of insecticide concentrations, we recreated variable doses by exposing a resistant Colombian Aedes aegypti strain to low (LC25) and high (LC75) concentrations of permethrin (type I) and lambda-cyhalothrin (type II) to identify concentration-dependent resistance mechanisms. Using genetic mutation analysis, enzyme activity assays, and RNA sequencing, we identified the molecular mechanisms these mosquitoes use to survive. Knockdown resistance (kdr) and detoxification enzymes contributed to some extent to resistance but varied by insecticide type and concentration. RNAseq identified that lambda-cyhalothrin upregulated genes for mitochondrial energy production, oxidative stress defense, immune signaling, and transfer RNAs, facilitating homeostasis under chemical stressors. Permethrin instead upregulated genes for cuticle thickening, cytochrome P450 enzymes, and odorant-binding proteins, which are associated with improved penetration barriers, and metabolic breakdown that intensified with higher concentrations. This reveals pyrethroid resistance as complex beyond classic mechanisms, as even low field doses favor stress tolerance or physical defenses to evade sprays. We detected transcripts that improve survival at high concentrations and could be selected in these mosquitoes. Carefully selecting the type of pyrethroid to be used and the dose should be an important factor in vector control. This optimizes current interventions, prolongs their efficacy, and aids researchers in modeling resistance to protect communities.

bioinformatics↗