Tick Repellents Research Articles

Drug Use Patterns in Wastewater and Socioeconomic and Demographic Indicators

Measuring drug use behaviors in individuals and across large communities presents substantial challenges, often complicated by socioeconomic and demographic variables. To detect spatial and temporal changes in community drug use by analyzing concentrations of analytes in influent wastewater and exploring their associations with area-based socioeconomic and sociodemographic metrics like the area deprivation index (ADI) and rural-urban commuting area (RUCA) codes. This longitudinal, cross-sectional wastewater study was performed from May 2022 to April 2023 and included biweekly influent wastewater samples of 39 analytes from 8 sampling locations across 6 wastewater treatment plants in southern Nevada. Statistical analyses were conducted in December 2023. It was hypothesized that wastewater monitoring of pharmaceuticals and personal care products (PPCPs) and high-risk substances (HRSs) could reveal true spatial and temporal drug use patterns in near-real time. Data collection of samples for PPCPs and HRSs was performed using mass spectrometry. Both ADI and RUCA scores were utilized to characterize neighborhood contexts in the analysis. The false discovery rate (FDR) method was utilized to correct for multiple comparisons (PFDR). Over the 12-month wastewater monitoring period, 208 samples for PPCPs and HRSs were collected, and analysis revealed an increase in the consumption of HRSs and the seasonal variation in PPCP use in southern Nevada. There was a significant increase in levels of stimulant-associated analytes, such as cocaine (β = 9.17 × 10-4; SE = 1.29 × 10-4; PFDR = 1.40 × 10-10), and opioids or their metabolites, notably norfentanyl (β = 1.48 × 10-4; SE = 1.88 × 10-4; PFDR = 1.66 × 10-12). In contrast, DEET, an active ingredient in mosquito and tick repellents, demonstrated a seasonal use pattern (β = -4.85 × 10-4; SE = 2.09 × 10-4; PFDR = 4.87 × 10-2). Wastewater from more disadvantaged or rural neighborhoods, as assessed through ADI and RUCA scores, was more likely to show a significant positive correlation with HRSs, such as cocaine (β = 0.075; SE = 0.038; P = .05) and norfentanyl (β = 0.004; SE = 0.001; P = 1.64 × 10-5). These findings suggest that wastewater monitoring of PPCPs and HRSs offers a complementary method to existing public health tools, providing timely data for tracking substance use behaviors and use of PPCPs at a population level.

Psychosocial Determinants of Lyme Disease Preventive Behavior Among Outdoor Recreationists

The incidence of Lyme disease (LD) has grown over time despite extensive awareness campaigns of disease risk. While previous research has explored public knowledge, perceptions, and attitudes toward tick-borne diseases, there is minimal research in understanding preventive behavior among individuals frequently engaging in outdoor recreation. This study addresses this gap by investigating the perceptions of LD preventive behavior, focusing on psychosocial factors influencing behavior. Utilizing an integrative framework incorporating the Health Belief Model and Social Cognitive Theory, we examined outdoor recreationist performance of three key preventive behaviors: tick checks, tick repellent use, and protective clothing. Data were collected through intercept surveys at Bradbury Mountain State Park (Maine, US). Findings indicate that tick-related knowledge and experience have a limited impact on preventive behavior, while efficacy beliefs and perceived benefits significantly influence behavior. In this paper we discuss the implications of these factors to both theory and practice in LD prevention studies.

Tick repellent activities of supercritical fluid extract from Chamaecyparis obtusa against Haemaphysalis longicornis

Supercritical fluid extraction (SFE) is a rapid, selective, and convenient method for sample preparation prior to the analysis of compounds in a volatile product of plant matrices. In this study, insecticidal activity and repellency were examined in a laboratory study to determine the active constituent of Chamaeparis obtusa and a supercritical fluid extract from Chamaeparis obtusa against hard tick Haemaphysalis longicornis.The repellency of C. obtusa oil was evaluated in comparison with two commercial repellents (Icaridin and DEET) against H. longicornis. Filter-paper diffusion assay revealed that C. obtusa oil (3.2 µg/cm2) had a 100 % repellency and icaridine (3.2 µg/cm2) had a 96.1 % repellency at 120 min. Repellencies of 31 compounds against H. longicornis were compared with the repellency of DEET at 3.2 µg/cm2. Responses varied according to the test compound and exposure time. Repellencies of α-terpinene, terpinene-4-ol, and α-terpineol were 100 % at 30 min post-treatment. They were 85.5 %, 56.4 %, and 68.9 %, respectively, at 120 min. C. obtusa oil, α-terpinene, terpinene-4-ol, and α-terpineol merit further study as potential fumigants or lead compounds for the control of H. longicornis.

Comparative analysis of essential oil efficacy against the Asian longhorned tick Haemaphysalis longicornis (Acari: Ixodidae).

This study evaluated the potential repellent and acaricidal effects of 4 essential oils (clove, eucalyptus, lavender, and mint) against the Asian longhorned tick Haemaphysalis longicornis, a vector of various tick-borne diseases in medical and veterinary contexts. Selected for their potential repellent and acaricidal properties, the 4 essential oils were tested on adult and nymph H. longicornis ticks at different concentrations. The experiment assessed mortality rates and repellency, particularly during tick attachment to host skin. There was a significant increase (p<0.05) in tick mortality and repellency scores across all groups. At a 1% concentration, adult tick mortality ranged from 36% to 86%, while nymph mortality ranged from 6% to 97%. Clove oil exhibited notable efficacy, demonstrating high mortality rates of nymphs and adults. Clove oil also displayed strong repellency properties, with a repellency index of 0.05, surpassing those of mint, eucalyptus, and lavender oils. Clove oil showed the highest effectiveness in deterring nonattached adult ticks (90%) and nymphs (95%) when applied to skin. Clove oil was the most effective against adult and nymph ticks, achieving mortality rates of 86% and 97%, respectively, and led to the highest nonattachment rates when applied to skin. In conclusion, essential oils such as clove, eucalyptus, lavender, and mint oils present promising results for tick population control.

Repellent activity of essential oils to the Lone Star tick, Amblyomma americanum

BackgroundThe Lone Star tick, Amblyomma americanum is important to human health because of a variety of pathogenic organisms transmitted to humans during feeding events, which underscores the need to identify novel approaches to prevent tick bites. Thus, the goal of this study was to test natural and synthetic molecules for repellent activity against ticks in spatial, contact and human fingertip bioassays.MethodsThe efficacy of essential oils and naturally derived compounds as repellents to Am. americanum nymphs was compared in three different bioassays: contact, spatial and fingertip repellent bioassays.ResultsConcentration response curves after contact exposure to 1R-trans-chrysanthemic acid (TCA) indicated a 5.6 μg/cm2 concentration required to repel 50% of ticks (RC50), which was five- and sevenfold more active than DEET and nootkatone, respectively. For contact repellency, the rank order of repellency at 50 μg/cm2 for natural oils was clove > geranium > oregano > cedarwood > thyme > amyris > patchouli > citronella > juniper berry > peppermint > cassia. For spatial bioassays, TCA was approximately twofold more active than DEET and nootkatone at 50 μg/cm2 but was not significantly different at 10 μg/cm2. In spatial assays, thyme and cassia were the most active compounds tested with 100% and 80% ticks repelled within 15 min of exposure respectively and was approximately twofold more effective than DEET at the same concentration. To translate these non-host assays to efficacy when used on the human host, we quantified repellency using a finger-climbing assay. TCA, nootkatone and DEET were equally effective in the fingertip assay, and patchouli oil was the only natural oil that significantly repelled ticks.ConclusionsThe differences in repellent potency based on the assay type suggests that the ability to discover active tick repellents suitable for development may be more complicated than with other arthropod species; furthermore, the field delivery mechanism must be considered early in development to ensure translation to field efficacy. TCA, which is naturally derived, is a promising candidate for a tick repellent that has comparable repellency to commercialized tick repellents.Graphical

Harmful and Harmless Soil-Dwelling Fungi Indicate Microhabitat Suitability for Off-Host Ixodid Ticks.

Following blood meals or questing bouts, hard ticks (Ixodidae) must locate moist off-host microhabitats as refuge. Soil-dwelling fungi, including entomopathogenic Beauveria bassiana (Bb), thrive in moist microhabitats. Working with six species of ixodid ticks in olfactometer bioassays, we tested the hypothesis that ticks avoid Bb. Contrary to our prediction, nearly all ticks sought, rather than avoided, Bb-inoculated substrates. In further bioassays with female black-legged ticks, Ixodes scapularis, ticks oriented towards both harmful Bb and harmless soil-dwelling fungi, implying that fungi-regardless of their pathogenicity-signal habitat suitability to ticks. Only accessible Bb-inoculated substrate appealed to ticks, indicating that they sense Bb or its metabolites by contact chemoreception. Bb-inoculated substrate required ≥24 h of incubation before it appealed to ticks, suggesting that they respond to Bb metabolites rather than to Bb itself. Similarly, ticks responded to Bb-inoculated and incubated cellulose but not to sterile cellulose, indicating that Bb detection by ticks hinges on the Bb metabolism of cellulose. 2-Methylisoborneol-a common fungal metabolite with elevated presence in disturbed soils-strongly deterred ticks. Off-host ticks that avoid disturbed soil may lower their risk of physical injury. Synthetic 2-methylisoborneol could become a commercial tick repellent, provided its repellency extends to ticks in diverse taxa.

Efficacy of unregulated minimum risk tick repellent products evaluated with Ixodes scapularis nymphs in a human skin bioassay

BackgroundThe majority of vector-borne disease cases in the USA are caused by pathogens spread by ticks, most commonly the blacklegged tick, Ixodes scapularis. Personal protection against tick bites, including use of repellents, is the primary defense against tick-borne diseases. Tick repellents registered by the Environmental Protection Agency (EPA) are well documented to be safe as well as effective against ticks. Another group of tick repellent products, 25(b) exempt or minimum risk products, use alternative, mostly botanically derived, active ingredients. These are considered to pose minimal risk to human health and therefore are exempt from EPA registration; efficacy testing is not mandated for these products.MethodsWe used a finger bioassay to evaluate the repellency against I. scapularis nymphs for 11 formulated 25(b) exempt products together with two positive control DEET-based EPA registered products. Repellency was assessed hourly from 0.5 to 6.5 h after product application.ResultsThe DEET-based products showed ≥ 97% repellency for all examined timepoints. By contrast, an average of 63% of ticks were repelled in the first 1.5 h after application across the 11 25(b) exempt products, and the average fell to 3% repelled between 2.5 and 6.5 h. Ten of the 11 25(b) exempt products showed statistically similar efficacy to DEET-based products at 30 min after application (repellency of 79–97%). However, only four 25(b) exempt products maintained a level of repellency similar to DEET-based products (> 72%) at the 1.5-h mark, and none of these products were effective in repelling ticks at the timepoints from 2.5 to 6.5 h after application.ConclusionsNeither the claims on the labels nor specific active ingredients and their concentrations appeared to predict the duration of efficacy we observed for the 25(b) exempt products. These products are not registered with the EPA, so the methods used to determine the application guidelines on their labels are unclear. Consumers should be aware that both the level of efficacy and the duration of repellency may differ among unregulated 25(b) exempt repellent products labeled for use against ticks. We encourage more research on these products and the 25(b) exempt active ingredients they contain to help determine and improve their efficacy as repellents under different conditions.Graphical

Knowledge, Attitudes, and Practices Regarding Ticks, Tick-Borne Diseases, and Ethnomedicine Among an at-Risk Population in Kerala.

Tick and tick-borne diseases (TBDs) are increasing annually, and the study of ticks has gained importance after the outbreak of Kyasanur Forest disease (KFD) in the South Western Ghats of India. Wayanad district of Kerala, with the highest tribal population in South India, is a KFD endemic state, owing to the lack of knowledge, attitude, and practice studies on TBDs and ethnomedicines against ticks. This study was carried out to assess their baseline knowledge, attitude, and ethnomedicinal practice against ticks. A structured questionnaire was used to conduct a survey of 499 tribal members living in forest fringe areas. Logistic regression analysis was performed to identify the factors that influence the knowledge, attitude, and practice of tribes on TBDs. More than 70% of the population visit the forests on a regular basis, with 65.7% of the population regularly exposed to tick bites; however, only 47.7% were aware of TBDs. About 47.4% of the respondents took precautions like therapeutics and natural remedies to avoid tick bites. Ten species of medicinal plant belonging to eight different families have been identified from the survey. The tribal population use these plants to repel ticks as well as treat tick bites. From the study, we concluded that the limited in-depth knowledge displayed by the tribes can be strengthened by conducting community programs such as awareness classes on TBD and its control measures. The ethnobotanicals identified can be used to formulate novel tick repellents in the future.

Efficacy of Unregulated Minimum Risk Products to Kill and Repel Ticks.

Human-biting ticks threaten public health in the United States. Registration by the Environmental Protection Agency of products to kill host-seeking ticks or repel ticks contacting humans is indicative of their safety and effectiveness. Unregulated minimum risk products, exempt from Environmental Protection Agency registration and often based on botanical oils, are proliferating in the marketplace, but there is concern about their effectiveness to kill and repel ticks. Evaluations of such products are limited in the published literature. A review showed considerable variability among minimum risk products to kill host-seeking blacklegged ticks, with effectiveness similar to chemical pesticide products for some minimum risk products but minimal impact on the ticks for other products. Evaluations of minimum risk tick repellents have typically focused on individual active ingredients rather than formulated products, which often combine multiple active ingredients. Consumers should be aware that effectiveness to kill and repel ticks can differ among unregulated minimum risk products.

Lemongrass essential oil and DEET inhibit attractant detection in infected and non-infected Ixodes scapularis ticks

Blacklegged tick, Ixodes scapularis Say (Arachnida: Ixodidae), is a growing health concern for humans as vectors the causative agent of Lyme disease, Borrelia burgdorferi, and many other pathogens. Given the potential health threat I. scapularis entails, and the need to find effective strategies to prevent tick bites, it is pivotal to understand the chemosensory system of ticks and their host-seeking behaviour when exposed to repellents. In this study, we investigated whether the exposure to synthetic and plant-derived repellents impairs the ability of I. scapularis to detect attractants and host volatiles (butyric acid), and ultimately how these repellents interfere with host-seeking behaviour in both wild and lab-reared ticks. Furthermore, we screened wild ticks used in electrophysiology and Y-tube behavioural assays for presence of pathogens (Borrelia, Anaplasma, and Babesia) to evaluate if the bacterial infection status would affect the detection of butyric acid under the exposure to repellents. We determined that the exposure to DEET, lemongrass essential oil, citral, and geraniol significantly inhibited the ability of both lab-reared and wild adult female I. scapularis to detect and respond to butyric acid. We found that tick infection status does not significantly impact host-seeking behaviour in adult female I. scapularis. The knowledge gained from our study contributes to advance our understanding of host-seeking behaviour in ticks and the impact that the exposure to repellent has on the tick chemosensory system. These findings will be important for elucidating the mechanism of repellence in ticks and for the development of effective tick repellent management tools.

Ixodes scapularis Is the Most Susceptible of the Three Canonical Human-Biting Tick Species of North America to Repellent and Acaricidal Effects of the Natural Sesquiterpene, (+)-Nootkatone.

Ticks are vectors of many human and animal zoonotic disease-causing agents causing significant global health and economic strain. Repellents and acaricides are integral to the human capacity for personal protection from tick bites. Nootkatone, a naturally occurring sesquiterpene found in the Alaskan cedar tree, grapefruit, and other sources, has been documented to be a potent acaricide. Research has also noted repellent effects against some tick species. In this study, our aim was to investigate the effect of synthetic, high-purity (+)-nootkatone on adult Ixodes scapularis, Dermacentor variabilis, and Amblyomma americanum ticks in an in vitro, vertical filter paper bioassay. (+)-nootkatone showed compelling tick repellency, but median effective concentrations (EC50) significantly differed among species. Ixodes scapularis were repelled at very low concentrations (EC50 = 0.87 ± 0.05 µg/cm2). Higher concentrations were required to repel D. variabilis (EC50 = 252 ± 12 µg/cm2) and A. americanum (EC50 = 2313 ± 179 µg/cm2). Significant post-exposure mortality, assessed 24 h after repellency trials, was also observed in I. scapularis but was absent entirely in D. variabilis and A. americanum. These tests demonstrate that nootkatone has a promising dual-action personal protection capacity against adult I. scapularis ticks, warranting further investigation in more natural environments and in the presence of host cues.

Repellent effects of Chinese cinnamon oil on nymphal ticks of Haemaphysalis longicornis, Rhipicephalus haemaphysaloides, and Hyalomma asiaticum.

The repellent activity of Chinese cinnamon oil (Cinnamomum cassia) on nymphal ticks (Haemaphysalis longicornis Neumann, Rhipicephalus haemaphysaloides Supino, and Hyalomma asiaticum Schulze and Schlottke) was evaluated in a sample Y-tube bioassay. The results were based on the vertical migration of ticks during the host-seek phase and showed a dose-dependent repellent effect of Chinese cinnamon oil on the tested nymphs after 6h. For H. longicornis, R. haemaphysaloides, and H. asiaticum at the concentrations (vol/vol) of 3, 3, and 1.5%, the repellent percentages over time were 68-97, 69-94, and 69-93%, respectively, which indicated strong repellent activities against ticks, similar to the positive control DEET (N,N-diethyl-3-methylbenzamide). Chinese cinnamon oil exerted the strongest effect on H. asiaticum nymphs. To our knowledge, this is the first study to investigate the repellent effects of Chinese cinnamon oil on ticks. Chinese cinnamon oil has considerable potential and should be developed as a practical tick repellent.

Biomonitoring Equivalents for N,N-Diethyl-meta-toluamide (DEET)

N,N-Diethyl-meta-toluamide (DEET) is widely used as an effective mosquito and tick repellent. DEET is absorbed systemically after applications to skin. Once absorbed, DEET is rapidly metabolized with the predominant metabolite being m-dimethylaminocarbonyl benzoic acid (DBA). DEET and metabolites are predominantly excreted in urine after being absorbed systemically. Exposures to DEET are typically biomonitored via measures of DEET and DBA in urine. In this evaluation, we review available health-based risk assessments and toxicological reference values (TRVs) for DEET and derive Biomonitoring Equivalent (BE) values for interpretation of population biomonitoring data. BEs were derived based on existing TRVs derived by Health Canada, yielding 38 and 23 mg/L DBA in urine for adults and 57 and 34 mg/L DBA in urine in children for the acute oral and intermediate dermal TRVs, respectively. The BEs for unchanged DEET in urine are 21 and 12 mg/L in adults and 4.5 and 2.7 mg/L in children for the acute oral and intermediate dermal TRVs. The BE values derived in this manuscript can serve as a guide to help public health officials and regulators interpret population based DEET biomonitoring data in a public health risk context.

Natural Clerodendrum-derived tick repellent: learning from Nepali culture

Ticks attaching to ear canals of humans and animals are the cause of otoacariasis, common in rural areas of Nepal. The plant Clerodendrum viscosum is used in multiple indigenous systems of medicine by ethnic communities in the Indo-Nepali-Malaysian region. Visiting the Chitwan National Park, we learned that in indigenous medicine, flower extract of C. viscosum is utilized to treat digestive disorders and extracts from leaves as tick repellent to prevent ticks from invading or to remove them from the ear canal. The objective of our study was to provide support to indigenous medicine by characterizing the in vivo effect of leave extracts on ticks under laboratory conditions and its phytochemical composition. We collected plant parts of C. viscosum (leaves and flowers) and mango (Mangifera indica) leaves at the Chitwan National Park, previously associated with repellent activity to characterize their effect on Ixodes ricinus ticks by in vivo bioassays. A Q-ToF high-resolution analysis (HPLC-ESI-QToF) was conducted to elucidate phenolic compounds with potential repellent activity. Clerodendrum viscosum and M. indica leaf extracts had the highest tick repellent efficacy (%E = 80–100%) with significant differences when compared to C. viscosum flowers extracts (%E = 20–60%) and phosphate-buffered saline. Phytochemicals with tick repellent function as caffeic acid, fumaric acid and p-coumaric acid glucoside were identified in C. viscosum leaf extracts by HPLC-ESI-QToF, but not in non-repellent flower extracts. These results support the Nepali indigenous medicine application of C. viscosum leaf extracts to repel ticks. Additional research is needed for the development of natural and green repellent formulations to reduce the risks associated with ticks resistant to acaricides.

A One Health Ecosystem Approach for Understanding and Mitigating Spill-Over of Tick-Borne Diseases in India’s Degraded Forests

Exposure to zoonotic diseases can trade-off against livelihood-critical activities, particularly for tropical forest-dependent communities. Inter-disciplinary ecosystem approaches are critical to understanding this zoonotic spillover since the ecological and socio-political processes that make people vulnerable are jointly studied across degraded ecosystems. Moreover, One Health co-production of research and tools with cross-sectoral stakeholders can bridge gaps in knowledge and disease management between sectors. The MonkeyFeverRisk project applied these approaches to a case study of human viral tick-borne disease, Kyasanur Forest Disease (KFD), affecting forest-dependent communities in the Western Ghats, south India, to inform management. Multiple tick species and vertebrate hosts are involved in Kyasanur Forest Disease Virus transmission, including wild rodents and shrews, monkeys and birds, while humans are “dead-end” hosts contracting the disease when bitten by infected ticks. By sampling across habitats within fragmented forests, we found that the risk of human exposure to infected ticks extends outside forests to forest edges, plantations, houses and gardens. The highest risk of human spillover was found in diverse agro-forestry landscapes, created when the moist evergreen forest is replaced with plantations and rice cultivation. Risks and impacts of KFD were highest for socially vulnerable, marginalised groups (e.g. lower caste, landless, elderly-headed households), exposed to ticks through occupations in forests, plantations and cropland. Aside from mortality, disease impacts include long-term, debilitating health issues, loss of income and reduced forest access. Key barriers to effective KFD prevention within these communities included limited information about KFD and its transmission, low efficacy of and mistrust in currently available vaccines and tick repellents, and livelihood concerns. Co-production delivered web-based tools to guide management, identifying high-risk areas, and education materials for local communities, health workers and managers detailing risks from ticks and tick-bite prevention measures.© The Authors 2023. Open Access. This article is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License. https://creativecommons.org/licenses/by-nc/4.0/

Repellent efficacy of 20 essential oils on Aedes aegypti mosquitoes and Ixodes scapularis ticks in contact-repellency assays

Cases of mosquito- and tick-borne diseases are rising worldwide. Repellent products can protect individual users from being infected by such diseases. In a previous study, we identified five essential oils that display long-distance mosquito repellency using a Y-tube olfactometer assay. In the current study, the contact repellent efficacy of 20 active ingredients from the Environmental Protection Agency’s (EPA) Minimum Risk Pesticides list were tested using Aedes aegypti and Ixodes scapularis. We utilized an arm-in-cage assay to measure complete protection time from mosquito bites for these active ingredients. To measure tick repellency, we used an EPA-recommended procedure to measure the complete protection time from tick crossings. We found that of the 20 ingredients tested, 10% v/v lotion emulsions with clove oil or cinnamon oil provided the longest protection from both mosquito bites and tick crossings. We conclude that in a 10% v/v emulsion, specific active ingredients from the EPA Minimum Risk Pesticides list can provide complete protection from mosquito bites and tick crossings for longer than one hour.

천연 진드기기피제 개발을 위한 블렌딩 에센셜오일의 진드기 기피효능에 관한 연구

In this study, an experiment was conducted to measure the tick repellent efficacy through the synergy effect according to the type and ratio of blending essential oil. The subjects were adults and nymphs of the Haemaphysalis longicornis, and the repellent efficacy was measured using the filter paper bioassay method. Based on the past research, citronella oil, geranium oil, vetiver oil, and neem oil were selected as a single treatment experiment since their repellent efficacy was confirmed. The first experiment revealed that the repellent efficacy of citronella oil and geranium oil were high. Afterwards, in order to investigate the synergy effect on tick repellent efficacy, experimental group was consisted of neem seed oil (carrier oil) that was blended with citronella and geranium oil, at a ratio of 1:1, 2:1, and 17:3 (15%). Also, negative control group was composed of ethanol that was blended with citronella and geranium oil at the same ratio of experimental group. As a result, the blending of citronella and neem seeds showed higher repellent efficacy in all blending ratios than the blending of geranium and neem seeds. In adult ticks, blending ratio of citronella and neem seeds was 1:1 and 17:3, showed the most significant difference of repellent efficacy. In nymph ticks, when the blending ratio of citronella and neem seed was 1:1 and 17:3, the repellent efficacy was the same as that of the positive control commercial repellent. In conclusion, it was confirmed that both nymph and adults ticks showed higher repellent efficacy when blended than single treatment. In this study, the synergy effect of the blending of citronella and neem seeds on the tick repellent effect has a high potential to replace synthetic repellents.

Effect of the combination of DEET and flupyradifurone on the tick Ixodes ricinus: Repellency bioassay and pharmacological characterization using microtransplantation of synganglion membranes

Ticks are vectors of many human and animal pathogens, and represent a major threat to public health. In recent years, an increase in tick-borne diseases has been observed, and new strategies are therefore needed in order to control tick numbers and reduce human tick bites. In the present study, we adapted the previous tick repellency bioassay based on the exploration behavior of the tick, using the ToxTrac software and video-tracking, to compare the repellent effect of two compounds on the tick Ixodes ricinus: N,N-diethyl-methyl-m-toluamide (DEET), and butenolide, flupyradifurone (FLU). We found that when applied alone, 10% DEET or FLU have no/or low repellency effect. But, the combination of both 10% DEET and FLU demonstrated a significant repellency effect against I. ricinus, similar to the repellency of 20% DEET. Using membrane microtransplantation, we evaluated the effect of DEET and FLU on native acetylcholine receptors expressed on the tick synganglion. We found that DEET has no effect on acetylcholine-evoked currents, but significantly reduced nicotine-induced current amplitudes. FLU induced an ionic current but was not able to reduce acetylcholine or nicotine evoked currents. The combination of both DEET and FLU strongly reduced nicotine-evoked currents. Finally, we demonstrated that our recording device for repellency, as well as the use of membrane microtransplantation, could be used as methods to study the mode of action of active compounds on ticks.

Spatial repellents transfluthrin and metofluthrin affect the behavior of Dermacentor variabilis, Amblyomma americanum, and Ixodes scapularis in an in vitro vertical climb assay.

Repellents serve an important role in bite protection. Tick repellents largely rely on biomechanisms that induce responses with direct contact, but synthetic pyrethroids used as spatial repellents against insects have received recent attention for potential use in tick protection systems. An in vitro vertical climb assay was designed to assess spatial repellency against Dermacentor variabilis, Amblyomma americanum, and Ixodes scapularis adult, female ticks. Climbing behavior was assessed with and without the presence of two spatial repellents, transfluthrin and metofluthrin. Repellency parameters were defined to simulate the natural questing behavior of ambushing ticks, including measures of detachment, pseudo-questing duration, climbing deterrence, and activity. Significant effects were observed within each parameter. D. variabilis showed the greatest general susceptibility to each repellent, followed by A. americanum, and I. scapularis. The most important and integrative measure of repellency was climbing deterrence-a measure of the spatial repellent's ability to disrupt a tick's natural propensity to climb. Transfluthrin deterred 75% of D. variabilis, 67% of A. americanum, and 50% of I. scapularis. Metofluthrin was slightly more effective, deterring 81% of D. variabilis, 73% of A. americanum, and 72% of I. scapularis. The present study poses a novel paradigm for repellency and reports a preliminary assessment of spatial repellent effect on tick behavior. Further research will assess spatial repellency in a more natural setting, scale exposure conditions, and incorporate host cues.

Repellency of novel catnip (Nepeta cataria) cultivar extracts against Ixodes scapularis and Haemaphysalis longicornis (Acari: Ixodida: Ixodidae)

Tick bites are a major public health concern due to the vector role that many tick species have in transmitting human pathogens. Synthetic repellents such as N‑diethyl-meta-toluamide (DEET) remain the standard for repellency. Still, there is a need for natural commercial alternatives with similar or better properties than DEET. We evaluated the repellency of two extracts, CR3 and CR9, derived for newly developed catnip cultivars on two tick species, Ixodes scapularis and Haemaphysalis longicornis. Dose-response in vitro assays showed that CR3 and CR9 extracts have similar repellency properties to DEET. At a 20% concentration, both CR3 and CR9 extracts exhibited a repellency of 100%. Catnip extracts maintained their repellency properties for at least 8 h. In a two-choice assay, I. scapularis, but not H. longicornis, was more sensitive to CR3 than DEET. In addition, CR3 reduces the life span of I. scapularis, suggesting that it has an acaricidal effect on ticks. In summary, CR3 and CR9 catnip extracts are promising tick repellents that should be further developed, alone or in combination with other tick repellents, and tested for their use as tick repellents for humans.