Activity of the plant-based repellent, TT-4302 against the ticks Amblyomma americanum, Dermacentor variabilis, Ixodes scapularis and Rhipicephalus sanguineus (Acari: Ixodidae)

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.

Orally delivered fipronil-laced bait reduces juvenile blacklegged tick (Ixodes scapularis) burdens on wild white-footed mice (Peromyscus leucopus)

While the topical acaricidal treatment of rodent pathogen reservoirs has been readily explored over the past several decades, oral systemic acaricidal treatment is only recently gaining traction as an alternative approach to the management of ticks and tick-borne pathogens. Recent laboratory tests have shown promise in the effectiveness of this systemic strategy against the blacklegged tick (Ixodes scapularis) and a Canadian field evaluation was recently published, but no recent field data from the United States yet exist. With this research, we sought to field deploy a commercially available fipronil-laced bait (Kaput® Flea Control Bait, Scimetrics LLC., Wellington, CO, USA; 0.005% fipronil; Environmental Protection Agency Reg. No. 72500-28), in an alternate use targeting white-footed mice (Peromyscus leucopus) to determine bait acceptance and potential impacts to juvenile I. scapularis burdens. Bait was readily accepted by wild P. leucopus and other rodent reservoirs. An ad libitum distribution strategy as well as placing smaller volumes of fipronil-laced bait within individual Sherman traps both resulted in significant reductions (57-94%) in juvenile I. scapularis burdens as compared to control over two years. The oral delivery of systemic acaricides shows promise in reduction of I. scapularis burdens on P. leucopus and should be further explored to determine effectiveness on host-seeking tick abundances, associated pathogen infection, and potentially incorporated into integrated tick management programs.

Clinical Practice Guidelines by the Infectious Diseases Society of America (IDSA), American Academy of Neurology (AAN), and American College of Rheumatology (ACR): 2020 Guidelines for the Prevention, Diagnosis and Treatment of Lyme Disease

This evidence-based clinical practice guideline for the prevention, diagnosis, and treatment of Lyme disease was developed by a multidisciplinary panel representing the Infectious Diseases Society of America (IDSA), the American Academy of Neurology (AAN), and the American College of Rheumatology (ACR). The scope of this guideline includes prevention of Lyme disease, and the diagnosis and treatment of Lyme disease presenting as erythema migrans, Lyme disease complicated by neurologic, cardiac, and rheumatologic manifestations, Eurasian manifestations of Lyme disease, and Lyme disease complicated by coinfection with other tick-borne pathogens. This guideline does not include comprehensive recommendations for babesiosis and tick-borne rickettsial infections, which are published in separate guidelines. The target audience for this guideline includes primary care physicians and specialists caring for this condition such as infectious diseases specialists, emergency physicians, internists, pediatricians, family physicians, neurologists, rheumatologists, cardiologists and dermatologists in North America.

Efficacy of a water-based botanical acaricide formulation applied in portable spray box against the southern cattle tick, Rhipicephalus (Boophilus) microplus (Acari: Ixodidae), infesting cattle

Ectoparasitism result in annual losses to livestock producers estimated to reach billions of dollars in tropical and subtropical parts of the world where the southern cattle tick, Rhipicephalus (Boophilus) microplus, is established because this invasive pest is also a vector of pathogens causing bovine babesiosis and anaplasmosis. Reintroduction of R. microplus could be economically devastating for the cattle industry in the United States. Novel technologies are necessary to manage populations of R. microplus that are resistant to multiple classes of synthetic chemicals widely used as acaricides to control ticks infesting livestock, and to mitigate the environmental impact of these synthetic acaricides. Bioassays with a water-based formulation of a commercially available botanical acaricide (Essentria® IC3) at 6.25 % against a laboratory strain of R. microplus was 100 % lethal against unfed larvae, and 94 % mortality was recorded against engorged female ticks. These results prompted documentation of efficacy on infested cattle using an acaricide delivery system mimicking field conditions, which is required to consider the use of a product by integrated tick management programs. Twelve tick naïve cattle were artificially infested with unfed larvae on days -19, -12 and -5. On day -2, ticks from the left-side of the body of each animal were manually counted. Depending on pre-treatment tick counts the animals were assigned into three separate treatment groups: i) water (untreated control); ii) coumaphos 0.3 % in water (positive control); and iii) botanical acaricide 6.25 % in water. Five days after the last infestation, cattle were doused in a spray box and moved to individual stalls to collect tick data for calculation of treatment efficacy. The percentage control, based on the reproduction of surviving engorged female ticks after treatment with the 6.25 % Essentria in water-based spray was 70 % against R. microplus. Coumaphos treatment had a mean percent control of 100 %. Whereas this application of Essentria® IC3 cannot be recommended as a stand-alone method to eradicate R. microplus, the 6.25 % botanical acaricide water-based spray could be part of integrated tick management to control populations of R. microplus resistant to organophosphates like coumaphos and other classes of commercially available synthetic acaricides.

Preliminary Evaluation of Human Personal Protective Measures Against the Nymphal Stage of the Asian Longhorned Tick (Acari: Ixodidae)

The invasive, human-biting Asian longhorned tick, Haemaphysalis longicornis Neumann, is establishing in the United States. This tick is a threat to public health in its native range in Asia, serving as a vector of severe fever with thrombocytopenia syndrome virus and Rickettsia japonica, the agent of Japanese spotted fever. However, there is a lack of published information specifically for H. longicornis concerning the efficacy of generally recommended personal tick bite prevention measures. We, therefore, evaluated permethrin-treated clothing and formulated human skin repellent products, representing the six repellent active ingredients generally recommended for tick bite prevention by the Centers for Disease Control and Prevention (CDC), against H. longicornis nymphs from a colony established with adult ticks collected in New York state. Reluctance of H. longicornis nymphs to stay in contact with nontreated human skin precluded the use of a human skin bioassay to optimally evaluate repellency. In a Petri dish choice bioassay, all tested product formulations were highly effective with estimated repellencies ranging from 93 to 97%. In addition, we observed strong contact irritancy of a summer-weight permethrin-treated garment against H. longicornis nymphs, with 96% of introduced ticks dislodging from the vertically oriented textile within 3 min. These preliminary studies indicate that personal tick bite prevention measures currently recommended by the CDC are effective against the invasive H. longicornis. However, additional studies are needed to explore the efficacy of the evaluated products against different life stages of H. longicornis, as well as ticks collected in the field rather than reared in the laboratory.

Behavioral responses of Ixodes scapularis tick to natural products: development of novel repellents

The spread of blacklegged ticks (Ixodes scapularis) and growing threat of Lyme disease transmission has increased demand for effective, safe and environmentally friendly repellent products. Plant-derived essential oils are natural products that exhibit insecticidal and repellant activities and represent a promising alternative to synthetic repellants. However, mechanisms by which ticks detect odor stimuli and how such stimuli may function as repellents are not well understood. We examined the repellent activity of selected essential oil components towards I. scapularis in short- and long-term dose-response trials. To determine the specific olfactory organs involved in detection of chemical stimuli, we tested tick behavioral response in repellency bioassays after removing appendages that house chemosensory sensilla (e.g., foretarsi or pedipalps). New prototype formulae were tested in longevity trials repelling up to 95% of tested ticks after 1 h post-application. This study provides new insight regarding tick olfaction and behavior, and innovative methods for selecting appropriate chemicals for development of novel plant-based repellent products for protection from ticks.

Acaricidal effect of Schinus molle (Anacardiaceae) essential oil on unengorged larvae and engorged adult females of Rhipicephalus sanguineus (Acari: Ixodidae)

The current concern about resistance to acaricides and the impact of toxic waste on the environment has led to the search of vegetal alternatives in the control of the brown tick of the dog Rhipicephalus sanguineus. Schinus molle L. (Anacardiaceae) derivatives have been associated with insecticidal, antimicrobial and antiprotozoal activities and essential oil showed to be lethal to R. microplus larvae. This study aimed at evaluating the acaricidal effect of essential oil of S. molle (EO_Sm) on engorged adult females and larval stages of R. sanguineus. One-hundred engorged females were obtained from the ears, interdigital spaces, neck, groin and base of the tail of two cross-bred dogs. The larvae package test was accomplished with 21-day-old larvae and five concentrations (v/v) of EO_Sm (0.125, 0.25, 0.50, 1 and 2%) in an anionic detergent, a synthetic acaricide (cypermethrin) and detergent and deionized water as controls. The immersion adult test was carried out with nine concentrations (0.125, 0.25, 0.50, 1, 2, 4, 8, 16, 20%) of the EO_Sm. At the concentration of 2%, EO_Sm caused 99.3% of larval mortality. In adults, inhibition of oviposition, egg hatching (EH) and reproductive efficiency (RE) values were dose-dependent from 4 to 20% EO_Sm; the lowest values of EH (29.62) and RE (22.61) were achieved with 20% EO_Sm. Strong and negative correlations were found between concentration of EO_Sm and EH (r = - 0.948) and between concentration of EO_Sm and RE (r = - 0.985). This study demonstrated for the first time the acaricidal effect of EO_Sm on larvae and reproductive parameters of engorged adult females of R. sanguineus.

Evaluation of four commercial natural products for repellency and toxicity against the lone star tick, Amblyomma americanum (Acari: Ixodidae)

Lone star ticks are aggressive ectoparasites of domestic and wild animals, as well as humans. These ticks can transmit many pathogens that cause disease including Erhlichia and tularemia. Common compounds used for personal protection and area sprays are N-diethyl-3-methyl benzamide (DEET) and permethrin, but public concern over personal and environmental safety require the development of new, safer products. In the current study, four commercially available products (Wondercide, Essentria IC³, Vet's Best, and Mosquito Barrier) were tested for both repellent and toxic effects against lone star tick nymphs and adults. Overall, all four products were more effective against nymphs than against adults. Wondercide and Essentria IC³ were as toxic to nymphs as permethrin at concentrations of 3.13% and higher, and as repellent as DEET at all concentrations. Nymphs were also repelled by Mosquito Barrier and Vet's Best, but these products had about half or less of the repellent effects of Wondercide and Essentria IC³ at most of the concentrations. Adult ticks were repelled similarly by all products at all tested concentrations, but at lower levels than nymphs. Toxicity of the four tested products on adults was similar at concentrations of 12.5% and below, less than half of what was observed with permethrin with declining effectiveness as concentrations decreased. Overall, these four products may offer a natural way to repel lone star ticks, but further field testing is needed to determine rates of application and residual activity.

Evidence for Personal Protective Measures to Reduce Human Contact With Blacklegged Ticks and for Environmentally Based Control Methods to Suppress Host-Seeking Blacklegged Ticks and Reduce Infection with Lyme Disease Spirochetes in Tick Vectors and Rodent Reservoirs

In the 1980s, the blacklegged tick, Ixodes scapularis Say, and rodents were recognized as the principal vector and reservoir hosts of the Lyme disease spirochete Borrelia burgdorferi in the eastern United States, and deer were incriminated as principal hosts for I. scapularis adults. These realizations led to pioneering studies aiming to reduce the risk for transmission of B. burgdorferi to humans by attacking host-seeking ticks with acaricides, interrupting the enzootic transmission cycle by killing immatures infesting rodent reservoirs by means of acaricide-treated nesting material, or reducing deer abundance to suppress tick numbers. We review the progress over the past three decades in the fields of: 1) prevention of human-tick contact with repellents and permethrin-treated clothing, and 2) suppression of I. scapularis and disruption of enzootic B. burgdorferi transmission with environmentally based control methods. Personal protective measures include synthetic and natural product-based repellents that can be applied to skin and clothing, permethrin sprays for clothing and gear, and permethrin-treated clothing. A wide variety of approaches and products to suppress I. scapularis or disrupt enzootic B. burgdorferi transmission have emerged and been evaluated in field trials. Application of synthetic chemical acaricides is a robust method to suppress host-seeking I. scapularis ticks within a treated area for at least 6-8 wk. Natural product-based acaricides or entomopathogenic fungi have emerged as alternatives to kill host-seeking ticks for homeowners who are unwilling to use synthetic chemical acaricides. However, as compared with synthetic chemical acaricides, these approaches appear less robust in terms of both their killing efficacy and persistence. Use of rodent-targeted topical acaricides represents an alternative for homeowners opposed to open distribution of acaricides to the ground and vegetation on their properties. This host-targeted approach also provides the benefit of the intervention impacting the entire rodent home range. Rodent-targeted oral vaccines against B. burgdorferi and a rodent-targeted antibiotic bait have been evaluated in laboratory and field trials but are not yet commercially available. Targeting of deer-via deer reduction or treatment of deer with topical acaricides-can provide area-wide suppression of host-seeking I. scapularis. These two deer-targeted approaches combine great potential for protection that impacts the entire landscape with severe problems relating to public acceptance or implementation logistics. Integrated use of two or more methods has unfortunately been evaluated in very few published studies, but additional field evaluations of integrated tick and pathogen strategies are underway.

Sustained efficacy of the novel topical repellent TT-4302 against mosquitoes and ticks

Mosquitoes and ticks are blood-feeding pests of humans and animals that can vector many important aetiological agents of disease. Previous research demonstrated that TT-4302 (Guardian(®) Wilderness) containing 5% geraniol applied to human subjects gave 5-6 h of repellency against mosquitoes (depending on species) and was repellent to ticks in vitro. This study was conducted to obtain an independent third-party evaluation of TT-4302 against Stegomyia aegypti (= Aedes aegypti) (Diptera: Culicidae) mosquitoes and to test the efficacy of the product in the field against ticks. TT-4302 provided an average of 6.5 h of repellency of ≥ 95% [Weibull mean protection time: 7.4 h, 95% confidence interval (CI) 5.8-11.3 h] for St. aegypti, whereas a 15% DEET formulation provided 4.7 h of repellency (Weibull mean protection time: 5.2 h, 95% CI 3.7-6.9 h). In tick field trials, the efficacy of TT-4302 did not differ significantly from that of a 25% DEET formulation against Amblyomma americanum (Ixodida: Ixodidae). TT-4302 was 81.3% repellent at 2.5 h after application, whereas DEET was 77.2% repellent at the same time-point. Results at 3.5 h after application were 71.4% for TT-4302 and 72.9% for DEET.

Evaluation of DEET and eight essential oils for repellency against nymphs of the lone star tick, Amblyomma americanum (Acari: Ixodidae)

DEET and Eight commercially available essential oils (oregano, clove, thyme, vetiver, sandalwood, cinnamon, cedarwood, and peppermint) were evaluated for repellency against host-seeking nymphs of the lone star tick, Amblyomma americanum. Concentration-repellency response was established using the vertical paper bioassay technique for each essential oil and compared with that of N,N-diethyl-3-methyl benzamide (DEET), a standard repellent compound present in many commercial repellent formulations. The effective concentration of DEET that repels 50% of ticks (EC50) was estimated at 0.02 mg/cm(2), while EC50s of the essential oils fall between 0.113 and 0.297 mg/cm(2). Based on EC50 estimates, oregano essential oil was the most effective among all essential oils tested, followed by clove, thyme, vetiver, sandalwood, cinnamon, cedarwood, and peppermint oils. None of the tested essential oils demonstrated a level of tick repellency found with DEET. Results from this study illustrated the challenge in search for more effective natural tick repellents.

Effectiveness of Garlic for the Control of Ixodes scapularis (Acari: Ixodidae) on Residential Properties in Western Connecticut

We conducted field trials to evaluate the ability of a garlic juice-based product to control or suppress nymphal activity of the blacklegged tick, Ixodes scapularis Say, at residential properties in Connecticut in 2009, 2010, and 2011. The product was applied at a rate of 0.2 g AI/m2. Percent control of nymphal densities achieved by the spray treatment at 6, 11, and 18 d postspray for the 3 yr was 37.0, 59.0, and 47.4%, respectively. Differences between nymphal densities were greatest during the first post-spray sampling period. While garlic may require multiple applications for the suppression of tick activity, this product could provide a minimal-risk option for the short-term control of nymphal I. scapularis in the residential landscape.

Present and future potential of plant-derived products to control arthropods of veterinary and medical significance

The use of synthetic pesticides and repellents to target pests of veterinary and medical significance is becoming increasingly problematic. One alternative approach employs the bioactive attributes of plant-derived products (PDPs). These are particularly attractive on the grounds of low mammalian toxicity, short environmental persistence and complex chemistries that should limit development of pest resistance against them.

Several pesticides and repellents based on PDPs are already available, and in some cases widely utilised, in modern pest management. Many more have a long history of traditional use in poorer areas of the globe where access to synthetic pesticides is often limited. Preliminary studies support that PDPs could be more widely used to target numerous medical and veterinary pests, with modes of action often specific to invertebrates.

Though their current and future potential appears significant, development and deployment of PDPs to target veterinary and medical pests is not without issue. Variable efficacy is widely recognised as a restraint to PDPs for pest control. Identifying and developing natural bioactive PDP components in place of chemically less-stable raw or 'whole’ products seems to be the most popular solution to this problem. A limited residual activity, often due to photosensitivity or high volatility, is a further drawback in some cases (though potentially advantageous in others). Nevertheless, encapsulation technologies and other slow-release mechanisms offer strong potential to improve residual activity where needed.

The current review provides a summary of existing use and future potential of PDPs against ectoparasites of veterinary and medical significance. Four main types of PDP are considered (pyrethrum, neem, essential oils and plant extracts) for their pesticidal, growth regulating and repellent or deterrent properties. An overview of existing use and research for each is provided, with direction to more extensive reviews given in many sections. Sections to highlight potential issues, modes of action and emerging and future potential are also included.