Prevention of Lyme disease

INTRODUCTION — Since the discovery of the Lyme disease spirochete, Borrelia burgdorferi, in 1982 and the establishment of Lyme disease as a reportable disease in the United States in 1991, reported Lyme disease cases have increased so dramatically that it is now the most commonly reported vector-borne disease in the United States. In 2019, nearly 35,000 confirmed and probable cases were reported in the United States [1,2]. However, the estimated number of new cases is close to 500,000 yearly. The taxonomy of Borrelia burgdorferi sensu lato spirochetes is being considered for revision, and the genus name may be represented as either Borrelia or Borreliella

Efforts to prevent Lyme disease have focused in four principal areas: personal protection, environmental intervention, prophylactic treatment, and vaccination. The effectiveness of any given preventive intervention is dependent on both the efficacy of the intervention and the level of acceptance by the target population [3]. Thus, effective Lyme disease prevention depends on selection of strategies that are both efficacious and practical for people in endemic regions.

Personal protection and environmental interventions for the prevention of Lyme disease and other tick-borne diseases will be reviewed here. The microbiology, epidemiology, clinical manifestations, diagnosis, and treatment of Lyme disease are discussed separately; the evaluation of a tick bite for possible Lyme disease, which includes a discussion of antibiotic prophylaxis, is also covered elsewhere. (See "Microbiology of Lyme disease" and "Epidemiology of Lyme disease" and "Clinical manifestations of Lyme disease in adults" and "Lyme disease: Clinical manifestations in children" and "Diagnosis of Lyme disease" and "Treatment of Lyme disease" and "Evaluation of a tick bite for possible Lyme disease".)

PERSONAL PROTECTION — Several strategies for personal protection against Lyme disease have been advocated [4,5]. These include:

●Checking for and removing ticks after outdoor activities.

●Bathing after outdoor activities where ticks are abundant.

●Placing dry clothes in dryers on high heat for a short period of time after outdoor activities.

●Wearing protective clothing.

●Using tick repellents, such as DEET, on skin and permethrin on clothing, according to manufacturer's instructions. Products should be US Environmental Protection Agency (or analogous regulatory agencies in other endemic regions) registered.

●Avoiding areas where ticks are abundant.

Checking for and removing ticks — Based on limited evidence of effectiveness, a theoretical basis for efficacy, and reasonable acceptability, we suggest tick checks and prompt tick removal following exposure to tick habitat. There is good experimental evidence that transmission of Borrelia species that cause Lyme disease in the United States (B. burgdorferi sensu stricto and B. mayonii) require more than 24 hours of attachment of Ixodes scapularis ticks, and the likelihood of transmission increases with duration of attachment [6]. This is generally felt to be true for other Lyme disease vectors (I. pacificus and I. ricinus) and other Lyme disease spirochetes (eg, B. afzelii) as well. Methods for safely removing ticks are discussed separately. (See "Evaluation of a tick bite for possible Lyme disease", section on 'Tick attachment' and "Evaluation of a tick bite for possible Lyme disease", section on 'Technique for tick removal'.)

Studies indicate that about 80 percent of residents of Lyme disease-endemic communities in Connecticut report checking themselves for ticks after outdoor activities [7,8]. Two case-control studies, which included 51 and 101 cases, respectively, suggested that tick checks might be effective in preventing Lyme disease, but the results were not statistically significant [9,10]. A subsequent study that included 364 cases and 349 matched controls showed a protective effect since cases were significantly less likely than controls to have performed tick checks within 36 hours of being outdoors (odds ratio 0.55, 95% CI 0.32-0.94) [5]. One other case-control study, including over 700 case patients and over 1000 controls, found that tick checks did not reduce the risk of Lyme disease [8]. While tick checks are unlikely to be harmful, there may be limits to an individual's ability to detect the small nymphal ticks that transmit Lyme disease (figure 1).

Bathing after exposure to tick-infested habitat — Bathing soon after exposure to tick habitat can reduce risk of Lyme disease. A case-control study conducted in Connecticut revealed that bathing within two hours of spending time in the yard was protective against Lyme disease (odds ratio 0.42, 95% CI 0.23-0.78) [5]. Although bathing is not expected to remove attached ticks, it could wash off ticks that have not yet attached, enhance finding ticks on skin, and reduce exposure to ticks retained in clothing.

Placing clothes in a dryer — Placing dry clothing briefly in a dryer on high heat after outdoor activities kills ticks on clothing. Although there is limited evidence and a theoretical basis for efficacy, this intervention may reduce exposure to ticks brought into the home.

In one study, adult and nymphal I. scapularis ticks in muslin bags were placed in a residential dryer along with dry towels; all the ticks were killed after four minutes of drying at high heat [11]. When placed in the dryer with wet towels, killing times were substantially longer: up to 50 minutes. Hot water washes also killed ticks, but only if the water temperature was ≥54°C (≥130°F). An earlier study using both Ixodes and Amblyomma ticks found variable mortality during washing, but drying with wet clothes on high heat for 60 minutes killed all ticks [12]. Shorter drying times with dry clothes were not evaluated.

Protective clothing — Based on limited evidence and a theoretical basis for efficacy, we suggest the use of long-legged and long-sleeved clothing that has been treated with permethrin or some similarly effective insecticide or repellent with low toxicity to humans to prevent Lyme disease among people who enter tick habitats in endemic areas.

A case-control study, which included over 700 case patients and over 1000 controls, indicated that wearing protective clothing had an effectiveness of 40 percent in preventing Lyme disease [8]. Another case-control study, which included 364 cases and 349 controls, did not show a significant difference between cases and controls in wearing long pants or light-colored clothing [5]. In a study in which 10 volunteers walked in a tick-endemic area wearing either light or dark clothing, Ixodes ricinus ticks seemed to be more attracted to light clothing than to dark clothing and the authors questioned whether ticks were more easily detected on light clothing [13]. In a study of community behaviors, 60 percent of residents in three Connecticut communities reported always wearing long pants when in wooded or brushy areas, and 30 percent reported sometimes practicing these measures [7]. The more intensive effort to tuck pants into socks does not seem as easy to adopt; only 10 to 40 percent of residents reported sometimes or always following the recommendation [5].

The efficacy of permethrin-treated clothing in preventing infection with Rickettsia, Ehrlichia, and Borrelia species (as determined by seroconversion) was evaluated in a randomized controlled study of 159 outdoor workers in a non-Lyme disease endemic area [14]. In this trial, there were 40 total seroconversions, but none to Borrelia. In addition, there was a nonsignificant reduction in the risk of seroconversion to Rickettsia and Ehrlichia among individuals wearing permethrin-impregnated clothing (risk ratio: 0.81; 95% CI 0.47-1.39). A subsequent randomized, placebo-controlled, double-blinded trial among 82 outdoor workers in Rhode Island and Massachusetts found that factory-impregnated permethrin clothing reduced tick bites by 58 percent relative to sham-treated clothing (95% CI 43-69 percent) [15]. Two smaller studies also indicated that permethrin-impregnated clothing protects against tick bites [16,17], and one study suggested that nootkatone-treated clothing repels ticks [18].

Tick repellents — Products containing DEET (N,N-diethyl-meta-toluamide) are effective tick repellents that can be applied to the skin and have been commercially available for many years. Other repellents (eg, picaridin, IR3535, lemon eucalyptus oil) can be used on the skin and some may be better tolerated [19]; however their equivalence to DEET for repelling ticks has not been well evaluated. Permethrin is an acaricide that can be applied to clothing to prevent tick bites but should not be applied directly to skin. (See 'Protective clothing' above.)

Given the theoretical basis for effectiveness, low risk of adverse events, and reasonable acceptability, we suggest the use of an efficacious tick repellent (eg, DEET) on skin and permethrin on clothing for people who enter tick habitat. This strategy is likely to be most effective in individuals who apply repellents meticulously, but might be impractical and less acceptable for people who live in tick-infested areas and are regularly exposed to tick habitat.

The effectiveness of tick repellents is probably most limited by lack of thorough application and the need for reapplication. Estimates of the proportion of Connecticut residents who report using repellents outdoors range from 27 to 70 percent, but probably fewer than 30 percent consistently practice this strategy [7,8]. One case-control study found no effectiveness of repellent use in preventing Lyme disease, but the numbers of both cases and controls who used repellent were low [9]. Another study showed a trend towards a reduction in risk of Lyme disease among individuals who wore repellent in the home yard, but the effect did not reach statistical significance (odds ratio 0.59, 95% CI 0.35-1.03) [5]. A larger study indicated that use of repellent had an effectiveness of 20 percent in preventing Lyme disease [8]. The toxicities of DEET and other repellents are low when applied according to the manufacturer's directions and published guidelines [20,21].

A more detailed discussion of tick repellents, including safety profiles and recommendations for use in children and pregnant women, is presented separately. (See "Prevention of arthropod and insect bites: Repellents and other measures".)

Avoiding tick habitat — In three Connecticut communities where Lyme disease is endemic, more than 70 percent of residents reported avoiding wooded areas to attempt reducing their exposure to infected ticks [7]. This strategy may be effective where isolated areas of high risk are focal and known, such as in Pacific coastal areas of North America and some areas of Europe [22]. However, in the northeastern United States tick habitat is often peridomestic, and residents may not be able to consistently avoid exposure [4]. In a northern California oak forest, researchers were more likely to acquire ticks when sitting on logs or gathering wood than when sitting on leaf litter, and tick densities were high on and around logs [23]. Thus, some activities and microhabitats might present higher risk of tick exposure within larger areas of tick habitat.

It seems prudent to recommend avoiding tick habitat when feasible, but such a recommendation is not likely to be practical or effective in highly-endemic areas where peridomestic tick exposure is common.

Educational interventions — Several studies have assessed the effectiveness of educational programs to promote personal protection against Lyme disease, with mixed results. In general, educational programs appear to improve knowledge, but efficacy in preventing tickborne infections is unproven.

In one study, the effects of an educational program to prevent tick-borne illness were evaluated in 30,164 passengers on ferries bound for Nantucket Island [24]. Boats were randomly assigned to either intervention or comparison educational programs. The intervention program promoted tick checks, avoidance of tick habitat, wearing protective clothing, repellent use, and early recognition of Lyme disease symptoms. The comparison program promoted prevention of bicycle and other road-related injuries. After the program, participants in the intervention group were more likely to report having checked themselves for ticks and taken precautions against tick bites. In addition, among the 12 percent of intervention participants who stayed on Nantucket for longer than two weeks, those who received the tick education program were less likely to report a subsequent tick-borne illness (relative risk [RR] 0.41, 95% CI 0.18-0.95). However, no protective effect was seen among the 88 percent of program participants who visited for two weeks or less (RR 1.04, 95% CI 0.67-1.63).

In a smaller study, 317 residents of Baltimore County, Maryland, were randomly assigned to one of two mail-based educational programs. One group received mailings promoting use of repellents and early detection and removal of ticks, and the comparison group received mailings about health promotion not related to tick-borne diseases [25]. The intervention appeared successful at promoting tick checks and positive attitudes about repellent use, but there was no meaningful difference between the two groups in anti-recombinant tick calreticulin antibody levels, a biological marker for tick attachment of three or more days’ duration.

A separate study described the outcomes of three community-based Lyme disease prevention programs (without control groups) in Connecticut [7]. In two communities, the proportion of residents who reported checking themselves for ticks increased over the time period of the intervention, and in one of these communities the use of tick repellents also increased, but the use of other personal protective measures either decreased or remained unchanged. Two other studies have indicated that immigrant populations might require particular attention to promote knowledge about prevention and early treatment of Lyme disease, and one of these studies indicated that a clinic-based educational intervention was effective in increasing knowledge about Lyme disease [26,27].

A study of school children at risk for Lyme disease evaluated the ability of a short in-class education program, based on social learning theory, to improve knowledge, attitude, and preventive behavior [28]. A total of 3570 school children in grades two to five received an educational intervention or were on a wait list as controls. Compared with the children in the control group, children in the intervention group significantly increased their overall knowledge of Lyme disease, and reported an increase in precautionary behavior, a positive attitude toward taking precautions, and self-efficacy.

ENVIRONMENTAL INTERVENTIONS — Environmental interventions to reduce the number of infected nymphal I. scapularis ticks have been proposed as a way to prevent tick-borne illnesses such as Lyme disease. These methods can target the tick directly, target the tick or spirochete through the reservoir hosts, or reduce human exposure to ticks (figure 2). Large-scaled trials aimed at assessing the efficacy of these interventions on reducing Lyme disease occurrence are extremely limited.

Targeting the tick — Traditional methods for controlling ticks include spraying or spreading pesticides that kill ticks (acaricides) onto vegetation or the ground. This approach has been shown to substantially reduce the number of ticks in treated areas as measured by tick drags or other entomologic methods; in experimental trials, typically greater than 80 percent reduction has been observed [29]. However, the percent tick reduction varies with the acaricide used and the method and timing of application. In addition, some areas (eg, vegetable gardens) may not be treatable for safety reasons, and some homeowners are reluctant to use chemical acaricides due to fears of environmental contamination and toxicity to family members and pets [8]. Chemicals derived from botanical sources, so called "natural products", hold promise as both tick repellents and acaricides [30,31], and certain fungi (Metarhizium anisopliae) have also been demonstrated to kill ticks [32].

Despite the ability to reduce tick abundance, residential acaricide applications have not been proven to reduce human-tick exposures or tickborne disease. In a blinded, randomized trial in the northeastern United States, yards of over 2700 households were treated with a single springtime application of either water or the acaricide bifenthrin [33]. During the four months following treatment, acaricide-treated properties had 63 percent fewer ticks than placebo-treated properties. However, there was no significant difference in the number of household members that reported finding an attached tick (approximately 17 percent in each group), or the number with self-reported or medically verified tick-borne disease (approximately 3 and 1.5 percent, respectively).

Targeting reservoir hosts — There are three blood-feeding stages of I. scapularis: larva, nymph, and adult. In general, the immature stages (larva and nymph) feed on a variety of hosts including rodents, insectivores, birds, medium-sized mammals (eg, raccoons, skunks, and opossums), and deer. In contrast, the adults feed preferentially on larger hosts, principally the white-tailed deer. These interactions make host-targeted approaches tempting as Lyme disease prevention strategies (figure 2). (See "Epidemiology of Lyme disease".)

Rodents — The first attempt at host-targeted intervention to prevent Lyme disease was to distribute cardboard tubes containing permethrin-treated cotton balls, which were gathered as nesting material by white-footed mice. These mice, Peromyscus leucopus, are a principal reservoir host for B. burgdorferi. This approach worked quite well when initially tested on islands or in some coastal regions [34,35], but was not as effective in other locations [36]. Variation in the importance of white-footed mice as reservoirs by geographic location and seasonal timing of introduction of treated cotton may play a role in the differing effectiveness of this method observed in these studies.

Another rodent-targeted intervention involves the use of bait boxes that attract a range of rodent reservoirs and treats them with an acaricide, fipronil, which is extremely long-lasting. Results of trials in Connecticut using this method to reduce the number of infected nymphal I. scapularis ticks have yielded mixed results, and reduction in human tickborne infections has not been demonstrated; effects may vary depending on the local endemicity of disease in ticks and humans [37,38]. Recently a large, randomized, blinded, placebo-controlled study in New York assessed the efficacy of rodent bait boxes used separately and in combination with Met52, a spray containing Metarhizium anisopliae fungi applied to the landscape. While bait box use was associated with fewer questing ticks and fewer ticks feeding on rodents, the interventions did not result in a significant difference in incidence of human infections [39]. Other potential rodent-targeted strategies in development include the use of oral outer surface protein A (OspA) vaccines for rodents [40] and antibiotic-treated baits [41].

Deer — Since adult I. scapularis feed almost exclusively on white-tailed deer, Odocoileus virginianus, acaricides could be applied directly to deer in order to kill ticks on the deer. A device developed by United States Department of Agriculture researchers that attracts deer to corn-loaded feeding stations and delivers acaricide to the deer via a series of paint rollers has been labeled the "four-poster" after the four paint rollers arrayed on the feeder [42]. This device has been shown to decrease the populations of questing ticks in Lyme disease-endemic areas [43].

There is limited evidence from a small study that use of the four-poster device reduced the incidence of the erythema migrans rash of Lyme disease in an endemic community in Connecticut [44]. A significant reduction in incidence was observed after implementation of the four-poster device compared with before implementation and in areas in which the four-poster device was used compared with control areas. However, the decrease was not statistically significant when the area in which the four-poster device was used was compared with an expanded control area, suggesting that the apparent effect might have been attributable to a general decreasing trend in Lyme disease incidence in both treatment and control areas. The acceptability of using the four-poster device has been partly limited by wildlife management concerns regarding the practice of baiting deer to feeding stations.

Another approach involves removing the primary host for adult ticks from the Lyme disease-endemic region. On islands and semi-isolated coastal locations, complete eradication of deer virtually eliminated tick populations [45]. The feasibility and effectiveness of deer elimination to reduce tick abundance has not been demonstrated in mainland communities [46]. As an example, within a small community in Connecticut, a controlled deer hunt that reduced the estimated deer population by 92 percent did not lead to a significant reduction in Lyme disease incidence, despite a reduction in tick abundance, but the study’s power to detect an effect on disease incidence was limited [44].

Integrated pest management — An integrated approach to host-targeted tick control, called integrated pest management, has been tested in New Jersey utilizing bait boxes for attracting rodents in conjunction with four-posters for attracting deer [47]. This method produced levels of tick control approaching 95 percent. (See 'Rodents' above and 'Deer' above.)

Landscape management — Another approach involves landscape management to decrease the suitable habitat for ticks, thereby reducing human exposure to ticks (figure 2). An evaluation of the landscape ecology of tick populations in a suburban setting in New York State demonstrated that tick populations are distributed as follows by habitat (in descending order of density): forest, ecotone (the transition zone between two plant communities, as between forest and lawn), ornamental plantings, and lawn [48].

Human exposure to ticks can likely be reduced by placing outdoor recreational equipment such as swing sets away from the forest edge, and by laying down wood chips or gravel between woods and lawns to physically delimit the zones of high tick density. Attempts to alter vegetation to decrease tick habitat include mowing vegetation, removing leaf litter, and burning vegetation [49,50]. Although these methods can be laborious, expensive, and must be sustained, they are generally readily accepted by the public and enthusiastically applied.

PROPHYLAXIS FOR TICK BITE — Antibiotic prophylaxis following a tick bite by an Ixodes tick is indicated in some cases. This issue is discussed in detail elsewhere. (See "Evaluation of a tick bite for possible Lyme disease", section on 'Antimicrobial prophylaxis'.)

VACCINATION — A vaccine (Lymerix), consisting of an adjuvanted full-length copy of the B. burgdorferi outer surface protein (OspA), was approved in 1998 for the prevention of Lyme disease [51]. Theoretical concerns were raised that the OspA antigen might increase the risk of autoimmune Lyme arthritis. However, there was no increase in the frequency of arthritis among individuals who received the OspA vaccine in clinical trials, and postmarketing surveillance indicated that the vaccine had a favorable safety profile [52-55]. The manufacturer discontinued production of the vaccine due to poor sales and it is no longer available [53].

New approaches to vaccine development are being explored, including the combination of multiple immunoprotective OspA epitopes in a single molecular formulation without the epitope that raised concern about autoimmune arthritis [56]. One such candidate vaccine is undergoing phase 2 trials in Europe and the United States [57]. Pre-exposure prophylaxis using anti-OspA monoclonal antibodies is also under evaluation [58].

SOCIETY GUIDELINE LINKS — Links to society and government-sponsored guidelines from selected countries and regions around the world are provided separately. (See "Society guideline links: Tick-borne infections (Lyme disease, ehrlichiosis, anaplasmosis, babesiosis, and Rocky Mountain spotted fever)".)

INFORMATION FOR PATIENTS — UpToDate offers two types of patient education materials, "The Basics" and "Beyond the Basics." The Basics patient education pieces are written in plain language, at the 5^th to 6^th grade reading level, and they answer the four or five key questions a patient might have about a given condition. These articles are best for patients who want a general overview and who prefer short, easy-to-read materials. Beyond the Basics patient education pieces are longer, more sophisticated, and more detailed. These articles are written at the 10^th to 12^th grade reading level and are best for patients who want in-depth information and are comfortable with some medical jargon.

Here are the patient education articles that are relevant to this topic. We encourage you to print or e-mail these topics to your patients. (You can also locate patient education articles on a variety of subjects by searching on "patient info" and the keyword(s) of interest.)

●Basics topics (see "Patient education: Lyme disease (The Basics)")

●Beyond the Basics topics (see "Patient education: Lyme disease prevention (Beyond the Basics)" and "Patient education: Lyme disease symptoms and diagnosis (Beyond the Basics)" and "Patient education: Lyme disease treatment (Beyond the Basics)")

SUMMARY AND RECOMMENDATIONS

●Personal protective measures – We suggest that individuals who enter tick habitat practice the following personal protective measures (Grade 2C):

•Use tick repellents, such as DEET, on skin and permethrin on clothing, according to manufacturer's instructions. Products should be US Environmental Protection Agency (or analogous regulatory agencies in other endemic regions) registered. (See 'Tick repellents' above.)

•Wear insecticide- or repellent-treated, long-legged and long-sleeved clothing. (See 'Protective clothing' above.)

•Place dry clothing briefly in a dryer after outdoor activities. (See 'Placing clothes in a dryer' above.)

•Check for and promptly remove ticks after exposure to tick habitat. (See 'Checking for and removing ticks' above.)

•Bathe after exposure to tick-infested areas, preferably within two hours after exposure. (See 'Bathing after exposure to tick-infested habitat' above.)

●Environmental insecticide – Area-wide dispersion of acaricides (pesticides that kill ticks) in Lyme disease-endemic regions can dramatically reduce tick populations. However, applications of residential acaricides have not been proven to reduce human-tick exposure or tickborne illness. (See 'Targeting the tick' above.)

●Targeting reservoir hosts – Host-targeted tick control strategies, such as bait boxes containing acaricides for rodents or application of acaricides to kill ticks on deer, may be effective for reducing Lyme disease risk in certain settings, but more definitive data are needed. (See 'Targeting reservoir hosts' above.)

●Landscape management – Human exposure to ticks can likely be reduced by placing outdoor recreational equipment such as swing sets away from the forest edge, and by laying down wood chips or gravel between woods and lawns to delimit the zones of high tick density. (See 'Landscape management' above.)

ACKNOWLEDGMENT — Edward Hayes, MD, passed away in May of 2013. UpToDate wishes to acknowledge Dr. Hayes' past work as an author for this topic.