Tick bites and Lyme disease in an endemic setting: problematic use of serologic testing and prophylactic antibiotic therapy

Seroprevalence of Infection by Borrelia Species Responsible for Lyme Disease in the French Alps: Analysis of 27,360 Serology Tests, 2015-2020

Objectives: Lyme borreliosis incidence is increasing in several areas; moreover, it has recently gained the public's attention. Apart from erythema migrans, Lyme disease diagnosis relies (among others) on serology test; however, the prevalence of positive enzyme-linked immunosorbent assay (ELISA) and western blot (WB) assay has been poorly studied in the general population. We aimed to approach the seroprevalence of infection by Borrelia species responsible for Lyme disease in the French Isere department using city laboratories data. Patients and Methods: We retrieved all serological tests for Borrelia species responsible for Lyme disease performed in the two main networks of city laboratories between 2015 and 2020. All patients with both ELISA and WB IgG were considered seropositive. Results: We analyzed 27,360 tests (ELISA/ELISA+WB). Mean age was 50.9 ± 20.3 years (ranges: 0-101), with 57.1% females. Overall, 11.7% had IgG detected by ELISA, and 4.7% had IgG detected by both ELISA and WB assay. Seropositive status was more frequent in males (7.0% vs. 2.9%, p < 0.001). Seropositivity rate increased with age after a first peak in childhood; men aged 61-70 years had the highest seropositivity rate (10.3%). In addition, seropositivity rate was higher in persons from a rural area. In multivariate analysis, older age, male gender and living in a rural area were independently associated with seropositivity. Seropositivity rate was stable on the 2017-2020 period. Conclusion: The seroprevalence of infection by Borrelia species responsible for Lyme disease is high in Isere; this probably reduces the predictive positive value for Lyme disease of ELISA and WB IgG, suggesting that this serological test should not be performed for nonspecific symptoms.

Assessment of Physician Knowledge, Attitudes, and Practice for Lyme Disease in a Low-Incidence State

Lyme disease (LD), caused by the bacterium Borrelia burgdorferi, is transmitted to humans in California through the bite of infected blacklegged ticks (Ixodes pacificus). Overall, the incidence of LD in California is low: approximately 0.2 confirmed cases per 100,000 population. However, California's unique ecological diversity results in wide variation in local risk, including regions with local foci at elevated risk of human disease. The diagnosis of LD can be challenging in California because the prior probability of infection for individual patients is generally low. Combined with nonspecific symptoms and complicated laboratory testing, California physicians need a high level of awareness of LD in California to recognize and diagnose LD efficiently. This research addresses an under-studied area of physicians' knowledge and practice of the testing and treatment of LD in a low-incidence state. We assessed knowledge and practices related to LD diagnosis using an electronic survey distributed to physicians practicing in California through mixed sampling methods. Overall, responding physicians in California had a general awareness of Lyme disease and were knowledgeable regarding diagnosis and treatment. However, we found that physicians in California could benefit from further education to improve test-ordering practices, test interpretation, and awareness of California's disease ecology with elevated levels of focal endemicity, to improve recognition, diagnosis, and treatment of LD in California patients.

Economic Burden of Reported Lyme Disease in High-Incidence Areas, United States, 2014–2016

Approximately 476,000 cases of Lyme disease are diagnosed in the United States annually, yet comprehensive economic evaluations are lacking. In a prospective study among reported cases in Lyme disease–endemic states, we estimated the total patient cost and total societal cost of the disease. In addition, we evaluated disease and demographic factors associated with total societal cost. Participants had a mean patient cost of ≈$1,200 (median $240) and a mean societal cost of ≈$2,000 (median $700). Patients with confirmed disseminated disease or probable disease had approximately double the societal cost of those with confirmed localized disease. The annual, aggregate cost of diagnosed Lyme disease could be $345–968 million (2016 US dollars) to US society. Our findings emphasize the importance of effective prevention and early diagnosis to reduce illness and associated costs. These results can be used in cost-effectiveness analyses of current and future prevention methods, such as a vaccine.

Diagnosis, Treatment, and Prevention Practices for Lyme Disease by Clinicians, United States, 2013-2015

OBJECTIVES

Although tick-borne diseases account for a large number of health care visits in the United States, clinical practices for tick bite and Lyme disease treatment and prevention are not well understood. The objective of this study was to better understand factors associated with clinical practices related to tick bites and Lyme disease.

METHODS

In 2013-2015, questions about tick-bite evaluation, Lyme disease diagnosis and treatment, appropriate use of Lyme disease testing, and tick-bite prevention were included in Porter Novelli's DocStyles survey, a nationally representative annual web-based survey of health care providers. We performed analyses of responses by provider license type and state-level incidence (high or low) of Lyme disease in 2019.

RESULTS

A total of 4517 providers were surveyed across the 3 study years. Overall, 80.9% of providers reported that they had evaluated at least 1 patient for a tick bite, 47.6% had diagnosed at least 1 patient with Lyme disease, and 61.9% had treated at least 1 patient for Lyme disease in the previous year. Providers from states with a high incidence of Lyme disease saw more patients for tick bites and Lyme disease than providers from states with a low incidence of Lyme disease. Few providers correctly chose Lyme disease testing as clinically useful in the hypothetical case of a patient from a state with a high incidence of Lyme disease with an arthritic knee (36.0%) or with new-onset atrioventricular block (39.5%), and respondents across all provider types incorrectly chose testing when not clinically indicated. Most providers (69.7%) reported routinely recommending tick-bite prevention methods to patients.

CONCLUSIONS

Many providers evaluate patients for tick bites and treat patients for Lyme disease, but knowledge about appropriate testing is low. Providers may benefit from tailored education about appropriate Lyme disease diagnosis, testing, and effective tick-bite prevention.

Clinical and economic outcomes evaluated in Lyme disease: a systematic review

BACKGROUND

The financial implications of Lyme disease (LD) can vary widely for both the health system and the individual patients experiencing the disease. The aim of this review was to summarize published data on clinical and economic outcomes associated with LD.

METHODS

A literature review was conducted to identify all studies of LD that incorporate both clinical outcomes and costs. Included studies were described and categorized based on costs consistent with best practices used in economic evaluation.

RESULTS

The most frequent costs identified focused on formal health costs and productivity losses were the most common costs identified outside of the health system. Travel and informal care costs were less frequently reported. Clinical and economic outcomes of LD are primarily studied through economic models or observational analyses and focus on formal health care.

CONCLUSIONS

This review provides and overview of existing evidence and recommendations for future economic analyses in LD.

Practices of Lyme disease diagnosis and treatment by general practitioners in Quebec, 2008-2015

BACKGROUND

Lyme disease (LD), a multisystem infection caused by the spirochete Borrelia burgdorferi sensu stricto (B. burgdorferi), is the most reported vector-borne disease in North America, and by 2020, 80% of the population in central and eastern Canada could live in LD risk areas. Among the key factors for minimising the impact of LD are the accurate diagnosis and appropriate management of patients bitten by ticks. In this study, the practices of Quebec general practitioners (GPs) on LD diagnosis and management of patients bitten by infected ticks are described.

METHODS

Eight years (2008 to 2015) of retrospective demographic and clinical data on patients bitten by infected Ixodes scapularis (I. scapularis) ticks and on the management of suspected and confirmed LD cases by Quebec GPs were analysed.

RESULTS

Among 50 patients, all the antimicrobial treatments of LD clinical cases were appropriate according to current guidelines. However, more than half (62.8%) of erythema migrans (EM) were possibly misdiagnosed, 55.6%, (n = 27) of requested serologic tests were possibly unnecessary and the majority (96.5%, n = 57) of prophylactic antimicrobial treatments were not justified according to current guidelines.

CONCLUSIONS

These observations underline the importance for public health to enhance the knowledge of GPs where LD is emerging, to minimise the impact of the disease on patients and the financial burden on the health system.

Tick bite and Lyme disease-related emergency department encounters in New Hampshire, 2010-2014

Lyme disease (LD) is a common tick-borne disease in New Hampshire (NH). While LD is a reportable condition and cases are counted for public health surveillance, many more people receive care for tick bites or diagnoses of LD than are reflected in surveillance data. NH's emergency department (ED) data system was queried for tick bite and LD-related encounters. Chief complaint text was queried for words related to LD or tick bites. International Classification of Diseases 9th Revision (ICD-9) codes were queried for the LD diagnosis code (088.81). Emergency department patient data were matched to reportable disease data to determine the proportion of ED patients reported to the health department as a suspected LD case. Data were analysed to calculate frequencies for key demographic and reporting characteristics. From 2010 to 2014, 13,615 tick bite or LD-related ED encounters were identified in NH, with most due to tick bites (76%). Of 3,256 patients with a LD-related ED encounter, 738 (23%) were reported to the health department as a suspected LD case. The geographic distribution of ED patients was similar to reported LD cases; however, the regions of the state that experienced higher rates of ED encounters were different than the regions that observed higher rates of reported LD cases. Seasonal distribution of ED encounters peaked earlier than reported LD cases with a second peak in the fall. While age and sex distribution was similar among ED patients and reported LD cases, the rates for children 5 years and younger and adults 65 years and older were greater for ED encounters. Patients frequently visit the ED to seek care for tick bites and suspected LD. Results of ED data analyses can be used to target education, in particular for ED providers and the public through timely distribution of evidence-based educational materials and training programmes.

Lyme disease testing by large commercial laboratories in the United States

BACKGROUND

Laboratory testing is helpful when evaluating patients with suspected Lyme disease (LD). A 2-tiered antibody testing approach is recommended, but single-tier and nonvalidated tests are also used. We conducted a survey of large commercial laboratories in the United States to assess laboratory practices. We used these data to estimate the cost of testing and number of infections among patients from whom specimens were submitted.

METHODS

Large commercial laboratories were asked to report the type and volume of testing conducted nationwide in 2008, as well as the percentage of positive tests for 4 LD-endemic states. The total direct cost of testing was calculated for each test type. These data and test-specific performance parameters available in published literature were used to estimate the number of infections among source patients.

RESULTS

Seven participating laboratories performed approximately 3.4 million LD tests on approximately 2.4 million specimens nationwide at an estimated cost of $492 million. Two-tiered testing accounted for at least 62% of assays performed; alternative testing accounted for <3% of assays. The estimated frequency of infection among patients from whom specimens were submitted ranged from 10% to 18.5%. Applied to the total numbers of specimens, this yielded an estimated 240 000 to 444 000 infected source patients in 2008.

DISCUSSION

LD testing is common and costly, with most testing in accordance with diagnostic recommendations. These results highlight the importance of considering clinical and exposure history when interpreting laboratory results for diagnostic and surveillance purposes.

U.S. healthcare providers' experience with Lyme and other tick-borne diseases

Surveillance indicates that tick-borne diseases are a common problem in the United States. Nevertheless, little is known regarding the experience or management practices of healthcare providers who treat these conditions. The purpose of the present study was to characterize the frequency of tick-borne diseases in clinical practice and the knowledge of healthcare providers regarding their management. Four questions about tick-borne diseases were added to the 2009 Docstyles survey, a nationally representative survey of >2000 U.S. healthcare providers. Topics included diseases encountered, management of patients with early Lyme disease (LD), provision of tick-bite prophylaxis, and sources of information on tick-borne diseases. Overall, 51.3% of practitioners had treated at least one patient for a tick-borne illness in the previous year. Among these, 75.1% had treated one type of disease, 19.0% two types of disease, and 5.9% three or more diseases. LD was encountered by 936 (46.8%) providers; Rocky Mountain spotted fever was encountered by 184 (9.2%) providers. Given a scenario involving early LD, 89% of providers would prescribe antibiotics at the first visit, with or without ordering a blood test. Tick-bite prophylaxis was prescribed by 31.0% of all practitioners, including 41.1% in high-LD-incidence states and 26.0% in low-incidence states. Tick-borne diseases are encountered frequently in clinical practice. Most providers would treat early LD promptly, suggesting they are knowledgeable regarding the limitations of laboratory testing in this setting. Conversely, providers in low-LD-incidence states frequently prescribe tick-bite prophylaxis, suggesting a need for education to reduce potential misdiagnosis and overtreatment.

Choosing wisely: the American College of Rheumatology's Top 5 list of things physicians and patients should question

OBJECTIVE

We sought to develop a list of 5 tests, treatments, or services commonly used in rheumatology practice whose necessity or value should be questioned and discussed by physicians and patients.

METHODS

We used a multistage process combining consensus methodology and literature reviews to arrive at the American College of Rheumatology's (ACR) Top 5 list. Rheumatologists from diverse practice settings generated items using the Delphi method. Items with high content agreement and perceived high prevalence advanced to a survey of ACR members, who comprise >90% of the US rheumatology workforce. To increase the response rate, a nested random sample of 390 rheumatologists received more intensive survey followup. The samples were combined and weighting procedures were applied to ensure generalizability. Items with high ratings underwent literature review. Final items were then selected and formulated by the task force.

RESULTS

One hundred five unique items were proposed and narrowed down to 22 items during the Delphi rounds. A total of 1,052 rheumatologists (17% of those contacted) participated in the member-wide survey, whereas 33% of those in the nested random sample participated; respondent characteristics were similar in both samples. Based on survey results and available scientific evidence, 5 items (relating to antinuclear antibodies, Lyme disease, magnetic resonance imaging, bone absorptiometry, and biologic therapy for rheumatoid arthritis) were selected for inclusion.

CONCLUSION

The ACR Top 5 list is intended to promote discussions between physicians and patients about health care practices in rheumatology whose use should be questioned and to assist rheumatologists in providing high-value care.

Evaluating frequency, diagnostic quality, and cost of Lyme borreliosis testing in Germany: a retrospective model analysis

Background. Data on the economic impact of Lyme borreliosis (LB) on European health care systems is scarce. This project focused on the epidemiology and costs for laboratory testing in LB patients in Germany. Materials and Methods. We performed a sentinel analysis of epidemiological and medicoeconomic data for 2007 and 2008. Data was provided by a German statutory health insurance (DAK) company covering approx. 6.04 million members. In addition, the quality of diagnostic testing for LB in Germany was studied. Results. In 2007 and 2008, the incident diagnosis LB was coded on average for 15,742 out of 6.04 million insured members (0.26%). 20,986 EIAs and 12,558 immunoblots were ordered annually for these patients. For all insured members in the outpatient sector, a total of 174,820 EIAs and 52,280 immunoblots were reimbursed annually to health care providers (cost: 2,600,850€). For Germany, the overall expected cost is estimated at 51,215,105€. However, proficiency testing data questioned test quality and standardization of diagnostic assays used. Conclusion. Findings from this study suggest ongoing issues related to care for LB and may help to improve future LB disease management.

Utilization of serology for the diagnosis of suspected Lyme borreliosis in Denmark: survey of patients seen in general practice

Background

Serological testing for Lyme borreliosis (LB) is frequently requested by general practitioners for patients with a wide variety of symptoms.

Methods

A survey was performed in order to characterize test utilization and clinical features of patients investigated for serum antibodies to Borrelia burgdorferi sensu lato. During one calendar year a questionnaire was sent to the general practitioners who had ordered LB serology from patients in three Danish counties (population 1.5 million inhabitants). Testing was done with a commercial ELISA assay with purified flagella antigen from a Danish strain of B. afzelii.

Results

A total of 4,664 patients were tested. The IgM and IgG seropositivity rates were 9.2% and 3.3%, respectively. Questionnaires from 2,643 (57%) patients were available for analysis. Erythema migrans (EM) was suspected in 38% of patients, Lyme arthritis/disseminated disease in 23% and early neuroborreliosis in 13%. Age 0-15 years and suspected EM were significant predictors of IgM seropositivity, whereas suspected acrodermatitis was a predictor of IgG seropositivity. LB was suspected in 646 patients with arthritis, but only 2.3% were IgG seropositive. This is comparable to the level of seropositivity in the background population indicating that Lyme arthritis is a rare entity in Denmark, and the low pretest probability should alert general practitioners to the possibility of false positive LB serology. Significant predictors for treating the patient were a reported tick bite and suspected EM.

Conclusions

A detailed description of the utilization of serology for Lyme borreliosis with rates of seropositivity according to clinical symptoms is presented. Low rates of seropositivity in certain patient groups indicate a low pretest probability and there is a notable risk of false positive results. 38% of all patients tested were suspected of EM, although this is not a recommended indication due to a low sensitivity of serological testing.

[Lyme disease: basis for treatment strategy, primary preventive care and secondary preventive care]

Lyme disease is the most common tick borne disease and is caused by Borrelia burgdorferi sensu lato. Ticks of the genus Ixodes are the vectors that transmit the infection to host mammals in endemic foci. Ixodes is infected by Borrelia at larval stage when it feeds on infected mammals. Man is an occasional host. The infection risk is linked to interaction between human and the natural environment. Strategies for prevention are closely related to the enzootic cycle of the Ixodes tick. Environmental measures to reduced tick density or host mammals are expensive, need to be repeated annually and cannot be applied to large areas. The primary prevention could be reduced to personal preventive measures such as reducing the amount of exposed skin and frequent checking for ticks. The risk of Lyme disease transmission after a tick bite is relatively low, and remains under 4%. The transmission rate depends on the duration of feeding. A rapide tick removal with fine tweezers or preferably special forceps and disinfection of the bite site appear to be the best technique. The absence of scientific evidence, and the risk of adverse events does not lead to recommending antimicrobial prophylaxis. Follow-up and educating the patients on the disease, clinical manifestation, and later primary prevention should be undertaken.

Economic impact of Lyme disease

Since 1975, Lyme disease has become the most common vectorborne inflammatory disease in the United States.

To assess the economic impact of Lyme disease (LD), the most common vectorborne inflammatory disease in the United States, cost data were collected in 5 counties of the Maryland Eastern Shore from 1997 to 2000. Patients were divided into 5 diagnosis groups, clinically defined early-stage LD, clinically defined late-stage LD, suspected LD, tick bite, and other related complaints. From 1997 to 2000, the mean per patient direct medical cost of early-stage LD decreased from $1,609 to $464 (p<0.05), and the mean per patient direct medical cost of late-stage LD decreased from $4,240 to $1,380 (p<0.05). The expected median of all costs (direct medical cost, indirect medical cost, nonmedical cost, and productivity loss), aggregated across all diagnosis groups of patients, was ≈$281 per patient. These findings will help assess the economics of current and future prevention and control efforts.

PNEUMONIA | Atypical

‘Atypical pneumonia’ refers to a clinical syndrome associated with pneumonia (typically mild, nonlobar) and diverse upper respiratory tract and extrapulmonary manifestations. Clinical features overlap with bacterial pneumonia, and co-infection with both typical (e.g., Streptococcus pneumoniae or other bacteria) and atypical pathogens may occur. ‘Atypical’ pathogens include Mycoplasma pneumoniae, Chlamydia pneumoniae, and Legionella spp. In large epidemiological studies, Mycoplasma pneumoniae has been implicated in 2–18% of community-acquired pneumonias; Chlamydia pneumoniae, in 2–8%; Legionella sp., 1–4%. Atypical pathogens lack cell walls and are resistant to β-lactam antibiotics but are usually susceptible to tetracyclines, macrolides, ketolides, and fluoroquinolone antibiotics. In this article, we also review other unusual causes of pneumonia which are transmitted by insects or vectors (e.g., Rocky Mountain spotted fever, cat scratch fever, Q fever, ehrlichiosis, Lyme disease, and tularemia). These diverse organisms are not found on Gram stain, and diagnosis requires special culture techniques or serological assays. We review the salient clinical and laboratory features of these various disorders, and discuss diagnostic and therapeutic strategies.

Molecular methods for ehrlichiosis and Lyme disease

This article reviews molecular techniques that have been developed and are effective in the clinical laboratory for the emerging tick-borne infections, ehrlichiosis and Lyme disease.

Lyme borreliosis

Lyme borreliosis is a multi-organ infection caused by spirochetes of the Borrelia burgdorferi sensu lato group with its species B burgdorferi sensu stricto, Borrelia garinii, and Borrelia afzelii, which are transmitted by ticks of the species Ixodes. Laboratory testing of Lyme borreliosis includes culture, antibody detection using ELISA with whole extracts or recombinant chimeric borrelia proteins, immunoblot, and PCR with different levels of sensitivity and specificity for each test. Common skin manifestations of Lyme borreliosis include erythema migrans, lymphocytoma, and acrodermatitis chronica atrophicans. The last two conditions are usually caused by B garinii and B afzelii, respectively, which are seen more frequently in Europe than in America. Late extracutaneous manifestations of Lyme borreliosis are characterised by carditis, neuroborreliosis, and arthritis. We present evidence-based treatment recommendations for Lyme borreliosis and review the prevention of Lyme borreliosis, including the Lyme vaccines.

Lyme disease--what is the cost for Scotland?

This paper analyses likely Lyme disease costs incurred by patients tested in the authors' laboratory over an 18 month period, based on patient histories and test results relating to 2110 samples submitted from laboratories serving 59% of the Scottish population. Cost analysis takes account of the direct costs of consultation, laboratory tests, antibiotic treatment and management of any sequelae, as well as indirect costs of the loss of healthy time through illness. Standard costs for each element are derived from published information, and the proportions applied to each patient category are estimated from studies described elsewhere in the literature. Of the sample, 295 patients had evidence of early Lyme disease and 31 had late Lyme disease symptoms. Based on these figures, the total annual cost for Lyme disease, when projected to the whole of Scotland, is estimated to be significant at 331,000 Pounds (range 47,000-615,000 Pounds). The range is inevitably wide because it was not possible to document complete clinical and management histories on individual patients. In addition, some late Lyme disease sequelae will require management for more than 1 year, and costs are also identified that could justifiably be included for all the other patients who tested negative for Lyme disease. These data raise the question of whether there is sufficient focus on prevention and the best management of this disease.

Cost-effectiveness analysis of the Lyme disease vaccine

OBJECTIVE

A vaccine for Lyme disease was approved in 1998 for use in the US. Given the high cost of the vaccine, the low risk of Lyme disease in many areas, and the largely curable nature of the disease, the cost-effectiveness of the vaccine in various risk groups is uncertain. This study was undertaken to examine the cost-effectiveness of the Lyme disease vaccine and the factors that influence its cost-effectiveness.

METHODS

We constructed a Markov decision-analysis model to evaluate the clinical effectiveness and cost-effectiveness of the Lyme disease vaccine in populations at various levels of risk for the disease. The probabilities of clinical events and costs were estimated from reports in the literature. Sensitivity analyses assessed the impact of potential variations of parameters on model results.

RESULTS

At the average national incidence of Lyme disease (0.0067%), the incremental cost-effectiveness of vaccination was approximately $1,600,000 per case averted when a yearly booster was given for 10 years after the standard initial vaccination regimen of 3 inoculations at 0, 1, and 12 months. For populations with an annual Lyme disease incidence of 1% (the incidence in several well-defined geographical areas of the US), the incremental cost-effectiveness was approximately $9,900 per case averted. Disease incidence had to exceed 10% before vaccination with yearly boosters became both more effective and more cost saving than no vaccination.

CONCLUSION

The Lyme disease vaccine is cost-effective only for individuals who live in areas where Lyme disease is endemic and who are frequently exposed to ticks.

Erythema migrans

EM is the most common manifestation of early Lyme disease, occurring in a high percentage of cases. Because this phase of infection with B. burgdorferi offers an excellent opportunity to treat this potentially systemic infection, front-line physicians must be familiar with its diagnosis. Although much attention has been paid to the classic form--the target lesion or bull's eye--there are variations that are more common. These include uniform coloration, lesions with necrotic or vesicular centers, and lesions with shapes that are not circular or oval. These findings must be interpreted in epidemiologic context. Serologic testing at this phase of the illness should not be done. It is unnecessary and potentially misleading; false-positive and false-negative tests can occur. Diagnosis is clinical. Prompt initiation of appropriate antibiotic therapy for 3 weeks cures most patients at this early stage of the disease. Clinicians should be aware that 15% of patients may be coinfected with a second tick-borne pathogen, which could alter the usual clinical manifestations and the response to treatment.

Psychiatric presentations of non-HIV infectious diseases. Neurocysticercosis, Lyme disease, and pediatric autoimmune neuropsychiatric disorder associated with streptococcal infection

Infectious diseases can cause an array of symptoms, including psychiatric symptoms. Psychiatrists serving the medically ill need to be aware not only of classic infectious diseases (e.g., neurosyphilis and HIV), but also of less commonly discussed infectious diseases (e.g., NCC, PANDAS, and Lyme disease). These examples represent an internationally endemic disease (e.g., NCC), a probable immunogenetic disease (e.g., PANDAS), and a frequently overdiagnosed and overtreated disease (Lyme disease).

Prevention of tick-borne diseases

Ticks are a part of the landscape where humans live, work, and play. Because ticks carry a wide range of organisms that potentially can cause disease in humans, many studies have focused on ways to reduce risk of these diseases. Ticks have biologically complex interactions with microorganisms and with their vertebrate hosts, on whom they depend for blood meals and survival. To consider ways to reduce the burden of tick-borne diseases in humans, it is necessary to understand the biology and ecology of ticks and their interface with humans. In many areas, changes in land use, reforestation, and patterns of human settlements have led to more abundant tick populations, increasing rates of infections in ticks, and increasing contact with human populations. Warmer winter temperatures in temperate regions may extend the transmission season for some ticks and pathogens. Although much of the discussion in this article has focused on I. scapularis and the Lyme disease spirochete (because they have been studied extensively), other tick-pathogen pairs may differ in risk factors for infection and transmission dynamics. Interventions studied to reduce the burden of tick-borne diseases include changing the environment, controlling vertebrate hosts, killing ticks, altering the behavior of humans, treating tick bites, and trying to protect humans through immunologic means (vaccine). All of these approaches have limitations and drawbacks. From a public health perspective, a plan that employs multiple strategies may be most effective. This article has reviewed what is known about preventive interventions, including the vaccine.

Laboratory testing for suspected Lyme disease

Laboratory testing for B. burgdorferi infection is intended to substantiate a physician's clinical judgment of whether a patient has Lyme disease or not. Cultivation of B. burgdorferi from a patient's skin or blood is the gold standard for demonstration of active infection, but it is expensive and lacks clinical sensitivity. Detection of spirochetal DNA in clinical samples by PCR has better sensitivity, but PCR for B. burgdorferi has not yet been standardized for more routine diagnostic testing. Detection of antibodies to B. burgdorferi is the most practical and common approach for laboratory work-up of a case of suspected Lyme disease. Serologic assays fall short of 100% sensitivity and specificity, however, and examination of a single specimen in time does not discriminate between previous and ongoing infection. Because of a background false positivity even among healthy populations of nonendemic regions, serologic testing is recommended only when there is at least a one in five chance, in the physician's estimation, that the patient has active Lyme disease. The pretest likelihood of the disease is determined by the physician in the context of epidemiologic and clinical facts of the case. This estimate can serve to reassure patients who are at low risk of B. burgdorferi infection but are seeking a Lyme test for complaints of a more nonspecific nature. Although new subunit serologic assays based on recombinant proteins are becoming available commercially, the longstanding two-test approach, in which a positive or indeterminate result with a standardized, sensitive ELISA test is followed by verification with a more specific Western blot assay, still provides the physician with a reasonably accurate and reliable assessment of the presence of antibodies to B. burgdorferi. More recent challenges for serologic testing are seropositivity in the population as the result of immunization with the Lyme disease vaccine and the emergence of new Borrelia species that cause Lyme disease-like illnesses.

Management of tick bites and early Lyme disease: a survey of Connecticut physicians

Practice guidelines have been published for the treatment of Lyme disease (LD). These guidelines have been challenged as inadequate. Two common LD management problems are antibiotic prophylaxis of deer tick bites (deer ticks may carry Borrelia burgdorferi, the spirochete that causes LD) and antibiotic treatment of erythema migrans, the pathognomonic rash of LD. A 1-page questionnaire was sent to a 13% (573/4300) sample of Connecticut physicians to define how they treat deer tick bites and erythema migrans. Questionnaires were returned by 320 (56%) of 573 physicians. Questionnaires were analyzed for the 267 physicians who saw patients with LD. Seventy (26%) of the 267 surveyed physicians prescribed antibiotic prophylaxis for patients with tick bites. B burgdorferi serology was ordered by 31% of physicians for patients with tick bites. Most surveyed physicians treated erythema migrans with doxycycline or amoxicillin for a mean of 21 days. Serology was ordered by 49% of physicians for patients with erythema migrans. Most physicians did not use prophylaxis for patients with deer tick bites. In addition, most of the physicians surveyed followed established guidelines for treating patients with erythema migrans. However, many of the physicians surveyed do serologic testing for patients with tick bites and/or erythema migrans. Serologic testing for these patients is usually not necessary.

Manifestations of tick-borne illness. Incidence and variety are increasing worldwide

The incidence and variety of diseases associated with tick bites have continued to grow worldwide. Lyme disease, the most common tick-borne disease in the United States, has received extensive media coverage because of its protean manifestations and propensity for causing chronic disease. Our ability to prevent, identify, and effectively treat Lyme disease and other tick-borne diseases has significantly improved in the last decade. Tick-borne illnesses should be one of the differential diagnostic considerations in patients with consistent clinical findings and exposure history. In addition, the prudent use of laboratory testing ensures an accurate diagnosis while avoiding the cost and risk of inappropriate diagnostic tests and antibiotic therapy.

Tick bite and Lyme borreliosis risk at a recreational site in England

The risk of tick bite and Lyme borreliosis in a forested area in England with public access was studied over a two-year period. Tick infestation levels were high with more than 1000 members of the public reporting for tick removal at a local clinic. Most of the attached ticks were nymphs (82%) and distinct differences in anatomical sites of attachment were observed in children and adults. Children sustained nymphal bites to the head, neck and axilla region much more frequently than adults (48 vs. 10%), whereas adults were bitten on the lower legs more frequently than children (46 vs. 9%). The vegetation was heavily infested with ticks and high numbers were particularly associated with areas used by deer. The average density of nymphs collected from the vegetation was 14.1 per 10 m2 (range 5.1-43.6). Infection rates of these nymphs determined by PCR and indirect IFA ranged from 5.2-17.0%, and the genospecies Borrelia valaisiana and B. garinii were detected, suggesting that birds may be important reservoir hosts in this area. It is estimated that, at the level of tick challenge observed here, at least 50 persons per year may be bitten by infected ticks at this site. However, no cases of Lyme borreliosis have been reported through the clinic follow-up procedure, and sera from 19 forest workers were negative for antibody to B. burgdorferi sensu lato. Despite the high challenge from tick bites, this particular recreational forest site poses a low risk of infection to the general public, and prophylactic antibiotic treatment or serological testing following a bite is not justified.

Lyme disease

Lyme disease, which is caused by Borrelia burgdorferi and transmitted in the United States primarily by Ixodes scapularis (the deer tick), is the most common vector borne disease in the United States. Its most frequent manifestation, a characteristic, expanding annular rash (erythema migrans), sometimes accompanied by myalgia, arthralgia, and malaise, occurs in nearly 90% of persons with symptomatic infection. Other manifestations of Lyme disease include seventh cranial nerve palsy, aseptic meningitis, and arthritis. Extensive coverage in the press about the serious effects of Lyme disease has led to widespread anxiety about this illness that is far out of proportion to the actual morbidity that it causes. This problem is exacerbated by the frequent use of serological tests to eliminate the possible diagnosis of Lyme disease in persons with only nonspecific symptoms (such as arthralgia or fatigue) who have a very low probability that Lyme disease is the cause of their symptoms. Consequently, misdiagnosis is frequent and is the most common cause of failure of treatment. The prognosis for most persons with Lyme disease is excellent.

Lyme borreliosis

Lyme borreliosis is a worldwide, multistage, and multi-system disease caused by borrelia spirochetes, which are transmitted by ixodes ticks. It is focally endemic in temperature climates of the northern hemisphere. Primary erythema migrans occurs at the site of inoculation. Secondary erythema migrans occurs at sites of hematogenous dissemination. Variations in genospecies account for variations in presentation, including borrelial lymphocytoma. Disseminated disease includes constitutional signs and symptoms, intermittent oligoarticular arthritis, meningitis, cranial neuritis, radiculoneuropathy, encephalopathy, atrioventricular block, and myopericarditis. Late persistent disease includes acrodermatitis chronica atrophicans, chronic arthritis, neurological impairment, and fatigue. There can be difficulties with both clinical and laboratory diagnosis. First-line oral therapies for early uncomplicated disease are doxycycline and amoxicillin. First-line intravenous therapy for complicated or resistant disease is ceftriaxone. Prevention includes avoiding tick habitats, dressing sensibly, judicious use of repellants, and early removal of imbedded ticks. Vaccination is indicated only for frequent or prolonged exposure to tick-infested habitat.

Lyme disease

Lyme disease (LD) is the most common tick-borne disease in the United States. The overall trend has been an average annual increase in reported cases since surveillance was initiated by the Centers for Disease Control and Prevention in 1982. Ixodes ticks often carry more than one potential pathogen, and co-infection with Borrelia burgdorferi and other organisms has been reported. The impact of dual infection upon the clinical course of LD is not known. Further studies of erythema migrans-like rashes in the Southern United States have indicated that it is likely caused by a related spirochetal organism. Case reports of unusual presentations have broadened our understanding of the clinical spectrum of LD. Studies in patients with chronic Lyme arthritis have indicated that an autoimmune process may be responsible for such cases. Results of two large, placebo-controlled trials of a recombinant Lyme vaccine have been reported and results indicate that the vaccine is safe and effective in preventing LD in adults.

Tick-borne pulmonary disease: update on diagnosis and management

Ticks are capable of transmitting viruses, bacteria, protozoa, and rickettsiae to man. Several of these tick-borne pathogens can lead to pulmonary disease. Characteristic clinical features, such as erythema migrans in Lyme disease, or spotted rash in a spotted fever group disease, may serve as important diagnostic clues. Successful management of tick-borne diseases depends on a high index of suspicion and recognition of their clinical features. Patients at risk for tick bites may be coinfected with two or more tick-borne pathogens. A Lyme vaccine has recently become available for use in the United States. Disease prevention depends on the avoidance of tick bites. When patients present with respiratory symptoms and a history of a recent tick bite or a characteristic skin rash, a differential diagnosis of a tick-borne pulmonary disease should be considered. Early diagnosis and appropriate antibiotic therapy for these disorders lead to greatly improved outcomes.

The cost effectiveness of vaccinating against Lyme disease

To determine the cost effectiveness of vaccinating against Lyme disease, we used a decision tree to examine the impact on society of six key components. The main measure of outcome was the cost per case averted. Assuming a 0.80 probability of diagnosing and treating early Lyme disease, a 0.005 probability of contracting Lyme disease, and a vaccination cost of $50 per year, the mean cost of vaccination per case averted was $4,466. When we increased the probability of contracting Lyme disease to 0.03 and the cost of vaccination to $100 per year, the mean net savings per case averted was $3,377. Since few communities have average annual incidences of Lyme disease >0. 005, economic benefits will be greatest when vaccination is used on the basis of individual risk, specifically, in persons whose probability of contracting Lyme disease is >0.01.

Lyme disease update. Current approach to early, disseminated, and late disease

A rational approach to diagnosis and treatment of Lyme disease requires an understanding of the endemic range of the tick vectors for B burgdorferi, the epidemiologic risk factors, and the spectrum of clinical manifestations. A two-step approach to serologic testing (ELISA followed by Western blot analysis of positive or equivocal results) can be useful if the pretest likelihood of Lyme disease is higher than 20%. Consideration should be given to the possibility of (1) a noninfectious disease with clinical features similar to those of Lyme disease or (2) coinfection with a second tick-transmitted organism. Late Lyme disease must be distinguished by clinical characteristics from fibromyalgia (the commonest source of misdiagnosis in several studies). Antibiotic therapy should be tailored to the extent of disease and limited to 4 weeks in most cases. Human vaccines based on an outer-surface protein from B burgdorferi have been tested in large-scale US clinical trials and may soon be approved for use in persons whose occupational or recreational activities place them at risk for B burgdorferi exposure.