Connaissance et prévention des borrélioses par piqûres de tiques

INTRODUCTION

European borreliosis, known to the general public as 'Lyme disease' in analogy with the American form, which it differs from in many points, is endemic in the area of Alsace and is a public health problem. The level of knowledge and prevention of the population with regard to the disease has never been assessed in France.

MATERIAL AND METHODS

A survey was conducted in all the national health examination centers in Alsace using a self-applied questionnaire. The data collected concerned the socio-demographical characteristics, knowledge on the disease, history of tick bites, fear the disease creates, frequency of visits to the forest, prevention habits when visiting the forest and the attitude adopted in the case of a tick bite.

RESULTS

Out of the 600 persons included, 99 (16.5 p.cent) had been bitten by ticks once or more over the past year. The existence of Lyme's disease was known to 74 p.cent of the consultants, 63 p.cent claimed they were worried by the disease and 43 p.cent knew that the first manifestation is redness spreading over the skin. Twenty-seven percent wore trousers and long sleeves when visiting the forest and 19 p.cent inspected their body carefully on their return. The persons least well informed were also those who did little to protect themselves against tick bites. They often were under 30 years old, lived in urban settings and had few diplomas. Those who had frequent spare time in forest and those who had a history of tick bites were the best informed and protected themselves better. The fear of the disease was associated with better knowledge and more appropriate behaviour.

DISCUSSION

This study shows that a large percent of the population in Alsace is exposed to tick bites. Tick bite borreliosis is relatively well known, but protection remains insufficient. Better knowledge of the disease is related to better prevention. Information and teaching campaigns for the general public could specifically target the young people, urban dwellers and those with few diplomas. Specific messages of prevention could be delivered to the most exposed at-risk subjects (i.e. those bitten by ticks or having leisure in forest) at the places of their leisure or medical consultations.

OspB antibody prevents Borrelia burgdorferi colonization of Ixodes scapularis

Borrelia burgdorferi outer surface protein OspB is expressed by spirochetes in the Ixodes scapularis gut. ospB is transcribed from a bicistronic operon with ospA, a known spirochete adhesion gene in the tick gut. Here we examine whether OspB also has a specific function in ticks. OspB specifically binds to a protein or protein complex within the tick gut. We also assessed whether selected nonborreliacidal OspB antibodies or F(ab)(2) fragments interfere with B. burgdorferi-tick attachment in vivo. We examined engorged ticks that fed on B. burgdorferi N40-infected scid mice that had been treated with OspB F(ab)(2) fragments. Control F(ab)(2) fragments did not interfere with B. burgdorferi colonization of the tick gut, whereas OspB F(ab)(2) fragments significantly inhibited the attachment of spirochetes to the tick gut. These studies show that nonbactericidal OspB antibodies interfere with B. burgdorferi colonization of I. scapularis, highlighting a specific role for OspB in spirochete- arthropod interactions and suggesting new antibody-mediated strategies for interfering with B. burgdorferi transmission.

[Guideline 'Lyme borreliosis']

Borrelia burgdorferi is the causative bacterial agent of Lyme borreliosis, a tick-transmitted infectious disease. The Dutch Institute for Health Care Improvement (CBO) has now issued a guideline on 'Lyme borreliosis'. Lyme borreliosis is classified as 'early', 'early disseminated', 'late' or as 'post-infectious complaints and symptoms'. Erythema migrans is the most common manifestation of early Lyme borreliosis. Frequent neurological manifestations of 'early disseminated Lyme borreliosis' include meningoradiculitis, meningitis and peripheral facial palsy, but Lyme carditis and arthritis also occur. Late Lyme borreliosis is characterised by skin abnormalities (acrodermatitis chronica atrophicans), chronic neuroborreliosis or chronic arthritis. Confirmation serology with respect to Borrelia is the most commonly used laboratory technique, but in early Lyme borreliosis the immune response may be absent. In addition, the mere presence of antibodies in the serum is no proof of an active infection with Borrelia and serology may yield false-positive reactions. Doxycycline and ceftriaxone are the most commonly used antibiotics in the various stages of Lyme borreliosis. Lyme borreliosis may be prevented by avoiding high-risk areas, keeping the skin covered as much as possible, and inspection of the skin after possible exposure to remove ticks within 24 hours. Laboratory tests after a tick bite are not recommended, nor is prophylactic treatment with antibiotics.

[Doubling of the number of cases of tick bites and lyme borreliosis seen by general practitioners in the Netherlands]

OBJECTIVE

To obtain detailed information about the current geographical distribution and incidence of tick bites and Lyme borreliosis in the Netherlands and to identify regional differences in the ecological risk factors that might be involved.

DESIGN

Retrospective questionnaire study.

SETTING

All Dutch general practitioner's (GP) practices.

METHODS

In April 2002, all GPs in the Netherlands were asked to complete a short questionnaire on the number of cases of tick bites and erythema migrans seen in 2001 and the size of their practice. Associations with possible risk factors were determined at the municipal level. Results were compared with the results of a similar study done in 1995.

RESULTS

The response of the GPs was 64.5% (4730/7330). Together, all GPs reported seeing approximately 61,000 patients in 2001 with tick bites and 12,000 patients with erythema migrans. The incidence of erythema migrans was estimated at 73 per 100,000 inhabitants. There were obvious risk areas. At the municipal level, tick bites and erythema migrans were positively associated with the area covered by forest, sandy soil, the number of roe deer and tourism. There was a negative association with the degree of urbanisation. Increases in tourism in areas with many ticks, new forests in urban regions and an increased number of horses were positively associated with the increase in tick bites and erythema migrans since 1994.

CONCLUSION

The number of patients with tick bites and erythema migrans seen by GPs in the Netherlands had doubled between 1994 and 2001. This increase may be attributed partly to changes in ecological risk factors and human behaviour. The number of cases of Lyme borreliosis may be reduced by giving prophylactic information annually about ticks and ways to remove them, plus additional education of patients about the recognition of erythema migrans.

The Lyme Wars: time to listen

Lyme disease represents a public health threat of major proportions. The murky science and acrimonious politics of Lyme disease have created barriers to reliable diagnosis and effective treatment of this protean illness. Two major clinical problems with the disease are the absence of a therapeutic end point in treating Borrelia burgdorferi, the spirochetal agent of Lyme disease, and the presence of tick-borne co-infections, such as babesiosis, anaplasmosis and bartonellosis, that may complicate the course of the illness. From a pathophysiological standpoint, the affinity of B. burgdorferi for multiple cell types and the presence of non-replicating forms of the spirochete have contributed to persistent infection and failure of simple antibiotic regimens. Newer approaches to the treatment of Lyme disease should take into account its clinical complexity in co-infected patients and the possible need for prolonged combination therapy in patients with persistent symptoms of this potentially debilitating illness. The risk and prevention of human transmission of Lyme disease merit further study.

Lyme borreliosis (Lyme disease): molecular and cellular pathobiology and prospects for prevention, diagnosis and treatment

Lyme borreliosis is a systemic infection caused by the spirochaete Borrelia burgdorferi, which is transmitted by tick bites and maintained in a delicately balanced ecological cycle. Recent increases in the population densities of tick hosts, the abundance of ticks and the proximity of man to natural tick habitats have led to an escalating worldwide incidence of Lyme borreliosis, and nonspecific clinical manifestations have yielded significant misunderstanding of the disease. After entry, B. burgdorferi activates local inflammation, yet evades host defences and facilitates dissemination by potentially masquerading with host components such as plasmin and complement. The extent of tissue injury is determined by the aggressiveness of host inflammation and immunological reactions, as well as by genetic attributes of the spirochaete. The clinical presentation can be highly varied, including early manifestations that are limited to erythema migrans and ranging to disseminated infection with arthritis, carditis, cranial nerve palsy, peripheral neuropathy, meningitis, or other manifestations. Diagnostic tests have improved, but are unhelpful during certain stages of infection. Therapy varies depending on the degree of involvement, and recovery is usually rapid and complete. Post-treatment clinical manifestations in the absence of evidence for active infection are still poorly understood. The understanding of how B. burgdorferi survives in the environment and interacts with human and mammalian hosts has improved. However, further advances in prevention and therapy depend on continued investigation of the ecological risks and improved understanding of the pathobiology of this obligate bacterial parasite.

An effective second-generation outer surface protein A-derived Lyme vaccine that eliminates a potentially autoreactive T cell epitope

The antigenic component of a common Lyme disease vaccine is recombinant outer surface protein A (rOspA) of Borrelia burgdorferi (Bb), the causative agent of Lyme disease. Coincidentally, patients with chronic, treatment-resistant Lyme arthritis develop an immune response against OspA, whereas those with acute Lyme disease usually do not. Treatment-resistant Lyme arthritis occurs in a subset of Lyme arthritis patients and is linked to HLA.DRB1*0401 (DR4) and related alleles. Recent work from our laboratory identified T cell crossreactivity between epitopes of OspA and lymphocyte function-associated antigen 1alpha(L) chain (LFA-1alpha(L)) in these patients. We generated a form of rOspA, FTK-OspA, in which the LFA-1alpha(L)/rOspA crossreactive T cell epitope was mutated to reduce the possible risk of autoimmunity in genetically susceptible individuals. FTK-OspA did not stimulate human or mouse DR4-restricted, WT-OspA-specific T cells, whereas it did stimulate antibody responses specific for WT-OspA that were similar to mice vaccinated WT-OspA. We show here that the protective efficacy of FTK-OspA is indistinguishable from that of WT-OspA in vaccination trials, as both C3H/HeJ and BALB/c FTK-OspA-vaccinated mice were protected from Bb infection. These data demonstrate that this rOspA-derived vaccine lacking the predicted cross-reactive T cell epitope, but retaining the capacity to elicit antibodies against infection, is effective in generating protective immunity.

Risk perceptions regarding ticks and Lyme disease: a national survey

BACKGROUND

Lyme disease (LD) is caused by the tickborne bacterium Borrelia burgdorferi and, in 2000, accounted for >90% of all reported cases of vectorborne illness in the United States. Aside from anecdotal and indirect evidence, little empirical evidence exists regarding what the U.S. public knows, says, or does about preventing LD.

OBJECTIVES

To examine knowledge, perceptions, and practices regarding prevention of tick bites and LD.

METHODS

In 1998, a random-digit-dial frame was used to collect a cross-sectional sample (n =1500) from the 48 coterminous states plus the District of Columbia, and an over-sample (n =250) from six states with the highest incidence of LD.

RESULTS

Forty percent of respondents reported doing something to avoid being bitten by ticks. Less than half (41%) used insect repellent. Ninety-two percent of those who had heard about LD stated their likelihood of ever getting the disease was </=50 on a 100-point scale (mean=29; standard deviation, 23.5). Being somewhat to very concerned about being bitten by ticks was strongly associated with taking preventive measures (odds ratio, 8.34; 95% confidence interval, 6.29-11.06).

CONCLUSIONS

Having seen ticks, being concerned about being bitten, perceiving insect repellent to be effective, having heard about LD, and knowing someone who had LD are the factors most predictive of specific tick-bite preventive behaviors (p <0.001). However, greater efforts are needed in promoting the effectiveness and safety of DEET-containing insect repellents.

A nonproliferating parvovirus vaccine vector elicits sustained, protective humoral immunity following a single intravenous or intranasal inoculation

An ideal vaccine delivery system would elicit persistent protection following a single administration, preferably by a noninvasive route, and be safe even in the face of immunosuppression, either inherited or acquired, of the recipient. We have exploited the unique life cycle of the autonomous parvoviruses to develop a nonproliferating vaccine platform that appears to both induce priming and continually boost a protective immune response following a single inoculation. A crippled parvovirus vector was constructed, based on a chimera between minute virus of mice (MVM) and LuIII, which expresses Borrelia burgdorferi outer surface protein A (OspA) instead of its coat protein. The vector was packaged into an MVM lymphotropic capsid and inoculated into naive C3H/HeNcr mice. Vaccination with a single vector dose, either intravenously or intranasally, elicited high-titer anti-OspA-specific antibody that provided protection from live spirochete challenge and was sustained over the lifetime of the animal. Both humoral and cell-mediated Th(1) immunity was induced, as shown by anti-OspA immunoglobulin G2a antibody and preferential gamma interferon production by OspA-specific CD4(+) T cells.

Immunogenicity of Borrelia burgdorferi arthritis-related protein

Immunization against arthritis-related protein (Arp) elicits antibody in mice that resolves arthritis but is not protective against challenge with Borrelia burgdorferi. In mice immunized against Arp, an unrelated 37-kDa protein (P37-42), outer surface protein A (OspA), or glutathione S-transferase (GT) and then challenged by syringe or tick, only OspA conferred protection. Passive transfer of Arp antiserum into infected SCID mice induced arthritis resolution, but antisera to P37-42, OspA, GT, or six overlapping Arp peptide fragments did not. Results suggest that the arthritis-resolving immunogenicity is specific to Arp, but the relevant epitopes may be conformational.

Factors Influencing the Utilization of Lyme Disease-Prevention Behaviors in a High-Risk Population

PURPOSE

To evaluate factors motivating high-risk individuals to implement Lyme disease-prevention behaviors.

DATA SOURCES

Patients presenting to the Lyme Disease Diagnostic Center in New York State completed a voluntary, anonymous questionnaire.

CONCLUSIONS

Of the 219 persons completing the questionnaire, participants who reported having had Lyme disease in the past were significantly more likely to use preventive behaviors than those without a history of Lyme disease (p = .01). Additionally, persons who reported having a family member or close friend with Lyme disease were more likely to use preventive behaviors than those without such a relationship (p = .02). Increasing age was associated with increased use of preventive behaviors only for participants without a history of Lyme disease (p = .04).

IMPLICATIONS FOR PRACTICE

These findings provide information that may be important in developing community prevention programs for Lyme disease. Younger persons without a history of Lyme disease should be targeted for programs that will educate them about Lyme disease.

[Biology of Ixodes ricinus (L.) and its pathogens in Wrocław area]

Within 2001-2003, a total of 4743 ticks of Ixodes ricinus were trapped from the forest area in Masyw Sliy (Lower Silesia, Poland) near Wrocław. Common distribution of ixodid ticks in all examined habitats, located near touristic routes, are potential loci of Lyme borreliosis in these recreational areas. Out of 1108 tick samples examined by the observation in DFM for the presence of spirochetes, 6.7% were positive. The highest percent of infected ticks (13.1%) was found in 2003.

Lyme borreliosis

Lyme borreliosis is the most common tick-transmitted disease in the northern hemisphere and is caused by spirochaetes of the Borrelia burgdorferi species complex. A complete presentation of the disease is an extremely unusual observation in which a skin lesion results from a tick bite and is followed by heart and nervous system involvement, and later on by arthritis. Late involvement of eye, nervous system, joints, and skin can also occur. The only sign that enables a reliable clinical diagnosis of Lyme borreliosis is erythema migrans. Other features of some diagnostic value are earlobe lymphocytoma, meningoradiculoneuritis (Garin-Bujadoux-Bannwarth syndrome), and acrodermatitis chronica atrophicans. The many other symptoms and signs have little diagnostic value. Microbial or serological confirmation of borrelial infection is needed for all manifestations of the disease except for typical early skin lesions. However, even erythema migrans might not be pathognomonic for Lyme borreliosis, especially in the southern part of the USA where there is no microbiological evidence for infection with the agent. Treatment with antibiotics is beneficial for all stages of Lyme borreliosis, but is most successful early in the course of the illness. Prevention relies mainly on avoiding exposure to tick bites but there is some interest in chemoprophylaxis and also in vaccine development following initial disappointments.

Diagnosis, treatment, and prevention of Lyme disease in children

The approaches to diagnosing and treating Lyme disease (LD) have been improved and refined as a result of basic and clinical research, and considerable practical experience. In addition, there have been recent studies that have allowed improvements in the ability to prevent infection with Borrelia burgdorferi. This paper will review the relevant literature and address recent developments in the diagnosis, treatment, and prevention of LD. Issues specifically related to the management of children will be identified. Controversies regarding treatment approaches will be examined in some detail. Understanding the clinical manifestations, or stage, of LD is crucial when approaching both diagnosis and treatment. Early localized disease is best diagnosed by recognizing the characteristic skin lesion, erythema migrans. Early disease will frequently, but not always, be accompanied by a detectable antibody response, particularly IgM antibody to the spirochete. Late disease, chiefly arthritis, is generally associated with high levels of IgG antibody. Western blot technology allows confirmation of enzyme immunoassay results and is especially useful when the latter is in the low or equivocal range. Early localized disease responds well to oral antibacterial therapy. Early disseminated disease, often associated with neurologic findings, may require parenteral therapy. The arthritis associated with LD frequently responds to oral antibacterials, but some refractory cases may require intravenous therapy, and occasionally surgery. Doxycycline is the oral antibacterial of choice, while amoxicillin and cefuroxime axetil are alternatives that may be preferred in young children. Owing to its long half-life and once daily dose administration, intravenous ceftriaxone has become the accepted standard for parenteral therapy. Tick avoidance has long been the mainstay for preventing LD. Antibacterial prophylaxis, using doxycycline, for tick bites has been shown to be an effective approach to prevention, but its relevance to pediatrics is uncertain. Vaccines designed to prevent infection have also been developed.

Evaluation of Venezuelan Equine Encephalitis (VEE) replicon-based Outer surface protein A (OspA) vaccines in a tick challenge mouse model of Lyme disease

Venezuelan Equine Encephalitis (VEE) virus replicon particles (VRPs) encoding Borrelia burgdorferi Outer surface protein A (OspA) were evaluated for their ability to induce an immune response and provide protection from tick-borne spirochetes. VRPs expressing ospA that accumulated intracellularly (VRP OspA) or that was secreted from host cells (VRP tPA-OspA) were tested. Both VRP OspA and VRP tPA-OspA expressed ospA in immunized mice. Mice vaccinated with VRPs expressing secreted OspA produced significant amounts of anti-OspA antibodies, whereas VRPs expressing intracellular OspA were less immunogenic. The VRP method of delivery induced a Th1 type immune response unlike the recombinant OspA protein in Freund's adjuvant, which induced a mixed (Th1 and Th2) immune response. The VRP tPA-OspA construct induced an immune response that reduced the bacterial load in feeding Ixodes scapularis and blocked transmission to the host. These results indicate that VRPs are capable of providing protection against tick-borne B. burgdorferi, and potentially can be used for developing improved vaccines against Lyme disease.

A DNA vaccine encoding the outer surface protein C from Borrelia burgdorferi is able to induce protective immune responses

The outer surface protein C (OspC) of Borrelia burgdorferi, the spirochete that causes Lyme disease, is a promising candidate for a vaccine against borreliosis. BALB/c and C3H/HeJ mice were immunized either with recombinant OspC protein or with plasmid DNA encoding OspC fused to the human tissue plasminogen activator leader sequence (pCMV-TPA/ZS7). The influence of the route of administering the DNA and the use of oligodeoxynucleotides containing CpG-motifs on the development of the immune response was investigated. In both mouse strains, protein as well as gene-gun immunization induced Th2 type responses, whereas needle injection of plasmid DNA resulted in Th1 type antibody production. Co-injection of CpG-motifs did not significantly modify the response type in any immunization group, as indicated by only marginal changes of antibody subclass distribution. The protection rate after challenge with 10(4) B. burgdorferi organisms per mouse was between 80% and 100% for all groups. These results demonstrate, for the first time, that a DNA vaccine encoding OspC of B. burgdorferi is suitable for inducing protection against Lyme borreliosis.

Asymptomatic infection with Borrelia burgdorferi

The natural history of asymptomatic seroconversion to Borrelia burgdorferi has been unclear. We report here, on the basis of a post hoc assessment, the frequency and outcome of asymptomatic seroconversion to B. burgdorferi in participants of a large Lyme disease vaccine trial. We show that infection with B. burgdorferi may be asymptomatic but that asymptomatic infection is unusual in the United States.