Lyme disease

Tick-Borne Bacterial, Rickettsial, Spirochetal, and Protozoal Infectious Diseases in the United States: A Comprehensive Review

Approximately 900 tick species exist worldwide, and they parasitize a variety of mammals, including humans; thus, ticks play a significant role in the transmission of infectious diseases. In the United States, tick-borne diseases are seasonally and geographically distributed; they typically occur during spring and summer but can occur throughout the year. Tick-borne diseases are endemic to a variety of geographic regions of the United States, depending on the species of tick commonly found in a specific locale. Specific tick-borne diseases are difficult to diagnose. Most patients have vague constitutional symptoms and nonspecific laboratory findings. Initially, serologic methods are of little benefit because they lack sensitivity early in the disease course. Therefore, a thorough history and physical examination are necessary for establishing a diagnosis. Antimicrobial regimens for tick-borne infections are poorly studied but well established. Tetracyclines and rifampin form the cornerstones of therapy for most tick-borne infections, but these agents may not be suitable for all patient populations. Therefore, no single agent can be chosen empirically to treat all tick-borne diseases. Because pharmacists are the most accessible health care providers, they are often asked how to treat tick-borne diseases. Thus, practitioners should be familiar with the ticks that inhabit their locale.

Progress and controversy surrounding vaccines against Lyme disease

Less than 20 years elapsed between the 1982 report of the identification and isolation of Borrelia burgdorferi and the licensure and marketing in the USA of a prophylactic vaccine against this pathogen. However, the manufacturer removed the vaccine from the market under 4 years after its release. The low demand undoubtedly was the result of limited efficacy, need for frequent boosters, the high price of the vaccine, exclusion of children, fear of vaccine-induced musculoskeletal symptoms and litigation surrounding the vaccine. Second-generation polyvalent outer surface protein (Osp)C vaccines may overcome some of these concerns but the precise antigenic components required for efficacy are uncertain. The development of the next generation of Lyme disease vaccines is in its infancy.

Lyme borreliosis: from infection to autoimmunity

Lyme borreliosis in humans is an inflammatory disease affecting multiple organ systems, including the nervous system, cardiovascular system, joints and muscles. The causative agent, the spirochaete Borrelia burgdorferi, is transmitted to the host by a tick bite. The pathogenesis of the disease in its early stages is associated largely with the presence of viable bacteria at the site of inflammation, whereas in the later stages of disease, autoimmune features seem to contribute significantly. In addition, it has been suggested that chronic persistence of B. burgdorferi in affected tissues is of pathogenic relevance. Long-term exposure of the host immune system to spirochaetes and/or borrelial compounds may induce chronic autoimmune disease. The study of bacterium-host interactions has revealed a variety of proinflammatory and also immunomodulatory-immunosuppressive features caused by the pathogen. Therapeutic strategies using antibiotics are generally successful, but chronic disease may require immunosuppressive treatment. Effective and safe vaccines using recombinant outer surface protein A have been developed, but have not been propagated because of fears that autoimmunity might be induced. Nevertheless, new insights into the modes of transmission of B. burgdorferi to the warm-blooded host have been generated by studying the action of these vaccines.

First culture isolation of Borrelia lonestari, putative agent of southern tick-associated rash illness

Southern tick-associated rash illness (STARI) is a Lyme disease-like infection described in patients in the southeastern and south-central United States, where classic Lyme disease is relatively rare. STARI develops following the bite of a lone star tick (Amblyomma americanum) and is thought to be caused by infection with an "uncultivable" spirochete tentatively named Borrelia lonestari. In this study, wild lone star ticks collected from an area where B. lonestari is endemic were cocultured in an established embryonic tick cell line (ISE6). The cultures were examined by dark-field microscopy for evidence of infection, and spirochete identity and morphology were evaluated by flagellin B and 16S rRNA gene sequence, by reaction to Borrelia-wide and B. burgdorferi-specific monoclonal antibodies, and by electron microscopy. Live spirochetes were first visualized in primary culture of A. americanum ticks by dark-field microscopy 14 days after the cell culture was inoculated. The sequences of the flagellin B and 16S rRNA genes of cultured spirochetes were consistent with previously reported sequences of B. lonestari. The cultured spirochetes reacted with a Borrelia-wide flagellin antibody, but did not react with an OspA antibody specific to B. burgdorferi, by indirect fluorescent antibody testing. Electron microscopy demonstrated organisms that were free and associated with ISE6 cells, with characteristic Borrelia sp. morphology. This study describes the first successful isolation of B. lonestari in culture, providing a much needed source of organisms for the development of diagnostic assays and forming a basis for future studies investigating the role of the organism as a human disease agent.

Acylated cholesteryl galactoside as a novel immunogenic motif in Borrelia burgdorferi sensu stricto

Borrelia burgdorferi sensu lato is the causing agent of Lyme disease, an infectious disease frequently occurring in the United States, Europe, and Northern Asia. Currently, diagnosis of and vaccination strategies against this pathogen are exclusively based on proteinaceous structures. Here we report on a novel class of immunogenic glycolipids purified from B. burgdorferi sensu stricto B31. Employing a butanol/water extraction procedure with subsequent Bligh/Dyer extraction of the organic phase, thin layer chromatography analysis revealed the presence of three distinct glycolipids, which were chemically analyzed employing combined gas-liquid chromatography/mass spectroscopy, matrix-assisted laser desorption/ionization mass spectrometry, and NMR. We identified acylated cholesteryl galactoside (ACG) next to cholesteryl galactoside and alpha-monogalactosyl-diacylglycerol. After extensive purification, the glycolipids investigated failed to cause proinflammatory responses in human cells transfected with human toll-like receptor (TLR)-2 or -4. However, we observed a marked recognition of ACG by sera derived from patients suffering from Lyme disease. These data indicate that newly described ACG is involved in developing host immunity during Lyme disease and thus may be useful for diagnosis and vaccination.

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.

Sudden deafness and Lyme disease

OBJECTIVES/HYPOTHESIS

Otolaryngological manifestations are common in Lyme disease, affecting up to 75% of patients. One of these symptoms is sudden deafness. Hearing loss has been frequently described in Lyme disease; on the other hand, titers seropositive for, the causal agent of this disease, have been found in almost 20% of cases of sudden deafness. No consensual information exists on the outcome of Borrelia-seropositive patients or on the importance of determining Borrelia antibody titers. The present study aimed to determine the prevalence of seropositivity for Borrelia in sudden deafness, describing clinical characteristics and outcomes.

STUDY DESIGN

This was a prospective observational study.

METHODS

Forty-seven consecutive patients with sudden deafness were enrolled in the study. Demographic data, the presence of tinnitus and vertigo, and low- and high-frequency pure-tone averages were recorded. The percentage of hearing recovery was determined. Data obtained from Borrelia-seropositive patients were described and compared with those from the seronegative group.

RESULTS

Titers positive for antibodies were present in 21.3% of the cases. Seropositive and seronegative groups of patients were homogeneous concerning age, sex distribution, the presence of tinnitus and vertigo, and high- and low-frequency hearing thresholds. Hearing outcome was not significantly different between the groups of patients.

CONCLUSIONS

No distinctive clinical characteristic was found between seropositive and seronegative subjects. The hearing outcome of treated Borrelia-seropositive patients was similar to that of the seronegative group.

Patterns of Lyme disease diagnosis and treatment by family physicians in a southeastern state

This study examined how often physicians in Georgia diagnose and treat Lyme disease as well as the criteria they use to reach a diagnosis of Lyme disease. A survey was sent to 1,331 family physicians in Georgia concerning how many cases of Lyme disease the physicians diagnosed, and the criteria used to make the diagnosis, during the preceding 12 months. Of 710 responses, 167 physicians treated 316 cases of Lyme disease without a firm diagnosis. In addition, 125 physicians diagnosed 262 cases of Lyme disease, 130 without serologic testing and 132 with serologic testing. Family Physicians in Georgia diagnose Lyme disease at a rate 40 times greater than the surveillance case rate reported in Georgia.

Lyme disease

Lyme disease is due to infection with a tick-borne spirochete, Borrelia burgdorferi. Risk for infection is confined to regions that contain the Ixodid tick vector. Characteristic skin, musculoskeletal, cardiac, ocular, and neurologic disorders are associated with the local, early dissemination and late stages of infection. Neurologic involvement can be seen at all stages, and involves both central and peripheral nervous system syndromes. The inability to easily culture B. burgdorferi and the lack of a reliable active infection assay have contributed to controversies in diagnosis and management. Because the vast majority of patients are seropositive, however, antibody testing is helpful to support the diagnosis of Lyme disease. With appropriate antibiotics, most patients do well. This infection provides an important model system to understand how interactions between an organism, vector, and host lead to disease. It also provides a model to study how infectious agents lead to neurologic disease.

Hyporesponsiveness to vaccination with Borrelia burgdorferi OspA in humans and in TLR1- and TLR2-deficient mice

The Lyme disease vaccine is based on the outer-surface lipoprotein (OspA) of the pathogen Borrelia burgdorferi, and 95% of vaccine recipients develop substantial titers of antibodies against OspA. Here, we identified seven individuals with very low antibody titers after vaccination (low responders). The macrophages of low responders produced less tumor necrosis factor-alpha and interleukin-6 after OspA stimulation and had lower cell-surface expression of Toll-like receptor (TLR) 1 as compared to normal cells, but normal expression of TLR2. TLRs activate innate responses to pathogens, and TLR2 recognizes lipoproteins and peptidoglycan (PGN). After OspA immunization, mice genetically deficient in either TLR2 (TLR2(-/-)) or TLR1 (TLR1(-/-)) produced low titers of antibodies against OspA. Notably, macrophages from TLR2(-/-) mice were unresponsive to OspA and PGN, whereas those from TLR1(-/-) mice responded normally to PGN but not to OspA. These data indicate that TLR1 and TLR2 are required for lipoprotein recognition and that defects in the TLR1/2 signaling pathway may account for human hyporesponsiveness to OspA vaccination.

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.

Neurologic aspects of Lyme disease

Lyme disease has emerged as a major infection with frequent neurologic manifestations. These manifestations probably reflect several predominantly indirect pathogenetic mechanisms and involve host, vector, and organism factors. With early diagnosis and appropriate antibiotic treatment, patients do well. Because culture is not reliable, diagnosis has relied on positive serology to document exposure. Serology should improve as second-generation assays become available. Although there is a preventive vaccine based on the lipoprotein OspA, newer vaccines in development may prove more desirable. Lyme disease provides a valuable model to study how infectious pathogens cause neurologic disease.

Erythema migrans after ceftriaxone treatment of aseptic meningitis caused by Borrelia burgdorferi

Erythema migrans is the characteristic exanthem of Lyme disease. The rash initially occurs at the site of inoculation; subsequently satellite lesions can occur. We describe an adolescent girl in whom the rash appeared after the initiation of ceftriaxone therapy for aseptic meningitis. We suggest that the occurrence of rash in this patient was a result of liberated toxin from local bacterial lysis.

Lyme disease and current aspects of immunization

Lyme disease is a tick-borne multisystem disease that affects primarily the skin, nervous system, heart and joints. At least three species of Borrelia burgdorferi sensu lato, namely Borrelia burgdorferi sensu stricto, Borrelia garinii, and Borrelia afzelii, can cause the disease. This review will focus mainly on the pathophysiology of Lyme arthritis, the long-term outcome of Lyme disease, and the recently licensed vaccine against Lyme disease.

Experimental induction of chronic borreliosis in adult dogs exposed to Borrelia burgdorferi-infected ticks and treated with dexamethasone

OBJECTIVE

To develop a method to experimentally induce Borrelia burgdorferi infection in young adult dogs.

ANIMALS

22 healthy Beagles.

PROCEDURE

All dogs were verified to be free of borreliosis. Twenty 6-month-old dogs were exposed to Borrelia burgdorferi-infected adult ticks and treated with dexamethasone for 5 consecutive days. Two dogs not exposed to ticks were treated with dexamethasone and served as negative-control dogs. Clinical signs, results of microbial culture and polymerase chain reaction (PCR) testing, immunologic responses, and gross and histologic lesions were evaluated 9 months after tick exposure.

RESULTS

Predominant clinical signs were episodic pyrexia and lameness in 12 of 20 dogs. Infection with B burgdorferi was detected in microbial cultures of skin biopsy specimens and various tissues obtained during necropsy in 19 of 20 dogs and in all 20 dogs by use of a PCR assay. All 20 exposed dogs seroconverted and developed chronic nonsuppurative arthritis. Three dogs also developed mild focal meningitis, 1 dog developed mild focal encephalitis, and 18 dogs developed perineuritis or rare neuritis. Control dogs were seronegative, had negative results for microbial culture and PCR testing, and did not develop lesions.

CONCLUSIONS AND CLINICAL RELEVANCE

Use of this technique successfully induced borreliosis in young dogs. Dogs with experimentally induced borreliosis may be useful in evaluating vaccines, chemotherapeutic agents, and the pathogenesis of borreliosis-induced arthritis.

Genomics-based identification of targets in pathogenic bacteria for potential therapeutic and diagnostic use

The availability of numerous complete microbial genome sequences has profoundly altered our understanding of a number of fundamental biological processes. For example the enzymes involved in aminoacyl-tRNA (AA-tRNA) synthesis, the key process responsible for the accuracy of protein synthesis, have been found to be highly species-specific. In particular, a number of pathogens contain certain pathways of AA-tRNA synthesis that are unrelated to those found in their mammalian hosts. Since AA-tRNA synthesis is indispensable for cell viability, the discovery of pathogen-specific pathways and enzymes presents novel therapeutic and diagnostic targets. Here we will review recent advances in the elucidation of AA-tRNA synthesis pathways and discuss the possible pharmaceutical exploitation of these discoveries. In particular, the integration of genomic and biochemical approaches to identify novel targets for the treatment of Chlamydial infections and the diagnosis and treatment of Lyme disease will be presented.