Seroprevalence of ehrlichiosis, Lyme borreliosis and tick-borne encephalitis infections in children and young adults in Slovenia

BACKGROUND: Little is known about the seroprevalence of ehrlichiosis in adults and much less about the same in children. METHODS: One hundred and forty-three healthy children and young adults (6-24 years of age, male to female ratio, 1:1) were assessed for the presence of antibodies to the agents of human granulocytic ehrlichiosis (HGE), human monocytic ehrlichiosis (HME), Borrelia burgdorferi sensu stricto (BB), and tick-borne encephalitis (TBE) virus in Slovenia, where tick-related infections are endemic. Antibodies to HGE and HME agents were assayed by indirect immunofluorescence, and antibodies to BB and TBE by enzyme-linked immunosorbent assay. A questionnaire about tick exposure was answered by all subjects. In the event of a positive result, a detailed interview was conducted. RESULTS: Of 143 study subjects, 22 (15.4%) had detectable antibodies to HGE agent, 22 (15.4%) were positive to BB, 18 (12.6%) were positive to TBE virus (12 of these were vaccinated) and 4 (2.8%) were positive to the HME agent. The history of persons seropositive to an HGE agent had been uneventful. CONCLUSIONS: Our study documents a high seroprevalence of HGE in children and young adults in Slovenia, similar to the seroprevalence of LB and higher than that of TBE and HME. Although the majority of these infections are probably asymptomatic or mild, active surveillance for acute HGE infections in children in areas endemic for tick-related infections is necessary.     

Tick-borne encephalitis

Tick-borne encephalitis (TBE) is viral zoonosis transmitted by the infected ticks harboring TBE virus. Mortality rate reaches 30% of in some cases. More than 10,000 patients were reported annually in Europe and Far-East Asia. In 1993, the first case of TBE was reported in Japan, and TBE virus was isolated, which showed TBE virus is endemic in Japan.     

Diffuse reversible alopecia in patients with Lyme meningitis and tick-borne encephalitis

Alopecia occurring after febrile bacterial and viral infection is a phenomenon well known since the beginning of the century. To evaluate the occurrence of alopecia in tick transmitted disease, 23 adult patients with Lyme meningitis and 71 patients with tick-borne encephalitis were included in a prospective study and were followed up for one year. Diffuse alopecia occurred within three months after the outbreak of disease in 3 out of 23 (13%) patients with Lyme meningitis and in 40 out of 71 (56.3%) patients with tick-borne encephalitis. The mean duration of alopecia was 2 to 3 months and alopecia was reversible in all patients.     

Prevention of Lyme borreliosis

Lyme borreliosis, the most common tick-borne disease in both North America and Europe, is acquired through the bite of certain tick species in the genus Ixodes. The number of Ixodes ticks in the environment can be reduced by relatively simple interventions such as removing leaf litter and brush, which increases exposure of the tick to sun and air and takes advantage of the tick's vulnerability to desiccation, or by application of acaricides to property. Deer elimination or exclusion, application of topical acaricides to mice or deer, and application of systemic acaricides to deer are more complex approaches. However, none of these methods for reducing tick numbers, nor any of the recommended personal prevention measures, such as reducing the amount of exposed skin, use of tick repellents on exposed skin or clothing, and frequent tick checks to remove attached ticks expeditiously, has been demonstrated to decrease significantly the incidence of Lyme borreliosis in humans. Only two strategies have been shown to do so. A recombinant outer surface protein A (OspA) vaccine was approximately 80% effective in clinical trials in the United States, and a single 200 mg dose of doxycycline given within 72 hours of an I. scapularis tick bite, was shown to be 87% effective. The OspA vaccine is no longer manufactured due to poor sales. Consequently, single-dose doxycycline prophylaxis is rapidly gaining acceptance in the United States. Limiting single-dose doxycycline to just the highest risk tick bites can be accomplished if the health care provider has learned to differentiate engorged from unengorged I. scapularis ticks. Limitations of single-dose doxycycline prophylaxis are that the majority of patients with Lyme borreliosis do not recall a tick bite, and that there is no evidence that other Ixodes transmitted infections, such as human granulocytic ehrlichiosis, would be prevented. A safe, effective, inexpensive and well-accepted vaccine would be welcome.     

Lyme disease: a confusing multisystem borreliosis

Lyme disease, a tick-borne infection caused by the spirochete Borrelia burgdorferi, involves many organ systems. Three clinical stages of involvement have been described; patients with the disease may have cutaneous, arthritic, neurologic, or cardiac symptoms, or a constellation of manifestations. Specific antibody testing and antibiotic agents are available for Lyme disease, but a high index of suspicion must be exercised to recognize atypical manifestations.     

Tick-borne diseases

Tick-borne diseases are the most common vector-borne illnesses in the United States. Lyme disease is the most common, but several others also occur. The ehrlichioses have only been identified as agents of human disease in the United States in the past few decades, and knowledge about them is still evolving. Rocky Mountain spotted fever is relatively common and can be severe, especially in children, if the diagnosis is not made quickly. Tularemia has long been known to cause disease in humans, but there is renewed interest because of its potential as a biologic warfare agent. These diseases can be severe or even fatal. Most of them are easily treatable when identified early. These diseases result from a variety of infectious agents including bacteria, rickettsia, viruses and protozoa, or they may be caused by substances produced by the tick. Most of these diseases present initially with nonspecific symptoms and are often difficult to recognize. Few definitive diagnostic tests are available. Therefore, knowledge of the epidemiology and common presentations, as well as the diagnostic options and treatments available, are important issues for family physicians.     

Risk assessment in Lyme borreliosis

A 3-year EU-funded project (EUCALB), initially involving 14 countries and more than 30 scientists and physicians, was undertaken with the main objective of identifying practical risk assessment criteria for Lyme borreliosis. A major part of the project was dedicated to the improvement of data quality. European case definitions were formulated and quality assurance schemes were developed for serological diagnosis and the detection of infection in ticks. Studies on the standardisation of immunoblot interpretation criteria are still in progress. Data on the clinical risk from tick bites were obtained and considerable progress was made in elucidating the complex ecology of the disease. A study on habitat assessment throughout Europe concluded that high risk was associated with highly heterogeneous recreational woodland and case data from both high and low incidence countries suggested that most infections were acquired in recreational areas. Considerable work is still required to relate clinical data to the epidemiology and ecology of the disease in order to assess risk in Lyme borreliosis.     

Lyme borreliosis and multiple sclerosis

There is now general consensus that tertiary Lyme borreliosis affecting the central nervous system does exist. Clinical, neuropathologic, laboratory and epidemiologic features indicate clearly that tertiary Lyme borreliosis of the CNS is a distinct entity and there is no etiologic association with multiple sclerosis.     

Tick-borne diseases

Tick-borne diseases have their peak incidence in the spring and summer. The different infections caused by tick vectors have certain geographic locations and unique clinical presentations. The most common tick-transmitted infection is Lyme disease. Early diagnosis of tick-borne disease is essential so that effective and, in some cases, lifesaving antibiotic therapy can be instituted. Preventive measures are simple.     

Tick-borne diseases

Ticks may transmit a variety of human pathogens and are second in importance only to the mosquito as a vector of human disease. The majority of tick-borne diseases are nonspecific in their initial clinical and laboratory presentation and may be confused with a variety of more common illnesses. A history of tick exposure is frequently not available. Although specific serologic tests exist for confirming the diagnosis of many of these diseases, the time required for confirmation of results makes them of little use in the acute situation. Recognition of the epidemiology of tick-borne pathogens and clinical suspicion are of key importance in making the appropriate diagnosis. Early and specific therapy is a principal factor in reducing the morbidity and mortality associated with these diseases.     

Multiple sclerosis and Lyme borreliosis

In a deductive approach the two disease entities of multiple sclerosis and chronic progressive neuroborreliosis are discussed. Various clinical features, seroepidemiology, neuroimaging, CSF findings, CSF serology, specific proteins within the CSF and antibodies against neuronal structures as well as the most recent findings of different dendritic cells within the CSF are discussed as a means of differentiating these two disease entities.     

Vaccination against Lyme borreliosis.

Lyme borreliosis is a worldwide family of tick-borne infections caused by the spirochete Borrelia burgdorferi sensu lato. It is the most common tick-borne human infection in the Western world. There are several subgroups of the spirochete. Two monovalent vaccines against this infection have been presented in the USA, both of which use the borrelial outer surface protein A (OspA) as antigen. The first of these vaccines has been released for general use. A European polyvalent vaccine using the antigen OspC is undergoing clinical trial in the Aland Islands in Finland. Lately, another antigen group, decorin-binding proteins (Dbp), has been considered for immunization purposes. A European vaccine must be effective against several subgroups of the borrelia spirochete, and this complicates the situation compared with that in the USA, where one spirochete subspecies dominates the scene.     

Antibiotic treatment of Lyme borreliosis

Unlike most bacterial infections, where diagnosis is by identification of the causal organism, diagnosis of infection by Borrelia burgdorferi (Lyme's borreliosis) relies mostly upon indirect techniques. This situation has some short-comings. As long as no technology permits a microbiological diagnosis of this infection, controversy will exist as to the clinical symptoms and the criteria for the cure of the disease. Despite the lack of consensus upon both the clinical definition and the treatment of Lyme's borreliosis, it is widely agreed that the affection is best understood if regarded as a progressive general infectious disease. Indeed, following a bite with local infection, there occurs a fairly rapid dissemination of the spirochaetes. In vivo therapeutic trials have shown the potential effectiveness of beta-lactams and tetracyclines, but no treatment is considered universally effective. Most of the first trials were empirical, as antibiograms were not used. Antibiotic concentrations reached with some oral therapies are too low for the protection of certain sites such as the central nervous system. In vitro studies conducted on various strains of B. burgdorferi both in the US and in Europe are very enlightening. Among the more perplexing results of some of these studies, it is worth noting the high resistance rate of some B. burgdorferi strains to penicillin, reported by Johnson et al. and by Preac Mursic et al. Therapy for Lyme's borreliosis is discussed in light of both the in vivo and in vitro studies.     

Late stage Lyme borreliosis in children

These cases illustrate that late stage Lyme borreliosis can occur in children without a history of tick bite or ECM; this disorder can manifest itself initially as a seventh cranial nerve palsy, heart block, or arthritis, and the arthritis syndrome can mimic oligoarticular juvenile rheumatoid arthritis. The diagnosis of Lyme borreliosis depends upon clinical recognition. In the absence of ECM, tests for antibodies to Borrelia burgdorferi can provide an invaluable tool in assisting in the diagnosis. Children who live in or visit areas endemic for Lyme borreliosis and who have arthritis, heart block, or neurologic disorders such as facial palsy should be tested for antibodies to Borrelia burgdorferi if no other cause for the disease syndrome is identified clinically.     

Lyme borreliosis and peripheral facial palsy

From 1994 to 1996, 114 consecutive patients older than 15 years who presented at the Department of Infectious Diseases, University Medical Centre, Ljubljana, fulfilled the criteria for inclusion into this study on the borrelial aetiology of peripheral facial palsy (PFP). The study was restricted to patients without a conceivable explanation for their PFP, erythema migrans or history of erythema migrans, clinical signs/symptoms of frank meningitis or any other neurological manifestation in addition to PFP. In 22 (19.3%) of these 114 patients borrelial infection was confirmed by one of the following: in 3 (13.6%) by the isolation of Borrelia burgdorferi sensu lato from cerebrospinal fluid (CSF), in 11 (50%) by the presence of intrathecal antibody production, and in 8 (36.4%) by seroconversion to borrelial antigens. Additional 20 (17.5%) patients interpreted as having had a probable borrelial infection, had positive (> or = 1:256) IFA IgM and/or IgG borrelial serum antibody titres, and in 9 (7.9%) patients borderline borrelial antibody titres (1:128) were found (interpreted as a possible infection). In 63 (55.3%) patients the serological tests remained negative. Lymphocytic pleocytosis was found at the first visit in 12/22 (54.5%) patients with confirmed borrelial infection, in 3/20 (15%) with probable infection, in 1/9 (11.1%) with possible infection, and in 10/63 (15.9%) patients with symptoms of unknown aetiology. Patients with confirmed borrelial infection had abnormal CSF findings significantly more often than did patients with symptoms of unknown aetiology (p = 0.0139 for lymphocytic pleocytosis and/or elevated CSF protein levels, and p = 0.0010 for lymphocytic pleocytosis). Local and systemic signs/-symptoms were also more common in patients with confirmed borrelial infection than in those with an symptoms of unknown aetiology (p = 0.0258). In Slovenia which is a highly endemic region for Lyme borreliosis, borrelial infection is a frequent cause of PFP in adult patients. PFP may occur early in the course of LB, prior to measurable antibody response, indicating the need for serologic follow-up. Abnormal CSF results and the presence of additional local and/or systemic symptoms are factors indicating a higher possibility of borrelial aetiology of PFP and should alert physicians to suspect LB.     

Epidemiology and diagnosis of Lyme borreliosis

The multisystem disease Lyme borreliosis is the most frequent tick-transmitted disease in the northern hemisphere. In Europe Lyme borreliosis is most frequent in Central Europe and Scandinavia (up to 155 cases per 100,000 individuals) and is caused by the species, B. burgdorferi sensu stricto, B. afzelii and B. garinii. The recently detected genospecies A14S may also play a role in skin manifestations. Microbiological diagnosis in European patients must consider the heterogeneity of borreliae for development of diagnostic tools. According to guidelines of the USA and Germany, serological diagnosis should follow the principle of a two-step procedure (enzyme-linked immunosorbent assay (ELISA) as first step, if reactive; followed by immunoblot). The sensitivity and standardization of immunoblots has been considerably enhanced by use of recombinant antigens (p100, p58, p41i, VlsE, OspC, DbpA) including those expressed primarily in vivo (VlsE and DbpA) instead of whole cell lysates. VlsE is the most sensitive antigen for IgG antibody detection, OspC for IgM antibody detection. At present, detection rates for serum antibodies are 20%-50% in stage I, 70%-90% in stage II, and nearly 100% in stage III Lyme disease. Detection of the etiological agent by culture or polymerase chain reaction (PCR) should be confined to specific indications and specialized laboratories. Recommended specimens are skin biopsy specimens, cerebrospinal fluid (CSF) and synovial fluid. The best results are obtained from skin biopsies with culture or PCR (50%-70%) and synovial tissue or fluid (50%-70% with PCR). CSF yields positive results in only 10%-30% of patients except when the duration of symptoms is shorter than 2 weeks (50% sensitivity). Methods which are not recommended or adequately documented for diagnosis are antigen tests on body fluids, PCR of urine, and lymphocyte transformation tests.