Tick-borne viral encephalitis in Finland. The clinical features of Kumlinge disease during 1959-1987

Immunological differentiation between tickborne encephalitis with and without concomitant neuroborreliosis

Cerebrospinal fluid lymphocyte subsets in patients with tickborne encephalitis (TBE) and in patients with TBE with concomitant neuroborreliosis (double infection) were analysed by flow cytometry. In the TBE group, higher percentages of CD4+DR+ T cells (p = 0.02) and CD25+ T cells (p = 0.0002) were observed, while in the group with double infection, higher percentages of CD19+ cells (p = 0.007), CD8+DR- T cells (p = 0.04), and CD3+CD71 + T cells (p = 0.0002) were found. It was concluded that several differences in immune cell parameters are present between the two groups of patients. Three variables (CD19+ cells, CD3+CD25+ T cells, CD3+CD71+ T cells) were included in the logistic regression model for calculation of probability for double infection. Flow cytometric characterisation of lymphocyte subsets in CSF can further substantiate the diagnosis of concomitant neuroborreliosis in patients with TBE.

Tick-bone encephalitis in Sweden in relation to aseptic meningo-encephalitis of other etiology: a prospective study of clinical course and outcome

A total of 149 patients with clinical symptoms of acute viral meningo-encephalitis were enrolled in this study from June 1991 to December 1993. Tick-borne encephalitis (TBE) was diagnosed in 85 of the 149 patients (males 54%, median age 42 years (range 15-78)). The initial clinical appearance of TBE was classified as mild (mainly meningeal; (n = 47), moderate (n = 31) or severe (n = 7), more or less encephalitic. The most common acute symptoms of encephalitis were ataxia (26%), altered consciousness (20%), decreased concentration or memory (9%), irritable response to light and sound (28%), tremor (9%) and dysphasia (9%). Spinal nerve paralysis (11%) occurred in all three clinical stages and did not correlate with the severity or duration of encephalitis. The duration of hospitalisation, the time on the sick-list and the time to recovery were significantly longer in TBE patients. All patients survived, but many patients with TBE suffered an extended period of neurological dysfunction. Of patients with TBE 80% (68/85) showed persisting symptoms of CNS dysfunction on follow-up at week 6, compared with 55% (35/64) of the patients with aseptic meningitis of other aetiology. The corresponding figures after 1 year were 40% (33/83) and 20% (13/64). One year after TBE 13 (28%) patients with initially mild, meningeal symptoms had decreased memory and decreased concentration capacity, dysphasia or ataxia. Spinal nerve paralysis persisted after 1 year in 5 of 9 patients with TBE. In conclusion, TBE in Sweden is associated with a significant morbidity and a post-TBE syndrome existed after 1 year in more than one third of the patients.

Flow cytometric analysis of lymphocytes in cerebrospinal fluid in patients with tick-borne encephalitis

INTRODUCTION

Cerebrospinal fluid (CSF) lymphocyte subsets were examined by flow cytometry in 33 patients with tick-borne encephalitis (TBE) in order to determine their values.

PATIENTS AND METHODS

Lymphocytes were isolated from CSF and lymphocyte subsets were determined: lymphocytes T (CD3+), lymphocytes B (CD19+), NK cells (CD3-CD56+), helper T cells (CD3+CD4+) and cytotoxic T cells (CD3+CD8+). The expression of IL-2 receptors (CD25+) and transferrin receptors (CD71+) on T cells and HLA-DR molecules on T cell subsets was examined. Furthermore, possible relationships among different TBE patient population variables (gender, age, severity of disease, duration of meningitis) were considered.

RESULTS

The analyses of the CSF lymphocyte population subsets are presented. Lymphocytes T (CD3+) were significantly higher in the CSF than in the peripheral blood as was the case with the T cells that expressed transferrin receptors (CD71). Lymphocytes B (CD19+) and NK cells (CD3-CD56+) prevailed in the peripheral blood. In the early course of the disease, a higher expression of HLA-DR molecules on T lymphocytes was observed, while later a higher expression of IL-2 receptors (CD25+) was observed.

DISCUSSION

Significant differences in lymphocyte subsets between the CSF and the peripheral blood were found. Significant time-dependent changes of CSF lymphocyte subsets during course of infection were observed. The results of the present study give us deeper insight into CNS cellular immunopathogenic mechanisms in patients with TBE.

Cognitive impairment after acute encephalitis: comparison of herpes simplex and other aetiologies

OBJECTIVE

To compare the cognitive defects after acute acyclovir treated herpes simplex encephalitis with those after other types of acute encephalitis.

METHODS

Seventy seven consecutive patients between 1985 and 1995 and 29 normal controls were studied. Of the 77 patients without concomitant neurological conditions, 17 had herpes simplex, one virus encephalitis (HSVE group), 27 had some other identified aetiology (non-HSVE group), and in 33 patients the cause was unknown. Acyclovir treatment was started less than four days after the first mental symptoms in 12 of 17 patients with HSVE. A thorough neuropsychological assessment was carried out about one month after the onset.

RESULTS

The HSVE group had deficits in verbal memory, verbal-semantic functions, and visuoperceptual functions more often than the non-HSVE group. The risk for cognitive defects was twofold to four-fold in the patients with HSVE compared with the non-HSVE patients. Two (12%) of the patients with HSVE and 12 (44%) of the non-HSVE patients were cognitively intact. Six patients with HSVE (46%) and 17 (89%) non-HSVE patients later returned to work. The lesions on CT or MRI were bilateral only in one patient with HSVE. The defects in the three patients with adenovirus infection were severe and resembled the amnesia after HSVE. Cognitive impairment, not previously reported, was found in encephalitis after rotavirus infection and epidemic nephropathy.

CONCLUSION

The recovery in the HSVE group was better than expected based on the medical literature. On the other hand there were surprisingly severe cognitive defects in encephalitis after other viruses. With early acyclovir treatment patients with the least severe HSVE were equivalent to those with non-HSV encephalitis with good outcome whereas those with the most severe non-HSV encephalitis were equivalent to those with HSVE with poor outcome.

Geographic correlation of multiple sclerosis with tick-borne diseases

An arboviral theory of multiple sclerosis (MS) is presented. Although high MS rates correlate with the distribution of certain population, high rates also correlate with the distribution of Ixodes genus tick viruses. These ticks and viruses are globally distributed by polar-migrating seabirds which are important food sources for island and coastal communities with high MS. Investigation of tick-borne viruses, especially those found in seabirds, in MS is warranted.

Herpes encephalitis is a disease of middle aged and elderly people: polymerase chain reaction for detection of herpes simplex virus in the CSF of 516 patients with encephalitis. The Study Group

OBJECTIVE

To assess the diagnostic potential of the polymerase chain reaction (PCR) in herpes simplex virus (HSV) encephalitis.

METHODS

Samples of CSF from 516 patients with encephalitis were studied for HSV-DNA by PCR.

RESULTS

Samples taken one to 29 days from the onset of symptoms from 38 patients (7.4%) were positive, 32 (6.2%) for HSV-1 and six (1.2%) for HSV-2. At follow up, eight of 28 patients studied were still HSV-PCR positive. A diagnostic serum:CSF antibody ratio to HSV but not to other viruses was detected in 25 of the 38 HSV-PCR positive patients thus supporting the initial PCR findings. Patients positive by HSV-PCR were concentrated in the age group > or = 40 years, and especially in patients aged 60-64 years, of whom nine of 24 (37.5%) were positive. The HSV-PCR was negative in all other patients with encephalitis of known or unknown aetiology. This group included 34 patients with a diagnostic serum:CSF antibody ratio to other viruses. A dual infection, HSV and another microbe, was considered possible in seven patients.

CONCLUSIONS

The HSV-PCR is a rapid and useful diagnostic method during the early phase of encephalitis. It may be useful in monitoring the efficacy of treatment and allowing the recognition of new features in the appearance of herpes encephalitis. The HSV-PCR test and antibody determinations from serum and CSF are complementary methods, which should both be applied in pursuit of clinical laboratory diagnosis of these conditions.

A 10-year follow-up study of tick-borne encephalitis in the Stockholm area and a review of the literature: need for a vaccination strategy

143 people treated for tick-borne encephalitis (TBE) were included in a retrospective follow-up study. Sequelae and epidemiological characteristics in 114 individuals were analysed. The case fatality rate and the prevalence of residual paresis were low, 1.4 and 2.7%, respectively. However, 40 (35.7%) individuals were found to have a postencephalitic syndrome after a median follow-up time of 47 months, and a majority (77.5%) of these were classified as moderate to severe. Various mental disorders, balance and co-ordination disorders and headache were the most frequently reported symptoms. Increasing age was correlated to a longer duration of hospital stay, longer convalescence and increased risk of permanent sequelae. Results from a neuropsychiatric questionnaire showed marked differences between the subjects with sequelae compared to controls. 57% had noticed a tick bite before admission, and 48% were aware of at least one person in their environment who previously had contracted TBE. 79% were permanent residents or visited endemic areas often and regularly. In conclusion, we have found that TBE in the Stockholm area has a low case fatality rate, but gives rise to a considerable number of different neurological and mental sequelae, which justifies vaccination of a defined risk population in endemic areas.

Thrombocytopenia, leukopenia and abnormal liver function tests in the initial phase of tick-borne encephalitis

One-hundred-seventy-five patients in whom bone marrow puncture had been performed at the Department of Infectious Diseases, University Medical Centre, Ljubljana, during the period from 1988 to 1992, were analysed in a retrospective study. In five out of these 175 patients, tick-borne encephalitis virus infection was confirmed by serological tests and in all of them bone marrow puncture was performed in the initial phase of the illness as part of diagnostic work-up in a patient with a febrile illness accompanied by leukopenia and thrombocytopenia. Bone marrow examination revealed minimal reactive changes or normal findings. In addition to leukopenia and thrombocytopenia, abnormal liver function tests were also found in four patients. All these patients later developed meningoencephalitis, i.e. they had clinically typical tick-borne encephalitis with biphasic course of the illness. In the initial phase of tick-borne encephalitis in addition to well-known leukopenia, thrombocytopenia and abnormal liver function tests may be found.

Lyme borreliosis in Lithuania

The first cases of Lyme borreliosis in Lithuania were diagnosed in 1987, since when the number of reported cases has varied between 50 and 300 per year. In 1988, 354 cases were found through active surveillance. During 1988-91, 3,820 Ixodes ricinus ticks were collected in Lithuania; 11% of adult and 1% of nymphal ticks were infected with borrelia as determined by dark-field microscopy. Infected ticks were found in 27/31 (87%) of the regions investigated. Two isolates of Borrelia were obtained by in vitro cultivation and were shown to be Borrelia burgdorferi according to their reactions with species-specific monoclonal antibodies. From a survey of 6,187 people we estimated that 2,811/100,000 of the Lithuanian population are bitten by ticks every year. The prevalence of antibodies to B. burgdorferi measured by indirect IFA in healthy people varied between 4% and 32%, depending upon occupation and exposure to ticks.

Antibody prevalence and clinical manifestations of Lyme borreliosis and tick-borne encephalitis in Swedish orienteers

Antibody prevalence and clinical manifestations of Lyme borreliosis (LB) and tick-borne encephalitis (TBE) were studied in 362 orienteers from the county of Stockholm during a large relay race in October 1990. From all participating orienteers, a blood sample was collected and a questionnaire completed. Antibody activity to Borrelia burgdorferi was measured using a sonicated whole spirochete antigen in an ELISA, and to TBE virus (TBEV) by ELISA and haemagglutination inhibition (HI) test. A past history of LB was reported by 6% of the orienteers and antibodies to B. burgdorferi were found in 9%. Antibody reactivity to B. burgdorferi was found in 1-2% of the sera from 3 different control groups comprising 502 persons living in non-endemic areas. The corresponding value was 9% in sera from a fourth control group consisting of 150 persons living in the city of Stockholm. A past history of TBE was reported by 1 orienteer (0.3%) and detectable antibodies to TBEV in non-immunized individuals were found in 1%. No antibody activity to TBEV could be detected in sera from the control individuals living in the 3 non-endemic areas, but in 5% of the controls from Stockholm. In this study, there was no indication that frequent or severe manifestations of LB or TBE are common among orienteers in Sweden.

Clinical manifestations and antibody prevalence of Lyme borreliosis and tick-borne encephalitis in Sweden: a study in five endemic areas close to Stockholm

Five populations, including 903 individuals living in 5 different areas close to Stockholm, were studied with regard to clinical manifestations and antibody prevalence of Lyme borreliosis (LB) and tick-borne encephalitis (TBE). The study areas involved 4 groups of islands in the Baltic Sea and 1 island in Lake Mälaren. Serum samples from each individual were tested for antibody activity to Borrelia burgdorferi using a sonicated whole spirochete antigen in an ELISA, and to TBE-virus (TBEV) by ELISA and haemagglutination inhibition. A history of LB was reported by 1-21% and antibodies to Borrelia burgdorferi were found in 7-29% of the participants from the various areas. An increasing seroprevalence with age was seen. In sera from 3 different control groups, including 502 individuals living in non-endemic areas, antibodies to Borrelia burgdorferi were detected in 1-2% and from 1 control group including 150 individuals living in the city of Stockholm, in 9%. A history of TBE was reported by 0-6% of the individuals and in non-immunized individuals seropositivity was seen in 4-22%, depending on the area investigated. No antibody activity to TBEV could be detected in sera from persons in the 3 control groups living in non-endemic areas, whereas 5% of the controls from Stockholm were found to be positive. The prevalence rates of antibodies to TBEV in persons vaccinated against TBE were 40%, 53% and 79% after 1, 2 and 3 injections, respectively.

Two-year survey of the incidence of Lyme borreliosis and tick-borne encephalitis in a high-risk population in Sweden

A survey was made over a two-year period (September 1987 to August 1989) of a population living in an area endemic for Lyme borreliosis and tick-borne encephalitis in Sweden. For each patient a blood sample was collected and a questionnaire completed annually. All sera were tested for an antibody response to Borrelia burgdorferi in an EIA using sonicated antigen and for an antibody response to the tick-borne encephalitis virus using an EIA and a haemagglutination inhibition test. Antibodies to Borrelia burgdorferi and tick-borne encephalitis virus were detected in 89 (25.7%) and 40 (11.6%) respectively of 346 samples collected in August 1987. In the first year of the study 14 of 303 subjects (4.6%) developed Lyme borreliosis and in the second year 9 of 277 subjects (3.2%). A significant increase in the antibody titre for Borrelia burgdorferi was seen in 14 of 303 (4.6%) subjects in the first year and 8 of 277 (2.9%) subjects in the second year. An earlier episode of Lyme borreliosis or an elevated antibody titre did not seem to protect against reinfection. One case of tick-borne encephalitis was seen each year. Seroconversion for tick-borne encephalitis virus was found in 3 of 258 (1.2%) subjects in the first year and 5 of 211 (2.4%) in the second year, excluding subjects who had undergone successful immunisation or had earlier been hospitalised for tick-borne encephalitis. The study thus demonstrated a high yearly incidence of tick-borne infections in a population at risk.

Prevalence of tick-borne encephalitis and Lyme borreliosis in a defined Swedish population

Sera from 346 individuals living on Lisö, an area south of Stockholm, endemic for tick-borne encephalitis (TBE) and Lyme borreliosis, were tested for antibody activity to TBE-virus (TBEV) and Borrelia burgdorferi, using a sonicate antigen, by haemagglutination-inhibition and ELISA, respectively. 10/346 (3%) individuals had a history of previous serologically confirmed TBE with encephalitic symptoms, and 33/346 (10%) had a history of previous erythema chronicum migrans (ECM). Four individuals (1%) had been treated for neuroborreliosis and another 4 (1%) for acrodermatitis chronica atrophicans (ACA). Antibodies to TBEV and B. burgdorferi were detected in 40/346 (12%) and 89/346 (26%) individuals, respectively. The seroprevalence of Lyme borreliosis increased with age, time spent on Lisö, and number of reported tick-bites. For TBE there was a correlation between seropositivity and time spent on Lisö only. In sera from 50 healthy blood-donors, living in a non-endemic area, no antibody activity to TBEV could be detected and only 1/50 (2%) had antibodies to borrelia. In sera from 150 age and sex matched control individuals, living in the city of Stockholm, antibody activity to TBEV and borrelia was found in 8/150 (5%) and 13/150 (9%), respectively.

Epidemiology of tick-borne encephalitis in Sweden 1956-1989: a study of 1116 cases

Tick-borne encephalitis (TBE) has occurred regularly in Sweden since it was first diagnosed in 1954. In Austria, where TBE is common, vaccination has been shown to reduce the incidence considerably. Since this vaccine is now available in Sweden we analysed 1116 cases of TBE from 1956 to October 1989 in order to define a strategy for vaccination. The cases were identified in the records from all infectious disease departments in Sweden complemented with data from the virological laboratories. All diagnoses were confirmed by a positive serological result. The analysis shows TBE to be concentrated to the archipelagos and coastline areas of the Baltic and the lake Mälar around Stockholm--about 85% of all cases came from the county of Stockholm. Conspicuous clustering occurred in some areas and the geographical distribution was remarkably constant over the time studied. As can be expected with a tick-borne infection, a strong seasonal variation was found, 85% of the cases occurring July to September. The age distribution showed the highest incidence from 20-70 years; there was a male majority in all age groups. Five patients died.

Incidence of tick-bite in man in Aland Islands: reference to the spread of Lyme borreliosis

The common tick Ixodes ricinus is a vector both for the virus of tick-borne viral encephalitis (Kumlinge disease, KD) and of Borrelia burgdorferi (Lyme borreliosis, LB). Bites of the tick are believed to be common in Aland, an island province of Finland in the Baltic Sea. KD has been seen there for many years, and cases of LB have been diagnosed lately. The purpose of this study was to find the incidence of tick-bite among the population with possible implications for the spread of LB. A questionnaire was sent to 561 persons greater than 8 years of age out of a total of 21,281 in order to record tick-bites and erythema chronicum migrans (ECM). The number of answers was 519 (92.5%). 441 persons (85%) had been bitten by ticks, 146 greater than 10 times. 14 probands had had ECM, 73 other rashes around the tick-bite. It is concluded that tick-bites are very common among the population, and thus conditions are favourable for the spread of any tick-borne infection such as LB. The number of patients with secondary or tertiary LB diagnosed in the area is presently 17. It is likely that there are many undetected cases in the area.