There are about 1500 cases of Lyme borreliosis (LB) registered annually in Lithuania, the average morbidity rate was 34/100 000 in 1991-2006. The high incidence of LB determines the high attention to the epidemiological situation. The analysis of the diseases patterns and causative factors is needed for management of the situation, development of disease preventive strategies, improving the diagnostics, providing recommendations and etc. The aim of the study is to assess epidemiological patterns of LB and the main factors (natural-climatic and social) leading to them in Lithuania 1995-2006. In this study LB incidence trends and risk factors are evaluated, correlation of various risk factors with LB incidence and abundance of ticks are assessed, the prevalence of tick bites and risk factors among the population are determined. This study has evaluated the possible ecological significance of newly formed biotope‘s to the LB spread. After molecular tests the prevalence and genotypes of Borrelia in Ixodes ricinus nymphs collected from different biotopes was determined. This study succeeded to detect until now not detected in Lithuania Borrelia miyamotoi belonging to relapsing fever group. The study results showed that nymps’ infectivity in Lithuania is 14.8%. The climatic (air temperature and snow cover) risk factors are the most important ones influencing the LB. LB natural habitat has the property to expand at the expense of areas where the incidence rate was previously low. / Lietuvoje kasmet registruojama apie 1500 susirgimų Laimo borelioze (LB), 1991-2006 m. vidutinis sergamumo rodiklis buvo 34/100 000 gyventojų. Aukštas sergamumo LB lygis sąlygoja didelį dėmesį šios ligos epidemiologinei situacijai. Jos dėsningumų ir priežastinių veiksnių analizė reikalinga situacijos valdymui, planuojant ir rengiant prevencines strategijas, gerinant diagnostiką, teikiant rekomendacijas visuomenei ir kt. Šio darbo tikslas – įvertinti LB epidemiologinius dėsningumus ir juos sąlygojančius svarbiausius veiksnius (gamtinius-klimatinius ir socialinius) Lietuvoje 1995–2006 m. Darbe išnagrinėti ir aprašyti LB sergamumo dėsningumai, įvertintos sergamumo tendencijos, atlikta LB rizikos veiksnių analizė ir nustatytos sąsajos su LB sergamumu ir erkių gausa, nustatytas erkių įkandimų ir rizikos veiksnių paplitimas tarp Lietuvos gyventojų. Šiame darbe įvertinta naujai susiformavusių biotopų galima ekologinė reikšmė LB plitimui, atlikus molekulinius tyrimus, nustatytas borelijų paplitimas ir genotipai Ixodes ricinus nimfose, surinktose skirtinguose biotopuose bei išaiškinta nauja, iki šiol Lietuvoje neaptikta grįžtamosios karštinės borelijų grupei priklausanti Borrelia miyamotoi. Šio darbo rezultatai parodė, kad nimfų infekuotumas Lietuvoje yra 14,8 proc.; svarbiausi sergamumą LB sąlygojantys rizikos veiksniai yra klimatiniai (vidutinė oro temperatūra bei sniego danga); LB gamtinis arealas turi savybę plėstis teritorijų, kuriuose sergamumas anksčiau buvo žemas, sąskaita.

Lietuvoje kasmet registruojama apie 1500 susirgimų Laimo borelioze (LB), 1991-2006 m. vidutinis sergamumo rodiklis buvo 34/100 000 gyventojų. Aukštas sergamumo LB lygis sąlygoja didelį dėmesį šios ligos epidemiologinei situacijai. Jos dėsningumų ir priežastinių veiksnių analizė reikalinga situacijos valdymui, planuojant ir rengiant prevencines strategijas, gerinant diagnostiką, teikiant rekomendacijas visuomenei ir kt. Šio darbo tikslas – įvertinti LB epidemiologinius dėsningumus ir juos sąlygojančius svarbiausius veiksnius (gamtinius-klimatinius ir socialinius) Lietuvoje 1995–2006 m. Darbe išnagrinėti ir aprašyti LB sergamumo dėsningumai, įvertintos sergamumo tendencijos, atlikta LB rizikos veiksnių analizė ir nustatytos sąsajos su LB sergamumu ir erkių gausa, nustatytas erkių įkandimų ir rizikos veiksnių paplitimas tarp Lietuvos gyventojų. Šiame darbe įvertinta naujai susiformavusių biotopų galima ekologinė reikšmė LB plitimui, atlikus molekulinius tyrimus, nustatytas borelijų paplitimas ir genotipai Ixodes ricinus nimfose, surinktose skirtinguose biotopuose bei išaiškinta nauja, iki šiol Lietuvoje neaptikta grįžtamosios karštinės borelijų grupei priklausanti Borrelia miyamotoi. Šio darbo rezultatai parodė, kad nimfų infekuotumas Lietuvoje yra 14,8 proc.; svarbiausi sergamumą LB sąlygojantys rizikos veiksniai yra klimatiniai (vidutinė oro temperatūra bei sniego danga); LB gamtinis arealas turi savybę plėstis teritorijų, kuriuose sergamumas anksčiau buvo žemas, sąskaita. / There are about 1500 cases of Lyme borreliosis (LB) registered annually in Lithuania, the average morbidity rate was 34/100 000 in 1991-2006. The high incidence of LB determines the high attention to the epidemiological situation. The analysis of the diseases patterns and causative factors is needed for management of the situation, development of disease preventive strategies, improving the diagnostics, providing recommendations and etc. The aim of the study is to assess epidemiological patterns of LB and the main factors (natural-climatic and social) leading to them in Lithuania 1995-2006. In this study LB incidence trends and risk factors are evaluated, correlation of various risk factors with LB incidence and abundance of ticks are assessed, the prevalence of tick bites and risk factors among the population are determined. This study has evaluated the possible ecological significance of newly formed biotope‘s to the LB spread. After molecular tests the prevalence and genotypes of Borrelia in Ixodes ricinus nymphs collected from different biotopes was determined. This study succeeded to detect until now not detected in Lithuania Borrelia miyamotoi belonging to relapsing fever group. The study results showed that nymps’ infectivity in Lithuania is 14.8%. The climatic (air temperature and snow cover) risk factors are the most important ones influencing the LB. LB natural habitat has the property to expand at the expense of areas where the incidence rate was previously low.

Lyme borreliosis (LB) is the most common vector-borne disease in the Northern Hemisphere. The infection is caused by spirochetes belonging to the Borrelia burgdorferi sensu lato complex, and it is transmitted to humans by ticks. LB is associated with several clinical manifestations, of which erythema migrans (EM) and neuroborreliosis (NB) are the most common inEurope. The course of the disease is usually benign, but can vary between individuals. The underlying pathogenic mechanisms are not fully understood, but the prognosis is probably determined by a complex interplay between the bacteria and the host’s immune response. Previous studies have indicated that a strong initial T helper (Th) 1-response followed by a Th2 response is beneficial for the clinical outcome in LB. The aims of this thesis were to follow the incidence of NB inJönköping County,Sweden, over time, to search for clinical and laboratory markers associated with the risk of developing long-lasting post-treatment symptoms, and to explore the role of the complement system as well as the relative balance between Th-associated cytokine/chemokine responses in LB. The number of NB cases, diagnosed by cerebrospinal fluid (CSF) analysis, increased from 5 to 10/100,000 inhabitants/year in Jönköping County during 2000-2005. Post-treatment symptoms persisting more than 6 months occurred in 13 %, and were associated with higher age, longer-lasting symptoms prior to treatment, higher levels of Borrelia-specific IgG in CSF, and reported symptoms of radiculitis. Facial palsy, headache and fever were frequent manifestations in children, whereas unspecific muscle and joint pain were the most commonly reported symptoms in older patients. Complement activation occurred both locally in the skin in EM and in CSF of NB patients. However, no activation could be detected in blood in NB patients. Elevated levels of C1q, C4 and C3a in CSF, along with correlation between C1q and C3a levels, suggest complement activation via the classical pathway locally in the central nervous system in NB. In vitro experiments with two clinical Borrelia isolates revealed that B. garinii LU59 induced higher complement activation in human plasma compared to B. afzelii K78 that recruited more of complement regulator factor H. To elucidate the role of complement in the phagocytosis process, experiments were performed using whole blood from healthy donors incubated with fluorescence-labelled spirochetes and different complement inhibitors. The results illustrated a central role of complement for phagocytosis of Borrelia spirochetes. We also studied the relative contribution of different Th-associated cytokines/chemokine responses in NB. The results support the notion that early NB is dominated by a Th1 response, eventually accompanied by a Th2 response. IL-17A was increased in CSF in half of the patients with confirmed NB, suggesting a hitherto unknown role of Th17 in NB. In conclusion, the risk of developing long-lasting post-treatment symptoms tend to increase mainly with age and duration of symptoms prior to treatment in NB. The complement system seems to play an important role in host defence to recognize and kill Borrelia spirochetes. However, complement activation in inappropriate sites or to an excessive degree may cause tissue damage, and therefore, the role of complement in relation to disease course needs to be studied further. Likewise, the role of Th17 in LB pathogenesis and host defence should be further evaluated in prospective studies.

Contexte La maladie de Lyme (ML), une zoonose transmise par une tique, est en émergence au Canada. Elle est à déclaration obligatoire au Québec depuis novembre 2003. Récemment, des cas ont été diagnostiqués chez des personnes n'ayant pas voyagé à l'extérieur de la province. La description complète des cas déclarés n'a pas été faite. L'objectif de cette étude est de décrire l'incidence, les manifestations cliniques et les facteurs de risque de la ML au Québec chez les cas signalés du 1er janvier 2004 au 31 décembre 2010. Méthode Une copie des dossiers de tous les cas signalés a été obtenue des DSP. Une grille standardisée a été utilisée pour la collecte des données. Les dossiers ont été classés selon la définition nosologique de 2010 (cas confirmé ou probable) à laquelle on a ajouté la catégorie "cas possible". Résultats Parmi les 108 cas signalés, 88 ont été retenus. Lors du reclassement, 40 dossiers ont changé de catégorie dont 23 cas considérés à l'origine comme non retenus. Parmi les 23 cas acquis au Québec, il y 3 cas confirmés, 11 probables et 9 possibles. Le nombre annuel de cas augmente progressivement, l'incidence passant de 0,01 à 0,28/100 000 entre 2004 et 2008. Les cas ont entre 2 et 86 ans (médiane de 43); 8 % ont moins de 10 ans et 58 % sont de sexe masculin. Un érythème migrant (EM), une arthrite ou une paralysie faciale ont été retrouvés chez 78 %, 20 % et 13 % des cas respectivement. L'EM est associé au sexe féminin (89 % vs 69 %, p=0,03). Les cas avec une paralysie faciale sont plus souvent hospitalisés (45 % vs 13 %, p<0,01). Seulement 34 % des cas ont été déclarés par un médecin, même si 98 % d'entre eux ont passé une sérologie pour la ML. Une activité en plein air, un séjour dans une zone endémique ou une piqûre de tique ont été rapportés par 87 %, 76 % et 31 % des cas respectivement. Discussion Le nombre de cas de ML augmente lentement au Québec. Le sud-ouest du Québec est à risque dû à la proximité géographique des zones endémiques. Les médecins n'ont déclaré qu'un tiers des cas et il y a une divergence entre la classification des DSP et celle de l'étude. Les caractéristiques cliniques des cas québécois sont similaires à celles observées aux États-Unis et en Allemagne, sauf pour la proportion de cas chez les enfants qui est plus faible qu'ailleurs.

<p>This thesis examines seasonal, diel and vertical distribution patterns of activity of host-seeking <i>Ixodes ricinus</i> (L.) ticks at three localities in south-central Sweden. In addition, by examining the prevalence of infection in ticks with Lyme borreliosis (LB) spirochetes, <i>Borrelia burgdorferi</i> s.l, information for estimating relative LB risk in humans and the effect of control measures directed against this tick vector is provided.</p><p>The seasonal activity pattern of <i>I. ricinus</i> was, in general, bimodal with peaks of activity in May-June and August-September. Tick densities were generally high at Torö and low at Kungshamn-Morga. The greatest variation in tick density occurred at the sample site level, which indicated a patchy distribution of ticks. The diel activity of adult <i>I. ricinus</i> sampled at Bogesund showed a distinct nocturnal activity peak while nymphal ticks exhibited no particular diel variation. At the meadow site, there was a strong negative association between activity of each tick stage and ambient air temperature, and larval ticks also showed a nocturnal activity peak. <i>I. ricinus</i> of all stages were present in the vegetation up to at least 140 cm above ground level. At Torö, host-seeking larvae were found at significantly lower levels (below 20 cm) in the vegetation compared to nymphs and adults (50-59 and 60-79 cm, respectively). Vegetation structure is likely to be the main factor governing tick vertical distribution at this locality. The northern limit of the geographical distribution of <i>I. ricinus</i> in Sweden corresponds with the southern boundary of the taiga zone, as well as with several other climatic or vegetational isoclines primarily associated with the vegetation period.</p><p>The prevalence rates of <i>Borrelia</i> spirochetes, recorded by phase-contrast microscopy in host-seeking <i>I. ricinus</i>, were 0% in larvae, 5.8-13.1% in nymphs and 14.5-28.6% in adult ticks. The human LB risk, estimated by the number of <i>Borrelia</i>-infected nymphs per hectare, was greater at Torö than at Kungshamn-Morga and greater in woodland than in open areas. The risk also possessed a bimodal seasonal pattern similar to that of subadult host-seeking activity. Controlling the number of infected nymphs through de-ticking of reservoir hosts seems not to be an effective control measure in Sweden due to the ubiquitous availability of alternative reservoir hosts.</p>

This thesis examines seasonal, diel and vertical distribution patterns of activity of host-seeking Ixodes ricinus (L.) ticks at three localities in south-central Sweden. In addition, by examining the prevalence of infection in ticks with Lyme borreliosis (LB) spirochetes, Borrelia burgdorferi s.l, information for estimating relative LB risk in humans and the effect of control measures directed against this tick vector is provided. The seasonal activity pattern of I. ricinus was, in general, bimodal with peaks of activity in May-June and August-September. Tick densities were generally high at Torö and low at Kungshamn-Morga. The greatest variation in tick density occurred at the sample site level, which indicated a patchy distribution of ticks. The diel activity of adult I. ricinus sampled at Bogesund showed a distinct nocturnal activity peak while nymphal ticks exhibited no particular diel variation. At the meadow site, there was a strong negative association between activity of each tick stage and ambient air temperature, and larval ticks also showed a nocturnal activity peak. I. ricinus of all stages were present in the vegetation up to at least 140 cm above ground level. At Torö, host-seeking larvae were found at significantly lower levels (below 20 cm) in the vegetation compared to nymphs and adults (50-59 and 60-79 cm, respectively). Vegetation structure is likely to be the main factor governing tick vertical distribution at this locality. The northern limit of the geographical distribution of I. ricinus in Sweden corresponds with the southern boundary of the taiga zone, as well as with several other climatic or vegetational isoclines primarily associated with the vegetation period. The prevalence rates of Borrelia spirochetes, recorded by phase-contrast microscopy in host-seeking I. ricinus, were 0% in larvae, 5.8-13.1% in nymphs and 14.5-28.6% in adult ticks. The human LB risk, estimated by the number of Borrelia-infected nymphs per hectare, was greater at Torö than at Kungshamn-Morga and greater in woodland than in open areas. The risk also possessed a bimodal seasonal pattern similar to that of subadult host-seeking activity. Controlling the number of infected nymphs through de-ticking of reservoir hosts seems not to be an effective control measure in Sweden due to the ubiquitous availability of alternative reservoir hosts.

Medicinsk entomologi

The present study aimed detection of a human pathogen B. bugdorferi sensu lato species in suspected Lyme borreliosis (LB) patients in Turkey by PCR analysis and supportive serologic tests. The 152 clinical samples (140 serum and blood, 10 cerebrospinal fluid (CSF), 1 synovial fluid, 1 skin biopsy specimens) from 140 patients sent from 22 different cities of Turkey to The Spirochetal Diseases Diagnosis Laboratory of Central Veterinary Control and Research Institute were analysed. Serum samples were subjected to ELISA with a commercial kit and all of the blood, CSF, synovial fluid and skin biopsy samples were examined by PCR. In PCR analysis two primer sets targeting the ospA gene located on the plasmid and ribosomal 23S rRNA gene of B. burgdorferi sensu lato were used. The results indicated that 32,1% (45 of 140) seropositivity was detectable by ELISA. Our results support that there is a risk of acquiring LB in different regions of Turkey. Although considerable positive detections were recorded using serologic tests,none of the specimens were positive in PCR analysis. Further studies on PCR based methods for detection of B. burgdorferi sensu lato in patients with a high clinical probability of LB apparently may require that the specimen should be taken in the early phases and before the administration of any therapeutic agent.

Lyme Borreliosisis is a multi-organ infectious disease caused by the spirochete Borrelia burgdorferi. The spirochete is transmitted to humans by tick bites. Neuroborreliosis (NB) is a disseminated form of the disease, in which the spirochetes invade the nervous system. In children, subacute meningitis and facial nerve palsy are typical clinical manifestations of NB. The aim of this thesis was to study clinical, immunological and laboratory characteristics in children being evaluated for NB in a Lyme endemic area of Sweden, in order to identify factors of importance for prognosis and clinical recovery. A total of 250 patients and 220 controls were included during 1998-2005, with a prospective and a retrospective part. Less than half (41%) of children with signs and symptoms indicative of NB get the diagnosis confirmed by detection of Borrelia specific flagella antibodies in CSF (clinical routine method). Surprisingly few patients were diagnosed as having other infectious or neurologic diseases and consequently, many patients ended up with an uncertain diagnosis. However, four new Borrelia antigens (DbpA, BBK32, OspC, IR6) were evaluated and performed well in laboratory diagnostics. If they were combined in a panel, together with the flagella antigen, the sensitivity was 82% and the specificity 100%, leading to improved diagnostic accuracy in children with NB, as compared to using the routine flagella antibody test alone. Clinical recovery at the 6-month follow-up (n=177) was generally good and nonspecific symptoms, such as headache and fatigue, were not more frequently reported in patients than in controls. No patient was found to have recurrent or progressive neurologic symptoms. However, permanent facial nerve palsy was found in 22% of patients at the 2-year follow-up, with consequences such as eye-closing problems, excessive tear secretion, pronunciation difficulties and cosmetic complaints. When cellular immune responses were investigated, the number of Borrelia-specific IL-4 and IFN-γ secreting cells in CSF was found to be more prominent in children with NB than in controls. Furthermore, a much stronger IL-4 response in CSF was seen in children as compared to adults with NB. This cytokine profile of children with NB is believed to represent an effective and balanced type1/type2 response in a relevant compartment, and could contribute to the less severe course of the disease seen in children as compared to adults with NB. No prognostic factors were found to influence the outcome in patients with “Confirmed NB” or facial nerve palsy. Nor was any specific cytokine profile, or antibody response to new Borrelia antigens in CSF, correlated to a less favorable clinical outcome. An NB prediction score test, based on clinical variables at admission, is suggested to help physicians to determine whether to start early antibiotic treatment, before results from Borrelia antibody tests are available. Results in this thesis support the notion that mononuclear pleocytosis in CSF, in patients being evaluated for NB, indicates that they are true NB cases despite the fact that an antibody response cannot yet be visualized. with the routine flagella test. Consequently, early antibiotic treatment in NB seems to be the correct course of action and over-treatment is not a substantial problem. / Borrelia-infektion hos barn och vuxna är den vanligaste fästingburna infektionen i Sverige och orsakas av en bakterie som heter Borrelia burgdorferi. Den sprids till människa via fästingbett och kan orsaka besvär från hud, leder, hjärtmuskel och nervsystem. När nervsystemet är infekterat kallas det Neuroborrelios. Denna avhandling handlar om Neuroborrelios hos barn i syd-östra Sverige, ett område med hög Borrelia-förekomst. Jag har studerat symtom, laborativa provsvar och tillfrisknande hos 250 barn med misstänkt Neuroborrelios under åren 1998-2005 och jämfört med friska barn. Dessutom har jag tittat närmare på vissa signalsubstanser inom immunförsvaret i blod och ryggvätska och vilken roll signalsubstanserna spelar för förlopp och utläkning av infektionen. Avhandlingen innehåller också en utvärdering av fyra nya diagnostiska test vid misstänkt Neuroborrelios hos barn. Det visar sig att mindre än hälften (41%) av barnen med misstänkt Neuroborrelios får diagnosen säkerställd med det befintliga Borrelia-testet (baserat på ett protein som kallas flagellin) som används rutinmässigt. Dock förblir diagnosen oklar för många barn (59%). De fyra nya Borrelia-testen (baserade på protein som kallas DbpA, BBK32, OspC och IR6) visar sig fungera bra och om man kombinerar dem med befintligt Borrelia-test, kan man säkerställa Neuroborrelios hos 82% av barnen med misstänkt infektion. Jag hoppas att dessa nya Borrelia-test i framtiden kan leda till förbättrad diagnostik hos barn som utreds för misstänkt Neuroborrelios. Immunförsvarets signalsubstanser, som analyserades i ryggvätska och blod, visade sig ha en viss profil hos barn med Neuroborrelios jämfört med barn utan Borrelia-infektion, men även jämfört med vuxna med Neuroborrelios. De immunologiska T cellerna producerade två olika sorters signalsubstanser, som kallas ”Interferon-γ” och ”Interleukin-4”. Denna immunologiska profil verkar fördelaktig och kan möjligen bidra till den i allmänhet goda utläkning av Neuroborrelios som man ser hos barn jämfört med vuxna. De vanligaste symtomen vid en Borrelia-infektion i nervsystemet är huvudvärk, trötthet, dålig aptit, feber och ont i nacken. Ansiktsförlamning är det vanligaste specifika neurologiska symtomet. Antibiotikabehandling ges till 69% av barnen och vid en 6 månaders uppföljning rapporterar patienterna god utläkning av de olika symtomen. Inget barn hade återkommande eller allvarliga neurologiska symtom vid uppföljningen. Däremot, barn med ansiktsförlamning visade sig få kvarstående besvär i viss utsträckning. När de undersöktes 2 år efter sin ansiktsförlamning förekom mild till måttlig kvarstående förlamning i 22% av fallen. Patienterna uppgav besvär av ökat tårflöde, sluddrigt tal, svårigheter med att stänga ögat och dessutom rapporterade många patienter att snedheten i ansiktet var kosmetiskt störande. Inga specifika symtom, laborativa prov, immunologiska signalsubstanser eller diagnostiska test visade sig vara kopplade till ökad risk för kvarstående besvär efter Neuroborrelios i allmänhet och inte eller hos patienter med ansiktsförlamning. En checklista har utarbetats med olika symtom som är typiska för barn med Neuroborrelios. Den föreslås kunna användas som beslutsunderlag för start av tidig antibiotikabehandling, redan innan svar på Borrelia-testen finns tillgängliga.

Erkinis encefalitas (EE) yra dažniausia ir sunkiausia virusinė nervų sistemos infekcija, neturinti specifinio priešvirusinio gydymo. Vienintelė efektyvi šios ligos profilaktikos priemonė yra vakcinacija. Nesant galimybių įvesti visuotinę vakcinaciją nuo EE mūsų šalyje, ypač svarbu nustatyti didžiausią šios ligos riziką turinčias gyventojų grupes, kurioms būtų teikiamas vakcinacijos prioritetas. Pagal tarptautines Laimo boreliozės (LB) diagnostikos ir gydymo gaires, klinikiniai sindromai ir jų trukmė yra svarbiausias šios ligos diagnostikos kriterijus. Serologiniai tyrimai vaidina tiktai pagalbinį vaidmenį patvirtinant diagnozę. Pagrindinis serologinių tyrimų trūkumas yra tas, kad jie neleidžia atskirti aktyvios infekcijos nuo buvusio kontakto su šios ligos sukėlėjais. Laimo boreliozės atveju tai labai svarbu, kadangi endeminiuose rajonuose nuo 1,8 iki 26 proc. sveikų žmonių turi šios ligos sukėlėjų antikūnus dėl buvusios besimptomės infekcijos praeityje. Neįmanoma teisingai interpretuoti LB serologinių tyrimų, nežinant LB paplitimo regione, kuriame šie tyrimai taikomi LB diagnostikai. Šis darbas yra pirmasis Lietuvoje LB sukėlėjų antikūnų paplitimo tyrimas, kuriame nustatytas dviejų pagrindinių erkių pernešamų ligų sukėlėjų antikūnų serokonversijos dažnis tyrimo laikotarpiu, didelio endemiškumo regione, tiriamųjų imtį sudarius atsitiktinės sluoksniuotos atrankos pagal amžių ir lytį principu. Šiame darbe ištirtos įvairių rizikos veiksnių sąsąjos su EE ir LB sukėlėjų paplitimu... [toliau žr. visą tekstą] / TBE is the most common and severe CNS affecting zoonosis. No specific treatment for TBE exists. Tick-borne encephalitis can be prevented by active immunization. Due to governmental financial shortages this vaccination is not included in the national program of imunoprophylaxis for the years 2014-2018. It is very important to find out groups for priority vaccination according to living area, age, leisure activities and occupational risk. Lyme borreliosis diagnosis should be based primarily on the clinical presentation and an assessment of tick exposure risk. In most cases laboratory diagnosis is only supporting clinical picture. Antibody assays still fall short of being completely sensitive and specific to distinguish acute and chronic infection. The diagnostic specificity of serum antibody tests is low because seropositivity in normal population ranges from 1.8% to 26% and LB IgM and IgG may persist for years. The interpretation of serological tests may also lead to misdiagnosis not knowing the seroprevalence of LB in the area. This is the first study of seroprevalence of LB and incidence of TBE and LB during a three year period in Lithuania. The study was conducted in high endemic areas and random samples stratified by gender and age groups were made. Only a few studies perform neutralization tests for detecting TBEV antibodies. Assumed risk factors for the prevalence of TBE and LB were established.