<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.

In Europe, Lyme disease is caused by the species Borrelia (B.) burgdorferi sensu stricto, B. garinii and B. afzelii. The disease is the most common vector-borne infection in Europe and the United States, and the resulting manifestation can involve the skin, nervous system, heart and joints. The symptoms that arise are associated with the Borrelia species causing the infection. The species most associated with neuroborreliosis is B. garinii whilst B. burgdorferi sensu stricto is associated with arthritis and B. afzelii is associated with dermatological symptoms. Lyme disease normally has three phases in untreated patients. The first phase is characterised by erythema migrans, a reddening of the skin around the area of the tick bite. If the disease develops to the second phase the patient will suffer from neuroborreliosis which is characterised by neurological symptoms such as headache and peripheral facial paralysis. Cerebrospinal fluid (CSF) analysis is used to diagnose neuroborreliosis. The diagnosis is complicated by variations between the different Borrelia species and that many healthy individuals have antibodies directed against Borrelia. Antibodies in CSF can be found in different diseases. The antibodies can be produced in the central nervous system or come across the blood-brain barrier and thus derive originally from the blood. By measuring the concentration of total albumin in serum and in CSF it can be determined if the antibodies present in the CSF have been produced in the central nervous system or if they originate from the blood. The typical manifestation in the last phase of Lyme disease is severe arthritis. The aim of this examination project was to compare two ELISAs for detection of antibodies directed to Borrelia. Indirect ELISAs from DAKO and Euroimmun were compared for the diagnosis of neuroborreliosis in 100 individuals. Borrelia specific antibodies of class IgM or IgG were found in 16 of 100 patients by DAKO’s ELISA and in 20 of the same 100 patients by Euroimmun’s ELISA. The reason that Euroimmun’s method detected more cases of neuroborreliosis is probably that this method detects antibodies directed to all three pathological species of Borrelia while DAKO’s method only detects antibodies directed to B. burgdorferi. In conclusion, this study indicates that Euroimmun’s method to detect antibodies of class IgM and IgG directed to Borrelia is superior to DAKO’s method. The obtained results were confirmed by Western blot analysis which gave results in accordance with those of Euroimmun’s ELISA.

Borrelia burgdorferi is a pathogenic spirochete which cycles between its arthropod vector and vertebrate host. If transmitted to humans, B. burgdorferi causes Lyme disease, an infection which can impair different organs, such as the skin, joints, nervous system and heart. Alterations in protein expression due to the different environments Borrelia encounters during its complicated life cycle require advanced adaptation mechanisms. The outer surface-exposed proteins play a critical role in survival and pathogenesis of Borrelia in different hosts and tissues, being involved in avoiding the host immune response, adhesion to different tissues and nutrient acquisition. This thesis aimed to characterize integral outer membrane proteins which play a role in solute and nutrient uptake, and provides support for their role in the environmental adaptation of Borrelia. In this thesis, three B. burgdorferi proteins, P13, BBA01 and P66, were shown to be porins, and characterized structurally and functionally using a combination of biochemical, biophysical and genetic methods. The channel-forming function of the 13 kDa protein, P13, was elucidated by a lipid bilayer assay. Post-translational processing of P13 occurred at the C-terminus by C-terminal processing protease (CtpA)-dependent cleavage. The membrane-spanning architecture of P13 was determined by epitope mapping and computer-based structural predictions which revealed that P13 is an unusual porin, not possessing the structural properties of conventional porins: rather than forming β-barrels, it is predicted to span the membrane with hydrophobic α-helices. p13 belongs to a paralogous gene family. The transcription of p13 and other gene family members during in vitro growth and in a mouse infection model was therefore investigated. The paralog BBA01, which has the highest sequence homology to P13, is expressed during in vitro growth in all three Lyme disease causing species, although at very low levels. Like P13, BBA01 is also processed by CtpA and exhibits very similar channel-forming activity. Furthermore, in the absence of P13, a proportion of total BBA01 protein is relocated to the bacterial surface with strong indications that BBA01 and P13 are functionally interchangeable. P66, an integrin binding protein, was also determined to be a porin. The oligomeric state of native P66, elucidated by chemical cross-linking, indicated that P66 forms trimers, as do the majority of conventional porins. Electron crystallography and a projection map of P66 crystals at 2.2 nm resolution revealed tetragonal unit cell symmetry with the area intercalated between the assembled protein structures consistent with the approximate expected size of the channel formed by P66. Finally, the biological relevance of two porins, P13 and P66, was demonstrated in a double mutant displaying a stress response as revealed by increased sensitivity to high osmolarity and elevated expression of the B. burgdorferi heat-shock protein HtrA homolog.

The incidence of tick-borne zoonoses such as Ehrlichiosis, Rocky Mountain Spotted Fever, and Lyme disease has steadily increased in the southeastern United States in recent years. According to the Centers for Disease Control and Prevention (CDC), the southeastern states accounted for 1,200 of the 27,000 total cases of Lyme disease reported in the U.S. in 2007. Although Ixodes scapularis is the most commonly recognized vector for the Lyme disease spirochete Borrelia burgdorferi, Dermacentor variabilis (a common vector for Rocky Mountain Spotted Fever) also has been shown to be a viable host for this pathogen. The purpose of the present study was to use PCR and DNA sequencing technologies to determine if Borrelia burgdorferi sensu lato is present in ticks and whole blood samples removed from raccoons and opossums trapped in south-central Kentucky. Raccoons and opossums were trapped in Barren and Warren counties of Kentucky between June 2007 and June 2008. Ticks were removed and stored in 70% ethanol. Sterile blood samples were collected into three 10 ml tubes containing the anticoagulant K2EDTA and stored at 4°C. Genomic DNA was extracted from ticks and blood samples using a QIAamp DNA mini kit and a QIAamp DNA blood mini kit (Qiagen) respectively. DNA samples were analyzed by polymerase chain reaction (PCR) for the presence of B. burgdorferi using oligonucleotide primers specific for the OspA gene. A total of 976 ticks were collected. Three different species were obtained from raccoons; Dermacentor variabilis, Amblyomma americanum, and Ixodes sp. Dermacentor variabilis was the only tick species found on opossums. Twenty-five percent (163/642) of the tick DNA samples were positive for Borrelia burgdorferi. Prevalence of B. burgdorferi by tick species was 24.4% (141/577) in D. variabilis, 40.6% (13/32) in A. americanum, and 27.6% (8/29) in I. scapularis. In the present study, 15.7% (8/51) of the total raccoon blood samples examined by PCR were positive for B. burgdorferi, while no opossum blood samples were positive. The high prevalence of B. burgdorferi in ticks common to raccoons and opossums observed in this study, as well as in a tick species that aggressively bites humans in the southeast U. S. (A. americanum), creates concern that there are ample opportunities for people to come in contact with the infected ticks on these animals. Future studies are urgently needed to fully assess the presence and prevalence of B. burgdorferi in Kentucky and other southeastern states in the U. S.

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.

Reproduction de : Thèse d'exercice : Pharmacie : Nantes : 2009. / Bibliogr.

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.

A cell's ability to sense and respond to mechanical signals highlights the significance of physical forces in biology; however, to date most biomedical research has focused on genetics and biochemical signaling. We sought to further understand the physical mechanisms that guide the cellular migrations that occur in a number of biological processes, such as tissue development and regeneration, bacterial infections and cancer metastasis. We investigated the migration of single cells and determined whether the biomechanics of these cells could be used to elucidate multi-cellular mechanisms. We first studied Borrelia burgdorferi (Bb), the bacterium that causes Lyme disease. We created a mathematical model based on the mechanical interactions between the flagella and cell body that explained the rotation and undulation of the cell body that occurs as the bacterium swims. This model further predicts how the swimming dynamics could be affected by alterations in flagellar or cell wall stiffnesses. Fitting the model to experimental data allowed us to calculate the flagellar torque and drag for Bb, and showed that Treponema pallidum (Tp), the syphilis pathogen, is biomechanically similar to Bb. Next, we used experimentally-determined parameters of Bb's motility to develop a population-level model that accounts for the morphology and spreading of the "bulls-eye" rash that is typically the first indicator of Lyme disease. This work supported clinical findings on the efficacy of antibiotic treatment regimes. Finally, we investigated the dynamics of epithelial monolayers. We found that intracellular contractile stress is the primary driving force behind collective dynamics in epithelial layers, a result previously predicted from a biophysical model. Taken together, these findings identify the relevance of physics in cellular migration and a role of mechanical signaling in biomedical science.

The objectives of this study were to determine the distribution of Borrelia burgdorferi (Bb), the bacterium that causes Lyme disease, and its tick vector (Ixodes scapularis) in the Thousand Islands in Ontario, and to assess the effects of various factors, including host populations, temperature, and vegetation, on the distribution of Bb and ticks in this new endemic region. Data were collected via drag sampling and small mammal trapping at 12 sites and multimodel inference was used to evaluate variables. There was inter-island variation in the abundance of ticks and prevalence of Bb in ticks. Important predictors of tick numbers and infection prevalence included deer abundance, distance to the United States, temperature, species richness, and relative mouse abundance. These results will contribute to management strategies to reduce Lyme disease risk in the Thousand Islands and to our understanding of the effects of biodiversity on disease risk. / Canadian Cooperative Wildlife Health Centre; Ontario Ministry of Natural Resources; Parks Canada; Public Health Agency of Canada; Ontario Graduate Scholarship