In North America, Borrelia burgdorferi is the primary causative agent of Lymedisease which is a growing health concern. The ability of B. burgdorferi to maintain chronic infection indicates that they are capable of immune evasion. A distinguishing characteristic of B. burgdorferi is the large number of sequences encoding predicted or known lipoproteins, including outer surface protein F (OspF). This study analyzes the specificity of the humoral immune response to B. burgdorferi B3 IMI OspF proteins during murine and human infection. Immunoblot analyses revealed a temporal expression of OspF proteins during infection and mapped the immunodominant epitopes which lie within the variable domains. To determine if OspF-related proteins are produced by other isolates, immunoblot analyses were performed using sera collected from mice and humans infected with diverse B. burgdorferi strains. Differences in the immunoreactivity profile to OspF proteins were seen among the infection sera tested. To identify the molecular basis of these differences, the ospF gene was isolated from several strains, sequenced and evolutionary analyses were conducted. These analyses revealed that OspF proteins show little diversity despite the separate geographic locations from which isolates originated. The high degree of OspF protein conservation seen in isolates from two distinct regions emphasizes the potential for OpsF proteins as vaccinogens or in serodiagnostic assays. Altogether, this study demonstrates the potential contribution of OspF proteins to immune evasion through its temporal expression during infection which may play specific roles at different stages of infection. Studies are underway to determine if inactivation of ospF genes through allelic exchange mutagenesis impacts on the pathogenicity of the Lyme disease spirochetes.

Die Gattung Borrelia gehört zur Abteilung der Spirochäten, einem alten Zweig der Bakteriendomäne, der nur entfernt mit Gram-negativen Bakterien verwandt ist. Sämtliche Arten dieser Gattung sind obligate Parasiten. Borrelien können in die Erreger zweier humaner Krankheiten eingeteilt werden: die Lyme-Borreliose und das Rückfallfieber. Borrelien besitzen mit 0.91 Mb ein sehr kleines Chromosom und sind daher in ihren metabolischen Fähigkeiten eingeschränkt. Folglich ist das Überleben sämtlicher Borrelienarten absolut abhängig von Nährstoffen, die von ihren Wirten bereitgestellt werden. Der Transport dieser Nährstoffe und anderer Moleküle über die äußere Membran wird durch porenformende Proteine, so genannte Porine ermöglicht. Porine sind wassergefüllte Kanäle, die in zwei Klassen unterteilt werden können: allgemeine Diffusionsporen und substratspezifische Porine. Aus dem Lyme-Borreliose Erreger Borrelia burgdorferi wurden bisher drei mutmaßliche Porine charakterisiert und beschrieben: P13, Oms28 und P66. Demgegenüber sind die Kenntnisse über Porine in Rückfallfieberarten rudimentär und es wurde bisher noch kein einziges Porin für Vertreter dieser Krankheit identifiziert. Unter Berücksichtigung dieses Hintergrunds war die allgemeine Zielsetzung dieser Arbeit, einen Einblick in die Porinzusammensetzung von sowohl Lyme Borreliose- als auch Rückfallfieber-Spirochäten zu erlangen. Dieses Ziel konnte erreicht werden, indem Porine aus den Außenmembranen von Borrelien isoliert und identifiziert wurden und anschließend biophysikalisch in künstlichen Lipidmembranen charakterisiert wurden. Ein Kapitel dieser Arbeit beschreibt die Identifizierung und Charakterisierung des ersten Porins aus Rückfallfiebererregern. Das porenformende Protein wurde aus den Außenmembranen von Borrelia duttonii, Borrelia hermsii und Borrelia recurrentis isoliert und Oms38 genannt, für „outer membrane-spanning protein of 38 kDa“. Die biophysikalische Charakterisierung mit der „black lipid bilayer“ Methode zeigte, dass Oms38 kleine, wassergefüllte Kanäle mit einer Einzelkanalleitfähigkeit von 80 pS in 1 M KCl bildet. Diese Kanäle sind nicht spannungsabhängig und leicht selektiv für Anionen mit einem Permeabilitätsverhältnis von Kationen zu Anionen von 0,41 in KCl. Ein homologes Protein zu Oms38 wurde in den Lyme Borreliose Erregern Borrelia burgdorferi, Borrelia garinii und Borrelia afzelii identifiziert. Das porenformende Protein dieser Arten weist eine hohe Sequenzhomologie zu Oms38 auf und zeigt ähnliche biophysikalische Eigenschaften, das heißt es formt Poren von 50 pS in 1 M KCl. Durch Titrationsexperimente konnte gezeigt werden, dass die Pore teilweise durch Dicarboxylate blockiert werden kann. Eine Auswertung dieser Versuche legte nahe, dass dieses Protein keine allgemeine Diffusionspore darstellt, sondern einen Kanal mit einer spezifischen Bindestelle für diese Komponenten. Daher wurde dieses Porin DipA genannt, was für „dicarboxylate-specific porin A“ steht. In einer anderen Versuchsreihe wurde gezeigt, dass das Porin P66 sowohl in Lyme Borreliose Erregern als auch in Rückfallfieberarten vorhanden ist. Hierfür wurden die Außenmembranen der Lyme Borreliose Erreger Borrelia burgdorferi, Borrelia afzelii und Borrelia garinii und der Rückfallfieberarten Borrelia duttonii, Borrelia recurrentis und Borrelia hermsii genauer untersucht. Mit Ausnahme des P66 Homologs von Borrelia hermsii rekonstituierten P66 Proteine aus allen Arten sehr aktiv in künstliche Membranen und formten Poren zwischen 9 und 11 nS in 1 M KCl. Die biophysikalischen Eigenschaften der Homologe wurden in Experimenten mit „black lipid bilayer“ Membranen ausführlich verglichen. Des Weiteren wurden Porendurchmesser und Konstitution des Borrelia burgdorferi Porins P66 genau untersucht. Hierfür wurde die P66 Einzelkanalleitfähigkeit in Anwesenheit von verschiedenen Nichtelektrolyten in künstlichen Lipidmembranen analysiert. Der effektive Durchmesser des P66 Wasserlumens wurde auf ~1.9 nm bestimmt. Darüber hinaus konnte P66 mit bestimmten Nichtelektrolyten wie PEG 400, PEG 600 und Maltohexaose blockiert werden. Weitere Blockierungsexperimente auf Einzelkanalebene deckten sieben Unterzustände von P66 auf, die auf ein P66 Heptamer schließen ließen. Dieser heptamere Charakter konnte durch Blue native PAGE Analysen bestätigt werden. Zusammenfassend beschreibt diese Dissertation detaillierte biochemische und biophysikalische Untersuchungen von Porinen aus sowohl Lyme Borreliose- als auch Rückfallfieber-Borrelien. Erkenntnisse aus dieser Arbeit bringen das Verstehen der Nährstoffaufnahme über Außenmembranen dieser streng wirtsabhängigen, pathogenen Spirochäten einen großen Schritt vorwärts. Ein fundiertes Wissen über oberflächenexponierte Proteine wie Porine ist Vorraussetzung für die Herstellung erfolgreicher Impfstoffe und Therapeutika gegen die von Borrelien verursachten Krankheiten. / The genus Borrelia belongs to the spirochete phylum, an ancient evolutionary branch of the domain bacteria that is only afar related to Gram-negative bacteria. Borreliae can be subdivided into the agents of the two borrelian-caused human diseases, Lyme disease and relapsing fever. Both disease patterns are closely related to the peculiar biology of Borrelia species and exhibit a wide spectrum of diverse clinical manifestations. Due to the small 0.91 Mb chromosome, borreliae have a lack of biosynthetic capacity. Thus, all Borrelia species are highly dependent on nutrients provided by their hosts. The transport of nutrients and other molecules across the outer membrane is enabled by pore-forming proteins, so-called porins. Porins are water-filled channels and can be subdivided into two different classes, general diffusion pores and substrate-specific porins. In terms of the Lyme disease agent Borrelia burgdorferi, three putative porins were characterized in previous studies: P13, Oms28 and P66. In contrast to Lyme disease species, the porin knowledge of relapsing fever Borrelia is low, which means that not any porin has actually been described for representatives of these agents. Thus, the general aim of this thesis was to provide insight into the porin content of both, Lyme disease and relapsing fever spirochetes. This aim could be achieved by isolating and identifying porins from Borrelia outer membranes and by biophysically characterizing them in artificial lipid membranes. In one chapter of this study, the first identification and characterization of a relapsing fever porin is presented. The pore-forming protein was isolated from outer membranes of Borrelia duttonii, Borrelia hermsii and Borrelia recurrentis and designated Oms38, for “outer membrane-spanning protein of 38 kDa”. Biophysical characterization of Oms38 was achieved by using the black lipid bilayer method and demonstrated that Oms38 forms small, water-filled channels with a single-channel conductance of 80 pS in 1 M KCl. The Oms38 channel did not exhibit voltage-dependent closure and is slightly selective for anions with a permeability ratio of cations over anions of 0.41 in KCl. Subsequently, a protein homologous to Oms38 was identified in the Lyme disease agents Borrelia burgdorferi, Borrelia garinii and Borrelia afzelii. The pore-forming protein of these species exhibits high sequence homology to Oms38 and similar biophysical properties, i.e. it forms pores of 50 pS in 1 M KCl. Interestingly, titration experiments revealed that this pore could be partly blocked by dicarboxylic anions, which means that this protein does not form a general diffusion pore but a channel with a binding-site specific for those compounds. Consequently, this porin was termed DipA, for “dicarboxylate-specific porin A”. In another set of experiments, it was shown that the porin P66 is present in both Lyme disease and relapsing fever species. Therefor, the outer membranes of the Lyme disease species Borrelia burgdorferi, Borrelia afzelii, Borrelia garinii and the relapsing fever species Borrelia duttonii, Borrelia recurrentis and Borrelia hermsii were closer investigated. Except of the P66 homologue of Borrelia hermsii P66 of all species was highly active in artificial lipid membranes, forming pores with huge single-channel conductances between 9 and 11 nS in 1 M KCl. Moreover, the channel diameter and the constitution of Borrelia burgdorferi P66 were investigated in detail. Therefor, the P66 single-channel conductance in the presence of different nonelectrolytes with known hydrodynamic radii was analyzed in black lipid bilayers. The effective diameter of the P66 channel lumen was determined to be ~1.9 nm. Furthermore, as derived from multi-channel experiments the P66-induced membrane conductance could be blocked by certain nonelectrolytes, such as PEG 400, PEG 600 and maltohexaose. Additional blocking experiments on the single-channel level revealed seven subconducting states and indicated a heptameric constitution of the P66 channel. This indication could be confirmed by Blue native PAGE analysis which demonstrated that P66 units form a complex with a corresponding mass of approximately 440 kDa. Taking together, this thesis describes detailed biochemical and biophysical investigations of both Lyme disease and relapsing fever Borrelia porins and represents an important step forward in understanding the outer membrane pathways for nutrient uptake of these strictly host-dependent, pathogenic spirochetes. Furthermore, it provides some knowledge of the outer-membrane protein composition of Borrelia spirochetes. A profound knowledge of surface-exposed proteins, such as porins, is one precondition for the production of a successful vaccine and the drug design against the two borrelian-caused diseases.

A Doença de Lyme-símile brasileira ou Síndrome Baggio-Yoshinari (SBY) é uma zoonose emergente, transmitida por carrapatos e até o momento, de descrição restrita ao território brasileiro. O agente etiológico da SBY era desconhecido até o presente trabalho. O objetivo principal do estudo foi identificar a etiologia da SBY. Foi selecionado 2 grupos de pacientes: grupo A (n=68) composto por pacientes com suspeita diagnóstica de SBY, a maioria na fase latente da doença; grupo B (n=10), composto por pacientes com diagnóstico de SBY, que apresentaram obrigatoriamente eritema migratório e que encontravam-se sintomáticos no momento da coleta. Foi utilizado também um grupo controle composto por indivíduos saudáveis e com epidemiologia negativa (n=50). Amostras de sangue foram coletadas para a realização de sorologias, culturas, análises microscópicas (óptica e eletrônica) e reação de cadeia da polimerase (PCR) para diferentes micro-organismos (Mycoplasma spp, Chlamydia spp e Borrelia spp). Além disso, foi realizado um estudo preliminar, através da PCR para Borrelia spp em 47 amostras de carrapatos oriundos de áreas de risco do Espírito Santo (sendo 17 Rhipicephalus microplus e 30 Rhipicephalus sanguineus), e amostras de sangue total de 27 bovinos e 26 equinos, animais estes oriundos da Universidade Federal Rural do Rio de Janeiro. Os resultados mostraram que a SBY não se trata de uma zoonose causada por um conjunto de micro-organismos como pensado inicialmente e sim pela Borrelia burgdorferi sensu lato. Descoberta essa que foi possível empregando-se novos primers amplificadores do principal gene envolvido na síntese do gancho flagelar da Borrelia, chamado flgE. A positividade para flgE foi confirmada em 6 pacientes do grupo B, 2 carrapatos, 1 bovino e 1 equino, os quais apresentaram homologia de 99% com o gene da proteína do gancho flagelar da Borrelia burgdorferi (flgE) depositado no GenBank (L43849). Esta importante descoberta, associada às pesquisas anteriores, permitiu definir a SBY como zoonose emergente e própria do país, causada pela bactéria B. burgdorferi na apresentação morfológica atípica, transmitida por carrapatos não pertencentes ao complexo Ixodes ricinus, responsável por manifestações clínicas semelhantes à Doença de Lyme, exceto pela grande frequência de sintomas recorrentes / Brazilian Lyme disease-like illness (BLDL) or Baggio-Yoshinari Syndrome (BYS) is an emerging zoonosis, transmitted by ticks and so far, restricted to the description of the Brazilian territory. The causative agent of BYS was unknown until now. The main objective of this study was to identify the etiology of BYS. We have selected two groups of patients: group A (n = 68) consisting of patients suspected of BYS, mostly in the latent stage of disease; group B (n = 10), composed of patients diagnosed with BYS, who had compulsorily erythema migrans and that were symptomatic at the time of blood collection. We also used a control group composed of healthy individuals with negative epidemiology (n = 50). Blood samples were collected, in which we performed serology, cultures, microscopic analysis (optical and electron) and polymerase chain reaction (PCR) for different microorganisms (Mycoplasma spp, Chlamydia spp and Borrelia spp). In addition, a preliminary study was conducted by PCR for Borrelia spp in 47 samples of ticks from risk areas at Espirito Santo State (being 17 Rhipicephalus microplus and 30 Rhipicephalus sanguineus), 27 cattle and 26 horses, being these animals from the Universidade Federal Rural do Rio de Janeiro. The results showed that BYS is not a zoonosis caused by a set of microorganisms as initially thought, but by Borrelia burgdorferi sensu lato. These findings were possible after employing new primers that are able to amplify portions of the main genes involved in the synthesis of the Borrelia flagellar hook protein, called flgE. We confirmed positivity for the flgE in 6 patients from group B, 2 ticks, a cow, and a horse, which showed 99% homology with the gene of Borrelia burgdorferi flagellar hook protein (flgE) deposited in GenBank (L43849). This important discovery, coupled with previous research, helped to define BYS as an emerging zoonosis particular from Brazil, caused by B. burgdorferi of atypical morphologic presentation, transmitted by ticks outside the Ixodes ricinus complex, responsible for clinical signs similar to Lyme disease, except for the high frequency of relapsing symptoms

A Doença de Lyme-símile brasileira ou Síndrome Baggio-Yoshinari (SBY) é uma zoonose emergente, transmitida por carrapatos e até o momento, de descrição restrita ao território brasileiro. O agente etiológico da SBY era desconhecido até o presente trabalho. O objetivo principal do estudo foi identificar a etiologia da SBY. Foi selecionado 2 grupos de pacientes: grupo A (n=68) composto por pacientes com suspeita diagnóstica de SBY, a maioria na fase latente da doença; grupo B (n=10), composto por pacientes com diagnóstico de SBY, que apresentaram obrigatoriamente eritema migratório e que encontravam-se sintomáticos no momento da coleta. Foi utilizado também um grupo controle composto por indivíduos saudáveis e com epidemiologia negativa (n=50). Amostras de sangue foram coletadas para a realização de sorologias, culturas, análises microscópicas (óptica e eletrônica) e reação de cadeia da polimerase (PCR) para diferentes micro-organismos (Mycoplasma spp, Chlamydia spp e Borrelia spp). Além disso, foi realizado um estudo preliminar, através da PCR para Borrelia spp em 47 amostras de carrapatos oriundos de áreas de risco do Espírito Santo (sendo 17 Rhipicephalus microplus e 30 Rhipicephalus sanguineus), e amostras de sangue total de 27 bovinos e 26 equinos, animais estes oriundos da Universidade Federal Rural do Rio de Janeiro. Os resultados mostraram que a SBY não se trata de uma zoonose causada por um conjunto de micro-organismos como pensado inicialmente e sim pela Borrelia burgdorferi sensu lato. Descoberta essa que foi possível empregando-se novos primers amplificadores do principal gene envolvido na síntese do gancho flagelar da Borrelia, chamado flgE. A positividade para flgE foi confirmada em 6 pacientes do grupo B, 2 carrapatos, 1 bovino e 1 equino, os quais apresentaram homologia de 99% com o gene da proteína do gancho flagelar da Borrelia burgdorferi (flgE) depositado no GenBank (L43849). Esta importante descoberta, associada às pesquisas anteriores, permitiu definir a SBY como zoonose emergente e própria do país, causada pela bactéria B. burgdorferi na apresentação morfológica atípica, transmitida por carrapatos não pertencentes ao complexo Ixodes ricinus, responsável por manifestações clínicas semelhantes à Doença de Lyme, exceto pela grande frequência de sintomas recorrentes / Brazilian Lyme disease-like illness (BLDL) or Baggio-Yoshinari Syndrome (BYS) is an emerging zoonosis, transmitted by ticks and so far, restricted to the description of the Brazilian territory. The causative agent of BYS was unknown until now. The main objective of this study was to identify the etiology of BYS. We have selected two groups of patients: group A (n = 68) consisting of patients suspected of BYS, mostly in the latent stage of disease; group B (n = 10), composed of patients diagnosed with BYS, who had compulsorily erythema migrans and that were symptomatic at the time of blood collection. We also used a control group composed of healthy individuals with negative epidemiology (n = 50). Blood samples were collected, in which we performed serology, cultures, microscopic analysis (optical and electron) and polymerase chain reaction (PCR) for different microorganisms (Mycoplasma spp, Chlamydia spp and Borrelia spp). In addition, a preliminary study was conducted by PCR for Borrelia spp in 47 samples of ticks from risk areas at Espirito Santo State (being 17 Rhipicephalus microplus and 30 Rhipicephalus sanguineus), 27 cattle and 26 horses, being these animals from the Universidade Federal Rural do Rio de Janeiro. The results showed that BYS is not a zoonosis caused by a set of microorganisms as initially thought, but by Borrelia burgdorferi sensu lato. These findings were possible after employing new primers that are able to amplify portions of the main genes involved in the synthesis of the Borrelia flagellar hook protein, called flgE. We confirmed positivity for the flgE in 6 patients from group B, 2 ticks, a cow, and a horse, which showed 99% homology with the gene of Borrelia burgdorferi flagellar hook protein (flgE) deposited in GenBank (L43849). This important discovery, coupled with previous research, helped to define BYS as an emerging zoonosis particular from Brazil, caused by B. burgdorferi of atypical morphologic presentation, transmitted by ticks outside the Ixodes ricinus complex, responsible for clinical signs similar to Lyme disease, except for the high frequency of relapsing symptoms

Lyme disease is one of the most common vector-borne diseases around the world, and the numbers of reported cases are quickly rising. Ixodes ticks are the principal vectors, while Borrelia burgdorferi sensu lato genospecies are the etiological agents of the disease. Climate change, namely global warming, and habitat modification, namely forest fragmentation, are hypothesized to play an active role in this rise in reported cases. An analysis of the primary literature, specifically of studies focused on North America and Europe, was conducted in order to investigate these hypotheses. These studies show that global warming has precipitated a growth in tick populations as well as a northward tick migration, thereby increasing the risk of Lyme disease in emergent and endemic areas alike, for Borrelia spirochetes quickly infect naïve tick populations. Furthermore, published studies support the idea that forest fragmentation near human population centers has also increased the risk of Lyme disease in North America, for edge habitats provide suitable conditions for ticks and provide edible vegetation for the animals on which ticks feed, animals which also serve as hosts for B. burgdorferi sensu lato. In contrast, a decrease in fragmentation was found to facilitate tick invasion and establishment in Europe. These studies demonstrate that anthropogenic habitat modifications of varying types can affect ticks and their host populations and increase the risk of Lyme disease near human population centers. However, more research needs to be done to truly understand the different factors that are precipitating the rising number of cases of Lyme disease since there are significant interactions between climate change, habitat modification, and other drivers not examined here. Furthermore, understanding how these drivers function in specific geographic locations can help scientists and public officials tailor local public health measures appropriately. Finally, researchers and pharmaceutical companies must develop a safe, long-lasting, and effective vaccine against the Lyme disease spirochete, for there is not one currently available. Although easily treatable if diagnosed early, Lyme disease can progress to debilitating disease. Unfortunately, the risk of contracting this illness is currently rising and will continue to rise unless effective preventative measures are employed.

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.

Uninfected larvae of Ixodes dammini, lxodes cookei, and Amblyomma americanum were fed on hamsters that had been injected intraperitoneally with a 0.5.ml sample of Borrelia burgdorferl (2.5 X 107 spirochetes per ml) 21 days earlier. A total of 108 of these larvae comprised of 36 1. dammini, 36 i. cookei, and 36 A. americanum were aseptically dissected and examined by darkfield and immunofluorescent microscopy for the presence of B. burgdorferl within 48 hours of feeding on the B. burgdorferi infected hamsters. The removal and examination of the midgut diverticula revealed that 32/36 (88.9%) of the l. dammini larvae contained B. burgdorferl. Only 5/36 (13.9%) of the l. cookei larvae and 7/36 of the A. americanum larvae harbored spirochetes in their midgut diverticula.A portion of the nymphs that molted from the above larvae were also dissected and examined by darkfleld and indirect immunofluorescent techniques. Borrelia burgdorferi were observed in the midgut diverticula of 94/107 (87.8%) of the l. dammini nymphs. None of the 30 (0%) l. cookei nymphs examined were found positive for spirochetes and only 1/60 (1.7%) of the A. americanum nymphs was found positive for B. burgdorrerl.A total of 83 lL dammini, 53 A. americanum, and 161. cookei nymphs reared from larvae that fed to repletion on hamsters infected with B. burgdorrerl were allowed to feed on uninfected hamsters to assess transmission of B. burgdorrerl. Transmission was demonstrated only by the l. dammlnl nymphs. The findings of this study suggest that it is extremely unlikely that l. cookei can serve as a vector for B. burgdorrerl, but do not rule out completely the possibility that A. americanum may be able to maintain B, burgdorrerl infections transstadially and, under certain conditions, transmit the organisms to vertebrate hosts. / Department of Physiology and Health Science

Uninfected nymphs of Ixodes scapularis and Amblyomma americanum were fed on hamsters that had been injected intraperitoneally with a 0.5 ml sample of Borrelia burgdorferi (2.5 X 10' spirochetes per ml) 30 days earlier. All nymphs fed to repletion and were then housed during the molting process. In order to assess their ability to transmit the spirochetes, the resulting l. scapularis and A. americanum adults were allowed to feed on uninfected rabbits.Dissection of the adult l. scapularis ticks revealed 9/12 (75%) to harbor motile spirochetes, identified as B. burgdorferi by darkfield microscopy, isolation in BSK II medium, and indirect immunofluorescent antibody staining with the monoclonal antibody H5332. Transmission was successful to one of two New Zealand White rabbits by these infected ticks.Dissection of the adult A. americanum ticks revealed 0/150 (0%) to harbor spirochetes. Transmission to each of three rabbits was unsuccessful. However, 5/90 (5.6%) cultures of midgut material from these same ticks, harbored non-motile spirochete-like bodies. The identity of these "spirochetes" is unknown. / Department of Biology

Thesis (M.S.)--University of Tennessee, Knoxville, 2009. / Title from title page screen (viewed on Mar. 18, 2010). Thesis advisor: Graham Hickling. Vita. Includes bibliographical references.

Thesis (Ph. D.)--University of Missouri-Columbia, 1999. / Typescript. Vita. Includes bibliographical references (leaves 70-85). Also available on the Internet.