Emerging or re-emerging tick-borne pathogens are expected to increase in prevalence and become more geographically widespread in Canada. Borrelia burgdorferi, the bacterium causing Lyme disease, is the most common vector-borne pathogen in North America, but additional tick-borne pathogens have started to be detected more frequently through surveillance efforts in Canada. The spread and transmission of these tick-borne pathogens are modulated by changes in the abundance and distribution of tick and host populations. Abiotic factors, such as temperature, precipitation, and snow, may affect tick and host abundances as well as host dispersal. Furthermore, biotic factors, such as the abundance and diversity of hosts, may alter tick abundance and consequent tick-borne disease risk. In this dissertation, I assess the historical associations and spatiotemporal changes of the tick vectors, hosts, and pathogens in Canada as well as the impact of abiotic and biotic factors on these key players. In Chapter 1, I present the first systematic assessment of the literature that identifies historical associations and spatiotemporal changes in the tick-host-pathogen disease systems in Canada over broad spatial and temporal scales. Borrelia burgdorferi was the most detected tick-borne pathogen and Ixodes scapularis harboured the greatest number of tick-borne pathogens. Several spatial outliers of high pathogen presence in ticks in addition to five spatiotemporal clusters were identified, which were located in areas of southern Canada with long-established tick populations. In addition, six spatiotemporal clusters of high pathogen presence were also identified, with four clusters associated with passive surveillance and two clusters related to active surveillance. In chapter 2, I concurrently evaluated high-resolution environmental and host-related factors to determine the relative impacts of abiotic and biotic factors on questing I. scapularis abundance in Ontario and Quebec. High-resolution abiotic factors were derived from remote sensing satellite imagery and meteorological towers, while biotic factors related to mammal hosts were derived from active surveillance data that I collected in the field. Important abiotic and biotic drivers of questing I. scapularis abundance were identified, which included monthly mean precipitation, accumulated snow, and mammal species richness. These results demonstrate the need to incorporate host active surveillance data with high-resolution environmental factors when trying to determine the key drivers impacting the abundance and distribution of tick populations and tick-borne pathogens. In Chapter 3, I analyzed the presence and prevalence of multiple tick-borne pathogens extracted from tick and small mammal specimens collected during field surveys in Ontario and Quebec. Three pathogen species were detected in ticks, which included Babesia odocoilei and B. burgdorferi in I. scapularis as well as Rickettsia rickettsii in Haemaphysalis leporispalustris. In small mammal hosts, three pathogen species were detected including B. odocoilei in one shrew, B. microti in one deer mouse, and Hepatozoon in one deer mouse and one white-footed mouse. My findings provide evidence that emerging or re-emerging tick-borne pathogens may be present outside currently defined risk areas identified by surveillance efforts in Canada. Finally, in chapter 4, I examined the effect of biotic factors related to I. scapularis and mammal hosts on the presence, prevalence, and diversity of pathogens in Ontario and Quebec using data from field surveys. Local infection prevalence ranged from 0% to 25.4% in questing ticks and from 0% to 16.7% in small mammal hosts. Local pathogen presence and prevalence were not impacted by I. scapularis abundance nor the abundance and diversity of mammal hosts. However, mammal species richness was a key predictor of the number of pathogen species. Collectively, my dissertation provides insight into the historical and contemporary relationships between ticks, hosts, and pathogens in Canada. My results demonstrate that additional tick species such as H. leporispalustris may be of public health importance due to their ability to maintain pathogens within the environment without needing a host. In addition, certain emerging or re-emerging tick-borne pathogens, such as B. odocoilei and R. rickettsii, were detected outside of currently defined risk areas in southeastern Quebec, which may impact future surveillance efforts in these regions. Furthermore, this work highlights the need for proactive and comprehensive surveillance efforts that test questing and feeding ticks of all life stages and species, as well as their hosts in areas outside currently defined risk areas or those targeted by sentinel surveillance to better determine the spread, transmission, and co-occurrence of tick-borne pathogens in Canada.

Ticks are important vectors of a wide variety of pathogens including protozoa, bacteria and viruses. Many of the viruses transmitted by ticks are of medical or veterinary importance including tick-borne encephalitis virus (TBEV) and Crimean- Congo hemorrhagic fever virus causing disease in humans, and African swine fever virus and Nairobi sheep disease virus affecting livestock. Although several studies have elucidated tick antimicrobial mechanisms including cellular immune responses such as nodulation, encapsulation and phagocytosis and humoral immune responses such as the JAK/STAT pathway, complement-like proteins, antimicrobial peptides, lectin like pattern-recognition molecules and lysozymes, very little is known about the innate immune response of ticks towards viral infection. This study therefore aimed to identify molecules that might be involved in the response of ticks to viral infection. The hypothesis was that TBEV infection leads to changes in the expression of immunity-related transcripts and proteins in Ixodes spp. tick cells and that at least some of these might be antiviral. Ixodes scapularis-derived cell lines IDE8 and ISE6 were chosen since I. scapularis is currently the only tick species with a sequenced genome and an Ixodes ricinus-derived cell line, IRE/CTVM19, was used because I. ricinus is the natural vector of TBEV. Basic parameters required to study the responses of tick cells to infection were determined, including levels of virus infection, kinetics of virus replication and production, formation of replication complexes and uptake of dsRNA or siRNA. The cell lines IDE8, ISE6 and IRE/CTVM19 were infected with either of two tick-borne flaviviruses, TBEV and Langat virus (LGTV), or with the mosquito-borne alphavirus Semliki Forest virus (SFV). Infection was characterised using techniques including plaque assay, luciferase assay, immunostaining and conventional, confocal and electron microscopy. Two time points for transcriptomics and proteomics analysis of TBEVinfected IDE8 and IRE/CTVM19 cells were selected: day 2 post-infection (p.i.) when virus production was increasing and day 6 p.i. when virus production was decreasing. RNA and protein were isolated from TBEV-infected and mock-infected tick cells at days 2 and 6 p.i. and RNA-Seq and mass spectrometric technologies were used to identify changes in, respectively, transcript and protein abundance. Differential expression of transcripts was determined using the data analysis package DESeq resulting in a total of 43 statistically significantly differentially expressed transcripts in IDE8 cells and 83 in IRE/CTVM19 cells, while differential protein representation using Χ2 test statistics with Bonferroni correction in IDEG6 software resulted in 76 differentially represented proteins in IDE8 cells and 129 in IRE/CTVM19 cells. These included transcripts and proteins which could affect stages of the virus infection, including virus entry, replication, maturation and protein trafficking, and also innate immune responses such as phagocytosis, RNA interference (RNAi), the complement system, the ubiquitin-proteasome pathway, cell stress and the endoplasmic reticulum (ER) stress response. After verification of sequencing data by qRT-PCR, the ability of several of the identified transcripts or proteins to affect virus infection was determined by knockdown experiments in IDE8 and IRE/CTVM19 cells using wild type LGTV, LGTV replicons or TBEV replicons. Knockdown of genes encoding proteins including the ER chaperone gp96 and the heat-shock protein HSP90 resulted in increased virus production in both cell lines, hinting at an antiviral role. In contrast, knockdown of calreticulin, another ER chaperone, resulted in a decrease in virus production in IRE/CTVM19 cells but not in IDE8 cells, implying a requirement for virus production. This functional genomics approach has identified possible novel genes/proteins involved in the interaction between flaviviruses and tick cells and also revealed that there might be antiviral innate immune pathways present in ticks additional to the exogenous RNAi pathway.

Cette thèse étudie certains évènements particuliers des carnets d'ordre - les "trades traversants". Dans le premier chapitre, on définit les trades traversants comme étant ceux qui consomment la liquidité présente dans le carnet d'ordres sur plusieurs limites, sans laisser le temps à la meilleure limite de se remplir par l'arrivée de nouveaux ordres limites. On étudie leurs propriétés empiriques en fournissant des statistiques de liquidité, de volume, de distribution de leurs temps d'arrivées, de clustering et de relaxation du spread. Leur impact de marché est supérieur à celui des trades classiques, et ce même à volume comparable : les trades traversants présentent donc un contenu informationnel plus grand. On propose deux applications au problème du lead-lag entre actifs/marchés, d'abord pour répondre à la question de savoir quel actif bouge en premier, et ensuite pour mesurer la force du signal des trades traversants dans le cadre d'une stratégie d'investissement basée sur le lead-lag entre actifs. Le chapitre suivant approfondit l'étude empirique du clustering de l'arrivée des trades traversants. On y modélise leur arrivée par des processus stochastiques auto-excités (les processus de Hawkes). Une étude statistique de la calibration obtenue avec des modèles à noyaux exponentiels pour la décroissance temporelle de l'impact est menée et assure une modélisation satisfaisante avec deux processus indépendants, un pour le bid et un pour l'ask. La classe de modèles proposée à la calibration est bien adaptée puisqu'il n'existe pas d'effet inhibiteur après l'arrivée d'un trade traversant. On utilise ces résultats pour calculer un indicateur d'intensité basé sur l'arrivée des trades traversants, et améliorer ainsi une stratégie d'investissement de type "momentum". Enfin, une calibration non-paramétrique du noyau de décroissance temporel d'impact fournit une décroissance empirique encore plus forte qu'une loi exponentielle, et davantage proche d'une loi-puissance. Le dernier chapitre rappelle une méthode générale de détection statistique de sauts dans des séries temporelles de prix/rendements qui soit robuste au bruit de microstructure. On généralise les résultats empiriques connus à de nouveaux indices financiers. On adapte cette méthode de détection statistique de sauts à des trajectoires intraday afin d'obtenir la distribution de la proportion de sauts détectés au cours de la journée. Les valeurs extrémales et les plus grandes variations de cette proportion se déroulent à des heures précises de la journée (14 :30, 15 :00 et 16 :30, heure de Paris), déjà rencontrées dans l'étude des trades traversants. Grâce à eux, on propose une explication des caractéristiques principales du profil intraday de la proportion de sauts détectés par le test, qui s'appuie sur une modification de la part relative de chacune des composantes de sauts dans la trajectoire des actifs considérés (la composante des mouvements continus et celle liée aux mouvements de sauts purs).

The cattle tick, Rhipicephalus (Boophilus) microplus is a tick of veterinary and health importance globally, transmitting Babesia bovis and B. bigemina. Tick control is important and needed to prevent livestock diseases caused by tick-transmitted pathogens. Traditionally, tick control methods have resulted in development of acaricide-resistant ticks, environmental pollution and meat and milk contamination. Therefore, there is a need for alternative method and vaccines directed against tick feeding. The aim of this study was to identify proteins involved in tick feeding, tickhost-pathogen interactions and tick reproduction. Consequently, these will help in identification of antigens with the ultimate goal of developing anti-tick vaccines. R. (B.) microplus female ticks were collected at five different feeding stages. RNA was isolated from the salivary gland extracts (SGEs). The cDNA libraries were synthesized and sequenced with the Illumina MiSeq technology. Transcriptome data was analyzed with CLC Genomics Workbench, Trinity and Minia. The SGEs were also used to isolate the fractions: membrane, soluble and pellet protein for proteomic analysis. The proteomics data was analysed with Mascot, X!Tandem and Scaffold. Both the transcriptome and proteome analysis revealed the presence of major secretory protein families such as Kunitz, lipocalins, serpins, cement proteins and metalloproteases, while the majority of transcripts coded for housekeeping genes. / National Research Foundation (South Africa) / Life and Consumer Science / M. Sc. (Life Science)

This diploma thesis addresses the topic of informing people of tick-borne encephalitis and vaccination against this disease. Our diploma thesis has four objectives in total. The first objective was to ascertain how many of the respondents were vaccinated against tick-borne encephalitis. The second and the third objectives were to demonstrate the reasons of vaccinated and unvaccinated respondents. The fourth objective was to analyze the attitudes of the respondents to publicization of the tick-borne encephalitis issue. As an infection with the natural focus, the disease is caused by a tick-borne encephalitis virus belonging among flaviviruses. The carrier is a sheep tick (Ixodes ricinus). Ticks live as parasites on reservoir animals, such as small rodents, ungulates and domestic animals. The clinical picture of the disease has mostly two stages and the symptomatologic form affects in particular adults and seniors. South Bohemia is a significant focus of tick-borne encephalitis with the sickness rate considerably exceeding the average of the Czech Republic. The most efficient prevention of the disease is vaccination. Two vaccines have been registered in the Czech Republic at present, namely FSME-Immun of Baxter and Encepur of Novartis. Both the vaccines are intended for children from 1 year of age. The basic vaccination scheme consists of 3 doses and the vaccinated person needs to be revaccinated every 3-5 years. It follows from the questionnaire research that 49 % of the total number of 136 respondents are vaccinated. As expected, the most frequent reason for vaccination (65 %) is the fear of becoming infected with tick-borne encephalitis. Other reasons are the interventions of the surrounding persons persuading the person to become vaccinated (19 %) and the financial contribution of the health insurance company or the employer (16 %). 35 % of the unvaccinated respondents do not plan to become vaccinated in the future. Approximately 40 % of the unvaccinated respondents feel that they do not need the vaccination or do not trust vaccination as such. 42 % of the unvaccinated persons would agree to vaccination if they received a financial contribution of the health insurance company or the employer, but nothing at all would convince 35 % of the unvaccinated respondents. It follows from the research that most respondents are satisfied with the quantity and the content of the information about tick-borne encephalitis. They do not think that anything should be changed in the system of informing of the disease. This thesis contributes to monitoring the trends in thinking of the public, and will eventuate in the finding which way the education of people about tick-borne encephalitis should be directed.

Tick proteins functioning in vital physiological processes such as blood meal uptake, digestion and reproduction are potential targets for anti-tick vaccines, since vaccination could disrupt these essential functions and ultimately affect tick survival. In this study we identified metzincin metalloproteases from R. microplus, the world’s most economically important external ectoparasite of cattle, as potential vaccine candidates since they are implicated to be essential to blood-cavity formation, bloodmeal digestion and reproduction in ixodid ticks. A vaccine derived from a single member of such a large family pose the obstacle of redundancy within the family, that may allow the function of the targeted family member to be taken up by other family members. Therefore the aim of this study was not only to focus on the physiological importance of each metzincin transcript, but also to investigate the differential gene expression network between the different metzincin family members. Eight transcripts encoding proteins containing the characteristic metzincin zinc-binding motif HEXXHXXG/NXXH/D and a unique methionine-turn were identified from native and in-house assembled R. microplus Expressed Sequence Tag databases. These were representative of five reprolysin-like and three astacin-like metzincin metalloproteases. Reverse transcription-PCR indicated that the reprolysins were most abundantly expressed in the salivary glands, whereas the astacins were most abundant in the midgut and ovaries. In vivo gene silencing utilizing RNA interference, was performed to assess a possible phenotype in silenced adult female R. microplus ticks during blood feeding and reproduction. RNAi against two reprolysins and one astacin significantly affected average egg weight as well as the oviposition rate. Moreover, integrated real time-PCR studies revealed an extensive cross organ network between the R. microplus metzincin transcripts, supporting the use of a combinatorial metzincinbased anti- R. microplus vaccine targeting multiple members of the large metzincin clan simultaneous. To conclusively evaluate the vaccination potential of the three identified metzincin candidates, the immunogenicity and protective properties of the recombinant proteins needs to be determined. Due to metalloproteases destructive activity and characteristics such as cysteine rich domains, only selected domains of the three candidates were expressed, using a cost effective Eshericia coli based expression system. Finally, the ability of each successfully expressed domain to elicit an immune response and serve as a protective antigen against R. microplus will be screened during vaccination trials in cattle. / Thesis (PhD)--University of Pretoria, 2013. / gm2013 / Biochemistry / unrestricted

No description available.

Louping ill virus (LIV) is a tick borne disease that causes mortality in red grouse, an economically important game bird of British uplands. The aim of this thesis is to extend previously published models of LIV , to consider the potential impact of different management strategies. In addition a new route of infection and the seasonal biology of both grouse and ticks will be explored. Grouse chicks are known to eat ticks as part of their diet in the first three weeks of life which may contribute to virus persistence if chicks consume infected ticks. This novel route of infection is incorporated in to the model which predicts that ingestion increases the range of host densities for which the virus is able to persist. The ingestion of ticks by grouse also reduces the tick population so that for low host densities the ingestion of ticks by grouse reduces the tick population so virus cannot persist. The model is adapted to take account of the seasonal biology of grouse and ticks. Although the temporal predictions of the seasonal models show some differences the addition of seasonality does not alter the model predictions of when LIV is likely to persist at different grouse and deer densities. Consequently seasonality is felt to be unimportant when considering management strategies. The treatment of sheep with acaricide in an attempt to reduce the tick population on a grouse moor is currently being trialled in Scotland. We use a model to predict the likely effect of this strategy at different deer densities. The number of ticks found attached to sheep varies so we consider the effect of tick attachment rates as well as acaricide efficacy. Although we predict that acaricide treated sheep can reduce the tick population and therefore LIV in grouse in some circumstances the treatment is less effective in the presence of deer. Consequently we use a model to make theoretical predictions of the effectiveness of acaricide treated deer as a control strategy for reducing LIV in red grouse. The effect of culling deer on LIV in grouse is also modelled and contrasted with the effect of acaricide use. It is predicted that acaricide treatment of deer could be highly effective, particularly if the deer density is first reduced by culling. Finally we considered the direct treatment of red grouse with acaricide. Female grouse can be given an acaricidal leg band which protects her directly and indirectly protects her chicks as they acquire some acaricide whilst brooding. Trials have suggested this can reduce tick burdens for individuals. We use the model to determine the potential effect that treating individual broods may have on the whole grouse population. The model predictions suggest that unless acaricide efficacy on chicks is high and long lasting treating individual broods is unlikely to reduce LIV in the whole population but will still provide some benefit for the individuals. The effectiveness of treatment is reduced by higher deer densities. The success of the management strategies considered in this thesis appear to be restricted by the presence of deer. It may therefore be that a combination of treatments including the treatment of deer may be of the greatest benefit to the grouse population.

The proposed thesis contributes to the basic knowledge in tick (Ixodes ricinus) and tick-borne pathogens (Borrelia burgdorferi sensu lato, tick-borne encephalitis virus) ecology in particular studying the spatial distribution, host associations and its causes and consequences in Central European habitats.

Published Article / A study was conducted to determine the differences between four breeds in respect of coat score, hide-thickness, tick burden and body condition score. The study was comprised of 40 heifers - 10 of each breed, namely Afrikaner, Braford, Charolais and Drakensberger. A subjective system of coat scoring, ranging from extremely short to very woolly, was used. Body condition score was measured subjectively, with 1 being emaciated and 9 being obese. Hide-thickness (in mm) and tick count were also determined. Between August 2007 and early March 2008, measurements were carried out on the same 10 animals of each breed, with highly significant differences in body condition score, hide-thickness and tick count being observed between the breeds in all instances. Coat scores differed significantly between breeds in the earlier and latter stages of the study becoming less significant midway through. A significant difference in body condition score within breeds was also found, while hide-thickness did not differ significantly within breeds.