Thesis (Ph.D.)--Murdoch University, 2007. / Thesis submitted to the Division of Health Sciences. Includes bibliographical references (leaves 145-189).

Inaug.-Diss.--Bonn. / Vita. "Literaturverzeichnis": p. 95-100.

AN ABSTRACT OF THE DISSERTATION OF Wendi Krista Middleton, for the Doctor of Philosophy degree in Health Education, presented on April 15, 2015 at Southern Illinois University Carbondale TITLE: TICK-BORNE DISEASES: ASSESSING THE KNOWLEDGE, ATTITUDES, AND BEHAVIORS OF COLLEGE STUDENTS. MAJOR PROFESSOR: Dr. Dhitinut Ratnapradipa Within the last few decades, the prevalence of tick-borne diseases (TBDs) has dramatically increased. Symptoms of TBDs are very similar to other illnesses and are often referred to as flu-like in nature. TBDs could be easily prevented, however, if people used proper prevention methods. If not treated early in the course of illness, tick-borne infections have the potential to cause serious health problems and even death. It is, therefore, extremely important that individuals use proper prevention strategies in order to reduce the risk of contracting TBDs. This research focused on the college population because these individuals represent one of the most active adult outdoor populations. While many students know that ticks carry diseases, it is thought that they have a poor understanding of the extent to which TBDs affect human health. Additionally, many experts believe that knowledge of health-related topics plays a major role in determining how individuals behave in regard to those concerns. Furthermore, a person's behavior strongly influences their risk of contracting a TBD. Information collected allowed for determining whether or not a person's knowledge and perceptions of tick-borne diseases have an influence on their prevention practices. As expected there was a lack of knowledge regarding tick-borne diseases. College students who volunteered to participate in this study indicated that they are unaware of the proper methods to use in order to prevent contracting TBDs. Thus, it was not surprising that they do not utilize correct prevention strategies. Additionally these students stated that more information about TBDs should be added to the curricula in college health courses. This research aimed to improve the psychometric properties of a newly created survey and assess college students' knowledge, attitudes, and associated behaviors regarding TBDs. Discovering the current knowledge of college students regarding TBDs has helped researchers in determining the effect that individual knowledge of TBDs has on a person's attitudes, and behaviors regarding prevention.

Flaviviruses are a single-stranded, positive sense, RNA virus that affect around 400 million people annually. Flaviviruses are transmitted by arthropod vectors, the most common vector being the mosquito. Currently, many mosquito control strategies are in use, these control strategies are diverse in both efficiency and cost. However, developing new vector control strategies is becoming increasingly important, due to climate changing affecting vector population distribution and the current limitations conventional control strategies face. Although many different control strategies exist, there is limited research pertaining to reducing viral infection in the vector. Reducing the transmission capabilities of vectors could help relieve the disease burden felt around the world. Aripo virus (ARPV), an insect-specific flavivirus, has ushered in opportunities to discover a novel approach to arbovirus control. The exclusionary effects of ARPV were explored as a means to eventually understanding superinfection exclusion (SIE) and utilizing it as a calculated defense against mosquito-borne disease. Aripo virus was evaluated for its SIE potential in vitro and experiments were performed to explore the possible mechanisms underlying SIE. Aripo virus showed significant exclusion against the flaviviruses tested, as well as an alphavirus. Additionally, West Nile virus was unable to adapt and overcome SIE barriers over 9 serial passages. Lastly, ARPV was superinfected with chimeric viruses to asses replication kinetics, and possible exclusionary bias was seen with non-structural genes. These data show ARPV is capable of reducing viral titer, as well as possible leads into understanding the underlying mechanism of SIE, a critical step in utilizing SIE as a strategy to combat vector-borne disease. / Master of Science in Life Sciences / Mosquitoes all around the globe spread disease causing pathogens. Infection with viral pathogens such as West Nile virus, Zika virus, and Japanese encephalitis virus can cause lifelong health effects or even death. Risk for increased spread of mosquito-vectored disease is on the rise. The continued effects of climate change, increasing temperatures away from the equator, and increased encroachment into natural areas for urban development, is opening the door for new infectious diseases spread by mosquitoes. There are many ways to curb the effects that these viral diseases can have on humans, including vaccines or mosquito repellents, and even eliminating mosquito populations is helping to reduce the effects of these important diseases. Sadly, no one method can solve the problem. The methods of dealing with mosquito transmitted disease are likely to be most effective when done in combination. The more countermeasures that attempt to stop the spread of disease, the greater dent in reducing the spread of disease. In this dissertation, we dive into the realm of stopping disease transmission before humans become a factor. If we can limit mosquito infections, then the disease has no way of reaching humans. An approach to controlling mosquito infections could lie within viruses themselves. Aripo virus, an insect-specific virus, is interesting in that it does not affect vertebrates, only mosquitoes. When Aripo virus infects mosquito cells at the same time as deadly viruses, the deadly viruses do not accumulate in the mosquito cells nearly as much. Within mosquito cells, Aripo virus was able to reduce the levels of West Nile virus, St. Louis encephalitis virus, Japanese encephalitis virus, Zika virus, and Mayaro virus. If the underlying concept of the method of Aripo virus induced exclusion of deadly viruses could be further understood, it could be used to reduce the spread of mosquito-related viral diseases.

Due to the rapid nature of microwave heating, the microbiological safety of foods prepared in the microwave has been in question for several years. Because foods are heated from the inside out and are strictly governed by their own internal properties such as ionic content, moisture level and specific heat, work must be done to further master control of such properties so microwave cooking can be more predictable, controlled and ensure control pathogens. This study concentrated on the effect of fat content, evaporative cooling and food type on the rate of food borne pathogen survival rates in microwave heated foods. Foods investigated in this study included fresh, raw broccoli spears; a regular, whole muscle breaded chicken patty and a fat free, breaded, formed chicken patty; and raw ground beef patties at three differing fat percentages. All foods were tested in triplicate. A Sharp® 1000W Light-Duty Commercial Microwave Oven was used to treat inoculated samples according to their recommended cooking times. Two sets of samples were treated, one wrapped with Saran™ Wrap and the other without wrap. F-values were determined for each product. Raw ground beef patties at fat contents of 30%, 15% and 7%, heated for the same time had F-values ranging from 0.03 to 126.20. The lower the fat content, the lower the lethality. Regular and fat free chicken tenders had similar patterns. F-values for fresh broccoli indicted that vegetative pathogens survived the recommended microwave process. Covering in Saran™ Wrap had some preventive effect on evaporative cooling depending on the food tested and significantly (p < 0.05) increased most F-values. Inoculated pack studies were performed in triplicate on each food with Listeria monocytogenes, Salmonella and Escherichia coli O157:H7. Survival was determined by presence or absence of growth of each pathogen after enrichment. Listeria monocytogenes survived in all samples except for the 30% fat ground beef patties. The Salmonella species had a lower survival rate; however, it was still present in uncovered 15% fat ground beef, covered 7% fat ground beef, uncovered chicken patties (both types) and in all broccoli samples tested. E. coli O157:H7 survived in all samples except the 30% fat ground beef samples. Results indicate that higher fat contents seem to ensure lower rates of pathogen survival. This was especially true for the raw ground beef, which had received no prior processing other than the grinding of the whole muscle. There were fewer survival differences in the preprocessed, frozen chicken patties. Both were shown to support no pathogen survival in covered samples, except the fat free chicken patties. Listeria monocytogenes was shown to consistently survive the suggested cooking time in these samples. This is consistent with expectations that fat free food samples would display more survival than regular fat samples. Overall, covering samples with Saran™ had little effect on pathogen survival rates. There were survival differences in some covered and uncovered samples consistent with expectations that covered samples would show less survival than uncovered, but further work including more samples would be necessary to ensure that the covered or uncovered variable made the true difference in pathogen survival. Finally, broccoli demonstrated consistent pathogen survival in all categories of testing. This indicates microwave oven prepared vegetables could be a prime source of pathogen transmission to consumers. Further work needs to concentrate on determining the correct processing times and parameters that need to be met to ensure safe food. / Master of Science

No description available.

Hepatitis E virus (HEV) is the main cause of acute viral hepatitis worldwide, predominantly in developing areas where it is endemic. Recently, HEV has gained more attention in the developed world, prompting several industrialized countries to assess seroprevalence rates using blood donor samples. The seroprevalence among Canadian blood donor samples collected from July 2013 - December 2015 was 5.84% (240/4,107). None of the 14,053 samples tested were positive for HEV RNA. There was no significant increase in the high-risk groups we tested. HIV was determined to be a significant risk-factor for HEV infection in a retrospective study of Kenya-based sex-worker cohorts, but not so in a Canadian cohort of HIV-positive intravenous drug users. Overall, HEV seroprevalence in Canada is lower than that published in other countries. This together with failing to detect HEV RNA in Canadian blood donations indicates that HEV currently poses low risk to the Canadian blood supply. / February 2017

A test facility was constructed to conduct experimental investigation of erosion caused by gas-borne ash particles. The test facility was used to carry out the main objective of the study which was the determination of the critical angle of attack that gives maximum erosion on the target material, mild steel, and the effect of particle velocity and concentration on the erosion of the target material. The tests were carried out using ash samples from three different Eskom fossil-fuelled power stations, namely Matimba Power Station, Matla Power Station and Lethabo Power Station. The selection of the ash samples was based on the ash chemical composition that has the highest content of the chemical elements that have a significant influence in the material erosion of the target material. These chemical elements are quartz and other abrasive materials. These ash samples had a high content of these erosive materials. The first test that was carried out in this study was the determination of the critical angle of attack that gives maximum erosion on the target material. It was decided to start by doing this test because the velocity and concentration tests needed a predefined critical angle of attack that gives maximum erosion on the target material. During the velocity and concentration tests the angle of attack was kept at the predefined critical angle of attack. The results in this study indicate that the critical angle of attack that gives maximum erosion on the target material is at 27º ± 3º orientation of the target surface. The velocity test results indicate that the material erosion rate increases with increasing velocity. The results produced a power relationship between erosion rate and velocity. In this power relationship the velocity exponent for the three ash samples was found to be in the range between 2.42 and 3.64. The concentration test results also indicate that the material erosion rate increases with increasing particle concentration. These results produced a linear relationship between erosion rate and particle concentration.

Arthropod-borne viruses, arboviruses, have the ability to replicate in both vertebrates and invertebrates and are transmitted to susceptible vertebrate hosts by vectors such as mosquitoes and ticks. Ticks are important vectors of many highly pathogenic arboviruses, including the flavivirus tick-borne encephalitis virus (TBEV) and the nairovirus Crimean-Congo haemorrhagic fever virus. In contrast, alphaviruses are principally mosquito-borne and have been isolated only rarely from ticks; ticks have not been implicated as their vectors. Nevertheless, the alphavirus Semliki Forest virus (SFV) replicates in cell lines derived from many different tick species, including those of the genus Ixodes, which includes vectors of TBEV and its lesspathogenic relative Langat virus (LGTV). In vertebrate cells, arboviruses generally cause cytopathic effects; however, arbovirus infection of arthropod cells usually results in a persistent low-level infection without cell death. While little is known about antiviral immunity in tick cells, the immune system of other arbovirus vectors such as mosquitoes has been studied extensively over the last decade. In insects, pathways such as RNA interference (RNAi), JAK/STAT, Toll, Imd and melanisation have been implicated in controlling arbovirus infection, with RNAi being considered the most important antiviral mechanism. In tick cells, RNAi has been shown to have an antiviral effect, but current knowledge of other immunity pathways is limited and none have been implicated in the antiviral response. In the present study, SFV and LGTV replication in selected Ixodes spp. tick cell lines was characterised and the Ixodes scapularis-derived cell line IDE8 was identified as a suitable cell line for this project. Potential antiviral innate immunity pathways were investigated; putative components of the tick JAK/STAT, Toll and Imd pathways were identified by BLAST search using available sequences from well-studied arthropods including the fruit fly Drosophila melanogaster. Using gene silencing, an attempt was made to determine whether these pathways play a role in controlling SFV and LGTV infection in tick cell lines. Selected genes were silenced in IDE8 cells using long target-specific dsRNA and cells were subsequently infected with either SFV or LGTV. Effects of gene silencing on virus replication were assessed by quantitative real time PCR (qPCR) or luciferase reporter assay. Effects on infectious virus production were measured by plaque assay. Replication of the orbivirus St Croix River virus (SCRV), which chronically infects IDE8 cells, was also quantified by qPCR after silencing of selected genes. Interestingly, SFV or LGTV infection of IDE8 cells resulted in a significant increase in SCRV replication, possibly as a result of interference with antiviral pathways by SFV and LGTV or possibly due to diversion of cellular responses from sole control of SCRV. No evidence for an antiviral role for the JAK/STAT or Toll pathways was found in IDE8 cells. However, an antiviral effect was observed for protein orthologues putatively involved in the RNAi response. Argonaute proteins play an important role in translation inhibition and target degradation mediated by RNAi, and silencing of selected Argonaute proteins resulted in a significant increase in SFV and SCRV replication. The carboxypeptidase CG4572 is essential for an efficient antiviral response in D. melanogaster, and supposedly involved in the systemic RNAi response. A putative tick orthologue of CG4572 was identified and this appeared to be involved in the antiviral response in IDE8 tick cells. When expression of CG4572 was silenced and cells subsequently infected with SFV or LGTV, replication of both viruses was significantly increased. In addition, it was shown that three mosquito orthologues of CG4572 also had an antiviral role against SFV in Aedes mosquito cells. In conclusion, of the tick cell lines investigated, IDE8 provided a suitable model system for investigating tick cell responses against arboviruses and new insight into the nature of the tick cell antiviral response was gained.

No description available.