Coital frequency is an important theoretical determinant of the rate at which an STI can spread through a population. Differences in frequency of sex may bias measures of condom use based on survey data because survey respondents who have infrequent sex and those who have frequent sex contribute equally to commonly used measures of condom use. Data on sexual behaviour are widely available from surveys but detailed information on coital frequency is seldom collected. This thesis examines the available information, examines the utility of a method to make the most use of existing data and investigates whether condom use measures are biased by differences in coital frequency using, for the most part, data from Australia and Tanzania. The existing data and literature show a lack of information on coital frequency for men and for unmarried people. Certain factors are correlated with coital frequency but there are no stable patterns of variation between different populations. Data from Australia and Tanzania show that condom use and coital frequency both vary according to the types of partnership for which they are reported. Further analysis of commonly used measures of condom use shows that these measure are influenced by differences in coital frequency and demonstrates that additional measures, describing the proportion of sex acts protected by condoms, provide complementary information. The scarcity of data on coital frequency is unlikely to be resolved by using the more widely available information on time since most recent sex. Although it is theoretically possible to work backwards from this to the number of sex acts in a given time period, this does not work in practice. Recommendations are made for improved methods to collect coital frequency information in large-scale surveys of the general population.

No description available.

Fasciolosis, a zoonotic infection in humans and livestock, is caused by fasciolid trematodes. The trematode lifecycle requires the infection of a molluscan intermediate host by motile miracidia which hatch from fluke eggs deposited in faeces of definitive host. The transmission of miracidia to snails is considered as the most vulnerable link in their life cycle, and hence has been the focus of considerable interest, in an attempt to reduce the transmission rate. This thesis explores factors involved in interaction between liver fluke miracidia and their snail intermediate host. The species of lymnaeid snails present on farms in Ireland where infected livestock with fasciolosis have been reported, have been identified and their genetic variability and population structure has been determined. The correlation between environmental characteristics and snail prevalence and fluke infection has been assessed (Results I and 11). Host finding and recognition abilities of the Fasciola hepatica miracidia have been studied. Chemotactic ability of the miracidia is found to be comprised and an alternate explanation for successful transmission of the fasciolosis, in which sna'ils were attracted towards the source of miracidia, has been discussed (Results Ill). The swimming patterns of miracidia, from three species of fasciolids, have been determined and analyzed and their responses to physical factors, such as, temperature and salt concentrations have been noted (Results IV). Responses to two anthelmintic drugs by the liver fluke miracidia have been studied, leading to the development of a new method of testing the efficiency of drugs on trematodes (Results IV). Immunofluorescent light microscopy, scanning and transmission electron microscopy have been used to study the structures involved in the movement of miracidia (Result V). The information derived from the experimental work in this thesis may help find an effective way to disrupt the snail-trematode interaction and thus prevent the transmission of fasciolosis

The thesis covered validation of quantitative polymerase chain reaction (qPCR) assays for the detection of the genital Mollicutes - M.genitalium, M.hominis, U.urealyticum, U.parvum, and relevant non Mollicute organisms found in the urogenital tract specifically T. vagina lis, G. vaginalis and S.agalactiae; a novel qPCR was developed for G.vaginalis. The assays were applied to (a) residual anonymised specimens from a Genitourinary Medicine clinic and (b) placental specimens collected with informed consent in pregnancies presenting in preterm labour; both approaches had appropriate ethical approval. The analysis allowed the prevalence, clinical significance and synergistic relationships of genital Mollicutes to be assessed in different anatomical sites (urethra, vagina, rectum) and different clinical conditions. The qPCR assays were highly reproducible, provided new observations and allowed novel findings to emerge from the overlapping stUdies. Mollicute infections are common and therefore commonly missed by current testing algorithms for STls. M.genitalium and U.parvum were significantly associated (p<0.001 and p=0.03 respectively) with non-chlamydial non-gonococcal urethritis in men attending GUM. U.parvum, which is a bacterial commensal of the vaginal micro-flora, showed a significant association with chorioamnionitis (p=0.002) in women delivering preterm and also demonstrated growth synergy (p=0.017) with G.vaginalis in bacterial vaginosis. A further synergy involving M.hominis and G.va!~inalis (p <0.0001 ) was also demonstrated in bacterial vaginosis and in the rectum of men who have sex with men. The association with preterm labour and with bacterial vaginosis suggests that disruption of the vaginal micro-flora in pregnancy could trigger serious obstetric complications involving commensal bacteria. It could also be speculated that the synergistic bacterial overgrowth seen in samples from the rectal mucosa is a factor in HIV transmission across an inflamed surface. The prevalence data and associations with important clinical conditions would support the need for more research on the role of Mollicutes and co-infection in both STls and infections in pregnancy.

Responses to venereal disease in the British army can only be understood if looked at in a wider context that takes in the attitudes of some of the most influential sectors of British society. Medical professionals, especially those advising and working with the British army, suggested that the problem would be better resolved ifVD was simply treated like any other disease; they called for treatment to be blame and stigma free. However, the British army found this impossible and resorted to an assortment of strategies that were relics of the past and were often at variance with each other. Troops lost pay and rights to leave if they contracted VD confirming that to become infected was a punitive offence; lectures confirmed to troops that to be celibate would not endanger health and to contract a venereal infection was letting down themselves, their comrades and the nation. At the same time the army provided military brothels and disinfectants to use after sex. This thesis examines the influences that obstructed a clear policy; it is only with a thorough investigation into the discourses that surrounded VD that we can appreciate the deficiency and ambiguity of the strategies adopted. The attitudes of the churches, the religious organisations, the voluntary groups and the popular press confirmed that certain groups were to blame and the result of these persistent and Ubiquitous views was that no clear course of action was ever universally accepted or implemented. VD like other social diseases generated responses that confirmed that VD was more than the 'common contagion' that some doctors would have preferred it to be. Strategies to combat it were complicated by the social construction of the disease, obscured by perceptions of who was most likely to catch it and fears over the repercussions for society and the nation, especially during a time when being different took on new meaning. Fears surrounding the infection of individual bodies metaphorically represented broader fears for the body ofthe nation and just as those from outside the nation were distrusted so were the 'infectors' within.

This thesis describes design, construction and evaluation in a BALB/c mouse model, for five novel Brucella specific DNA vaccines. Brucellosis is worldwide zoonosis of economic significance that poses a significant threat to both animal and human health. Vaccination of livestock can be valuable for reducing transmission and facilitating control. Development of an efficacious non-living vaccine is therefore a valuable goal in brucellosis research. Five candidate antigens were identified within the Brucella melitensis 16M genome. In silico selection was supported by confirming transcription of the selected genes from cultured Brucella, and evidence of candidate protein immunogenicity in Brucella infected sheep. Eukaryotic and prokaryotic expression plasmids were constructed for each candidate antigen. The protective efficacy of six DNA vaccine constructs was evaluated in a BALB/c model of brucellosis. From this evaluation, two protective antigens were identified for further study: Invasion protein B and the 25 kDa outer membrane protein. The DNA vaccines p-omp25 and p-ialB were shown to have equivalent protective efficacy in the mouse model to that achieved through vaccination with the live vaccine strain Rev.1. DNA vaccine mediated protection was associated with production of specific antibodies and priming of both CD4+ and CD8+ IFN-y secreting cells. High numbers of CD8+ cells were observed for the p-omp25 vaccine, whereas CD4+ cells and antibodies were more prevalent following pialB vaccination. The vaccines were found to be most effective when three homologous booster vaccinations were used. Single dose vaccination afforded only modest levels of protection. Attempts to improve delivery of DNA vaccines through adsorption of DNA to cationic liposomes was partially successful in that there was a notable increase in specific humoral immune responses. However, these increases were not associated with increased cell mediated immunity or protective efficacy.

No description available.

Chlamydia trachomatis is the leading infectious cause of preventable blindness and the most common sexually transmitted bacterium worldwide. Trachoma presents an environment in which to investigate chlamydial pathogenicity, the conjunctivae serving as an accessible model with an objectively observable phenotype. The Bijagós Archipelago is a unique setting where trachoma is hyperendemic. The primary aims of this study were to use novel molecular, bioinformatic and geostatistical approaches in conjunction with population-based clinical and epidemiological metadata to investigate the micro-epidemiology of ocular C. trachomatis and active trachoma in this population. The prevalence of trachoma and ocular C. trachomatis infection have been documented, and socio-environmental risk factors have been identified that may be important in the implementation of trachoma elimination activities in these communities. A strong association was found between C. trachomatis ocular load (estimated using droplet digital PCR) and the level of conjunctival inflammation. Geostatistical analyses suggest that ocular C. trachomatis load may be important in transmission, as spatial clusters of high load infections were identified, whilst spatial clusters of low load infections were absent. This study includes the first population-based pathogen genome-wide association scan (GWAS) for C. trachomatis, using high quality next generation whole genome sequence data obtained directly from clinical samples. The genomewide associations with conjunctival inflammation (incE) and C. trachomatis load (mutY and CTA_0271) present genes involved in specific biological characteristics of C. trachomatis, the functions of which suggest that early interactions with host cells are important in C. trachomatis pathogenesis. Pathogen GWAS, applied in this context, is a powerful approach in the identification of multiple targets for further study in pathogenesis and directed study of potential vaccine candidates, allowing a greater understanding of association and interaction of genes on a genome-wide scale. Following a single round of mass drug treatment with oral azithromycin (MDA) in these communities the prevalence of active trachoma and ocular C. trachomatis were significantly reduced. Individual and median loads of C. trachomatis were reduced and the highest burden of disease and infection were concentrated in young children. Spatial clustering of infection identified using geostatistical tools was intensified following MDA, but the number of clusters of high load infections was reduced. The severity of conjunctival inflammation was reduced following MDA. This study suggests that chlamydial load is important in disease pathogenesis and may be important in transmission of infection. Geospatial tools may be useful in the context of MDA to identify clusters of infection and thresholds of C. trachomatis bacterial load that may be important foci of transmission. The association between conjunctival inflammation and C. trachomatis load may reflect pathogen virulence. This is supported by the presence of genome-wide associations with C. trachomatis load and conjunctival inflammation identified by pathogen GWAS. Further epidemiological, in vitro and in silico studies are required to provide a more complete picture of the relationship between disease severity, bacterial load and chlamydial diversity in the context of transmission and elimination dynamics.

Presently, clinical management of sexually transmitted infection (STI) is performed empirically, in the absence of microbiological diagnosis and consequentially the use of suboptimal antimicrobial therapy. Current diagnostic methodologies cannot facilitate the polymicrobial detection required to identify the potential multiple organisms that contribute to STI's. In order to meet this requirement a PCR coupled micro array capable of detecting the presence or absence of 23 organisms relevant to STI was developed and evaluated. This method was applied to explore the differential organism prevalence in 129 first void urine specimens in patients of varying symptomology, revealing the absence of Lactobacilli may be associated with urethritis. Findings of this study also documented the inadequacy of Gram stained urethral smear (GSUS) for identification and stratification of urethritis cases. Performance of rapid automated urine flow cytometric (AUFC) of urinary white cell count (UWCC) as a potential replacement for GSUS was validated in a separate study of male clinic attendees (n=436). UWCC testing demonstrated significantly enhanced specificity when compared to GSUS; universal application of this method would have significantly improved identification of urethritis cases at the point of care. The degree of urethral inflammation implied by UWCC analysis exhibited a stronger association with pathogen load of Mycoplasma genitalium when compared to Chlamydia trachomatis. A notably high prevalence of azithromycin resistant M. genitalium infection was observed amongst study participants; subsequent phylogenetic analysis implied this finding was applicable beyond this patient population. The findings of this thesis contribute new approaches to tackling the inadequacies of current empirical approaches to STI management. Modification of treatment guidelines in light of these findings and adoption of UWCC testing may improve treatment efficacy and enhance detection of nongonococcal urethritis and related syndromes. Results observed also provide an insight into the pathogenic mechanisms of different STI organisms in relation to host inflammatory responses.

Chlamydia trachomatis is an obligate intracellular bacterium, responsible for the most prevalent bacterial sexually transmitted infection and is the leading cause of acquired blindness worldwide. Chlamydiae survive and replicate within a specialised intracellular membrane-bound compartment known as the inclusion. Inclusion biogenesis requires manipulation of host processes by translocated bacterial effectors. Despite Chlamydia targeting at least one effector into the nucleus, surprisingly little is known about how and why the bacteria interact with this major organelle. The aim of the work presented in this thesis was to examine the consequences of Chlamydia infection on nuclear architecture, organisation and function. Structurally, nuclei of cells infected with C. trachomatis become highly lobulated, reminiscent of both laminopathy and transformed cells. Analysis of the nuclear lamina (NL) demonstrated that lamin A/C is enriched at the inclusion-proximal face of the nuclear envelope (NE) and depleted elsewhere around the nuclear periphery. Lamin B is reduced and nuclear pore complexes (NPCs) are depleted in the inclusion-proximal lamin A/C-enriched region. Other NL scaffolding proteins including SUN proteins and emerin are unaffected. Transmission electron microscopy revealed a minimal distance of ~100 nm is maintained between the NE and inclusion membrane (IM), showing a classical membrane contact site does not form. Lamin A/C enrichment and NPC depletion occur independently of existing cellular NPC-free islands present in the NE, and are specific to C. trachomatis rather than C. muridarum. Functionally, these infection-associated NE alterations are promoted by bacterial factors and can recover following induced bacterial killing or inclusion clearance. Host nuclear protein transport ceases in the NPC-depleted region, whereas host nuclear mRNA distribution is unaffected. Associated local changes in host chromatin architecture occur, since heterochromatin accumulates at the inclusion-proximal face of the nuclear periphery at NPC-depleted and lamin A/C-enriched zones. Lamin A/C changes are the driving force behind the NE modifications, as the NPC-depletion and heterochromatin accumulation is absent when cells lacking lamin A/C are infected with C. trachomatis. Remarkably, in these knockout cells, inclusions are larger and more bacterial progeny are produced. Computationally, chlamydial proteins of unknown function that may be translocated to the nucleus or NE were identified. A tool was developed to generate a consensus secondary sequence from multiple available prediction software. Using this tool, the chlamydial proteome was searched for proteins similar in secondary structure to known cellular NE or NE-interacting proteins. Three proteins were identified, of which CT350 and CT384 are predicted to be type III secretion substrates. When ectopically expressed in HeLa cells, CT384 localised to the nucleus and resulted in aberrant nuclear architecture. Taken together, the data demonstrate that Chlamydia profoundly manipulates nuclear architecture from within the inclusion, and via interactions at the inclusion-proximal region of the NE constructs a lamin A/C-enriched platform to drive localised redistribution of heterochromatin and changes in host gene expression.