No description available.

No description available.

Adherence to artemisinin-based combination therapies (ACTs) for malaria is important for effective treatment. This thesis compares adherence to ACTs obtained in the public and private retail sectors, describes an intervention to improve dispenser knowledge and patient adherence, and addresses challenges of measuring patient adherence to ACTs. A cluster randomised trial of a text message intervention targeted at dispensers in Accredited Drug Dispensing Outlets (ADDOs) was conducted in Tanzania to improve provision of advice on artemether-lumefantrine (AL) and as a result patient adherence. An observational study was also conducted among patients obtaining AL from public health facilities. In a third study, smart blister packs that recorded when pills were removed were used to assess the validity of self-report. Adherence was measured as completion of all doses (“completed treatment”) and completion of each dose at the correct time (“timely completion”). The intervention improved dispenser knowledge, but had no effect on patient completion of treatment (intervention 68.3%, control 69.8%, p [adjusted] = 0.6), or timely completion (intervention 33.1%, control 32.6%, p [adjusted] = 0.9). ADDO patients were wealthier, more educated, older, sought care later in the day, and were less likely to test positive for malaria than health facility patients. The adjusted odds of completed treatment and of timely completion for ADDO patients were 0.65 (95% CI: 0.43, 1.00) and 0.69 (95% CI: 0.47, 1.01) times that of health facility patients. Timely completion, but not completed treatment, was lower by smart blister packs than by self-report (37% vs. 24%, p<0.0001). Adherence to AL in both sectors was suboptimal. As the private sector continues to be important for malaria treatment, better understanding is needed of which aspects of patient care are most important to maximise adherence and how methods of assessing adherence can be improved.

Sulphadoxine pyrimethamine resistance (SPR) emerged soon after SP was introduced as first line therapy for malaria in Africa during the 1990s. This thesis presents the first attempt to describe the spatio-temporal distribution of SPR in sub-Saharan Africa. Molecular and in vivo SPR data were gathered from primarily published sources onto a handwritten and digital template, recording the precise geo-location of every data point. The most commonly used methods were the World Health Organisation 1973 and 1996 protocols to measure in vivo efficacy and PCR-RFLP for molecular studies. Consistent data gaps with both SPR measures were found in Botswana, Burundi, Cape Verde, Eritrea, Somalia, Togo and Mauritius (chapter two). Three broad categories of molecular resistance emerged, reflecting the distribution patterns of dhfr and dhps point mutation prevalence: (1) scarce partially resistant mutations namely dhps 436A and 613S which are not increasing significantly over time, (2) emerging resistance mutations such as dhfr 164L and dhps 581G which are rare but increasing within distinct geographical foci and (3) major resistance mutations namely dhps 437G and 540E, which are widespread with significantly increased prevalence over time and regional differences (chapter three). Statistical analysis showed that the sensitive dhfr allelic haplotype frequencies decreased over time in all regions whilst the triple mutant increased. The models developed for dhps haplotypes showed a clear East-West divide with the double mutant dominating East Africa and the single mutant occurring mainly in West Africa (chapter four). Standardised in vivo efficacy data were matched with dhfr and dhps haplotypes using the nearest geographic location and study year and then modelled. These analyses showed for the first time, a clear effect of the frequency of dhps allelic haplotypes on SP efficacy (chapter five). These findings are important in the context of continued use of SP in sub-Saharan Africa for intermittent preventive treatment and support the use of molecular surveillance to inform policy on SP use.

Background: Current malaria vector control programmes rely on insecticides with rapid contact toxicity. However, spatial repellents can also be applied to reduce man-vector contact, with the ultimate goal of reducing malaria transmission. Objectives and methods: The overall goal of my PhD thesis was to evaluate existing spatial repellents as potential tools for malaria control. This thesis focused on characterizing the effect of pyrethroid spatial repellents on mosquito behaviour indoors and outdoors. Emphasis was placed on the effect on entomological parameters that influence malaria transmission. Experiments were conducted in experimental huts in a malaria endemic village in rural south eastern Tanzania and in a semi-field system against laboratory reared Anopheles gambiae sensu stricto mosquitoes. Results and conclusions: Transfluthrin and Metofluthrin coils and DDT reduced human vector contact through deterrence, irritancy/excito-repellency and blood-feeding inhibition. Pyrethroid coils were shown to cause excitation and increased activity of mosquitoes in the presence of humans. Transfluthrin coils did not hinder attraction of mosquitoes to humans but prevented mosquitoes from biting and blood feeding. This way coils provided area wide protection for up to 15m and prolonged anti-feeding for 12 hours. There was no evidence of Transfluthrin induced repellency (directional movement of mosquitoes away from humans) under outdoor conditions. Locally developed Transfluthrin hessian strips also prevented mosquitoes from biting. This thesis elucidates the mode of action of spatial repellents: spatial repellents reduce human – vector contact and induce mortality, hence directly affect ma: human biting rate, m: mosquito density and p: mosquito survival which are among the most important parameters of the vectorial capacity of a mosquito population. This information is critical for the development of target product profiles for spatial repellent products. This study shows that spatial repellents may be a suitable complementary option where mosquitoes feed in the early evening and rest outdoors.

The Philippines is targeting malaria elimination by 2020. To reach this goal, it is important to locate all residual foci of malaria and where possible, aggressively diagnose and treat every malaria infection. In low endemic provinces malaria transmission becomes focal in hard-to-reach areas where asymptomatic people do not actively seek treatment and thus, continue to perpetuate transmission. This study aimed (a) to estimate prevalence of Plasmodium species in three malaria-endemic provinces in Mindanao, (b) to measure malaria transmission intensity in these provinces using antibody markers of exposure to P. falciparum and P. vivax AMA-1 and MSP-119 antigens, (c) to determine polymorphisms in pfcrt, pfmdr1 and pvmdr1 genes, and (d) to discuss implications of these findings to malaria elimination in Mindanao. Cross-sectional surveys were conducted to a total of 2,628 consenting participants across all ages in the provinces of Sarangani, South Cotabato and Tawi-Tawi from 2010 to 2013. The RDT FalciVax™ was used for field diagnosis of malaria in Sarangani Province and South Cotabato Province for P. falciparum and P. vivax infection while microscopy was used in Tawi-Tawi Province for field diagnosis of malaria. Finger-prick blood spots on filter paper were collected from participants for PCR diagnosis, genotyping of pfcrt, pfmdr1 and pvmdr1 genes, and screening antibodies to P. falciparum and P. vivax AMA-1 and MSP-119 antigens using indirect ELISA. Blood spots were also collected from patients presenting with malaria symptoms from selected municipalities of Sarangani Province and South Cotabato Province as a pilot survey. Overall malaria prevalence by PCR was 3.7% in Sarangani Province, 10% in South Cotabato Province and 4.2% in Tawi-Tawi Province. P. falciparum prevalence by PCR was higher than P. vivax prevalence in Sarangani Province and Tawi-Tawi Province but the opposite was found in South Cotabato Province. There was one imported case of P. malariae in South Cotabato and there were no P. knowlesi and P. ovale infections found in the three provinces surveyed. There were disagreements in diagnosing P. falciparum and P. vivax using antigen detection, microscopy and PCR and these were attributed to sampling low parasite-density infections from small volume of peripheral blood spotted on filter paper. The pfcrt codons 72-76 haplotypes CVMNK (27.4%), CVIET (59.7%) and SVMNT (9.7%) were described in 62 P. falciparum isolates from Mindanao. The pfcrt mutant A144T and L160Y alleles were not found among P. falciparum isolates with pfcrt K76T mutant allele but lacked the pfcrt A220S mutation. The pfmdr1 86N- 184F-1034S-1042N-1246D haplotype, which was repeatedly associated with higher parasite survival following artemether-lumefantrine treatment, was found in seven P. falciparum isolates from Mindanao. Genotyped P. vivax isolates from Mindanao have the wild type pvmdr1 91N allele, which corresponded to pfmdr1 codon 86. The pvmdr1 Y976F mutant allele, which has been reported in chloroquine-resistant P. vivax in other countries, was found in 55.6% (5/9) P. vivax isolates successfully genotyped in this codon while the pvmdr1 1076L wild-type allele was found in three P. vivax isolates successfully genotyped in this codon. Combined seroprevalence to P. falciparum and P. vivax AMA-1 and MSP-119 antigens suggested that exposure to P. falciparum was higher than exposure to P. vivax in Sarangani Province and Tawi-Tawi Province. Overall seroprevalence to P. falciparum and P. vivax was 18.9% and 14.6% in Sarangani Province respectively. In Tawi-Tawi Province the overall seroprevalence to P. falciparum and P. vivax was 18.2% and 12.9% respectively. The opposite was observed in South Cotabato Province where overall seroprevalence to P. falciparum (3.4%) was lower than the overall seroprevalence to P. vivax. The seroconversion rates (λ) for P. falciparum and P. vivax malaria were estimated using simple reversible catalytic models. In Sarangani Province the SCR for P. falciparum (0.014, 95%CI 0.010-0.020) was lower than SCR for P. vivax (0.019, 95% CI 0.010-0.036). A model allowing two forces of infection was used to estimate SCR for P. falciparum in Tawi-Tawi. Results suggested that there was a change in P. falciparum transmission in Tawi-Tawi Province approximately 25 years before the survey was conducted. The estimated SCR for P. falciparum was 0.041 (95% CI 0.017-0.098) in Tawi-Tawi Province before 1987. The model suggested that SCR was reduced to 0.007 (95% CI 0.005-0.009) after 1987 to the time of survey. In South Cotabato the SCR for P. falciparum was very low (0.004, 95% CI 0.001-0.016). There was no SCR estimated for P. vivax in South Cotabato because seropositivity was equally distributed across age groups. Findings in this study were held back by sample size and low-density parasite infections in small number of infected humans. Nevertheless, this provided important baseline data for malaria epidemiology in Mindanao.

Control of chlamydia infections in young people is a public health priority reflected in a National Screening Programme for 15-24 year olds. However, effective screening interventions may exacerbate health inequality if uptake is different across social groups. This thesis aims to i) examine the prevalence and socioeconomic patterning of chlamydia infections, and ii) conduct formative research to inform a Peer-Supported Chlamydia Screening intervention. I conducted a systematic review of chlamydia prevalence in Europe, North America and Australia and found strong evidence of heterogeneity in prevalence estimates among 16-24 year olds and mixed evidence of an association between measures of social disadvantage and higher infection risk. Chlamydia prevalence and social variation at age 17 were further examined in the Avon Longitudinal Study of Parents and Children birth-cohort. After missing data analysis, chlamydia prevalence was 1.4% (0.8, 2.0); 1.7% (0.8,2.6) in women; 1.0% (0 .3, 1.7) in men. Infection was strongly associated with several measures of social disadvantage. Using grounded theory approaches, in-depth and key informant interviews and non-participant observation in further education colleges, the formative study revealed that a peer-screening intervention could build on existing social phenomena such as frequent and open conversations about sexual health, sharing information and experiences, moral and emotional support and humour. The majority of interview participants indicated that they would be willing to participate in the intervention. The intervention may promote uptake of screening through four mechanisms: 1. acknowledging personal relevance of screening; 2. increasing perceived benefits; 3. reducing perceived costs; and 4. providing opportunities for spontaneous testing. The acceptability and effectiveness of the intervention may be enhanced by offering a choice of self-test kits or cards, wider promotion of pro-screening norms, and attractive and humorous promotional materials. No evidence was found to suggest that the intervention would be less acceptable amongst the socially disadvantaged.

Influenza is a highly contagious and acute respiratory infection caused by influenza virus in the mucosa of the respiratory tract. Both seasonal and pandemic influenza continue to cause substantial morbidity and mortality in humans. The 2009 pandemic H1N1 (pH1N1) influenza and the potential of a highly pathogenic avian H5N1 (aH5N1) pandemic highlighted the need for effective preventative strategies. Understanding the development of natural immunity following the pH1N1 pandemic may provide important information on host protective immunity in humans, which could inform future more effective vaccination strategies against influenza. In this thesis, naturally developed mucosal immunity to 2009 pH1N1 virus was studied in children and adults using cells derived from human nasal-associated lymphoid tissue (NALT). Firstly, the frequency of HA-specific memory B cells in human NALT to pH1N1 virus and their ability to produce cross-reactive antibodies were studied. Patients who had serological evidence of previous exposure to pH1N1 virus developed large numbers of IgG memory B cells in NALT that produce crossreactive neutralizing antibodies against a number of influenza subtypes upon pH1N1 virus antigen stimulation. The presence of such memory B cells in human NALT appears to have primed the host for cross-reactive mucosal memory response against other H1N1 and the highly pathogenic aH5N1 virus strains. These findings may have important implications in future vaccination strategies against influenza. Secondly, serum specific anti-pH1N1 HA IgG antibodies were analysed using ELISA. HA-specific antibody levels to pH1N1 in adults were significantly higher than that of children. The results may suggest that adults had been exposed to more cross-reactive influenza viruses than children, and developed more cross-reactive memory responses against some influenza viruses than in children. Significantly higher HA-specific IgG antibody titres to pH1N1 HA (measured using ELISA) were found in subjects who had HAI titres≥40 than in those with HAI antibody titre<40. This suggests that following the 2009 pH1N1 pandemics, large numbers of people developed anti-pH1N1 HA antibodies to both the circular head and the stalk regions of HA which may have broader protective immunity. Thirdly, HA-specific memory CD4+ T cell response to pH1N1 virus was shown in tonsillar cells from children and adults. This suggests that following the 2009 pandemic H1N1 influenza, humans developed memory T cell response to the pH1N1 HA protein antigen at the mucosal level in the nasopharynx. There appeared to be an age-associated increase in this memory response. Finally, mucosal antibody responses in NALT to HAs of a number of influenza A viruses were investigated following in vitro stimulation of adenotonsillar cells with LAIV vaccine which contains a 2009 pandemic H1N1 virus, a seasonal H3N2 and a B influenza strain. Significant antibody responses of all 3 isotypes (IgG, IgA and IgM) to the HA of pandemic H1N1 virus were observed in tonsillar cells following LAIV stimulation. It suggests that the in vitro model of human NALT using adenotonsillar cell culture could be used to study the LAIV-induced immune responses which may predict the immunogenicity and efficacy of candidate LAIV vaccines in humans.

Despite the success of recent global malaria control efforts, which. have halved global malaria mortality since 2000, malaria is still one of the world's most deadly diseases causing an estimated half a million deaths, mostly among African children, and around a quarter of billion clinical episodes every year as reported in 2014 1. Drug resistance is one of the most important challenges to malaria elimination. To contain drug resistance, many efforts have been put forth including improvement of surveillance systems and mass treatment in order. to stop or slow down the transmission of the resistant strain. To find out whether a population-level treatment strategy can have any benefit in containing drug resistance, mathematical models are an appropriate approach to this problem and individual-based models allow us to have a better understanding of the effect of individual heterogeneities on the outcome. The first part of the thesis is about building and validating an individual based microsimulation. The model is implemented as an individual-based discrete-time event simulation model in C++. The behaviors and the state changes of human individuals are determined by relevant events and mathematical formulas. This integrated model combines components that reproduce the most important features of malaria transmission and epidemiology: the infectiousness of human populations; clinical model of acute illness; heterogeneities in individuals' age, biting-rate level, drug absorption, drug action, multiple parasite populations, and human immunity. To validate this individual-based model, two types of validation have been done. The model's parameters were obtained from field or clinical data were used directly in the model. For those parameters that cannot be obtained directly from literature review, sensitivity analysis has been done to find how variation in parameter values affects certain key features of malaria epidemiology .

Vaccination is the most effective way to control a global disease such as tuberculosis (TB); however, conventional intradermal (ID) injection of the licensed TB vaccine, BCG, provides only limited protection. Mucosal delivery of vaccines to pulmonary surfaces is a loqical approach to generate a protective immune response at the primary site of infection. Non-human primate (NHP) models have been used to compare the safety and immunogenicity of mucosal and ID TB vaccination strategies using BCG and modified vaccinia virus Ankara expressing TB antigen 85A (MVA85A). Mucosal vaccination strategies were well tolerated and induced potent antigen-specific CD4 and CD8 T-cell responses, including polyfunctional T-cells in the lung and peripheral immune compartment. Systemic immune responses induced by mucosal BCG revaccination and MVA85A boost vaccination were relatively transient, whereas antigen-specific responses detected in mucosal tissues and bronchoalveolar lavage (BAL) samples were more persistent. Unlike ID vaccination, aerosol vaccination with MVA85A did not induce a detectable serum anti-vector antibody response. Polyfunctional CD4 T-cells were detected in BAL and peripheral blood mononuclear cells (PBMC) following aerosol and ID BCG vaccination. The immunogenicity of aerosol-delivered BCG was dose dependent and consisted of both Th 1 and Th 17 cytokine responses. The aerosol BCG-induced T -cell response measured in BAL and PBMC was significantly delayed relative to ID-vaccination, with a similar trend apparent in serum anti-PPD IgG levels. Mucosal CD4 and CD8 populations were polarised toward an effector memory phenotype, whereas frequencies of peripheral central memory T-cells increased significantly, and remained elevated, following aerosol vaccination. Expression of the 04131 integrin lung homing markers remained consistently high on C04 and C08 T-cells isolated from BAL, and varied on peripheral T -cells. These studies indicate, that delivery of TB vaccines to the pulmonary surfaces is practical and safe, with the potential to target the cell-mediated immune response to the lung. The comparison of aerosol and ID BCG vaccination highlighted differences in the mycobacteria-specific immune response that may contribute to the enhanced protection previously reported from aerosol BCG studies, and will inform future investigations of mucosal TB vaccination strategies.