Many infectious diseases are spread through interactions between susceptible and infectious individuals. Keeping track of where each exposure to the disease took place, when it took place, and which individuals were involved in the exposure can give public health officials important information that they may use to formulate their interventions. Further, knowing which individuals in the population are at the highest risk of becoming infected with the disease may prove to be a useful tool for public health officials trying to curtail the spread of the disease. Epidemiological models are needed to allow epidemiologists to study the population dynamics of transmission of infectious agents and the potential impact of infectious disease control programs. While many agent-based computational epidemiological models exist in the literature, they focus on the spread of disease rather than exposure risk. These models are designed to simulate very large populations, representing individuals as agents, and using random experiments and probabilities in an attempt to more realistically guide the course of the modeled disease outbreak. The work presented in this thesis focuses on tracking exposure risk to chickenpox in an elementary school setting. This setting is chosen due to the high level of detailed information realistically available to school administrators regarding individuals' schedules and movements. Using an agent-based approach, contacts between individuals are tracked and analyzed with respect to both individuals and locations. The results are then analyzed using a combination of tools from computer science and geographic information science.

225 leaves printed on single pages, preliminary pages i- xxiii and numbered pages 1-203. Includes bibliography, list of abbreviations, list of definitions, list of tables and figures and list of appendices. / Digitized at 330 dpi color PDF format (OCR), using KODAK i 1220 PLUS scanner. / Thesis (MNutr (Interdisciplinary Health Sciences))--University of Stellenbosch, 2005. / ENGLISH ABSTRACT: "A comprehensive package of care for the Prevention of Mother- To-Child Transmission (PMTCT) of HIV" states that all mothers participating in the PMTCT Programme should receive education that will enable them to make informed decisions about infant feeding options. Rapid, same-day HIV testing and results that are available immediately, enable health care workers to be responsible for providing pre- and post-test counselling (which includes infant feeding options) on the same day. This could place a tremendous workload and time pressure on the health care workers. The aim of this study was to determine how "informed" is the literate mother's decision regarding infant feeding options, who participated in the PMTCT Programme, in the Gert Sibande District, Mpumalanga, South Africa. Method: Data was collected from health care workers and mothers on the PMTCT Programme at 23 PMTCT sites in the Gert Sibande District, with the help of 6 field workers and the PMTCT site manager at each PMTCT site, by means of once-off, self-administered questionnaires, which had been previously tested and validated. Results: Health care workers' attitude towards the PMTCT Programme was positive, although some (14%) indicated that what was expected of them was not achievable in their working environment. The most prominent change relating to the personal preferences of health care workers regarding infant feeding options for HIV-infected mothers, after attending the 5-day PMTCT course, was from formula-feeding to breast-feeding. Most (65%) indicated it was possible to stay neutral in a counselling session regardless of personal preference for infant feeding and 60% of those who could not stay neutral, still thought it was in the mother's best interest to be counselled by them. Most (98%) agreed mothers had the right to make informed decisions and 80% agreed mothers were able to make such a decision. Most (67%) health care workers indicated that not enough staff was stationed at PMTCT sites, only 53% used the feeding option cards when counselling mothers and indicated that more educational material was needed. Sixty one percent of the health care workers demonstrated the preparation of the formula to the mothers and allowed the mothers to demonstrate back to them. Between 49-82% and 37-56% of the health care workers knew the correct answers to knowledge questions relating to breastfeeding and formula-feeding, respectively. Not one health care worker, nor mother, knew all the steps in preparing a formula feed. Most (80%) mothers made decisions based on information provided to them by health care workers and only a small (13%) percentage were influenced by the community to practise a different feeding option than what they had chosen. Conclusions: The attitude, personal preferences, knowledge of and resources available to health care workers, influenced the decision made by mothers regarding infant feeding options and seeing that most mothers made their decision, based on information provided by health care workers, it is concluded that mothers can only make an informed decision about infant feeding options if they are advised appropriately by well trained, equipped and informed health care workers. / AFRIKAANSE OPSOMMING: "A comprehensive package of care for the Prevention of Mother-To-Child Transmission of HIV", vermeld dat moeders, wat deelneem aan die Voorkoming van Moeder-Tot-Kind Oordrag (VMTKO) progam, voorligting behoort te ontvang ten opsigte van voedingsopsies vir hul babas, sodat hulle in staat sal wees om 'n ingeligte keuse te maak. Gesondheidswerkers is verantwoordelik om voorligting voor en na die HIV toets te gee, wat die voedingsopsies vir babas insluit, op dieselfde dag. Dit kan 'n ontsaglike werkslading op die gesondheidswerkers plaas. Die doel van die studie was om te bepaal hoe "ingelig" is die geletterde moeder se keuse ten opsigte van voedingsopsies, wat deelneem aan die VMTKO program, in die Gert Sibande distrik, Mpumalanga, Suid-Afrika. Metode: Die data is ingesamel by 23 VMTKO-klinieke en -hospitale in die Gert Sibande distrik onder gesondheidswerkers en moeders op die VMTKO-program, met behulp van 6 veldwerkers en VMTKO-bestuurders, deur middel van eenmalige, selfvoltooide vraelyste, wat van tevore getoets en gevalideer was. Resultate: Die gesondheidswerkers se houding teenoor die VMTKO-program was positief, alhoewel 14% aangedui het dat wat van hulle verwag word nie prakties of moontlik is in hul werksomgewing nie. Die prominentste verandering rakende die persoonlike voorkeure van die gesonheidswerkers teenoor voedingsopsies vir HIV -geinfekteerde moeders, na die 5-dag VMTKO kursus, was van formulevoeding na borsvoeding. Meeste (65%) het aangedui dit is moontlik om neutraal te bly gedurende 'n voorligtingssessie, ten spyte van persoonlike voorkeure vir voedingsopsies en 60% van die wat nie neutraal kon bly nie, het steeds gedink dit is in die beste belang van die moeder om deur hulle voorgelig te word. Meeste (98%) het saamgestem dat dit die moeder se reg is om 'n ingeligte keuse te maak en 80% het saamgestem dat die moeder wel in staat is om so 'n besluit te neem. Meeste (67%) gesondheidswerkers het aangedui dat personeel tekorte bestaan by die VMTKO klinieke en hospitale. Slegs 53% gebruik die voedingsopsie kaarte gedurende 'n voorligtingsessie met die moeder en het aangedui dat meer voorligtingsmateriaal benodig word. Een en sestig persent van die gesondheidswerkers het die voorbereiding van die formulevoeding aan die moeders gedemonstreer en het moeders toegelaat om ook die demonstrasie te doen. Nege en veertig tot twee en tagtig persent en 37-56% van die gesondheidswerkers kon die korrekte antwoorde verskaf vir vrae oor borsvoeding en formulevoeding, afsonderlik. Nie een gesondheidswerker of moeder kon al die stappe vir die voorbereiding van die formulevoeding noem nie. Meeste (80%) moeders maak keuses gebaseer op inligting wat aan hulle verskaf word deur die gesondheidswerkers en slegs 'n klein persentasie (13%) word beinvloed deur familielede om die teenoorgestelde voedingsopsie te praktiseer as wat hulle gekies het. Gevolgtrekking: Die houding, persoonlike voorkeure, kennis van en hulpbronne beskikbaar aan die gesongheidswerkers, beinvloed die besluit wat moeders neem ten op sigte van voedingsopsies en aangesien die moeders hulle besluit baseer op inligting wat deur die gesondheidswerkers aan hulle gegee word, word die gevolgtrekking gemaak dat moeders slegs 'n ingeligte keuse aangaande voedingsopsies kan maak indien hulle voorligting ontvang deur goed opgeleide en ingeligte gesondheidswerkers.

PhD (Mathematics) / Department of Mathematics and Applied Mathematics / In this study, we developed multiscale models of vector-borne diseases. In general, the transmission of vector-borne diseases can be considered as falling into two categories, i.e. direct transmission and environmental transmission. Two representative vector-borne diseases, namely; malaria which represents all directly transmitted vector-borne diseases and schistosomiasis which represents all environmentally transmitted vector-borne diseases were studied. Based on existing mathematical modelling science base, we established a new multiscale modelling framework that can be used to evaluate the effectiveness of vector-borne diseases treatment and preventive interventions. The multiscale models consisted of systems of nonlinear ordinary differential equations which were studied for the provision of solutions to the underlying problem of the disease transmission dynamics. Relying on the fact that there is still serious lack of knowledge pertaining to mathematical techniques for the representation and construction of multiscale models of vector-bone diseases, we have developed some grand ideas to placate this gap. The central idea in multiscale modelling is to divide a modelling problem such as a vector-bone disease system into a family of sub-models that exist at different scales and then attempt to study the problem at these scales while simultaneously linking the sub-models across these scales. For malaria, we formulated the multiscale models by integrating four submodels which are: (i) a sub-model for the mosquito-to-human transmission of malaria parasite, (ii) a sub-model for the human-to-mosquito transmission of malaria parasite, (iii) a within-mosquito malaria parasite population dynamics sub-model and (iv) a within-human malaria parasite population dynamics sub-model. For schistosomiasis, we integrated the two subsystems (within-host and between-host sub-models) by identifying the within-host and between-host variables and parameters associated with the environmental dynamics of the pathogen and then designed a feedback of the variables and parameters across the within-host and between-host sub-models. Using a combination of analytical and computational tools we adequately accounted for the influence of the sub-models in the different multiscale models. The multiscale models were then used to evaluate the effectiveness of the control and prevention interventions that operate at different scales of a vector-bone disease system. Although the results obtained in this study are specific to malaria and schistosomiasis, the multiscale modelling frameworks developed are robust enough to be applicable to other vector-borne diseases. / NRF

L’Organisation mondiale de la santé animale (OIE) est l’institution internationale responsable de la mise en place des mesures sanitaires associées aux échanges commerciaux d’animaux vivants. Le zonage est une méthode de contrôle recommandée par l’OIE pour certaines maladies infectieuses, dont l’influenza aviaire. Les éclosions d’influenza aviaire été extrêmement coûteuses pour l’industrie avicole partout dans le monde. Afin d’évaluer la possibilité d’user de cette approche en Ontario, les données sur les sites de production avicole ont été fournies par les fédérations d’éleveurs de volailles ce cette province. L’information portant sur les industries associées à la production avicole, soit les meuneries, les abattoirs, les couvoirs, et les usines de classification d’œufs, a été obtenue par l’entremise de plusieurs sources, dont des représentants de l’industrie avicole. Des diagrammes de flux a été crée afin de comprendre les interactions entre les sites de production et les industries associées à ceux-ci. Ces industries constituaient les éléments de bas nécessaires au zonage. Cette analyse a permis de créer une base de données portant sur intrants et extrants de production pour chaque site d’élevage avicole, ainsi que pour les sites de production des industries associées à l’aviculture. À l’aide du logiciel ArcGIS, cette information a été fusionnée à des données géospatiales de Statistique Canada de l’Ontario et du Québec. La base de données résultante a permis de réaliser les essais de zonage. Soixante-douze essais ont été réalisés. Quatre ont été retenus car celles minimisaient de façon similaire les pertes de production de l’industrie. Ces essais montrent que la méthode utilisée pour l’étude du zonage peut démontrer les déficits et les surplus de production de l’industrie avicole commerciale en Ontario. Ceux-ci pourront servir de point de départ lors des discussions des intervenants de l’industrie avicole, étant donné que la coopération et la communication sont essentielles au succès du zonage. / The World Organisation for Animal Health (OIE) is the international reference body for international trade standards for live animals. Zoning is a method of controlling certain infectious diseases, including avian influenza, recommended by the OIE for use when appropriate. Avian influenza outbreaks have been extremely costly to the poultry industry throughout the world. In order to assess whether this approach was possible in Ontario, data on poultry industry production sites were provided by the Ontario poultry marketing boards. Zone borders were formed based on two criteria. The first criterion was the supply of essential products and services such that within-zone commercial poultry production could be maintained. The second was the contiguity of the zone’s territory. Four associated industries were identified which provide essential products and services: feed mills, abattoirs, hatcheries, and egg grading stations. A product flow analysis was completed to understand the direction of product movements between the poultry production sites and the sites of the four associated industries. This analysis was used to create a database of input requirements and output production capacity from each type of poultry production site. Using ArcGIS, this information was merged with geospatial data from Statistics Canada on Ontario and Quebec to create the database used for zoning scenarios. Seventy-two scenarios were completed; of these, four were chosen which minimized production loss over the whole industry. These scenarios demonstrate that the method used for the zoning study can identify the production deficits and surpluses of the commercial poultry industry in Ontario. These scenarios can serve as a starting point for discussion among industry stakeholders, as cooperation and communication are essential to the success of zoning.

L’Organisation mondiale de la santé animale (OIE) est l’institution internationale responsable de la mise en place des mesures sanitaires associées aux échanges commerciaux d’animaux vivants. Le zonage est une méthode de contrôle recommandée par l’OIE pour certaines maladies infectieuses, dont l’influenza aviaire. Les éclosions d’influenza aviaire été extrêmement coûteuses pour l’industrie avicole partout dans le monde. Afin d’évaluer la possibilité d’user de cette approche en Ontario, les données sur les sites de production avicole ont été fournies par les fédérations d’éleveurs de volailles ce cette province. L’information portant sur les industries associées à la production avicole, soit les meuneries, les abattoirs, les couvoirs, et les usines de classification d’œufs, a été obtenue par l’entremise de plusieurs sources, dont des représentants de l’industrie avicole. Des diagrammes de flux a été crée afin de comprendre les interactions entre les sites de production et les industries associées à ceux-ci. Ces industries constituaient les éléments de bas nécessaires au zonage. Cette analyse a permis de créer une base de données portant sur intrants et extrants de production pour chaque site d’élevage avicole, ainsi que pour les sites de production des industries associées à l’aviculture. À l’aide du logiciel ArcGIS, cette information a été fusionnée à des données géospatiales de Statistique Canada de l’Ontario et du Québec. La base de données résultante a permis de réaliser les essais de zonage. Soixante-douze essais ont été réalisés. Quatre ont été retenus car celles minimisaient de façon similaire les pertes de production de l’industrie. Ces essais montrent que la méthode utilisée pour l’étude du zonage peut démontrer les déficits et les surplus de production de l’industrie avicole commerciale en Ontario. Ceux-ci pourront servir de point de départ lors des discussions des intervenants de l’industrie avicole, étant donné que la coopération et la communication sont essentielles au succès du zonage. / The World Organisation for Animal Health (OIE) is the international reference body for international trade standards for live animals. Zoning is a method of controlling certain infectious diseases, including avian influenza, recommended by the OIE for use when appropriate. Avian influenza outbreaks have been extremely costly to the poultry industry throughout the world. In order to assess whether this approach was possible in Ontario, data on poultry industry production sites were provided by the Ontario poultry marketing boards. Zone borders were formed based on two criteria. The first criterion was the supply of essential products and services such that within-zone commercial poultry production could be maintained. The second was the contiguity of the zone’s territory. Four associated industries were identified which provide essential products and services: feed mills, abattoirs, hatcheries, and egg grading stations. A product flow analysis was completed to understand the direction of product movements between the poultry production sites and the sites of the four associated industries. This analysis was used to create a database of input requirements and output production capacity from each type of poultry production site. Using ArcGIS, this information was merged with geospatial data from Statistics Canada on Ontario and Quebec to create the database used for zoning scenarios. Seventy-two scenarios were completed; of these, four were chosen which minimized production loss over the whole industry. These scenarios demonstrate that the method used for the zoning study can identify the production deficits and surpluses of the commercial poultry industry in Ontario. These scenarios can serve as a starting point for discussion among industry stakeholders, as cooperation and communication are essential to the success of zoning.

Indiana University-Purdue University Indianapolis (IUPUI) / With effective antiretroviral therapy (ART), cardiovascular diseases (CVD), are emerging as a major cause of morbidity and death in the aging population with HIV infection. Although this increase in CVD could be partially explained by the toxic effects of combined anti-retroviral therapy (ART), more recently, HIV infection has emerged as an independent risk factor for CVD. However, it is unclear how HIV can contribute to CVD in patients on ART, when viral titers are low or non-detectable. Here, we provide several lines of evidence that HIV-Nef, produced in infected cells even when virus production is halted by ART, can lead to endothelial activation and dysfunction, and thus may be involved in CVD. We demonstrate that HIV-infected T cell-induced endothelial cell activation requires direct contact as well as functional HIV-Nef. Nef protein from either HIV-infected or Nef-transfected T cells rapidly transfers to endothelial cells while inducing nanotube-like conduits connecting T cells to endothelial cells. This transfer or transfection of endothelial cells results in endothelial apoptosis, ROS generation and release of monocyte attractant protein-1 (MCP-1). A Nef SH3 binding site mutant abolishes Nef-induced apoptosis and ROS formation and reduces MCP-1 production in endothelial cells, suggesting that the Nef SH3 binding site is critical for Nef effects on endothelial cells. Nef induces apoptosis of endothelial cells through both NADPH oxidase- and ROS-dependent mechanisms, while Nef-induced MCP-1 production is NF-kB dependent. Importantly, Nef can be found in CD4 positive and bystander circulating blood cells in patients receiving virally suppressive ART, and in the endothelium of chimeric SIV-infected macaques. Together, these data indicate that Nef could exert pro-atherogenic effects on the endothelium even when HIV infection is controlled and that inhibition of Nef-associated pathways may be promising new therapeutic targets for reducing the risk for cardiovascular disease in the HIV-infected population.

Since the earliest reported cases of HIV/AIDS probably in 1959 in Africa, there has been a consistent progression in the new HIV/AIDS infection cases. In South Africa, Gauteng, records one of the highest HIV/AIDS prevalence rates in the country. The Department of Health (DOH) South Africa conducts ongoing studies on HIV/AIDS at provincial levels; these studies monitor the prevalence of HIV/AIDS amongst pregnant women attending antenatal clinics, as a tool for determining and monitoring the prevalence, trends, patterns and spread of the disease in the general population. This study analyses sentinel and spatial data collected from the (DOH) and Statistics South Africa (StatsSA) respectively, and depicts them in the form of spatial maps, and then critically analyses the spatial patterns that occur. The research findings would hopefully contribute to the overall knowledge of HIV/AIDS and provide framework and relevant literature for further investigation. / Geography / M.Sc. (Geography)

Since the earliest reported cases of HIV/AIDS probably in 1959 in Africa, there has been a consistent progression in the new HIV/AIDS infection cases. In South Africa, Gauteng, records one of the highest HIV/AIDS prevalence rates in the country. The Department of Health (DOH) South Africa conducts ongoing studies on HIV/AIDS at provincial levels; these studies monitor the prevalence of HIV/AIDS amongst pregnant women attending antenatal clinics, as a tool for determining and monitoring the prevalence, trends, patterns and spread of the disease in the general population. This study analyses sentinel and spatial data collected from the (DOH) and Statistics South Africa (StatsSA) respectively, and depicts them in the form of spatial maps, and then critically analyses the spatial patterns that occur. The research findings would hopefully contribute to the overall knowledge of HIV/AIDS and provide framework and relevant literature for further investigation. / Geography / M.Sc. (Geography)