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Doctoral Degrees (Environmental Science)

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Browsing Doctoral Degrees (Environmental Science) by Author "Appleton, Christopher Charles."

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    The epidemiology of malaria in Zambia.
    (2003) Chimumbwa, John Mulenga.; Sharp, Brian Leslie.; Appleton, Christopher Charles.
    Nearly half of the world's population lives in tropical and temperate climates where they may be at risk from one or more vector borne diseases. Approximately 2.1 billion people, living in more than 100 countries are at risk from malaria. While the malaria situation has improved in some places, the overall prevalence in Africa, Asia and the Americas continues to deteriorate. This has led nations, institutions, organisations and agencies including the World Health Organisation to call for development of new and innovative approaches to its surveillance and control. In nature, maintenance of malaria transmission involves a complex interaction between the mosquito vector, the human host, the disease organism, and both the internal and external environments. An understanding of this complex relationship is the key to the prevention, control and eventual eradication of malaria. Malaria prevention and control programmes do not only have to be based on sound knowledge of how these factors interrelate, but also on an application of the political will of the concerned authorities. This study attempts to identify some determinants of malaria and to characterise it in epidemiological zones in Zambia. The study aims at contributing to the body of knowledge that would support implementation of an evidence-based national malaria programme. This study has come at an opportune time when there is renewed focus on malaria prevention and control globally. It is hoped that these aspects of the malaria programme in Zambia will not have to be rewritten in the foreseeable future, instead will be improved upon in order to progress to the delivery of quality assured malaria services as close to the family as possible based on the principles of community-health partnerships. The study is presented in a series of chapters; each developed as a follow up to the previous one and forms a bridge to the next. In this way, it enables the reader to build a relatively complete picture of the malaria situation in the country. However, some repetitions could not be avoided with regard to descriptions of study sites. In the chapters dealing with health systems and quantification of malaria risk, the country (Zambia) is taken as the study site. The remaining sections are based on specific sites, selected on the basis of their representing different aspects of the malaria situation in the country. Mapping of households and other referral points provided the basis upon which a Malaria Information System would in future be built. One of the two study sites was special because most of the previously conducted malaria research in Zambia has been conducted at this site. While the other was not only new in terms of malaria research, it also represented locations in the high rainfall zone in Zambia. The introductory chapter sets out the general principles of Geographical Information System (GIS), malariology, entomology, and health systems. The chapter reviews the current global burden of malaria including its implications for economic development of endemic subSaharan African countries, and discusses progress made in the light of drug and insecticide resistance and the changing global weather patterns. This section examines the position of the African continent in relation to the global malaria eradication era and the possible reasons why it was excluded from the global malaria eradication campaign of 1956-1969. It goes on to analyse new obstacles being faced in rejuvenating global interest in malaria programmes, starting with Primary Health Care through to the principles of Roll Back Malaria (RBM). It also emphasizes special Africa-specific initiatives related to malaria, such as the MARA/ARMA collaboration which (through the use of GIS) is providing a basis for evidence-based decision making. The fist chapter deals with the historical aspects of malaria control in Zambia. It traces how malaria was successfully controlled over a period of 46 years. It starts with a rural set up where copper mineral deposits were discovered. From there it traces the history of malaria control spanning almost eight decades to the present day. It outlines the major milestones in both the malaria programme and in the political history of the country; from a British protectorate , through Federation to the present day nation, Zambia. The chapter demonstrates how malaria can be controlled in an intense transmission situation, using a combination of simple and relatively cost-effective interventions. It also demonstrates that political will is an essential element to disease control. The second chapter examines the role of health systems in the delivery of quality, efficient and cost-effective services to the population. It examines the adequacy of health services in the light of time-limited Roll Back Malaria goals, according to the Abuja Declaration of 2000. This chapter analyses the capacity of the local health system to deliver on its health vision of taking quality assured health services (Malaria services) as close to the family as possible. Together, these goals are examined in terms of population accessing the facilities within 30 minutes' walking distance. Chapter three focuses on identifying factors that facilitate or hinder households acquiring and using Insecticide Treated Nets (ITNs) in the same locality. Specifically, distance of households to some reference points is examined. Also the effects of social, economic and educational status of heads of households are analysed. Together all parameters are analysed statistically to isolate the important reasons why some homes acquire ITNs while others do not. The study concludes with an analysis of the importance of ITN s in averting malaria among users. Some anecdotal evidence resented on the value of ITN s in reducing malaria incidence in the general population is presented. GIS is employed in the fourth chapter to produce a malaria endemicity risk map for the country. It employs population Plasmodjum faldparum infection rates. It proposes stratification and compares it with existing expert opinions and the climate-based Fuzzy Logic predictive model. The resultant malaria risk map is verified against existing maps and expert opinions. The chapter then discusses application for local decision making on policy and action. Chapter number five is dedicated to identifying and studying the bionomics of malaria vectors at two sites. It reviews existing literature on this subject, from 1929 to date. It identifies possible malaria vectors, their behaviour and ecology at two sites representing two extreme situations of malaria endemicity in the country. The combination of Anopheles vector densities and their reliance on temperature and rainfall are analysed and the implications discussed. The chapter also looks at possible ways forward for the country in the light of the paucity of information in this respect. P. faldparum infection rates are estimated together with their entomological inoculation rates and possible implications for malaria transmission potential. The final section (chapter six), highlights the major lessons and their implications for global goals and local health policies. It also outlines the way forward chapter by chapter.
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    Geohelminth transmission among slum-dwelling children in Durban, South Africa.
    (2001) Mosala, Thabang Innocentia.; Appleton, Christopher Charles.; Olsen, Annette.
    Geohelminthiasis is a serious problem in city slums and despite being easily treatable in the short term, its elimination enjoys a low priority by parents, teachers and public health authorities. This is partly due to the greater emphasis given to the AIDS and TB programmes. This study of the prevalence, intensity, and reinfection rates of single and multiple geohelminth (Ascaris lumbricoides, Trichuris trichiura and Necator americanus) infections in young children living in slums (informal settlements) in the Durban Unicity is a first for an African city and one of few similar studies anywhere in the world. The geohelminth status was assessed by means of a baseline survey of ten different slums, followed by two further surveys, one after 4Y:z - 6 months and another after 12 months. Infections were measured by microscopic examination of faeces before and after chemotherapy, and risk factors within and between slums were identified by means of a quantifiable questionnaire. The study showed that: 1. The slums have a high endemicity and transmission rate of geohelminth infections. 2. The sub-tropical climate and environment ensured a high survival rate of infective stages. 3. A. lumbricoides had a high prevalence and intensity, followed by T. trichiura with a moderately high prevalence and light intensity. A small proportion of children had intensities of these helminths an order of magnitude higher than previously recorded from rural areas of South Africa. N americanus had a very low prevalence and a very light intensity. 4. Egg output from follow-up 1 to follow-up 2 increased 4.6 fold for A. lumbricoides and 9.4 fold for T. trichiura. 5. Albendazole proved to be a very effective drug against A. lumbricoides and N americanus but not as effective against T. trichiura. 6. The infection and reinfection rates of A. lumbricoides and T. trichiura proved to be influenced by different risk factors. 7. The most important risk factors included topographical position of the slum, quality of the dwelling, number of inhabitants, geophagy and source of fruit and vegetables. II Whereas the ideal solution to the geohelminth problem in the slums would be to upgrade the slum and its inhabitants, this is not an immediately viable option. The challenge of geohelminth control in these slums must be to determine the degree of environmental contamination by human faeces containing infective eggs, to ascertain the survival rate of the eggs and larvae and to implement a control programme together with suitable education of the inhabitants. The Parasite Control Programme should take into consideration that many slum-dwelling children do not go to school and need to be treated at home. A further factor that will have to be taken into account is that lack of influx control to urban areas will mean the continual reinfection of slum-dwellers by the movement from the rural areas.