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. / Thesis (Ph.D.)-University of Natal, Durban, 2001.