Browsing by Author "Sharp, Brian Leslie."

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The application of geographical information systems to infectious diseases and health systems in Africa.
(2000) Tanser, Frank Courteney.; Solarsh, Geoffrey C.; Sharp, Brian Leslie.
The health sector has not yet begun to explore the full potential of geographical information system (GIS) technology for health research and planning. The goal of this thesis is to demonstrate this potential in Africa through the application of GIS to the most important health issues in the continent. In excess of 23,000 homesteads are mapped and interviewed throughout Hlabisa district, Kwa-Zulu Natal using differential global positioning systems (GPS). I use the GIS to analyse mode health care usage patterns. 87% of homesteads use the nearest clinic and travel an average distance of 4.72 km to do so. There is a significant logarithmic relationship between distance from clinic and usage by the homesteads (r2 = 0.774, p<0.0001). I propose the distance usage index (DUI) as a composite spatial measure of clinic usage. The index is the sum of the distances from clinic to all actual client homesteads divided by the sum of the distances from clinic to all homesteads within its distance-defined catchment. The index encompasses inclusion, exclusion and strength of patient attraction for each clinic. The DUI highlights significant disparities in clinic usage patterns across the district (mean = 110%, SD =43.7). The results of the study have important implications for health planning in Africa. I use GIS/GPS technology to quantify the spatial implications of a shift towards community-based treatment of tuberculosis using the DOTs strategy in Hlabisa. The mean distance from each homestead in the district to nearest supervision point is measured using a GIS. The shift in treatment strategy from hospital to community-based between 1991-1996 reduces the mean distance to treatment point from 29.6 km (94% of the population > 5km) to 1.5 km (entire population < 5km). GIS effectively documents and quantifies the impact of community-based tuberculosis treatment on access to treatment. I produce the first quantifiable evidence of a relationship between distance to roads and HIV prevalence using a GIS. HIV prevalence was measured through anonymous surveillance among pregnant women in Hlabisa and stratified by clinic attended. Assuming women attend the nearest clinic, the mean distance from homesteads to a primary or secondary road for each clinic catchment is strongly correlated with HIV prevalence (r = 0.66; p = 0.002). Further research is needed to better understand this relationship both at ecological and individual levels.I develop a methodology that has numerous applications to health systems provision in developing countries where limited physical access to primary health care is a major factor contributing to the poor health of populations. I use an accessibility model within a GIS to subdivide an area into units of equal workload using a range of physical and social variables. The methodology could be used to ergonomically design programmes for home-based care and tuberculosis directly observed treatment. It could also be used as a basis for more efficient distribution of community health workers. I use high-resolution long-term rainfall and temperature data to produce the first malaria seasonality (length, start and end of transmission season(s)) maps for Africa. I relate the model to population data and estimate the population exposure in a variety of transmission settings. I investigate the relationship between predicted length of transmission season and parasite ratio from 2335 geo-referenced studies of children <10 years across Africa. The research is the first to correlate actual malaria survey data with model predictions at a continental scale. The seasonality model corresponds well with historical expert opinion maps and case data. A significant logarithmic relationship is detected between predicted length of transmission season and parasite ratio (r2=0.712, p=0.001). I recompute the changes in the disease likely to occur as a result of global warming. The seasonality model constitutes an important first step towards an estimate of continental intensity of transmission.
Aspects of the epidemiology of malaria in Natal Province, Republic of South Africa.
(1990) Sharp, Brian Leslie.; Van den Ende, Jan.
This study investigated aspects of the epidemiology of malaria in the Natal province of the Republic of South Africa. In this study the Collins English dictionary definition of epidemiology is used where it is defined as the branch of medical science concerned with the occurrence, transmission and control of an epidemic disease. Malaria has been a notifiable disease in the Republic of South Africa since 1958. Retrospective malaria case data from the Natal province as a whole was analyzed and the data from the KwaZulu and Natal areas of the province compared. Malaria cases were reported from 35 of the 65 magisterial districts in Natal province during the study period. In the Natal areas 91.5% of the cases were reported from eight districts and in the KwaZulu areas 96.4% of the cases came from three districts or as imports from Mozambique. The overall attack rate for both the Natal and KwaZulu areas using the total population figures for each area were very similar for the period 1986-1988 at 0.71 and 0.70 per 1000 head of population for the respective areas. The disease showed a distinct seasonal pattern in the KwaZulu areas with 86.9% of the cases being classified as indigenous and only 13.1% as imported. In the Natal areas, however, the seasonal pattern was not as marked and only 12.1% of the cases were recorded as indigenous and in excess of 82% as imported. Three species of the Anopheles gambiae complex were found to occur sympatrically in Natal province, namely: An. arabiensis, An. quadriannulatus and An. merus. Of these species An. arabiensis was found to occur at five localities during or after the notification of indigenous malaria cases from these areas. Due to the sympatric distribution of these species particular emphasis was placed on species identification and in particular the biting behaviour and control of An. arabiensis was investigated. The study found both morphological and behavioural differences between populations of An. arabiensis from those areas of the province with an intra-domiciliary residual insecticide vector control programme and those from the unsprayed areas. In the unsprayed areas the majority of the indoor resting An. arabiensis had fed on man whereas in the sprayed areas the majority of the indoor resting An. arabiensis were bovine fed. In the sprayed areas, however, the majority of the An. arabiensis caught leaving huts had fed on man. The percentage survival of bloodfed An. arabiensis caught leaving huts in the DDT sprayed area was in excess of 72%. The data strongly suggest that optimal control of An. arabiensis will not be achieved using the current control strategy of the annual application of intra-domiciliary DDT.
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.
Knowledge, attitudes and perceptions of both the community and traditional healers with regard to diagnosis and treatment of malaria in KwaZulu Natal.
(2000) Dladla, H. R.; Scott, Dianne.; Sharp, Brian Leslie.
This study aimed at investigating the knowledge, perceptions and attitudes of both the community and traditional healers with regard to the diagnosis and treatment of malaria in KwaZulu Natal with special reference to Ndumu in the magisterial district of Ingwavuma. Ingwavuma is one of the two northern magisterial district of KwaZulu Natal Province which is regarded as the highest malaria risk district in South Africa as a whole. The area has a warm temperature, 27-32°C, which is favourable for the development of the Anopheles mosquito. The factors predisposing the community to malaria infections were the socio-economic status of the area which is characterised by poverty. unemployment, poor housing and illiteracy, cross border migration, drug resistance, the agricultural development and irrigation scheme. Efficient control measures like house spraying a residual insecticide to control malaria vector mosquitoes, passive surveillance and active case detection with definitive diagnosis and treatment in place to prevent and control the upsurge of the disease The objectives of the study were to ascertain the knowledge. attitudes and perceptions of traditional healers in regard to malaria diagnosis and treatment and that of the community in relation to malaria treatment and diagnosis by traditional healers. The ultimate objective was to identify possible forms of collaboration between the traditional and the modern health services. The study was conducted from sections 2 - 10 of Ndumu where the population was 13 047 and 1300 households. A random sample of 173 respondents from the community and 70 traditional healers were selected for interview. Qualitative and quantitative methodologies were used in order to collect numerical and descriptive information. Data was collected using semi- structured questions and two sets were made: for traditional healers and the community. The study showed that the community was well aware of the signs of malaria but their knowledge was not supported by definitive testing and diagnosis of the condition. It came out that there are forms of health services available at grass root levels for example. self - help. where an individual tried on his own to combat he offending symptoms of the disease, family support systems, where family members especially the elder member gave support and assisted during the times of ill-health, the use of traditional healers, the malaria control camp, clinics and the hospital. The community supported the idea of collaboration between healers and the malaria control team and expressed their willingness to attend the services of a trained healer. Traditional healers confirmed the fact that some community members utilize traditional healers services and also expressed their wish to see the two forms of health services working together to control malaria.
Malaria vector populations associated with the agricultural development at Mamfene, Northern KwaZulu-Natal, South Africa.
(1995) Obala, Andrew Ambogo.; Appleton, Christopher Charles.; Sharp, Brian Leslie.; Le Sueur, David.
The irrigation farming methods on the Makhathini Flats are thought to be responsible for recent increase in malaria cases in the Mamfene area of northern KwaZulu-Natal despite ongoing malaria control activities. Their coincidence with the period of intensive fanning is an interesting one. This study was therefore carried out to determine the relationship between larval habitats and adult mosquito population in malaria transmission using Geographic Information System (GIS). Four types of breeding sites were utilised by malaria vectors in Mamfene, viz; types 1, II, III and IV. Habitat type I was tap pools, type II was irrigation spillage in agricultural land, type III was spillage outside but adjacent to the agricultural land and type IV was depression pools located both in the Balamhlanga swamp and inland. The cumulative larval density in all habitats peaked in March 1995 (20/man-hr), with irrigation spillage (type III) recording the highest density index (33/man-hr) as compared to tap pools (type I) which recorded 32.8/man-hr while other waterbodies recorded I3 .4/man-hr (type II) and O.5/man-hr (type IV) respectively. Subsamples of both larvae and adults of An. gambiae group were identified by the Polymerase Chain Reaction (PCR) technique. Of the larvae identified, 94.1 % and 5.9% (n=289) were An. arabiensis and An. quadriannulatus respectively while in the adult component, the composition was 98.7% and 1.3% (n=303) for An. arabiensis and An. quadriannulatus respectively. This confirmed An. arabiensis as the dominant malaria vector in Mamfene area while the exophilic behaviour of An. quadriannulatus was portrayed. Of the An. gambiae group dissected for parity, 51 .5%) were found parous. This is an indication that the population was old and was able to maintain transmission locally despite ongoing vector control measures. The Global Positioning System (GPS) was used to position larval and adult mosquito sampling sites. The spatial distribution of adult mosquitoes from the breeding sites were plotted using GIS soft ware (Map Info ) and the distance between the breeding sites and study houses were measured using a utility distance tool. With the aid of GIS, the adult mosquito density in houses could be used as an indicator to locate the breeding sites in the vicinity. The importance of these findings in terms of application in cost-effective malaria control cannot be over-emphasized.
The role of Anopheles arabiensis (Diptera: Culicidae) in malaria transmission and control in Gokwe and Binga districts, Zimbabwe..
(1996) Masendu, Hieronymo Takundwa.; Sharp, Brian Leslie.; Appleton, Christopher Charles.
Opportunistic feeding behaviour and partial exophily make An. arabiensis much more difficult to control by indoor residual spraying than any other vector in the Afro-tropical region. The persistent malaria outbreaks in Zimbabwe despite decades of indoor house spraying prompted this investigation into the role of An. arabiensis in malaria transmission and assessment of the possible impact of this control measure. The study was conducted in the malaria endemic districts of Binga and Gokwe. An. gambiae complex mosquitoes were collected from artificial outdoor resting sites, and from human dwellings by i) daytime hut searches, ii) pyrethrum spray catches and iii) exit window traps. Mosquito components were processed to enable: i) the distinction of An. arabiensis from An. quadriannulatus and An. merus on the basis of the pale band at the junction of the hind leg 3/4 tarsomeres; ii) species identification and scoring of inversion polymorphism on the basis of the X chromosome and autosomes respectively; iii) the determination of blood meal sources using the Ouchterlony precipitin test; and iv) identification of An. gambiae s.l. using polymerase chain reaction (PCR) and enzyme electrophoresis techniques. Entomological assessment of residual spraying included determining: the vector resting densities indoors and outdoors, bioassay and insecticides susceptibility tests. Data were also collected on hut profiles, knowledge-attitudes-practices surveys, and household malaria prevalence . surveys. An. arabiensis and An. quadriannulatus were found in sympatry in Binga and Gokwe, and in addition, An. merus was found in Gokwe. Most species identifications were made using PCR; which was found to have 7.5% and 41.6% levels of error for An. arabiensis and An. quadriannulatus respectively, using the cytogenetic technique as benchmark. The pale band technique yielded > 80% correct identification for An. arabiensis but the extent of overlap in the pale band lengths between An. arabiensis and An. quadriannulatus renders the method unsuitable for distinguishing these two species. Inversions 2Rb and 3Ra were found floating in An. arabiensis, with 60% frequency in the former. The Wright's F statistic value of -0.0416 indicated an excess of heterozygotes, and a state of panmixis in the vector population. No significant differences were observed between 2Rb karyotypes in host choice. Human blood indices among indoor (0.82), exit trap (0.98) and outdoor resting (0.30) specimens suggested exophilic behaviour. This was corroborated by the high fed:gravid ratios of 6.8: 1 and 11.6: 1 in sprayed and non-sprayed dwellings respectively. This was worsened by a high feeder-survivor index (FSI) of 93 % among exit trap specimens. The susceptibility to deltamethrin coupled with residual efficacy nine weeks post-spray indicated the suitability of the insecticide. Rural dwellings were suitably built for spraying but had no mosquito proofing. Personal protective measures are hardly known; sleeping outdoors occurs in Siabuwa. While An. arabiensis bites humans indoors the partial exophily it exhibits is a threat to indoor residual insecticide spraying. An integrated malaria control approach is recommended.
Susceptibility and resistance to insecticides among malaria vector mosquitoes in Mozambique.
(2003) Casimiro, Sonia Lina Rodrigues.; Appleton, Christopher Charles.; Sharp, Brian Leslie.
Insecticide resistance in malaria vector mosquitoes reduces the efficacy of insecticide in killing and can therefore cause a major problem for malaria vector control by insecticides. In Mozambique, pyrethroid resistance in Anopheles funestus was first detected in December 1999 in the southern corner of Maputo Province. Since then, various collections have been made at selected sites throughout the country and WHO standard susceptibility tests and biochemical assays were conducted to determine the susceptibility status and the major resistance mechanisms, in the Fl generation of field collected mosquitoes. Three malaria vector species: Anopheles funestus s.s., Anopheles gambiae s.s. and Anopheles arabiensis were identified in this study by Polymerase Chain Reaction (PCR) and their distributions plotted. The susceptibility data indicate that the Anopheles funestus s.s population in southern Mozambique is widely resistant to pyrethroid and with low levels of carbamate resistance evident at six localities. No resistance to organophosphate and DDT was observed at any study sites. Biochemical tests indicate the presence of an altered acetlylcholinesterase in all collection localities with the exception of Massinga district. Elevated esterase activity with substrate a-naphthyl acetate were detect in Boane with a probable role in organophosphate resistance. Elevated GST were detected in Boane, Moamba and Catembe. Very low levels monooxygenase titres were registered in all the localities in Mozambique, which suggest that this resistance mechanism is not operating in these areas. Pyrethroid resistance in the Anopheles gambiae complex was detected only in Anopheles arabiensis from one locality. No resistant to other groups of insecticide were observed. Altered acetlylcholinesterases were registered in all collection localities and in both species: Anopheles gambiae s.s. and Anopheles arabiensis. Elevated esterase with substrate a-naphthyl acetate were detected in Anopheles arabiensis at only one locality. Elevated GSTs were detected at all localities and in both species. The implications of the findings for malaria vector control in Mozambique are discussed.