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Epidemiology of Malaria in a Holoendemic Area of Rural

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Epidemiology of Malaria in a Holoendemic Area of Rural Ruprecht-Karls-University Heidelberg Institute of Hygiene Department of Tropical Hygiene and Public Health EPIDEMIOLOGY OF MALARIA IN A HOLOENDEMIC AREA OF RURAL BURKINA FASO Inaugural dissertation to obtain the degree of Dr. med. at the Medical Faculty of the Ruprecht-Karls-University Heidelberg Submitted by: Corneille TRAORE from Bomborokuy / Burkina Faso May 2003 Dekan: Prof. Dr. med. Dr. h.c. H.-G. Sonntag Referent: Prof. Dr. rer. nat. H. Becher Table of Contents List of abbreviations v 1 INTRODUCTION 1.1 History of malaria control 1 1.2 Global burden of malaria 3 1.3 Epidemiology of malaria 3 1.3.1 General considerations 3 1.3.2 Biological determinants 4 1.3.3 Malaria transmission 7 1.3.4 Malaria morbidity 10 1.3.5 Malaria mortality 16 1.3.6 Socio-demographic factors 19 1.3.7 Climatic and geographical parameters and malaria 20 1.3.8 Socio-economic parameters 21 1.3.9 Community knowledge about malaria 24 1.4 Statement of the problem in Burkina Faso 25 1.5 Aims of the study 26 2 STUDY DESIGN AND METHODS 2.1 Study area 27 2.2 Study design 31 2.2.1 Entomological study 32 2.2.2 Zinc supplementation study 33 2.2.3 ITN study 34 2.2.4 Community factors and malaria study 35 2.2.5 Chloroquine efficacy study 36 2.2.6 Mortality study 37 2.3 Malaria morbidity data 38 2.4 Data management and analysis 38 2.5 Ethical consideration 39 3 RESULTS 3.1 Malaria transmission 40 3.1.1 Vector species and transmission intensity 40 3.1.2 Parasites species 41 3.2 Malaria morbidity 42 3.2.1 Study children 42 3.2.2 Malaria incidence 42 3.2.3 Malariometric parameters by village and age group 45 3.2.4 Malariometric parameter comparison by subarea 51 3.3 Malaria mortality 53 3.4 Demographic, environmental and socio-economic factors 55 3.4.1 Age and sex dependence of malaria 55 3.4.2 Ethnicity and malaria parameters 56 3.4.3 Environmental parameters 57 3.4.4 Socio-economic factors 57 3.5 Community knowledge about malaria 58 3.5.1 Knowledge and perception of malaria 59 3.5.2 Knowledge of causes and transmission of malaria 60 3.5.3 Malaria prevention and treatment 62 3.5.4 Mosquito net prevalence, characteristics and use 64 3.6 Malaria treatment seeking behaviour 67 3.7 Clinical efficacy of chloroquine 70 4 DISCUSSION AND CONCLUSIONS 4.1 Discussion of the study 72 4.1.1 Methodology and design of the study 72 4.1.2 Malaria transmission 72 4.1.3 Malaria morbidity 73 4.1.4 Malaria mortality 73 4.1.5 Risk factors for malaria 74 4.1.6 Community factors associated with malaria 74 4.1.7 Malaria treatment seeking behaviour 76 4.1.8 Clinical efficacy of chloroquine 76 4.2 Conclusions 77 5 SUMMARY 78 6 REFERENCES 80 7 CURRICULUM VITAE 96 8 ACKNOWLEDGEMENTS 97 List of abbreviations ARI Acute Respiratory Infection CNRFP Centre National de Recherche et de Formation sur le Paludisme CRSN Centre de Recherche en Santé de Nouna DDT Dichloro-diphenil-trichloro-ethane DSS Demographic Surveillance System EIR Entomological Inoculation Rate FGD Focus Group Discussions INDEPTH International Network for continuous Demographic Evaluation of Populations and their Health INSD Institut National de la Statistique et de la Démographie ITN Insecticide Treated Net MIM Multilateral Initiative on Malaria PRAPASS Projet de Recherche-Action pour l’amélioration des Soins de Santé SSA Sub-Saharan Africa VER Vital Events Registration GIS Geographic Information System 1 INTRODUCTION 1.1 History of malaria control The control of malaria remains one of the world’s greatest public health challenges. First rationale malaria control efforts were only possible after the discovery of the parasite life cycle a century ago. The fight to control malaria through out the world achieved major successes in the 1950s and 1960s after the discovery and systematic use of new tools including residual insecticides, such as dichloro-diphenil-trichloro-ethane (DDT) and new anti-malarial drugs such as chloroquine and amodiaquine (4-aminoquinolines). The application of these effective residual insecticides and drugs led to eradication in parts of the world with low levels of transmission and good infrastructure (WHO, 1999). Africa was not part of the global eradication effort because of the high malaria endemicity. In addition, infrastructure was not developed, settlements were dispersed and there were few trained people to manage these programmes and financial resources were very limited (Najera et al.1991). The global malaria eradication programme was abandoned in 1969, due to technical reasons such as the resistance of the mosquito vector to DDT and resistance of malaria parasites to commonly used drugs (proguanil, pyrimethamine and choroquine), and to failure of the programme in nearly all of the poor tropical countries. The few demonstration projects that had been set up in Africa had also shown that it was not possible to apply existing vector control measures effectively in such areas of very high transmission intensity. In 1992, the WHO convened a malaria conference in Amsterdam which gave a new impetus to malaria control efforts and approved a revised Global Malaria Control Strategy (WHO 1993). The strategy enlisted four basic elements for malaria control: · Early diagnosis and prompt treatment; · Implementation of selective, sustainable, preventive measures including vector control; · Early detection, containment, and prevention of epidemics; · Fostering regular assessment of affected countries´ malaria situation, especially ecological, social and economic determinants of the disease, by strengthening local capacities for basic and applied research. This new strategy now faces major problems in endemic countries such as: - Increasing resistance of the malaria parasite to choroquine and pyrimethamine- sulfadoxine - Poor coverage of health infrastructure for diagnosis and treatment in the rural areas - Resistance of the mosquito to insecticides including DDT, one of the few affordable insecticides - Shortage of well trained personnel, scarce financial resources and finally the major problem with strategic planning for malaria control. There is thus a need for continuous development of new antimalarial drugs and insecticides, which need to be affordable for the majority of poor populations living at risk for malaria in southern countries. Although it would be a breakthrough if an effective malaria vaccine or more effective vector control tools would become available, this is not likely to happen in the near future. However, the renewed emphasis on tools such as insecticide impregnated bednets, and the improvement of their efficacy and effectiveness by, for instance, using more appropriate fabrics and insecticides, could improve on the state of malaria control in malaria endemic countries especially in Africa (Carnevale et al. 1988; Rozendaal 1989; D’Alessandro et al.1995; Lengeler and Snow 1996; Lengeler 1998; Lengeler et al.1998). The 1999 World Health Report (WHO 1999) declared malaria to be one of the two priority issues in international health, the second was smoking. In the same year, WHO launched the global initiative Roll Back Malaria. This programme is developing a new, sector-wide partnership to combat the disease at global, regional, country and local levels. The Roll Back Malaria initiative calls for well co-ordinated action that makes it an integral part of wider development processes (Roll Back Malaria 2000). These ideas have been taken up, for instance, by the Multilateral Initiative on Malaria, an alliance of organisations and individuals aiming at maximising the impact of scientific research on malaria in Africa, by promoting intensified, co-ordinated international research activities (MIM 1999). 1.2 Global burden of malaria Malaria is the most important parasitic disease in the world and remains of highest public health importance. In 1994, the global incidence of malaria has been estimated at 300-500 million clinical cases annually, causing 1.5 to 2.7 million deaths each year (WHO,1997). More than 90 % of this malaria burden occurs in sub-Saharian Africa (SSA), where severe malaria disease and death mainly occur among young children of rural areas with little access to health services (Greenwood et al. 1987a; Snow et al.1999). In SSA malaria accounts for an estimated 25% of all childhood mortality below age of five excluding neonatal mortality (WHO 1997). Recent studies suggest that this percentage might even be higher because of the contribution of malaria as indirect cause of death (Alonso et al. 1991, Molineaux 1997). According to WHO and the World Bank, malaria is responsible for an annual loss of 35 million disability adjusted life years (DALYs) worldwide (World Bank, 1993). It has furthermore been estimated that about 40% of all fever episodes in SSA are caused by malaria (Brinkmann & Brinkmann 1991). The epidemiological situation of malaria is worsening with the spread of drug resistance in the parasite and insecticide resistance in the vector. More evidence points to significantly increasing malaria morbidity and mortality is SSA due to the development by Plasmodium falciparum of resistance to existing first-line drugs such as chloroquine and sulphadoxine/pyrimethamine (Trapé 2001). 1.3 Epidemiology of malaria 1.3.1 General considerations WHO outlined concepts and strategies for each of the eight major endemic settings and malaria paradigms (WHO, 1993). Emphasis was placed on tailoring malaria control to the local situation; i.e. considering the social, ecological and political context of a given area and its overall health and development plans. Acquisition of information on the burden of malaria relies on advancing our understanding of malaria epidemiology which requires investigation of the complex relationships between the malaria parasite, the vector, the host and the environment (Bloland et al.1999). The burden of illness attributable to malaria varies substantially between countries within tropical Africa and even between different regions of the same country.
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