Cost-Effectiveness of Indoor Residual Spraying for Malaria Prevention in a Region with High Insecticide-Treated Bed Net Coverage 公开

Stelmach, Rachel (2015)

Permanent URL: https://etd.library.emory.edu/concern/etds/gq67jr30j?locale=zh
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Abstract

The Tanzania National Malaria Control Program (NMCP) has reduced the burden of malaria in mainland Tanzania, but resource constraints threaten its capacity to maintain and expand its achievements. This thesis presents a decision-tree cost-effectiveness analysis of an indoor residual spraying (IRS) program combined with an insecticide-treated bed net (ITN) distribution program, compared to ITN distribution alone. The primary outcome of interest is the expected economic cost to society per case of malaria averted in children in mainland Tanzania under the age of 5. IRS data are drawn from campaigns in northwest Tanzania between 2008 and 2012; all other data are drawn from published literature. Through one-way sensitivity analyses, probabilistic sensitivity analysis, and scenario analyses, the effects of variations in insecticide resistance, the malaria parasitemia prevalence rate, and IRS tactics are also examined. In the base case, the combination of ITN distribution and IRS is expected to be more expensive and more effective than the ITN-only intervention (incremental cost per case averted (ICER): $152.36). Important drivers of variability in cost per case averted are the number of IRS rounds required, insecticide costs for IRS, the ITN usage rate, the prevalence of parasitemia, and the probability that an infected child develops symptoms. Compared to blanket spraying, targeted spraying is expected to lead to a higher number of malaria cases per person targeted (between 0.211 and 0.256 versus between 0.050 and 0.076), but the cost per case averted is expected to be lower (ICER: $41.70). In a scenario of increasing pyrethroid resistance, the expected cost per case averted is expected to be higher than in the base case (ICER: $192.12). The NMCP should pursue blanket IRS spraying only in the northern and southern regions, which have the highest prevalence of malaria. If the cost per case averted of blanket spraying exceeds the NMCP's willingness to pay, targeted spraying provides a valid alternative, but it will probably lead to a higher incidence of malaria. A malaria program that employs multiple methods of prevention and control will improve the cost-effectiveness of all its interventions.

Table of Contents

Table of Contents
CHAPTER 1: INTRODUCTION 1
1.1 INTRODUCTION AND RATIONALE 1
1.2 PROBLEM STATEMENT 2
1.3 PURPOSE STATEMENT 4
1.4 RESEARCH QUESTIONS 4
1.5 SIGNIFICANCE STATEMENT 5
1.6 DEFINITION OF TERMS 5
CHAPTER 2: COMPREHENSIVE REVIEW OF THE LITERATURE 9
2.1 INTRODUCTION 9
2.2 MALARIA IN TANZANIA 9
2.3 TANZANIA MALARIA CONTROL STRATEGIES 11
2.3.1 History of malaria programs in Tanzania. 11
2.3.2 Case detection and management. 14
2.3.3 Intermittent preventive treatment in pregnancy (IPTp). 17
2.3.4 Insecticide-treated bed nets (ITNs). 19
2.3.5 Indoor residual spraying (IRS). 21
2.4 IRS 21
2.4.1 Description of IRS. 22
2.4.2 Effectiveness of IRS. 24
2.4.3 Combining IRS and ITNs. 25
2.4.4 Current IRS in Tanzania. 28
2.4.5 Lessons learned from prior IRS campaigns. 29
2.5 ECONOMIC ANALYSES 35
2.5.1 Case management. 36
2.5.2 IPT. 36
2.5.3 ITNs. 37
2.5.4 IRS. 38
2.6 DISCUSSION OF AVAILABLE EVIDENCE 44
CHAPTER 3: PROJECT CONTENTS 46
3.1 METHODOLOGY 46
3.1.1 Introduction. 46
3.1.2 Population and Sample. 46
3.1.3 Research design. 46
3.1.4 Procedures. 47
3.1.5 Instruments. 49
3.1.6 Plans for data analysis. 58
3.1.7 Ethical considerations. 60
3.1.8 Limitations and delimitations. 60
3.2 RESULTS 62
3.2.1 Values. 62
3.2.2 Base case. 65
3.2.3 One-way sensitivity analyses. 67
3.2.4 Probabilistic sensitivity analysis. 73
3.2.5 Scenario: best- and worst-case. 74
3.2.6 Scenario: targeted spraying. 75
3.2.7 Scenario: increased pyrethroid resistance. 76
CHAPTER 4: DISCUSSION, CONCLUSION, AND RECOMMENDATIONS 78
4.1 DISCUSSION 78
4.1.1 Baseline findings. 78
4.1.2 Prevalence of malaria. 79
4.1.3 Insecticide costs and resistance. 80
4.1.4 Targeted spraying. 81
4.1.5 Strengths and weaknesses. 82
4.1.6 Suggestions for future research. 83
4.2 CONCLUSION AND RECOMMENDATIONS. 84
APPENDIX I: DECISION TREE 86
APPENDIX II: IN-KIND CONTRIBUTIONS: DATA COLLECTION INSTRUMENT 88
APPENDIX III: ADDITIONAL SENSITIVITY ANALYSES 101
REFERENCES 103

List of Figures

Figure 1: Tornado diagrams 76
Figure 2: Sensitivity analyses on number of IRS rounds required 68
Figure 3: Sensitivity analyses on cost of insecticides for IRS 68
Figure 4: Sensitivity analyses on number of people covered per ITN 79
Figure 5: Sensitivity analyses on cost of an ITN 79
Figure 6: Sensitivity analyses on prevalence of ITN usage 71
Figure 7: Sensitivity analyses on probability of developing symptoms 71
Figure 8: Sensitivity analyses on prevalence of parasitemia 72
Figure 9: Probabilistic sensitivity analysis of incremental cost versus incremental effectiveness for IRS and ITNs versus ITNs only 74

Figure A1: Partial decision tree 1 86
Figure A2: Partial decision tree 2 86
Figure A3: Sensitivity analyses on cost of ITN distributors' labor 101
Figure A4: Sensitivity analyses on cost of IEC for ITNs 102
Figure A5: Sensitivity analyses on cost of administrative labor for ITNs 102

List of Tables

Table 1: IRS cost categories 51
Table 2: ITN cost categories 53
Table 3: Cost of illness components 54
Table 4: Probability values 62
Table 5: Non-annualized cost values (2011 USD) 63
Table 6: Other estimated values 65
Table 7: Input values for probabilistic sensitivity analysis 73
Table 8: Input values for best- and worst-case scenario analyses 74
Table 9: Input values for targeted spraying scenario analysis 76
Table 10: Values for increased pyrethroid resistance scenario analysis 76

Table A1: Decision tree parameters 87

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