Characteristics of Bed Net Use and Malaria Incidence During Sick Visits in a Cohort of Malawian Children Living in an Area of Insecticide Resistance Open Access

Nagy, Barbara Ann (2014)

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Characteristics of Bed Net Use and Malaria Incidence During Sick Visits in a Cohort of Malawian Children Living in an Area of Insecticide Resistance

By Barbara A. Nagy

Background: Insecticide treated bed nets (ITN) are one of the main pillars ofefforts to control malaria, but the emergence of insecticide resistance threatens to reverse gains made in malaria control over the past decade. This study examines the effectiveness of ITNs in an area with known pyrethroid resistance.

Methods: A cohort of 1201 Malawian children aged 6-59 months, living in an area of high pyrethroid resistance, was cleared of parasitemia at baseline, given deltamethrin impregnated ITNs and followed at sick visits for one year. Rapid diagnostic tests for P. falciparum malaria were done at each visit. Data from 806 sick visits were analyzed using multivariate logistic regression to examine the relationship between net use last night and malaria parasitemia, controlling for potential confounders. Odds ratios, confidence intervals and p values were calculated to create a final model generating adjusted odds ratios and confidence intervals.

Results: The final model contained four covariates significantly associated with malaria parasitemia: net use (best, good or worst quality nets); age; caregiver's education; and season; and demonstrated that best quality ITNs (less than 36 months of age, without holes) exerted a significant protective effect against malaria incidence (aOR 0.4, 95% CI 0.2, 0.7) compared with no bed net. Children 48-59 months of age had increased odds of malaria compared with 6-11 month olds (aOR 1.67, 95% CI 0.95, 2.91). Maternal completion of primary school greatly increased the odds that a child used a bed net on the night before sick visit (OR 10.3, 95% CI 1.4, 75.4). Distribution of enough ITNs to cover all household members increased the percentage of children below five years using ITNs by 14.7%, to 93.7%.

Conclusions: ITNs retained their protective effectiveness in an area of Malawi with high levels of pyrethroid resistance as long as they were newer and had few holes, because physical barriers of intact nets and irritant properties of pyrethroids remained important. Age shift in malaria incidence indicates that malaria control interventions should be extended to older age groups. Distribution of sufficient ITNs to cover all household inhabitants significantly increases use by young children. Maternal primary education strongly favors ITN use by children.

Table of Contents

Table of Contents

Chapter 1: 1

Background and Rationale.1

Problem Statement.2

Research Questions, Purposes and Aims.3

Definition of Terms.4

Chapter 2: Review of the Literature.5

Insecticide Treated Bed Nets.5

Insecticide Resistance.7

Durability of Long-Lasting Insecticide Treated Bed Net.11

Qualitative Evaluation of Bed Net Use. 13

Diagnosis and Treatment of Malaria. 14

Chapter 3: Methods.16

Study Design.16

Description of the Study Population.16

Study Procedures.19

Statistical Analysis.21

Ethical Considerations.23

Chapter 4: Results.24

Descriptive Results. 24

Univariate Analysis.30

Multivariate Analysis.33

Limitations of the Study.35

Chapter 5: Discussion and Conclusions.37 Discussion.37 Conclusions.39 Bibliography.40

Appendix A: Insecticide-treated net effectiveness in a setting of significant

pyrethroid resistance: an observational cohort study or malaria incidence

in children in Malawi, CDC Protocol version 7.43

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