Presented at 2013 ASTMH Conference.

1. Background
Effect of Age of ITN Owned by Households on Malaria Parasite Infection Among
Children Under Five Years of Age in Angola
Methods
Insecticide treated nets (ITNs) are effective for malaria control and provide protection to individuals sleeping under them and those living
in households that own them. ITNs are manufactured to have a long lasting protective effect; however, the effect of the age of ITNs in
households on malaria parasitemia under country-specific context and programmatic conditions is not well documented, particularly in
Angola. Using 2011 malaria indicator survey (MIS) this study examined the association between the age of ITNs in households and malaria
parasite prevalence among children under five years of age in Angola. ITNs that were obtained shortly before the survey may not protect
children from malaria infection because the infection may have happened before the acquisition of the net. Conversely, ITNs that were
obtained a longer time ago may be less protective due to wear and tear of the net, or reduction in efficacy of the insecticide.
Results
• Angola 2011 MIS was conducted February– May
2011.
• Survey sample powered to provide estimates for
urban and rural, and four malaria endemicity regions
(Figure 2) .
• Households interviewed were 8,030 with and 8,512
children under five year of age.
• All under five children tested for malaria parasite
with microcopy and rapid diagnostic test .
• A logistic regression performed to assess the effect of the age of
ITNs in households and malaria parasite prevalence among under
five children.
• Model adjusted for eight covariates: sex of child, age of child,
mother’s education, household had been sprayed or not,
household size, household wealth quintiles, area of residence,
and malaria epidemiologic zones.
• All covariates checked for collinearity and interaction.
• Only one child per household included in the model to avoid
cluster effects.
Summary
Children from households that had owned ITNs for 2-6 months before the survey were
significantly less likely to have malaria parasitemia compared to those from households
without ITNs (OR = 0.28, 95% CI: 0.10-0.84). ITNs that had been owned for one month or
less, or for more than six months, were not protective. ITNs remain protective against
malaria in Angola, however, when assessing their effects on parasite prevalence the age of
the net in the household should be considered. These findings provide useful information,
particularly when assessing the impact of ITN interventions on the reduction of malaria
burden.
Acknowledgments
The authors would like to acknowledge the President’s Malaria Initiative impact evaluation team for
Angola. This study was made possible by support from the U.S. Agency for International Development
(USAID) under the terms of Cooperative Agreement GPO-A-00-03-00003-00. The opinions expressed are
those of the authors and do not necessarily reflect the views of USAID, or the United States Government.
Variables N Odds Ratio (95% CI) p value
ITN ownership by age of net
No ITN 1,558 1.0
ITN owned for 1 month or less 61 0.27 (0.03-2.31) 0.232
ITN owned for 2-6 months 255 0.28 (0.10-0.84) 0.023
ITN owned for 6-12 months 152 0.44 (0.12-1.60) 0.212
ITN owned for more than 12 months 83 0.29 (0.06-1.40) 0.124
Sex
Male 1,032 1.0 <0.001
Female 1,077 0.95 (0.71-1.28) 0.744
Age of child
6-23 months 602 1.0 <0.001
24-59 months 1,507 1.08 (0.96-1.21) 0.207
Mother's Education
None 706 1.0
Primary 1,157 0.96 (0.71-1.32) 0.822
Secondary and Higher 246 1.3 (0.44-3.85) 0.642
Household sprayed last 12 months
No 1,965 1.0
Yes 144 0.5 (0.23-1.08) 0.077
Household size
3 or less members 193 1.0 <0.001
4-5 members 736 2.34 (1.25-4.36) 0.008
6-7 members 662 1.92 (1.01-3.63) 0.044
8 or more members 518 2.02 (1.04-3.92) 0.038
Wealth quintile
Least poor 507 1.0
Second 618 1.98 (1.00-3.86) 0.049
Third 363 6.87 (3.57-13.20) <0.001
Fourth 280 6.57 (3.37-12.82) <0.001
Poorest 341 3.82 (1.94-7.55) <0.001
Residence
Rural 1,337 1.0
Urban* 772 0.11 (0.05-0.24) <0.001
Malaria Epidemiologic Zones
Hyperendemic 532 1.0 <0.001
Mesoendemic stable 564 0.47 (0.32-0.68) <0.001
Mesoendemic unstable 592 0.24 (0.16-0.37) <0.001
Luanda 421 0.67 (0.21-2.07) 0.482
N = 1937 (Model restricted to one child under-five years per household to avoid cluster effects); Pseudo R2: 0.1925; p < 0.05; CI = Confidence Interval;
Figure 1: Location of Angola Data Source Statistical AnalysisFigure 2: Malaria endemicity zones
Ana Franka koh1, Rebecca Winter2, Yazoume Ye1
1MEASURE Evaluation/ICF International, 2MEASURE DHS, ICF International
37 35
0
10
20
30
40
50
60
70
80
90
100
any net ITN
%householdsownatleastone
Figure 3: Household ownership of any nets and ITNs
Source: MIS 2011
41
21
0
10
20
30
40
50
60
70
80
90
100
with children under-five without children under-five
%householdsownatleastone
Source: MIS 2011
Figure 4: ITN ownership in households with and without under five children
Table 1: Logistic regression outputs: The effect of ITNs ownership by age of net on malaria parasitemia
Figure 5: Household ownership of ITNs, by malaria epidemiologic zone
24 27 27 26
0
10
20
30
40
50
60
70
80
90
100
Hyperendemic Mesoendemic stable Mesoendemic
unstable
Luanda
%sleptunderITNpreviousnight
Figure 6: ITN use among under five children by malaria epidemiologic zone
30
36 37 35
0
10
20
30
40
50
60
70
80
90
100
Hyperendemic Mesoendemic stable Mesoendemic
unstable
Luanda
%householdsownatleastone
Source: MIS 2011
Source: MIS 2011