Insecticide-treated net use before and after mass distribution in a fishing community along Lake Victoria, Kenya: successes and unavoidable pitfalls

Abstract

Background: Insecticide-treated nets (ITNs) have proven instrumental in the successful reduction of malaria incidence in holoendemic regions during the past decade. As distribution of ITNs throughout sub-Saharan Africa (SSA) is being scaled up, maintaining maximal levels of coverage will be necessary to sustain current gains. The effectiveness of mass distribution of ITNs, requires careful analysis of successes and failures if impacts are to be sustained over the long term.

Methods: Mass distribution of ITNs to a rural Kenyan community along Lake Victoria was performed in early 2011. Surveyors collected data on ITN use both before and one year following this distribution. At both times, household representatives were asked to provide a complete accounting of ITNs within the dwelling, the location of each net, and the ages and genders of each person who slept under that net the previous night. Other data on household material possessions, education levels and occupations were recorded. Information on malaria preventative factors such as ceiling nets and indoor residual spraying was noted. Basic information on malaria knowledge and health-seeking behaviours was also collected. Patterns of ITN use before and one year following net distribution were compared using spatial and multi-variable statistical methods. Associations of ITN use with various individual, household, demographic and malaria related factors were tested using logistic regression.

Results: After infancy (<1 year), ITN use sharply declined until the late teenage years then began to rise again, plateauing at 30 years of age. Males were less likely to use ITNs than females. Prior to distribution, socio-economic factors such as parental education and occupation were associated with ITN use. Following distribution, ITN use was similar across social groups. Household factors such as availability of nets and sleeping arrangements still reduced consistent net use, however.

Conclusions: Comprehensive, direct-to-household, mass distribution of ITNs was effective in rapidly scaling up coverage, with use being maintained at a high level at least one year following the intervention. Free distribution of ITNs through direct-to-household distribution method can eliminate important constraints in determining consistent ITN use, thus enhancing the sustainability of effective intervention campaigns.

Figure 1

Location of study site in the Gembe East area of Mbita District of Nyanza Province, and locations of individual households that were part of the intervention and surveillance.

Figure 2

Fraction of household members who slept under an ITN the previous evening before and after mass distribution. Spatial patterns of ITN use are illustrated using inverse distance weighting interpolation.

Figure 3

Getis-Ord Gi* statistics for each household to measure spatial clustering of household ITN use as a percentage of total number of residents. Colors represent areas of statistically significantly high levels of ITN use (red) and significantly low levels of ITN use (blue).

Figure 4

Number of ITNs by the number of people living in the home. Gray line represents the expected trend of ownership given the number of people and a criterion for universal coverage which assumes at least one net per two people. Blue line (with confidence bands) indicates the observed trend.

Figure 5

Patterns of ITN use by age both before and after mass distribution. Lines are produced using a local regression smoothing technique. Patterns of males and females are presented for comparison.