Options and considerations for maintaining universal coverage and use of long-lasting insecticidal nets (LLIN) in sub-Saharan Africa

Abstract

Malaria causes over 600,000 deaths annually, primarily among young children in sub-Saharan Africa. Long lasting insecticidal nets (LLIN) are the primary vector control measure to prevent malaria. Currently, mass campaigns are the primary channel for distributing LLIN to achieve universal coverage, but fail to maintain high levels of intra-household access to LLIN between campaigns. Identifying ways to maintain consistent high rates of access and use are crucial to achieving declines in malaria burden. The aim of this thesis was to improve the evidence-based development of continuous ITN distribution strategies in malaria endemic countries, through a better understanding of the options for distribution channels, and through an improved understanding of determinants of net use and the impact of behaviour change communication. These results showed that for continuous distribution strategies, over a ten year period there is a significant amount of excess LLIN distributed through mass campaigns, and that program and overall costs can be made more efficient by distributing the optimal number of nets through a combination of continuous distribution channels that reach the majority of the at-risk population. In the case of Tanzania, ANC and EPI distribution plus a school channel delivering nets each year to pupils in every other class of primary and secondary school was most likely to sustain universal coverage. Qualitative data collected in Zanzibar and Bukoba (Tanzania) demonstrated that participants’ conceptualization of risk and aspects of comfort (getting a good night’s sleep, avoiding biting pests) appeared to play a large role in personal decisions to use nets consistently or not. Barriers to comfort were frequently cited as reasons not to use a net consistently. These data offer a strong way forward for messaging to maintain LLIN use even as malaria burden decreases, by focusing on the non-malaria benefits of LLIN use. We also applied the universal coverage indicators validated in 2013 to the Nigeria 2010 MIS to illustrate their utility for LLIN program planning. The analysis comparing actual against potential use showed that ITN utilization was good overall with only 19% of people with access not using the ITN, but with a significant difference between the North, where use was excellent (use gap 11%), and the South (use gap 36%). When we expanded the comparisons of intra-household (or population) access and LLIN use to 41 DHS and MIS surveys from 2005-2012, the median proportion of users compared to those with access was high, at 82.1%. Linear regression of use against access showed that 89.0% of household members with access to nets used them the night before, demonstrating that the gap was primarily driven by lack of intra-household access. We examined 14 household surveys from Ghana, Senegal, Nigeria and Uganda to assess intra-household re-allocation of nets, which was sensitive to current household net ownership and the time elapsed since mass distribution. Of the repurposed nets (<1% overall), the were already considered too torn, indicating they had already served out their useful life for malaria prevention. National programs and donor agencies should remain confident that overall, their investments in LLIN are being appropriately used. Finally, we evaluated a BCC intervention intended to promote care and repair behaviours to extend net life. Exposure to the intervention was strongly correlated with increased positive attitude towards care and repair, and increases in attitude were positively correlated with observed net repairs, and with the proportion of nets in serviceable condition. Estimated median net lifespan was approximately one full year longer for nets in households with a positive attitude compared to negative attitude towards care and repair. This thesis demonstrates that high rates of use of LLIN are the norm rather than the exception, and that use is primarily driven by intra-household access – that is, households having enough nets for their family members. Reaching and maintaining high levels of access will require concerted efforts to determine the best continuous distribution strategy based on a given country (or region’s) operational capacity to deliver nets, and mass campaigns are by no means obsolete. Program planners must take into account the best options for continuous distribution of nets through optimal channels, as delivering the correct number of nets will eventually lead to cost savings over time, as excess nets are minimized, and replacement occurs when nets are needed, rather than at pre-determined intervals. Behaviour change communication has already contributed to high LLIN use rates, and has been demonstrated herein to significantly impact median net lifespan. National plans that optimize both distribution strategies and accompanying BCC strategies will be necessary to ensure continuing protection of all individuals at risk of malaria, and to maximize investments.