Net Use Conditional on Access – Why Are People Not Using Nets?

Since we know that access to a net within the household is one of the primary drivers of net use, increasing the number of nets in each household’s possession would substantially increase use in many countries. Indeed, evaluations of national population-based surveys have determined that 20 out of 26 PMI focus countries have achieved population use:access ratios above the RBM target of 0.80 (ITN use access report), meaning that of the population that has access to a net, over 80% use them (although some of these surveys have not been updated in over a decade and likely have a different net situation). Among PMI countries, the peak proportion of a population with access was 79%

in the Uganda 2014–2015 MIS (which was following Uganda’s first universal coverage campaign in May 2013–August 2014) (USAID, 2016b), and the lowest post-2010 proportion was 11% in the 2011 Cameroon DHS (their first UCC was in 2011. As of 2014, the proportion of people with access has increased to 37%) (USAID, 2016a). While progress has been made, there is still much work to be done.

In the meantime, one area for continued research is the proportion of the population with access to a net who choose not to use one, which is, on average, around 20% (Koenker, Ricotta and Olapeji, 2017). There are currently a number of indicators that have been developed to quantify net access and use. As described in RBM’s Household Survey Indicator Guide for Malaria Control and reported in the PMI Malaria Operational Plans and Vectorworks’ ITN Access and Use Report, “Proportion of population with access to an ITN within their household” is the indicator of choice for measuring population access to nets. This indicator is useful for informing ITN distribution programs (i.e. PMI, NMCP) where and to what extent there is a need for achieving higher ITN coverage (MEASURE Evaluation et al., 2013; Koenker, Ricotta and Olapeji, 2017). In this thesis, this indicator has been refined to provide a more accurate reflection of net access within a household, as on many occasions, more than the recommended two people sleep under a net, and in others, only one person uses a net, leaving an unused but available space. In the RBM indicator calculation, the total number of individuals who could use a net (number of ITNs x 2) is divided by the number of individuals who spent the previous night in surveyed households, which does not account for the “alternate” use patterns mentioned. In the access indicator presented here, the number of people who did or could have slept under a net (i.e. a space under a net was available for their use) is calculated. Use among those with access, called here the use/access proportion (UAP), is the number of individuals who slept under a net, divided by access. While the calculation of this indicator is less straightforward than RBM’s (one must count nets and sleepers together rather than just nets), it provides a more accurate picture of net use which can then be incorporated into studies about net use behavior, as demonstrated in Chapters 5 and 6. As stated extensively in these two chapters, there are many reasons why individuals choose to or are unable to use a net, even with one available, including level of nuisance mosquitos or sleeping space structure of the

household. To that end, the goal of these manuscripts was to determine whether there was a quantifiable relationship between both household-level and remotely sensed environmental variables and reported net use among individuals with access to a net.

In Chapter 5, the humidex, which is an indicator of how hot it feels to a person and is a combination of temperature and atmospheric water vapor, was evaluated. In Chapter 6, rainfall the month preceding the survey (used as a measure of nuisance mosquito biting), and a modelled temperature product comprised of a variety of meteorological data products (to understand personal comfort due to the environment) were used. In this thesis, the only significant environmental predictor of net use was increased rainfall in two surveys conducted during the rainy season (Angola and Tanzania), adding evidence to the scientific literature that mosquito density vis a vis rainfall is an important consideration when assessing net use among those with access. As malaria transmission can continue throughout the year, it is important for malaria programs to emphasize net use year-round and to explore alternative measures, either by making net use more desirable in the hot, dry season (for example, by providing fans to use under the net) or controlling vectors in a different fashion (such as by using IRS, spatial repellents, larvaciding in appropriate settings, etc).

Net use among those with access was also affected by household wealth status, both positively and negatively depending on the country. In both surveys in Ghana (Chapter 5) and the Nigeria MIS (Chapter 6), net use was lower in wealthier households. This could be due to several reasons. Wealthier households tend to have better access to housing improvements like window screens and closed eaves that act as vector control (Tusting et al., 2017). The reduced presence of mosquitoes could then be a reason to not need to use nets. Along with this, having a decreased perception of vulnerability to malaria has been shown to decrease net use (Auta, 2012). In contrast, net use increased with wealth in Mali

and Tanzania. Taylor and colleagues (Taylor, Florey and Ye, 2017) and Galactionova and colleagues (Galactionova et al., 2017) found that net ownership and use are both more pro-rich in Tanzania, and that these indicators are more equitably distributed in Mali (possibly explaining why net use in the “richest” wealth quintile was not significantly different from the poorest quintile). One study found livelihood and cultural issues with net use, in Tanzania, specifically migrant farming (Dunn, Le Mare and Makungu, 2011), which made it harder for families to use their nets. Regardless of the direction of influence wealth has on net use, there needs to be a more detailed understanding of why these differences exist (beyond just access to interventions) to know whether nets are the best solution in these locations (e.g. people with screened housing probably do not need to rely as much on nets), and how strategies to improve net use can be targeted if they are the best solution in an area.

The final theme found in this thesis affecting net use among those with access was sleeping arrangements and net allocation within the household. Chapter 6 demonstrated that even when people had “theoretical” access to a net, one of the strongest predictors of net use was the number of nets per person in the household (although this was not true in all cases, such as Angola, or Ghana in Chapter 5). In addition, in Mali and Tanzania, the more rooms used for sleeping in the household per person, the fewer net users there were.

This indicates that even when households meet the basic requirements of “enough” nets at one per two people, it might not be enough to ensure 100% net use. Households with extended families residing in the same compound, the presence of visitors, having adolescent children, sleeping outdoors, attending events away from the home, and having multi-use rooms where it is difficult to hang a net have all been cited as reasons for non-use of nets when one is available (Toé et al., 2009; Iwashita et al., 2010; Pulford et al., 2011; Monroe et al., 2014, 2015; Kateera et al., 2015; Plucinski et al., 2015). If households

had the ability to acquire the number of nets they needed for their unique situation, net use would likely increase. Solving this in a sustainable and equitable manner to ensure equitable access to nets across all population strata will require careful thought as to the best way to approach this issue, and will likely entail a combination of mass campaigns, continuous distribution channels, and private markets (Galactionova et al., 2017).