Bed net care practices and associated factors in western Kenya

Insecticide-treated nets (ITNs) and long-lasting insecticidal nets (LLINs) are effective malaria prevention tools. Notably, ITNs have reduced malaria incidence by half in children under 5 in areas of stable malaria transmission [1]. The primary strategy for malaria prevention in sub-Saharan Africa, according to the World Health Organization (WHO), has become the distribution of LLINs [2]. To achieve their optimal effectiveness, bed nets must be available as a resource (supply), accessible to households (ownership and universal access), used regularly (use) and well maintained to maximize efficacy (care and repair).

While some LLIN distribution programmes have shifted to combinations of continuous and mass distribution models [3], many malaria control programmes still distribute LLIN every 3–5 years, the anticipated optimal lifespan of a LLIN [4]. Initiated in 2005 under President George W. Bush, the President’s Malaria Initiative (PMI) developed a network of monitoring sites to measure realistic LLIN durability and lifespan in home conditions [5, 6]. Studies from these monitoring sites find variable serviceable lifespans generally between 2 and 3 years, though significant damage noticed from as little as 6 months to 4.5 years, with differences by net brand and variations in insecticidal activity and attrition [5, 7‐15]. These studies also suggest that inadequate bed net maintenance behaviours contribute to this shortened lifespan [8].

In an effort to standardize terminology for research into bed net maintenance attitudes and practices, the PMI-funded NetWorks project established the phrase “care and repair”. The project developed a conceptual framework of the knowledge, attitudes, intentions, social norms, and behaviours related to care and repair practices [16]. Proper care and repair of LLINs increases their effective longevity, maintaining higher and more stable coverage of vector control between mass community distributions [5, 8, 9]. Recommended LLIN care practices include hanging nets up while not in use, washing gently and infrequently and with no soap or mild soap, drying indoors or in the shade, and repairing holes [17]. Reported adherence to these practices has been mixed, with high adherence to some practices and low adherence to others. A study in Laos examined maintenance behaviours 2–3 years after LLIN distribution and found that 38.2% of households followed the recommended washing frequency, 83% followed drying recommendations, and 32.7% of households with torn LLINs had repaired them [18]. However, the results showed weak associations between maintenance behaviours and malaria knowledge and prevention attitudes [18], obfuscating how educational interventions may be designed to improve adherence. Other studies qualitatively describe how caring for the family and saving money motivate bed net care and repair, though few LLINs in the study area were actually repaired [19, 20]. Perceptions of social acceptability and colour of the LLIN have also been associated with washing frequency, possibly due to social implications of having a dirty net [21‐23].

These previous studies demonstrate that while social norms and individual perceptions and knowledge influence how LLIN care and repair is conducted, these relationships are complex and vary among communities. Additionally, the NetWorks conceptual framework includes environmental factors such as household attributes that may influence the practicality of adhering to optimal care and repair practices [16]. This study examines associations between care and repair behaviours and attitudes and environmental factors from the NetWorks conceptual framework [16] in western Kenya (Fig. 1). Understanding factors related to appropriate net care and repair behaviours will clarify what messaging or other intervention strategies are needed, and where/how they should be targeted to extend the real-world longevity of LLINs.

Net ownership was greater in the lowlands where 98% of households owned at least one net compared to 68.6% of households in the highlands (Table 2). Most households had one sleeping structure, though households in the highlands tended to have both more individuals in the household as well as more sleeping structures than in the lowlands, where 29.6% vs. 10.2% had more than one structure, respectively. Females are primarily responsible for net care [30], thus it is important to understand attributes of female household heads. In both sites, most female household heads had some primary education or have completed primary education (Table 2).

Net care adherence scores were generally low (adherent) in both the highlands and lowlands of western Kenya. Nets had median adherence scores of 2 and 4, respectively, with 0 being the optimal score out of a possible 14. However, there are a few key care behaviours that could be targeted for improvement in the lowlands. Net storage, washing frequency, and drying are the key areas for interventions to address.

Tying up nets or storing them in a safe space while not in use during the day prevents physical damage. This practice may also increase the amount of time a net appears clean, which may lead to less frequent washing. Focus group participants in Senegal reported that tying up nets during the day is a best practice for preventing damage, and removing the net and storing it in a safe space is also a good practice particularly when children are likely to pull on hanging nets [19]. A ‘trials of improved practices’ study in the Peruvian Amazon region found that some households that did not remove their nets during the day developed ways of tying the nets and covering them with plastic so they could remain hanging during the day and still be protected from damage [31]. In this study, variables associated with leaving a net hanging rather than tied up during the day were varied, and span attitudes and environmental factors in both the highlands and lowlands. This suggests that there is no one factor that influences net storage behaviour, but a combination of various factors do. Harvey and others reported 15 different reasons a household left a net hanging, the most common of which included lack of time, someone rests under the net during the day, feeling lazy, or forgetting to remove the net [31], indicating that it is inconvenient and time consuming to remove nets during the day. Tying up nets during the day is less labor and time intensive, and prevents damage compared to nets left hanging over sleeping spaces during the day.

Frequent washing can degrade both the physical and chemical integrity of LLINs, so current recommendations are to wash LLINs at most every 3 months [16]. Many nets are washed more frequently than the current recommendations. In the lowlands nearly 80% of nets were washed < 3 months prior to the survey. Other studies have found variable washing frequencies spanning from 1.5 washes per year on average in Uganda [32] to up to 8 washes per month in Mali [33]. Additionally, 31% of nets were washed more frequently than the recommended practice in a Kenyan study conducted among the southern coastal districts [34]. These differing wash frequencies across studies make generalizability difficult, however the reasons for doing so seem to be less related to knowledge of preferred practices and more related to social and structural factors. Nets simply get dirty quickly, and households (due to personal or social acceptability reasons) prefer to wash nets when they are dirty [18, 21, 22, 31, 33, 35]. Similarly in the present study, washing frequency was associated with environmental factors, and not with knowledge and attitudes like net care knowledge, perception of malaria risk, or confidence in ability to prevent malaria. Although there is great variation across studies, it is important to monitor the practice and understand why households perform variable washing practices due to the significant implications for net longevity.

Soap type and net brand may be modifying factors with washing frequency depending on the pH level of the soap. Bar soaps and mild detergents cause less damage to insecticide levels on nets compared to bleach. In this study, no nets were reported to be washed with bleach, though the brands or pH levels of soaps and detergents used could not be determined. A washing trial measuring insecticide residual after set time intervals of 6 or 12 months following net distribution in Uganda found that nearly all (99.6%) of nets in the region were washed with mild soap (pH 9–10) and the remaining nets washed with detergent [36] while this study found a greater proportion of nets were washed with detergent (21.2% of nets in the highlands and 53.5% of nets in the lowlands). With respect to adherent soap type practices, the Ugandan study found that insecticide integrity differed by net brand and net generation within net brands [36]. Washing nets with more stringent detergents rather than mild soap may impact insecticide integrity. A study in western Kenya tested insecticide effectiveness by measuring how many mosquitoes were able to feed through nets and how many mosquitoes died after net exposure after 5, 10, and 15 washes with a detergent commonly used in rural areas [37]. Even after only 5 washes with detergent, up to 17.6% of mosquitoes were able to feed through nets and up to 83.3% of mosquitoes remained alive 24 h after net exposure depending on net brand [37]. Though this study did not compare mosquito ability to feed or mosquito mortality after exposure to nets washed without detergent, this suggests that while net brand also plays a role, insecticide integrity is noticeably compromised even after 5 washes with detergent [37]. For consistent messaging, recommendations should continue to emphasize the use of no or very mild soaps for net washing, regardless of net brand.

Drying nets in the sun is not recommended because direct sunlight degrades insecticides [4]. As many nets are dried in the sun in the lowlands, proper net drying is a key net care component to be addressed. Another study in Kenya found that 64.9% of nets were dried in the sun [38], and nets were observed drying in direct sunlight in Uganda as well [39]. These results suggest that knowledge and attitudes, particularly a lack of knowledge of appropriate net drying influence this particular care practice. Learning net care from a community event was associated with better net drying adherence, suggesting education campaigns geared toward community settings may be effective in improving net drying practices in the lowlands sites.

Net care and repair practices are likely quite different between communities, regions, and countries, making comparisons and generalizability between sites and other studies difficult. This highlights the importance of LLIN monitoring after distributions in different locations to track and respond to local trends of net ownership, use, and maintenance. The President’s Malaria Initiative (PMI) hosts a LLIN durability monitoring repository (http://​www.​durabilitymonito​ring.​org) to track LLIN field durability among different locations [5] and is an excellent resource for comparing results across studies.

“Net condition” was classified based on standard images provided in the survey forms (see Additional file 1), but this was not a standard method of measuring net condition. Using a proportional hole index would have been a standard and more comparable method of collecting this information, but was unavailable for these analyses. Additionally, net repair practices were not measured, so this could not be included in the net care adherence score.

To describe net storage during the day, nets that were removed during the day were categorized as a moderately adherent practice. However, it is unknown where the nets were placed during the day, so there is potential for misclassification if these nets are removed to a space that makes them prone to damage rather than a safe storage space.

It is possible that the person reporting for the household may not be the same person who cares for the nets, which could lead to misclassification. However, there were options for “don’t know” in survey items, hopefully limiting this occurrence. Additionally, social acceptability bias is possible as individuals might report better care practices than are actually performed, particularly if they have high knowledge of net care. Another limitation is the inability to distinguish between activities conducted at community events and net distributions. There may be misclassification if some individuals consider a distribution to be a community event. This is unlikely to change the results, however, as in the lowlands almost no one reported receiving education during a distribution and both community events and distributions in the highlands were associated with better adherence.

There was high adherence to recommended net care practices in western Kenya. Net care and repair is influenced by various attitudes and environmental factors. There is little evidence that behaviour change is needed in the highlands sites of western Kenya. In the lowlands, promoting methods for tying up nets during the day, coupled with messaging to emphasize infrequent washing and drying nets in the shade may be an appropriate intervention. If there are concerns about net longevity following a distribution, the need for behaviour change interventions should be assessed in local contexts to target specific practices and the driving forces underlying those practices.