Introduction

Malaria results in over 600,000 deaths per year globally. Approximately 95 percent of all malaria cases and deaths occur in sub-Saharan Africa, with 80% of those deaths in children under 5 years of age. Significant reductions in malaria mortality have occurred since 2000 [1]. These successful campaigns were primarily focused on the mass distribution of insecticide treated mosquito bednets (ITNs). These efforts also added anti-malaria methods like indoor residual insecticide spraying (IRS), rapid diagnostic tests and improved medical treatments. ITN access remains the priority of malaria prevention efforts as they are inexpensive, long-lasting and relatively easy to use. These nets are traditionally attached on indoor structures to hang over beds. They prevent mosquitoes, which transmit the malaria parasite, from biting vulnerable family members while they sleep. ITNs have long been proven to the be most effective prevention method to protect people from malaria [2–4]. Providing ITNs to communities in malaria endemic regions reduces all-cause child mortality by 17 percent [5].

Despite these interventions, malaria continues to be a significant problem around the world. In countries like Senegal, these measures have helped, but malaria is still a main cause of death in children [6–7]. This study took place in the region of Kedougou, in rural southeastern Senegal, where there is high malaria prevalence despite wide availability of ITNs [8].

Based on our experiences distributing thousands of nets in this region, we believed that the people were highly educated about malaria and very receptive to ITNs. Anecdotal observations from living in one village there led us to suspect that the available nets were not providing optimal protection because of factors that made them impractical for long-term daily use. In particular, we noted that sharp edges on bedding materials damaged the nets, shortening their useful lifespan. In addition, we saw many people sleeping outdoors, where they had no nets, to escape the stifling heat inside their huts. If outdoor sleeping because of heat is a significant factor impeding the prevention of malaria, then climate change will be exacerbating this problem. Global warming is already affecting health around the world, with vulnerable populations disproportionately suffering from its impacts [9]. Sub-Saharan Africa is not spared from this phenomenon. Over the last century, the mean temperature in southeast Senegal has steadily increased, with the average daily temperature increasing from 27.5 Celsius (81.5 Fahrenheit) in 1929 to 29.7 (85.5) in 2023 [10]. This warming favors conditions for mosquito population growth and malaria transmission.

We thus thought it would be important to determine whether our observations in one village were generalizable to the region. The goal of the study was to identify social and environmental factors that could be impeding malaria control by diminishing effective net usage. In addition to outdoor sleeping and net damage, we considered the knowledge and perceptions of malaria and ITNs, and community health priorities. The intended outcome of this research is to provide actionable information to adapt and maximize access to evidence-based malaria prevention.

The primary hypothesis of this study was that for adequate protection from malaria-bearing mosquitoes, people in this region need more than the officially recommended 0.56 nets per person. We further hypothesized that net fragility and outdoor sleeping were major factors contributing to the insufficiency of nets.

Materials and methods

Study framework

This study’s research question asked what were the barriers to using an available ITN for people in rural Senegal? A secondary question of this research is how can we quantify the identified barriers and report them in an actionable way that further improves malaria prevention? To address these questions, this study used a framework (Fig 1) used by the Peace Corps specifically to look at malaria control in rural sub-Saharan Africa [16]. This framework combines important aspects of previous models and incorporates a state of sustainability [17]. The Peace Corps framework has potential to guide effective interventions, based on a community’s assessment of barriers to regular ITN use.

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Fig 1. Study theoretical model. Adapted from McLaughlin and Peace Corps. This model integrates important social ecological factors and applies them to rural Senegal malaria prevention.

https://doi.org/10.1371/journal.pone.0313456.g001

We practiced community-based participatory research by incorporating local stakeholders into the research team. Input from these community members informed the study’s design, implementation, analysis and interpretation. Our survey questions were adapted from the 2008–2009 Senegal Malaria Indicator Survey [8]. A range of open-ended questions were added to the survey to assess key components of behavior, with special attention to barriers of ITN use. We also encouraged the surveyors to include observations and relevant comments on the survey. Survey questions are available for review in the appendix (S1-S3 Files).

Results

All 164 selected households were successfully surveyed, giving a 100% response. Most individual questions had responses over 96%. The question with the lowest response had a 93% response. The 164 households represented 1806 people or about 21% of the total population of the Bandafassi region. 152 heads of household gave updated information on household size.

The 20 selected villages were an average of 9.7 kilometers away from the nearest staffed health care facility. The average distance from a health care facility for all 37 area villages was 9.3 kilometers. The 20 selected villages had an average population of 350 people. The average population per village of all 37 area villages was 235 people. The average household size was 11.9 people.

Discussion

In a rural Senegalese population with a high malaria burden, our survey found a need of 0.86 nets per person. This is 54% higher than the current WHO recommendation of 0.56 nets per person [19]. The WHO recommendation for the number of nets per person has existed since 2010. The WHO suggests the “ratio can be adjusted as needed if there are data that support such adjustment” [20]. It has been suggested that the ratio calculation may need to be adjusted for the early damage of nets and its effect on ITN retention. This study’s findings suggests that the ratio should be adjusted further to account for the substantial degree of outdoor sleeping.

A major strength of this study is that the lead researcher lived in this area as a Peace Corps volunteer and established positive relationships with community leaders. These connections continued for many years via the public health work of the non-profit organization, Netlife. These past partnerships and the use of local languages helped create a strong, multifaceted study team. Pilot testing helped to create a culturally accepted final version of the survey. The trust from these past relationships and the culturally sensitive administration of the surveys contributed to the 100% response.

A potential limitation of our data is that the number of nets needed by families was based on the head of household’s assessment. It would be more objective to observe all household members and how they use their sleeping spaces at night, however it is hard to imagine how to carry that out practically or ethically. Nevertheless, there could be a concern that heads of household would ask for more nets than necessary. To address this, we analyzed open-ended direct observations by the surveyors. Overall, when compared with these observations, the participant responses showed some underestimates, some overestimates and many appropriate estimates of requested nets. So, we found there was no systematic bias of heads of household overestimating their families’ ITN needs. Also, the surveyor observations did not take into account potential outside sleeping spaces; doing so would have pushed all the participant responses in the direction of being underestimates of need for nets.

Our survey was conducted in 2012 and so could now be outdated. However, members of our team have visited these villages multiple times since then (as recently as 2023), and the situation with heat and outdoor sleeping has only become more pronounced. We therefore believe it now requires urgent attention, as one can expect that global warming will make the problem even worse. We have made regular observations of outdoor sleeping. Most household compounds have outdoor structures used during the day for shade or for food preparation. During the evenings, many family members drink tea and talk on these structures. Because of the heat, many people prefer to sleep the first part of the night outdoors, because there is better airflow outdoors than in the huts. When cool enough, most family members wake up and move to the sleeping spaces inside the huts. Regularly, family members would sleep one-third to one-half of the night outside. Although we observed mosquito nets being used on some outdoor structures (S1–S4 Figs), this was rare. Most household members only have enough nets for their indoor sleeping spaces.

The regularity with which these rural Senegalese people discussed heat/outdoor sleeping in their survey responses is consistent with this being an important issue. Because outdoor sleeping increases the number of sleeping spaces used by each family, it increases the number of nets needed to provide protection from mosquitos. In addition, if nets are used outside, they wear out faster. For example, the structures used for outdoor sleeping tend to have many sharp points, and nighttime winds cause the nets to regularly catch on these points. (S4 File) Very few ITNs are truly designed for outdoor spaces [21,22]. Consistent with Killeen and Grand Challenges in Global Health, this study supports the need to expand interventions to the outdoors [22,23].

Prior to this survey, few studies had specifically investigated outdoor sleeping as a barrier to ITN use. Studies conducted near Lake Victoria and in Burkina Faso found that outdoor sleeping was infrequent [24,25]. In contrast, we found outdoor sleeping to be extremely prevalent, consistent with reports from Niger and Iran [26,27]. Heat has been found to be a significant barrier to ITN use, and causes this study population to regularly sleep outside [28–31].

ITN use is a cornerstone of malaria prevention, and if increasing barriers exist, it will be difficult to maintain past successes to fight malaria. Despite significant steady reductions in malaria mortality from 2000 to 2015, there has been a recent resurgence. The estimated 2025 Africa death rate is now 51.8 people per 100,000, whereas the previous prediction for 2025 had been 15.9 [1,32]. While there are many possible explanations for this underperformance, the increase in outdoor sleeping does not help the situation. We should provide more nets for people who sleep outside, and research should be conducted to develop modified nets more suitable for outdoor use.

If outdoor sleeping increases with rising temperatures, it could affect other evidence-based interventions like indoor residual spraying (IRS). In the past, it has been proven that the use of ITNs and IRS together is more protective against malaria than either intervention alone [33]. Additional research may be required to determine the effect of IRS to protect people sleeping on outdoor structures [34,35]. As in previous studies, this population expressed concerns about the durability of nets [36–40]. Study responses and our observations indicate that village bedframes often have jagged edges that increase the risk of rips in ITNs. When ITNs get dirty, people will wash the nets to improve their appearance in the home. However, some of the washing and drying techniques are abrasive and it is likely that many nets are overwashed. Previous studies verify that misunderstandings about ITN washing can damage the nets [41–45]. Future alterations of ITNs or community interventions that decrease over-washing will increase durability of the nets.

In addition, participants regularly discussed other potential solutions, such as village educators. One example of the success in community engagement to fight malaria is PECADOM PLUS (Prise en charge à domicile), which is a Senegalese Ministry of Health developed program that Peace Corps volunteers help to extend into the rural communities [46]. Community participation like this has been found to reduce disease burden [47–51]. Maintaining a high level of community involvement is also very important to sustain high levels of ITN use where malaria rates are decreasing [52–54].

It is important to note that the failure to achieve optimal protection with nets in these villages is not related to a lack of acceptability of ITNs or a lack of awareness about malaria. This study’s responses were saturated with positive comments about nets. Participants demonstrated knowledge about the deadly nature of malaria, the vulnerability of children, the economic benefits of avoiding illness, and even the life cycle of Plasmodium.

Conclusions

In a rural Senegalese population with a high malaria burden, our survey indicated a need for 0.86 insecticide treated nets per person. This is 54% higher than the current WHO recommendation of 0.56 ITNs per person.

Our findings suggest that there are not enough nets because routine village conditions lead to considerable net damage, and because the heat leads people to sleep outdoors, where they likely do not have mosquito nets. With global warming, we suspect this population will spend even more time sleeping outside, aggravating the current insufficiency. To help accelerate the decline of malaria mortality, further research should investigate optimal interventions to address this challenge, including nets designed for outside use and for higher durability.

Supporting information

Acknowledgments

This work could not be done without the lifelong efforts of Bandafassi health post nurse, Mactar Mansaly. Thank you to all the assisting professionals at the University of Rochester Department of Pediatrics. Thank you to Anne Longtine MD and Carrie Vargo MD. Thank you to the Bandafassi area village health workers, the people of Thioke Thian, the local Peace Corps Volunteers, the members of the Programme National de Lutte contre le Paludisme, and the Senegal Ministry of Health.