Malaria is the world's most important and deadly tropical mosquito-borne parasitic disease (Badmos et al., 2021). It is caused by the protozoan Plasmodium parasites, which are transmitted by female mosquitoes of the genus Anopheles. Vector control is the backbone of malaria control and elimination strategies. There are two core vector control interventions used: insecticide-treated nets (ITNs) and indoor residual spraying of insecticides (IRS) (WHO, 2022). ITNs provide protection from biting mosquitoes harbouring the malaria parasite as well as killing them, whereas IRS acts as a repellent or kills mosquitoes that rest indoors after they have taken a blood meal (Pluess et al., 2010). A scaling up of the deployment of these interventions has significantly contributed to major reductions in overall malaria burden during recent decades, averting an estimated 2 billion malaria cases and 11.7 million malaria deaths between 2000 and 2021 (WHO, 2022).

Despite significant advances in the fight against malaria, transmission still occurs at significant levels in most endemic settings of tropical Africa (Antonio-Nkondjio et al., 2019; Oladipo et al., 2022). Current core interventions including ITNs and/or IRS are struggling to reduce malaria transmission, even when they are optimally deployed. In the future, the situation may become still worse owing to the emergence and rapid spread of insecticide resistance in mosquito vector populations, which represents a threat to insecticide-based vector control strategies (Ranson and Lissenden, 2016; Barbosa et al., 2018). To achieve the overarching goal of malaria elimination, additional supplementary vector control interventions should be considered. These interventions should be implemented simultaneously with, but not in lieu of, optimal coverage with ITNs or IRS in order to accelerate reduction in disease transmission intensity (WHO, 2017).

The large part of malaria transmission occurs in subtropical and tropical rural areas through the bites of endophagic infected mosquito vectors, which are active between dusk and dawn (Huho et al., 2013; Sherrard-Smith et al., 2019; Githeko et al., 1996). These mosquitoes are attracted by human odour and enter houses at night through open windows, doors and eaves (Njie et al., 2009). The entry of disease-transmitting vectors into human habitations can therefore be effectively prevented by screening the windows, doors and eaves of houses (Abong'o et al., 2022; Mburu et al., 2018). This technology, which has historically helped in the control of malaria in many parts of the tropics, has been largely ignored since the 1950s. More recently, housing improvement is increasingly being recognized as an important determinant of health outcomes, and the WHO has reintroduced it as an effective malaria control strategy in their Global Vector Control Response strategy 2017–2030 (WHO, 2017a, WHO, 2017b).

Several studies conducted in locations across Sub-Saharan Africa have evaluated the effect of housing improvement as supplemental malaria control strategy. The techniques used consisted of modification of existing house structure, or the design and building of new mosquito proof houses, and results have shown reductions of indoor-biting and resting mosquitoes (Abong'o et al., 2022; Animut et al., 2013; Wanzirah et al., 2015; Lwetoijera et al., 2013; Kua and Lee, 2021; Nguela et al., 2020). Moreover, numerous trials have reported reduced malaria incidence in people living in improved houses compared to those living in unimproved ones (Tusting et al., 2017; Bradley et al., 2013 24. Snyman et al., 2015; Getawen et al., 2018). However, none of these studies were conducted in rural deep forested environments, where malaria epidemiology is more complex with high transmission occurring year-round and sustained by several vector species exhibiting a different ecology and biology. In this study, the impact of improving houses through eave screening on indoor malaria vector densities was evaluated as a malaria vector control intervention in a deep forested area in south Cameroon.