Varying levels of protection against Plasmodium falciparium infection were conferred on non-users of long lasting insecticidal nets (LLINS) sleeping in rooms where different number of LLINS were hung in hyper endemic state of West Africa.

The use of Long Lasting Insecticidal Nets (LLINs) has greatly reduced the health and economic impact posed by malaria. This study evaluated the residual effect of LLINs on malaria parasite infections among non-LLIN users sleeping in rooms where nets were hung. This study was carried out at Federal University of Agriculture Abeokuta, Ogun State, Nigeria. A total of 259 students were systematically recruited into this study and were classified into two groups of LLINs users and non-users. The LLIN users were further classified according to the proportion of net usage and this includes; < 50%, exactly 50% and > 50% respectively. Finger prick blood samples were collected from the participants and microscopically analysed for the presence of parasites. Demographic characteristics were also recorded. A general prevalence of 40.5% positivity for malaria was recorded among the study population. A significantly high prevalence (p < 0.05) of malaria was recorded among non-users of LLINs compared to users (AOR 4.66, 95%CI 1.27-17.06). A significantly low prevalence of malaria parasite infection was recorded among non-users of LLINs occupying rooms where LLINs was hung compared with non-users from rooms where LLIN were not used. Furthermore, a reduction in prevalence of malaria and parasite densities was observed among non-users of LLINs (occupying rooms where LLINs was hung) as the proportion of LLIN usage increased in such rooms (p < 0.05). This study showed that some level of protection may be conferred on non-users of LLINs staying in rooms where LLINs are hung. © Indian Society for Parasitology 2020.