Abstract
BackgroundIn a context of large-scale implementation of malaria vector control tools, such as the distribution of long-lasting insecticide nets (LLIN), it is necessary to regularly assess whether strategies are progressing as expected and then evaluate their effectiveness. The present study used the case–control approach to evaluate the effectiveness of LLIN 42 months after national wide distribution. This study design offers an alternative to cohort study and randomized control trial as it permits to avoid many ethical issues inherent to them.MethodsFrom April to August 2011, a case–control study was conducted in two health districts in Benin; Ouidah–Kpomasse–Tori (OKT) in the south and Djougou–Copargo–Ouake (DCO) in the north. Children aged 0–60 months randomly selected from community were included. Cases were children with a high axillary temperature (≥37.5 °C) or a reported history of fever during the last 48 h with a positive rapid diagnostic test (RDT). Controls were children with neither fever nor signs suggesting malaria with a negative RDT. The necessary sample size was at least 396 cases and 1188 controls from each site. The main exposure variable was “sleeping every night under an LLIN for the 2 weeks before the survey” (SL). The protective effectiveness (PE) of LLIN was calculated as PE = 1 − odds ratio.ResultsThe declared SL range was low, with 17.0 and 27.5 % in cases and controls in the OKT area, and 44.9 and 56.5 % in cases and controls, in the DCO area, respectively. The declared SL conferred 40.5 % (95 % CI 22.2–54.5 %) and 55.5 % (95 % CI 28.2–72.4 %) protection against uncomplicated malaria in the OKT and the DCO areas, respectively. Significant differences in PE were observed according to the mother’s education level.ConclusionIn the context of a mass distribution of LLIN, their use still conferred protection in up to 55 % against the occurrence of clinical malaria cases in children. Social factors, the poor use and the poor condition of an LLIN can be in disfavour with its effectiveness. In areas, where LLIN coverage is assumed to be universal or targeted at high-risk populations, case–control studies should be regularly conducted to monitor the effectiveness of LLIN. The findings will help National Malaria Control Programme and their partners to improve the quality of malaria control according to the particularity of each area or region as far as possible.
Highlights
In a context of large-scale implementation of malaria vector control tools, such as the distribution of long-lasting insecticide nets (LLIN), it is necessary to regularly assess whether strategies are progressing as expected and evaluate their effectiveness
In the Ouidah– Kpomasse–Tori (OKT) district, 17.0 % of the cases and 27.5 % of the controls had slept under a LLIN every night during the previous 2 weeks compared to 44.9 % of cases and 56.5 % of the controls in the DCO district
This study identified other factors significantly associated with uncomplicated clinical malaria
Summary
In a context of large-scale implementation of malaria vector control tools, such as the distribution of long-lasting insecticide nets (LLIN), it is necessary to regularly assess whether strategies are progressing as expected and evaluate their effectiveness. LLIN remains the most common and effective tool used to prevent malaria [4]. For the purpose of reducing malaria case incidence rates by 75 % by 2015, operational research is needed to understand effectiveness of vector control interventions [4]. The proof of malaria morbidity reduction has become the major objective of the National Malaria Control Programme (NMCP) in Benin, and few studies at the community level have been conducted on this subject [7]. Do the investigators currently have adequate and operational indicators to evaluate malaria control tools such as LLIN in the context of universal coverage? For example are malaria control strategies effective? What about LLIN effectiveness in the context of vectors resistance to pyrethroid insecticide? Do the investigators currently have adequate and operational indicators to evaluate malaria control tools such as LLIN in the context of universal coverage?
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