Prevalence and associated risk factors of asymptomatic malaria in Nigeria: a systematic review and meta-analysis

Abstract

BACKGROUND: Asymptomatic malaria presents a significant barrier to malaria elimination efforts, particularly in endemic countries like Nigeria. Despite its public health relevance, no national-level pooled estimate of its prevalence and associated risk factors currently exists for Nigeria. This systematic review and meta-analysis aimed to synthesize existing data to estimate the prevalence of asymptomatic malaria and identify affected populations and risk factors across Nigeria. METHODS: A systematic search of PubMed, Google Scholar, and Scopus was conducted to identify observational studies reporting the prevalence of asymptomatic malaria in Nigeria. The review protocol was registered with PROSPERO (CRD42024591788). Eligible studies were screened using Rayyan software, and relevant data were extracted into Microsoft Excel. Meta-analysis was performed using Stata version 15.0. A random-effects model was applied to estimate the pooled prevalence. Heterogeneity was assessed using meta-regression and subgroup analyses, while publication bias was evaluated using funnel plot visualization. RESULTS: A total of 25 studies were included in the meta-analysis. The pooled prevalence of asymptomatic malaria in Nigeria was estimated at 33% (95% CI 26-41). Prevalence varied by population subgroup, ranging from 25% in the general population to 52% in children. Risk factor analysis revealed an overall prevalence of 19% related to education level, 36% based on sex, and 39% associated with insecticide-treated net (ITN) usage. CONCLUSION: This review highlights a high prevalence of asymptomatic malaria in Nigeria, particularly among children. While asymptomatic infections sustain transmission, current evidence underscores the need to prioritize proven transmission-reduction tools. With reduced transmission, the asymptomatic reservoir can then be more effectively addressed through complementary strategies.