Prevalence and Diagnostic Detection of Asymptomatic Malaria Parasitaemia among Apparently Healthy Community Dwellers in Benue South, Nigeria

Abstract

Background: Malaria control programmes have traditionally focused on symptomatic infections, yet individuals who harbour parasites without current symptoms may sustain transmission while remaining outside routine case-detection pathways. The epidemiology of asymptomatic malaria in Benue South, North-Central Nigeria, remains insufficiently characterized. Objectives: This study assessed the prevalence of asymptomatic malaria parasitaemia among apparently healthy community dwellers and compared parasite detection by rapid diagnostic testing (RDT) and light microscopy. Methods: A community-based cross-sectional study was conducted between August and October 2024 among apparently healthy residents aged ≥15 years in selected rural and semi-urban communities of Otukpo and Okpokwu Local Government Areas (LGAs), Benue State, Nigeria. Participants were selected using a multistage sampling approach. Information on socio-demographic characteristics, malaria prevention practices, healthcare access and selected environmental exposures was obtained using a structured questionnaire. Venous blood samples were examined using malaria RDTs and Giemsa-stained thick and thin blood films. Parasite density was estimated using the standard white-cell-count assumption. Descriptive statistics were used to summarize the study population and diagnostic findings. Results: A total of 275 participants were studied; 123 (44.73%) were male and 152 (55.27%) females. The largest age group was 15–29 years (107; 38.91%). Microscopy detected malaria parasitaemia in 88 participants, corresponding to a prevalence of 32.0% (95% CI 26.5–37.5%), whereas RDT detected infection in 55 participants, corresponding to 20.0% (95% CI 15.3–24.7%). Thus, microscopy identified 12 percentage points more positive participants than RDT, with a descriptive prevalence ratio of 1.60. Among microscopy-positive participants, 74/88 (84.09%) had parasite densities below 1,000 parasites/µL, while 14/88 (15.91%) had densities ≥1,000 parasites/µL. Malaria prevention information had reached 72.0% of participants, while 53.82% reported always using insecticide-treated nets. Stagnant water was reported near the homes of 64.0% of participants. Conclusion: A substantial proportion of apparently healthy residents of Otukpo and Okpokwu LGAs harboured microscopically detectable malaria parasites. The higher proportion detected by microscopy than RDT highlights the importance of maintaining quality-assured microscopy capacity for community surveillance, particularly where parasite densities may be low. The findings support continued investment in vector control, community-level prevention and surveillance approaches that recognize asymptomatic infection as part of the malaria reservoir.