Temporal and spatial trends of the prevalence of infections caused by Plasmodium parasites among rural community members in three regions with varying transmission intensities in Mainland Tanzania.

BACKGROUND: Recent reports showed persistence of malaria transmission and disease burden in rural communities, which has limited the impact of ongoing control and elimination strategies. This study investigated temporal and spatial trends of the prevalence of infections caused by Plasmodium parasites among community members from three regions with heterogeneous transmission intensities, following intensive use of different malaria control interventions in the past 20 years in Mainland Tanzania. METHODS: Community surveys were conducted from 2021 to 2023, and involved 8166 individuals aged ≥ 6, living in rural communities in three regions of Kigoma, Ruvuma and Tanga. Structured questionnaires were used to collect demographic, anthropometric, clinical, parasitological, bed net use, type of house (traditional or modern), and socio-economic status (SES) data. The trends of the prevalence of infections caused by Plasmodium parasites detected using rapid diagnostic tests (RDTs) were determined using descriptive statistics and, and factors associated with the infections were determined using modified Poisson regression. The results were presented as crude (cPR) and adjusted prevalence ratios (aPR), with their corresponding 95% confidence intervals (CI). RESULTS: The overall prevalence was 23.2% (n = 1896), with significant variations across regions and years (22.9% in 2021, 20.6% in 2022, and 26.9% in 2023; p < 0.001). School children (5- < 15 years; p < 0.001) and males (p < 0.001) had significantly higher prevalence in all years. The prevalence increased consistently in individuals with a history of fever within 48 h before the survey, from 40.1% in 2021 to 45.7% in 2022 (p = 0.049), and further to 58.6% in 2023 (p < 0.001). The prevalence and odds of infections were significantly higher among individuals who were not using bed nets (p ≤ 0.003) and those living in households with traditional houses (p < 0.001) or low SES (p < 0.001). CONCLUSION: The prevalence of infections caused by Plasmodium parasites varied significantly over the 3 years, in the three regions, and among individuals with different demographic and clinical features. The highest prevalence was in 2023, and among school children, males, individuals with a fever history, and participants living in households with traditional houses or low SES. These findings underscore the need for targeted and adaptive malaria control strategies to address emerging hotspots and vulnerable groups or populations.