Trends of malaria prevalence among individuals from rural communities in three regions with varying transmission intensities in Mainland Tanzania; Data from 2021 - 2023 community cross-sectional surveys

Abstract Background Recent reports showed the persistence of malaria transmission and disease burden in rural communities, which have limited the impact of ongoing control and elimination strategies. This study investigated the trends of malaria prevalence among community members from three regions of Mainland Tanzania with varying transmission intensities. Methods Community surveys were conducted from 2021 to 2023 and involved individuals aged ≥6 months in three regions Kigoma and Ruvuma (with high malaria transmission intensities) and Tanga (moderate transmission). Interviews were conducted using structured questionnaires, to collect anthropometric, clinical, parasitological (testing for malaria using rapid diagnostic tests (RDTs), type of house and socio-economic status (SES) data. Modified Poisson regression was used to identify factors associated with malaria infections and the results were presented as crude (cPR) and adjusted prevalence ratios (aPR). Results Malaria infections by RDTs were detected in 1,896 (23.2%, n=8,166) individuals, with significant variations across regions and years (22.9% in 2021, 20.6% in 2022, and 26.9% in 2023; p<0.001). The highest prevalence of malaria infections was in Kigoma in 2023 (35.6%) while the lowest was in Tanga in 2022 (10.5%). School children (5 – <15 years) had significantly higher prevalence (38.2% in 2021, 26.2% in 2022, and 34.4% in 2023 (p<0.001) as did males (26.7% in 2021, 25.4% in 2022 and 31.2% in 2023, p<0.001). Higher likelihood of malaria infections was in school children (aPR: 1.94, 95% CI: 1.67 – 2.25, p<0.001), males (aPR=1.24 95%CI: 1.14–1.34, p<0.001), individuals living in traditional houses (aPR=1.14, 95% CI: 1.01 – 1.28, p = 0.037), among individuals with moderate (aPR=1.27, 95% CI: 1.13 – 1.43, p<0.001) or low SES (aPR = 1.39, 95% CI: 1.24 – 1.55, p<0.001), and those with fever at presentation (axillary temperature ≥37.5°C; aPR = 1.34, 95% CI: 1.09 – 1.64, p = 0.005) or fever history within 48 hours before the survey (aPR = 3.55, 95% CI: 3.26–3.87, p<0.001). The likelihood of infections was also higher in Ruvuma (aPR=1.98, 95%CI: 1.77–2.21, p<0.001) and Kigoma (aPR=1.28, 95%CI: 1.15–1.42, p<0.001) regions compared to Tanga. The likelihood of malaria infections was similar among participants based on bed net ownership (aPR: 1.27, 95%CI: 0.80 – 2.01, p = 0.306) or use (aPR: 1.01, 95%CI: 0.64 – 1.50, p=0.920). Conclusion The study showed spatial and temporal variations of malaria prevalence, with the highest prevalence in 2023 and the lowest in 2022. Groups at higher risk of malaria infections included school children, males, participants with fever, low or moderate SES, and those who lived in traditional houses. Targeted interventions are urgently needed for areas with persistently high transmission and vulnerable groups, particularly in rural communities.