Browsing by Author "Francis, Filbert"

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Prevalence of subpatent Plasmodium falciparum infections in regions with varying transmission intensities and implications for malaria elimination in Mainland Tanzania
(PMC PubMed Central, 2025-03-26) Seth, Misago; Popkin-Hall, Zachary; Madebe, Rashid; Budodo, Rule; Bakari, Catherine; Lyimo, Beatus; Giesbrecht, David; Moshi, Ramadhani; Mbwambo, Ruth; Francis, Filbert; Pereus, Dativa; Mbata, Doris; Challe, Daniel; Mandai, Salehe; Chacha, Gervas A; Kisambale, Angelina; Mbwambo, Daniel; Aaron, Sijenunu; Lusasi, Abdallah; Lazaro, Samwel; Mandara, Celine; Bailey, Jeffrey; Juliano, Jonathan; Gutman, Julie; Ishengoma, Deus
Background Subpatent Plasmodium falciparum infections, defined as infections with parasite density below the detection limit of routine malaria diagnostic tests, contribute to infectious reservoirs, sustain transmission, and cause the failure of elimination strategies in target areas. This study assessed the prevalence of subpatent P. falci parum infections and associated risk factors in 14 regions of Mainland Tanzania. Methods The study used samples randomly selected from RDT‑negative dried blood spots (DBS) (n = 2685/10,101) collected in 2021 at 100 health facilities across 10 regions of Mainland Tanzania, and four communities in four addi tional regions. The regions were selected from four transmission strata; high (five regions), moderate (three regions), low (three regions), and very low (three regions). DNA was extracted by Tween‑Chelex method, and the Pf18S rRNA gene was amplified by quantitative polymerase chain reaction (qPCR). Logistic regression analysis was used to assess the associations between age groups, sex, fever status, and transmission strata with subpatent infection status, while linear regression analysis was used to assess the association between these factors and subpatent parasite density. Results Of the selected samples, 525/2685 (19.6%) were positive by qPCR for P. falciparum, and the positivity rates varied across different regions. Under‑fives (aOR: 1.4, 95% CI 1.04–1.88; p < 0.05) from health facilities had higher odds of subpatent infections compared to other groups, while those from community surveys (aOR: 0.33, 95% CI 0.15–0.72; p = 0.005) had lower odds. Participants from very low transmission stratum had significantly lower odds of subpatent infection compared to those from high transmission stratum (aOR = 0.53, 95% CI = 0.37–0.78; p < 0.01). The log‑trans formed median parasite density (interquartile range) was 6.9 (5.8–8.5) parasites/µL, with significantly higher parasitae mia in the low transmission stratum compared to a very low one (11.4 vs 7.0 parasites/µL, p < 0.001). Conclusion Even in very low transmission settings, the prevalence of subpatent infections was 13%, and in low trans mission settings it was even higher at 29.4%, suggesting a substantial reservoir that is likely to perpetuate transmis sion but can be missed by routine malaria case management strategies. Thus, control and elimination programmes may benefit from adoption of more sensitive detection methods to ensure that a higher proportion of subpatent infections are detected.
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
(Springer Nature, 2025-09-30) Challe, Daniel; Petro, Daniel; Francis, Filbert; Seth, Misago; Madebe , Rashid; Mandai, Salehe; Budodo, Rule; Kisambale,Angelina; Chacha, Gervas; Moshi, Ramadhan; Mbwambo , Ruth; Pereus, Dativa; Bakari, Catherine; Mbata, Doris; Lyimo, Beatus
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.
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
(medRxiv, 2025-02-14) Challe, Daniel; Petro, Daniel; Francis, Filbert; Seth, Misago; Madebe, Rashid; Mandai, Salehe; Budodo, Rule; Kisambale, Angelina; Chacha, Gervas; Moshi, Ramadhan; Mbwambo, Ruth; Pereus, Dativa; Bakari, Catherine; Mbata, Doris; Lyimo, Beatus; Kanyankole, Grace; Aaron, Sijenunu; Mbwambo, Daniel; Kajange, Stella; Lazaro, Samwel; Kapologwe, Ntuli; Mandara, Celine; Makene, Vedastus; Deus S. Ishengoma
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.
Varying Malaria Rapid Diagnostic Test Accuracy by Regional Transmission Level and Demographics in Tanzania
(The American Journal of Tropical Medicine and Hygiene, 2025-12-04) Wiener, Danielle; Seth, Misago; Mandara, Celine; Madebe, Rashid; Popkin-Hall, Zachary; Giesbrecht, David; Bakari, Catherine; Lyimo, Beatus; Pereus, Dativa; Francis, Filbert; Mbwambo,Daniel; Aaron, Sijenunu; Lusasi, Abdalah; Lazaro, Samwel; Sheahan, Timothy; Parr, Jonathan; Bailey, Jeffrey; Ishengoma, Deus; Juliano, Jonathan
Malaria remains a significant global health burden, with �263 million cases across 83 countries. It is essen- tial to quickly and accurately detect cases to control the spread of the disease. Given the widespread use of malaria rapid diagnostic tests (mRDTs) for case management and surveillance, it is crucial to understand test reliability. Clarifying how mRDT results differ from real-time polymerase chain reaction (qPCR) test results, as well as the nature of additional vari- ance by test manufacturer, will be useful for reducing measurement bias. After comparing three national standard mRDTs and a research mRDT with qPCR results from a 2021 cross-sectional study in Tanzania, differences were found in terms of age, sex, and regional malaria transmission rate. The research test underperformed overall, with poor sensitivity across transmission strata. After comparing the research mRDT to standard mRDTs, the odds ratios indicated that transmission intensity may affect mRDT agreement and diagnostic performance. These results offer pertinent information on test accuracy and decrease outcome misclassification for malaria prevalence.