Malaria Species Positivity Rates Among Symptomatic Individuals Across Regions of Differing Transmission Intensities in Mainland Tanzania.

BACKGROUND: Recent data indicate that non-Plasmodium falciparum species may be more prevalent than thought in sub-Saharan Africa. Although Plasmodium malariae, Plasmodium ovale spp., and Plasmodium vivax are less severe than P. falciparum, treatment and control are more challenging, and their geographic distributions are not well characterized. METHODS: We randomly selected 3284 of 12 845 samples collected from cross-sectional surveys in 100 health facilities across 10 regions of Mainland Tanzania and performed quantitative real-time PCR to determine presence and parasitemia of each malaria species. RESULTS: P. falciparum was most prevalent, but P. malariae and P. ovale were found in all but 1 region, with high levels (>5%) of P. ovale in 7 regions. The highest P. malariae positivity rate was 4.5% in Mara and 8 regions had positivity rates ≥1%. We only detected 3 P. vivax infections, all in Kilimanjaro. While most nonfalciparum malaria-positive samples were coinfected with P. falciparum, 23.6% (n = 13 of 55) of P. malariae and 14.7% (n = 24 of 163) of P. ovale spp. were monoinfections. CONCLUSIONS: P. falciparum remains by far the largest threat, but our data indicate that malaria elimination efforts in Tanzania will require increased surveillance and improved understanding of the biology of nonfalciparum species.

Dynamics of malaria vector composition and Plasmodium falciparum infection in mainland Tanzania: 2017-2021 data from the national malaria vector entomological surveillance.

BACKGROUND: In 2015, Tanzania National Malaria Control Programme (NMCP) established a longitudinal malaria vector entomological surveillance (MVES). The MVES is aimed at a periodical assessment of malaria vector composition and abundance, feeding and resting behaviours, and Plasmodium falciparum infection in different malaria epidemiological strata to guide the NMCP on the deployment of appropriate malaria vector interventions. This work details the dynamics of malaria vector composition and transmission in different malaria epidemiological strata. METHODS: The MVES was conducted from 32 sentinel district councils across the country. Mosquitoes were collected by the trained community members and supervised by the NMCP and research institutions. Three consecutive night catches (indoor collection with CDC light trap and indoor/outdoor collection using bucket traps) were conducted monthly in three different households selected randomly from two to three wards within each district council. Collected mosquitoes were sorted and morphologically identified in the field. Thereafter, the samples were sent to the laboratory for molecular characterization using qPCR for species identification and detection of P. falciparum infections (sporozoites). ELISA technique was deployed for blood meal analysis from samples of blood-fed mosquitoes to determine the blood meal indices (BMI). RESULTS: A total of 63,226 mosquitoes were collected in 32 district councils from January 2017 to December 2021. Out of which, 39,279 (62%), 20,983 (33%) and 2964 (5%) were morphologically identified as Anopheles gambiae sensu lato (s.l.), Anopheles funestus s.l., and as other Anopheles species, respectively. Out of 28,795 laboratory amplified mosquitoes, 13,645 (47%) were confirmed to be Anopheles arabiensis, 9904 (34%) as An. funestus sensu stricto (s.s.), and 5193 (19%) as An. gambiae s.s. The combined average entomological inoculation rates (EIR) were 0.46 (95% CI 0.028-0.928) for An. gambiae s.s., 0.836 (95% CI 0.138-1.559) for An. arabiensis, and 0.58 (95% CI 0.165-0.971) for An. funestus s.s. with variations across different malaria transmission strata. Anopheles funestus s.s. and An. arabiensis were predominant in the Lake and South-Eastern zones, respectively, mostly in high malaria transmission areas. Monthly mosquito densities displayed seasonal patterns, with two peaks following the rainy seasons, varying slightly across species and district councils. CONCLUSION: Anopheles arabiensis remains the predominant vector species followed by An. funestus s.s. in the country. Therefore, strengthening integrated vector management including larval source management is recommended to address outdoor transmission by An. arabiensis to interrupt transmission particularly where EIR is greater than the required elimination threshold of less than one (< 1) to substantially reduce the prevalence of malaria infection.

Estimating population ITN access at council level in Tanzania.

BACKGROUND: Since 2013, the National Malaria Control Programme in mainland Tanzania and the Zanzibar Malaria Elimination Programme have implemented mass insecticide-treated net (ITN) distribution campaigns, routine ITN distribution to pregnant women and infants, and continuous distribution through primary schools (mainland) and community leaders (Zanzibar) to further malaria control efforts. Mass campaigns are triggered when ITN access falls below 40%. In this context, there is a need to monitor ITN access annually to assess whether it is below threshold and inform quantification of ITNs for the following year. Annual estimates of access are needed at the council level to inform programmatic decision-making. METHODS: An age-structured stock and flow model was used to predict annual net crops from council-level distribution data in Tanzania from 2012 to 2020 parameterized with a Tanzania-specific net median lifespan of 2.15 years. Annual nets-per-capita (NPC) was calculated by dividing each annual net crop by mid-year council projected population. A previously fit nonparametric conditional quantile function for the proportion of the population with access to an ITN (ITN access) as a function of NPC was used to predict ITN access at the council level based on the predicted NPC value. These estimates were compared to regional-level ITN access from large household surveys. RESULTS: For regions with the same ITN strategy for all councils, predicted council-level ITN access was consistent with regional-level survey data for 79% of councils. Regions where ITN strategy varied by council had regional estimates of ITN access that diverged from the council-specific estimates. Predicted ITN access reached 60% only when "nets issued as a percentage of the council population" (NPP) exceeded 15%, and approached 80% ITN access when NPP was at or above 20%. CONCLUSION: Modelling ITN access with country-specific net decay rates, council-level population, and ITN distribution data is a promising approach to monitor ITN coverage sub-regionally and between household surveys in Tanzania and beyond.

Implementation research of a cluster randomized trial evaluating the implementation and effectiveness of intermittent preventive treatment for malaria using dihydroartemisinin-piperaquine on reducing malaria burden in school-aged children in Tanzania: methodology, challenges, and mitigation.

BACKGROUND: It has been more than 20 years since the malaria epidemiologic shift to school-aged children was noted. In the meantime, school-aged children (5-15 years) have become increasingly more vulnerable with asymptomatic malaria prevalence reaching up to 70%, making them reservoirs for subsequent transmission of malaria in the endemic communities. Intermittent Preventive Treatment of malaria in schoolchildren (IPTsc) has proven to be an effective tool to shrink this reservoir. As of 3rd June 2022, the World Health Organization recommends IPTsc in moderate and high endemic areas. Even so, for decision-makers, the adoption of scientific research recommendations has been stifled by real-world implementation challenges. This study presents methodology, challenges faced, and mitigations used in the evaluation of the implementation of IPTsc using dihydroartemisinin-piperaquine (DP) in three councils (Handeni District Council (DC), Handeni Town Council (TC) and Kilindi DC) of Tanga Region, Tanzania so as to understand the operational feasibility and effectiveness of IPTsc on malaria parasitaemia and clinical malaria incidence. METHODS: The study deployed an effectiveness-implementation hybrid design to assess feasibility and effectiveness of IPTsc using DP, the interventional drug, against standard of care (control). Wards in the three study councils were the randomization unit (clusters). Each ward was randomized to implement IPTsc or not (control). In all wards in the IPTsc arm, DP was given to schoolchildren three times a year in four-month intervals. In each council, 24 randomly selected wards (12 per study arm, one school per ward) were chosen as representatives for intervention impact evaluation. Mixed design methods were used to assess the feasibility and acceptability of implementing IPTsc as part of a more comprehensive health package for schoolchildren. The study reimagined an existing school health programme for Neglected Tropical Diseases (NTD) control include IPTsc implementation. RESULTS: The study shows IPTsc can feasibly be implemented by integrating it into existing school health and education systems, paving the way for sustainable programme adoption in a cost-effective manner. CONCLUSIONS: Through this article other interested countries may realise a feasible plan for IPTsc implementation. Mitigation to any challenge can be customized based on local circumstances without jeopardising the gains expected from an IPTsc programme. Trial registration clinicaltrials.gov, NCT04245033. Registered 28 January 2020, https://clinicaltrials.gov/ct2/show/NCT04245033.

Annual distributions of insecticide-treated nets to schoolchildren and other key populations to maintain higher ITN access than with mass campaigns: a modelling study for mainland Tanzania.

BACKGROUND: Since 2013, the National Malaria Control Programme in mainland Tanzania has deployed annual distributions of insecticide-treated nets (ITNs) through primary schools to maintain ITN access and use. This School Net Programme (SNP) is slated to be used throughout mainland Tanzania by 2023. This modelling study projects ITN access under different ITN distribution strategies and quantification approaches. METHODS: A stock and flow model with a Tanzania-specific ITN decay rate was used to calculate annual net crops for four different ITN distribution strategies, varying quantification approaches within each strategy. Annual nets-per-capita (NPC) was derived from net crop and a standardized population projection. Nonparametric conditional quartile functions for the proportion of the population with access to an ITN (ITN access) as a function of NPC were used to predict ITN access and its variability. The number of ITNs required under the varying quantification approaches for the period 2022-2030 was calculated. RESULTS: Annual SNP quantified using a "population times 15%" approach maintained ITN access between 80 and 90%, when combined with reproductive and child health (RCH) ITN distribution, requiring 133.2 million ITNs. The same strategy quantified with "population times 22%" maintained ITN access at or above 90%, requiring 175.5 million ITNs. Under 5-year mass campaigns with RCH distribution for pregnant women and infants, ITN access reached 90% post-campaign and fell to 27-35% in the 4th year post-campaign, requiring 120.5 million ITNs over 8 years. 3-yearly mass campaigns with RCH reached 100% ITN access post-campaign and fell to 70% in the 3rd year post-campaign, requiring 154.4 million ITNs. CONCLUSION: Given an ITN retention time in Tanzania of 2.15 years, the model predicts that mass campaigns conducted every 3 years in mainland Tanzania will not maintain ITN access at target levels of 80%, even with strong RCH channels. Mainland Tanzania can however expect to maintain ITN access at 80% or above by quantifying SNP using "population × 15%", in addition to RCH ITN delivery. This strategy requires 14% fewer ITNs than a 3-year campaign strategy while providing more consistent ITN coverage. Meeting the targets of 80% ITN use would require maintaining 90% ITN access, achievable using a "population times 22%" quantification approach for SNP.

The use of routine health facility data for micro-stratification of malaria risk in mainland Tanzania.

BACKGROUND: Current efforts to estimate the spatially diverse malaria burden in malaria-endemic countries largely involve the use of epidemiological modelling methods for describing temporal and spatial heterogeneity using sparse interpolated prevalence data from periodic cross-sectional surveys. However, more malaria-endemic countries are beginning to consider local routine data for this purpose. Nevertheless, routine information from health facilities (HFs) remains widely under-utilized despite improved data quality, including increased access to diagnostic testing and the adoption of the electronic District Health Information System (DHIS2). This paper describes the process undertaken in mainland Tanzania using routine data to develop a high-resolution, micro-stratification risk map to guide future malaria control efforts. METHODS: Combinations of various routine malariometric indicators collected from 7098 HFs were assembled across 3065 wards of mainland Tanzania for the period 2017-2019. The reported council-level prevalence classification in school children aged 5-16 years (PfPR5-16) was used as a benchmark to define four malaria risk groups. These groups were subsequently used to derive cut-offs for the routine indicators by minimizing misclassifications and maximizing overall agreement. The derived-cutoffs were converted into numbered scores and summed across the three indicators to allocate wards into their overall risk stratum. RESULTS: Of 3065 wards, 353 were assigned to the very low strata (10.5% of the total ward population), 717 to the low strata (28.6% of the population), 525 to the moderate strata (16.2% of the population), and 1470 to the high strata (39.8% of the population). The resulting micro-stratification revealed malaria risk heterogeneity within 80 councils and identified wards that would benefit from community-level focal interventions, such as community-case management, indoor residual spraying and larviciding. CONCLUSION: The micro-stratification approach employed is simple and pragmatic, with potential to be easily adopted by the malaria programme in Tanzania. It makes use of available routine data that are rich in spatial resolution and that can be readily accessed allowing for a stratification of malaria risk below the council level. Such a framework is optimal for supporting evidence-based, decentralized malaria control planning, thereby improving the effectiveness and allocation efficiency of malaria control interventions.

Estimation of bed net coverage indicators in Tanzania using mobile phone surveys: a comparison of sampling approaches.

BACKGROUND: Threats to maintaining high population access with effective bed nets persist due to errors in quantification, bed net wear and tear, and inefficiencies in distribution activities. Monitoring bed net coverage is therefore critical, but usually occurs every 2-3 years through expensive, large-scale household surveys. Mobile phone-based survey methodologies are emerging as an alternative to household surveys and can provide rapid estimates of coverage, however, little research on varied sampling approaches has been conducted in sub-Saharan Africa. METHODS: A nationally and regionally representative cross-sectional mobile phone survey was conducted in early 2021 in Tanzania with focus on bed net ownership and access. Half the target sample was contacted through a random digit dial methodology (n = 3500) and the remaining half was reached through a voluntary opt-in respondent pool (n = 3500). Both sampling approaches used an interactive voice response survey. Standard RBM-MERG bed net indicators and AAPOR call metrics were calculated. In addition, the results of the two sampling approaches were compared. RESULTS: Population access (i.e., the percent of the population that could sleep under a bed net, assuming one bed net per two people) varied from a regionally adjusted low of 48.1% (Katavi) to a high of 65.5% (Dodoma). The adjusted percent of households that had a least one bed net ranged from 54.8% (Pemba) to 75.5% (Dodoma); the adjusted percent of households with at least one bed net per 2 de facto household population ranged from 35.9% (Manyara) to 55.7% (Dodoma). The estimates produced by both sampling approaches were generally similar, differing by only a few percentage points. An analysis of differences between estimates generated from the two sampling approaches showed minimal bias when considering variation across the indicator for households with at least one bed net per two de facto household population. CONCLUSION: The results generated by this survey show that overall bed net access in the country appears to be lower than target thresholds. The results suggest that bed net distribution is needed in large sections of the country to ensure that coverage levels remain high enough to sustain protection against malaria for the population.

Improvements in malaria surveillance through the electronic Integrated Disease Surveillance and Response (eIDSR) system in mainland Tanzania, 2013-2021.

BACKGROUND: Tanzania has made remarkable progress in reducing malaria burden and aims to transition from malaria control to sub-national elimination. In 2013, electronic weekly and monthly reporting platforms using the District Health Information System 2 (DHIS2) were introduced. Weekly reporting was implemented through the mobile phone-based Integrated Disease Surveillance and Response (eIDSR) platform and progressively scaled-up from 67 to 7471 (100%) public and private health facilities between 2013 and 2020. This study describes the roll-out and large-scale implementation of eIDSR and compares the consistency between weekly eIDSR and monthly DHIS2 malaria indicator data reporting, including an assessment of its usefulness for malaria outbreak detection and case-based surveillance (CBS) in low transmission areas. METHODS: The indicators included in the analysis were number of patients tested for malaria, number of confirmed malaria cases, and clinical cases (treated presumptively for malaria). The analysis described the time trends of reporting, testing, test positivity, and malaria cases between 2013 and 2021. For both weekly eIDSR and monthly DHIS2 data, comparisons of annual reporting completeness, malaria cases and annualized incidence were performed for 2020 and 2021; additionally, comparisons were stratified by malaria epidemiological strata (parasite prevalence: very low < 1%, low 1 ≤ 5%, moderate 5 ≤ 30%, and high > 30%). RESULTS: Weekly eIDSR reporting completeness steadily improved over time, with completeness being 90.2% in 2020 and 93.9% in 2021; conversely, monthly DHIS2 reporting completeness was 98.9% and 98.7% in 2020 and 2021, respectively. Weekly eIDSR reporting completeness and timeliness were highest in the very low epidemiological stratum. Annualized malaria incidence as reported by weekly eIDSR was 17.5% and 12.4% lower than reported by monthly DHIS2 in 2020 and 2021; for both 2020 and 2021, annualized incidence was similar across weekly and monthly data in the very low stratum. CONCLUSION: The concurrence of annualized weekly eIDSR and monthly DHIS2 reporting completeness, malaria cases and incidence in very low strata suggests that eIDSR could be useful tool for early outbreak detection, and the eIDSR platform could reliably be expanded by adding more indicators and modules for CBS in the very low epidemiological stratum.

Sub-national stratification of malaria risk in mainland Tanzania: a simplified assembly of survey and routine data.

BACKGROUND: Recent malaria control efforts in mainland Tanzania have led to progressive changes in the prevalence of malaria infection in children, from 18.1% (2008) to 7.3% (2017). As the landscape of malaria transmission changes, a sub-national stratification becomes crucial for optimized cost-effective implementation of interventions. This paper describes the processes, data and outputs of the approach used to produce a simplified, pragmatic malaria risk stratification of 184 councils in mainland Tanzania. METHODS: Assemblies of annual parasite incidence and fever test positivity rate for the period 2016-2017 as well as confirmed malaria incidence and malaria positivity in pregnant women for the period 2015-2017 were obtained from routine district health information software. In addition, parasite prevalence in school children (PfPR5to16) were obtained from the two latest biennial council representative school malaria parasitaemia surveys, 2014-2015 and 2017. The PfPR5to16 served as a guide to set appropriate cut-offs for the other indicators. For each indicator, the maximum value from the past 3 years was used to allocate councils to one of four risk groups: very low (< 1%PfPR5to16), low (1- < 5%PfPR5to16), moderate (5- < 30%PfPR5to16) and high (≥ 30%PfPR5to16). Scores were assigned to each risk group per indicator per council and the total score was used to determine the overall risk strata of all councils. RESULTS: Out of 184 councils, 28 were in the very low stratum (12% of the population), 34 in the low stratum (28% of population), 49 in the moderate stratum (23% of population) and 73 in the high stratum (37% of population). Geographically, most of the councils in the low and very low strata were situated in the central corridor running from the north-east to south-west parts of the country, whilst the areas in the moderate to high strata were situated in the north-west and south-east regions. CONCLUSION: A stratification approach based on multiple routine and survey malaria information was developed. This pragmatic approach can be rapidly reproduced without the use of sophisticated statistical methods, hence, lies within the scope of national malaria programmes across Africa.

Dihydroartemisinin-piperaquine effectiveness for seasonal malaria chemoprevention in settings with extended seasonal malaria transmission in Tanzania.

Effectiveness of dihydroartemisinin-piperaquine (DP) as seasonal malaria chemoprevention (SMC) was assessed in Nanyumbu and Masasi Districts. Between March and June 2021, children aged 3-59 months were enrolled in a cluster randomized study. Children in the intervention clusters received a monthly, 3-days course of DP for three consecutive months regardless of malaria infection status, and those in the control clusters received no intervention. Malaria infection was assessed at before the first-round and at 7 weeks after the third-round of DP in both arms. Malaria prevalence after the third-round of DP administration was the primary outcome. Chi-square tests and logistic regression model were used to compare proportions and adjust for explanatory variables. Before the intervention, malaria prevalence was 13.7% (161/1171) and 18.2% (212/1169) in the intervention and control clusters, respectively, p < 004. Malaria prevalence declined to 5.8% (60/1036) in the intervention clusters after three rounds of DP, and in the control clusters it declined to 9.3% (97/1048), p = 0.003. Unadjusted and adjusted prevalence ratios between the intervention and control arms were 0.42 (95%CI 0.32-0.55, p < 0.001) and 0.77 (95%CI 0.53-1.13, p = 0.189), respectively. SMC using DP was effective for control of malaria in the two Districts.Trial registration: NCT05874869, https://clinicaltrials.gov/ 25/05/2023.

Understanding Antenatal Care Service Quality for Malaria in Pregnancy through Supportive Supervision Data in Tanzania.

Malaria in pregnancy (MiP) is associated with maternal anemia, spontaneous abortion, and infant and maternal death. In Tanzania, MiP service data are collected through routine Malaria Services and Data Quality Improvement (MSDQI) supportive supervision rounds at antenatal care (ANC) facilities. Using structured assessment tools, the U.S. President's Malaria Initiative Impact Malaria Project reviewed two annual rounds of MSDQI data (492 facilities in 2021 and 522 facilities in 2022), including ANC records and client satisfaction interviews. We assessed coverage of key MiP care components, used logistic regression to analyze uptake of the recommended three or more doses of intermittent preventive treatment in pregnancy (IPTp3+), and assessed client satisfaction. Coverage of most MiP care components exceeded 80%; however, only 38% of women received all components. Odds of receiving IPTp3+ were much lower among late ANC initiators than among those who initiated ANC during their first trimester (odds ratio [OR], 0.46; 95% CI, 0.38-0.57). Uptake of IPTp3+ increased almost exponentially by number of ANC visits. Women with seven visits were 30 times more likely than those with three visits to receive IPTp3+ (OR, 30.71; 95% CI, 11.33-83.22). Just 54% of clients had anemia screening and only 46% received IPTp3+. Client satisfaction with services and provider communication was high (98% and 97%, respectively); only 8% of client visits exceeded 3 hours. Increased ANC visits could boost IPTp3+ coverage. Routine MSDQI supportive supervision data are useful to assess quality of care, identify service delivery gaps, and guide policies to improve quality of MiP services.

Evidence of artemisinin partial resistance in North-western Tanzania: clinical and drug resistance markers study.

Background: Artemisinin-based combination therapies (ACTs) are the recommended antimalarial drugs for the treatment of uncomplicated malaria. The recent emergence of artemisinin partial resistance (ART-R) in Rwanda, Uganda and Eritrea is of great concern. In Tanzania, a nationwide molecular malaria surveillance in 2021 showed a high prevalence of the Kelch13 (K13) 561H mutation in Plasmodium falciparum from the north-western region, close to the border with Rwanda and Uganda. This study was conducted in 2022 to evaluate the efficacy of artemether-lumefantrine (AL) and artesunate-amodiaquine (ASAQ) for the treatment of uncomplicated falciparum malaria and to confirm the presence of ART-R in Tanzania. Methods: This single-arm study evaluated the efficacy of AL and ASAQ in eligible children aged six months to 10 years at Bukangara Dispensary in Karagwe District, Kagera Region. Clinical and parasitological responses were monitored for 28 days according to standard WHO protocol. Mutations in K13 gene and extended haplotypes with these mutations were analysed using Sanger and whole genome sequencing data, respectively. Findings: 176 children (88 in each AL and ASAQ group) were enrolled and all achieved the defined outcomes. PCR-corrected adequate clinical and parasitological response (ACPR) was 98.3% (95% CI: 90.8-100) and 100.0% (95% CI: 95.8-100) for AL and ASAQ, respectively. Parasitaemia on day 3 was observed in 11/88 (12.5%) and 17/88 (19.3%) in the AL and ASAQ groups, respectively. The half-life of parasitaemia was significantly higher (>6.5 hrs) in patients with parasitaemia on day 3 and/or mutations in K13 gene at enrolment. Most patients with parasitaemia on day 3 (8/11 = 72.7% in the AL group and 10/17 = 58.8% in the ASAQ group) had 561H mutation at enrolment. The parasites with K13 mutations were not similar to those from south-east Asia and Rwanda, but had the same core haplotype of a new 561H haplotype reported in Kagera in 2021. Interpretation: These findings confirm the presence of ART-R in Tanzania. A context-specific strategy to respond to artemisinin partial resistance is urgently needed. Although both AL and ASAQ showed high efficacy, increased vigilance for reduced efficacy of these ACTs and detection of ART-R in other parts of the country is critical.

Prevalence of non-falciparum malaria infections among asymptomatic individuals in four regions of Mainland Tanzania.

BACKGROUND: Recent studies point to the need to incorporate the detection of non-falciparum species into malaria surveillance activities in sub-Saharan Africa, where 95% of the world's malaria cases occur. Although malaria caused by infection with Plasmodium falciparum is typically more severe than malaria caused by the non-falciparum Plasmodium species P. malariae, P. ovale spp. and P. vivax, the latter may be more challenging to diagnose, treat, control and ultimately eliminate. The prevalence of non-falciparum species throughout sub-Saharan Africa is poorly defined. Tanzania has geographical heterogeneity in transmission levels but an overall high malaria burden. METHODS: To estimate the prevalence of malaria species in Mainland Tanzania, we randomly selected 1428 samples from 6005 asymptomatic isolates collected in previous cross-sectional community surveys across four regions and analyzed these by quantitative PCR to detect and identify the Plasmodium species. RESULTS: Plasmodium falciparum was the most prevalent species in all samples, with P. malariae and P. ovale spp. detected at a lower prevalence (< 5%) in all four regions; P. vivax was not detected in any sample. CONCLUSIONS: The results of this study indicate that malaria elimination efforts in Tanzania will need to account for and enhance surveillance of these non-falciparum species.

Evidence of artemisinin partial resistance in northwestern Tanzania: clinical and molecular markers of resistance.

BACKGROUND: In 2021, nationwide malaria molecular surveillance revealed a high prevalence of a validated artemisinin resistance marker, the kelch13 (k13) Arg561His mutation, in the Kagera region of northwestern Tanzania. We aimed to investigate the efficacy of artemether-lumefantrine and artesunate-amodiaquine and to confirm the presence of artemisinin partial resistance (ART-R) in the Karagwe district of this region. METHODS: This single-arm, therapeutic efficacy study was carried out at the Bukangara dispensary in the Karagwe district of the Kagera region in northwestern Tanzania. Eligible participants were aged between 6 months and 120 months, had confirmed Plasmodium falciparum asexual parasitaemia, and met other inclusion criteria according to WHO's standard protocol. Participants were enrolled, treated sequentially with either artemether-lumefantrine or artesunate-amodiaquine, and assessed clinically and parasitologically for 28 days as per WHO protocol. Parasitaemia was measured every 8 h until day 3, on day 7, and then during weekly follow-up visits until day 28. Mutations in the k13 gene and extended haplotypes with the mutations were analysed, and comparisons were made with previous samples collected in the same region of Kagera and in Rwanda and southeast Asia. The primary endpoint was PCR-corrected cure rate. FINDINGS: Between April 29 and Sept 1, 2022, 343 patients were screened, of whom 176 were enrolled: 88 in each treatment group. The PCR-corrected cure rate was 98% (95% CI 91-100) in the artemether-lumefantrine group and 100% (96-100) in the artesunate-amodiaquine group. Persistent parasitaemia on day 3 occurred in 11 (13%) of 88 patients in the artemether-lumefantrine group and 17 (19%) of 88 patients in the artesunate-amodiaquine group. Arg561His mutations on day 0 and parasitaemia on day 3 were reported in eight (9%) of 87 patients in the artemether-lumefantrine group and ten (12%) of 86 patients in the artesunate-amodiaquine group. The median parasite clearance half-life in patients harbouring parasites with Arg561His mutation was 6·1 h in the artemether-lumefantrine group and 6·0 h in the artesunate-amodiaquine group. Parasites with the Arg561His mutation were not similar to those from southeast Asia and Rwanda but had similar haplotypes to parasites reported in the same Tanzanian region of Kagera in 2021. INTERPRETATION: This study confirms the presence of ART-R in Tanzania, although artemether-lumefantrine and artesunate-amodiaquine showed high efficacy. A context-specific response strategy and vigilance to detect the reduced efficacy of current antimalarial treatments and ART-R in other parts of the country are urgently needed. FUNDING: The Bill & Melinda Gates Foundation and the US National Institutes of Health.

Plasmodium falciparum pfhrp2 and pfhrp3 gene deletions among patients enrolled at 100 health facilities throughout Tanzania: February to July 2021.

Plasmodium falciparum with the histidine rich protein 2 gene (pfhrp2) deleted from its genome can escape diagnosis by HRP2-based rapid diagnostic tests (HRP2-RDTs). The World Health Organization (WHO) recommends switching to a non-HRP2 RDT for P. falciparum clinical case diagnosis when pfhrp2 deletion prevalence causes ≥ 5% of RDTs to return false negative results. Tanzania is a country of heterogenous P. falciparum transmission, with some regions approaching elimination and others at varying levels of control. In concordance with the current recommended WHO pfhrp2 deletion surveillance strategy, 100 health facilities encompassing 10 regions of Tanzania enrolled malaria-suspected patients between February and July 2021. Of 7863 persons of all ages enrolled and providing RDT result and blood sample, 3777 (48.0%) were positive by the national RDT testing for Plasmodium lactate dehydrogenase (pLDH) and/or HRP2. A second RDT testing specifically for the P. falciparum LDH (Pf-pLDH) antigen found 95 persons (2.5% of all RDT positives) were positive, though negative by the national RDT for HRP2, and were selected for pfhrp2 and pfhrp3 (pfhrp2/3) genotyping. Multiplex antigen detection by laboratory bead assay found 135/7847 (1.7%) of all blood samples positive for Plasmodium antigens but very low or no HRP2, and these were selected for genotyping as well. Of the samples selected for genotyping based on RDT or laboratory multiplex result, 158 were P. falciparum DNA positive, and 140 had sufficient DNA to be genotyped for pfhrp2/3. Most of these (125/140) were found to be pfhrp2+/pfhrp3+, with smaller numbers deleted for only pfhrp2 (n = 9) or only pfhrp3 (n = 6). No dual pfhrp2/3 deleted parasites were observed. This survey found that parasites with these gene deletions are rare in Tanzania, and estimated that 0.24% (95% confidence interval: 0.08% to 0.39%) of false-negative HRP2-RDTs for symptomatic persons were due to pfhrp2 deletions in this 2021 Tanzania survey. These data provide evidence for HRP2-based diagnostics as currently accurate for P. falciparum diagnosis in Tanzania.

Malaria knowledge, attitude, and practice among communities involved in a seasonal malaria chemoprevention study in Nanyumbu and Masasi districts, Tanzania.

Background: Utilization of malaria interventions is influenced by, among other things, the level of knowledge and attitude that the community has toward the infection as well as the available interventions. This study assessed malaria knowledge, attitudes, and practices on malaria infection and interventions in Masasi and Nanyumbu districts, Tanzania. Methods: A community-based cross-sectional survey was conducted between August and September 2020, among the heads of households having at least one under-five child. Information on knowledge, attitudes, and practices on malaria infection and interventions was gathered from the heads of the households using a structured questionnaire. The knowledge level was classified into low, moderate, and high. Attitudes were classified into positive and negative, whereas the practices were classified into good and poor. Children aged between 3 and 59 months were screened for malaria infection using a malaria rapid diagnostic test (mRDT). The proportion of the households' heads with high level of knowledge was the primary outcome. Proportions were compared using Chi-square or fisher's test, and logistic regression analysis was used as appropriate. Results: A total of 1,556 household heads were interviewed, 1,167 (75.00%) were male, and according to marital status, 1,067 (68.57%) were couples. All the household heads had some knowledge of malaria, but 47.33% (736/1,555) and 13.83% (215/1,555) of them had moderate and high knowledge, respectively. The level of knowledge on malaria was significantly influenced by gender [adjusted odds ratio (aOR) = 0.72, 95.00% confidence interval (CI) = 0.56-0.94, p = 0.017], level of education (aOR = 1.50, 95.00% CI = 1.04-2.16, p = 0.03), and the occupation of the household head (aOR = 1.90, 95.00% CI = 1.22-2.96, p = 0.004). Majority of the households [83.87% (1,305/1,556)] had bed nets hanging on the sleeping spaces. Of the household heads possessing bed nets, 85.10% (514/604), 79.62% (586/736), and 95.35% (205/215) of them had a low, moderate, and high level of knowledge on malaria infection, respectively (trend x 2 = 31.53, p < 0.001). The majority [95.04% (1,474/1,551)] of the household heads perceived sleeping under the bed net to be beneficial. Furthermore, 15.56% (94/604), 14.67% (108/736), and 7.44% (16/215) of the household heads with low, moderate, and high knowledge, respectively, had children with malaria infection (trend x 2 = 9.172, p = 0.01). Conclusion: The study population had a good level of knowledge about malaria infection, and a good attitude toward malaria interventions, and the majority of them were using bed nets.

Spatio-temporal modelling of routine health facility data for malaria risk micro-stratification in mainland Tanzania.

As malaria transmission declines, the need to monitor the heterogeneity of malaria risk at finer scales becomes critical to guide community-based targeted interventions. Although routine health facility (HF) data can provide epidemiological evidence at high spatial and temporal resolution, its incomplete nature of information can result in lower administrative units without empirical data. To overcome geographic sparsity of data and its representativeness, geo-spatial models can leverage routine information to predict risk in un-represented areas as well as estimate uncertainty of predictions. Here, a Bayesian spatio-temporal model was applied on malaria test positivity rate (TPR) data for the period 2017-2019 to predict risks at the ward level, the lowest decision-making unit in mainland Tanzania. To quantify the associated uncertainty, the probability of malaria TPR exceeding programmatic threshold was estimated. Results showed a marked spatial heterogeneity in malaria TPR across wards. 17.7 million people resided in areas where malaria TPR was high (≥ 30; 90% certainty) in the North-West and South-East parts of Tanzania. Approximately 11.7 million people lived in areas where malaria TPR was very low (< 5%; 90% certainty). HF data can be used to identify different epidemiological strata and guide malaria interventions at micro-planning units in Tanzania. These data, however, are imperfect in many settings in Africa and often require application of geo-spatial modelling techniques for estimation.

Malaria species positivity rates among symptomatic individuals across regions of differing transmission intensities in Mainland Tanzania.

Recent data indicate that non- Plasmodium falciparum species may be more prevalent than previously realized in sub-Saharan Africa, the region where 95% of the world's malaria cases occur. Although Plasmodium malariae, Plasmodium ovale spp., and Plasmodium vivax are generally less severe than P. falciparum , treatment and control are more challenging, and their geographic distributions are not well characterized. In order to characterize the distribution of malaria species in Mainland Tanzania (which has a high burden and geographically heterogeneous transmission levels), we randomly selected 3,284 samples from 12,845 samples to determine presence and parasitemia of different malaria species. The samples were collected from cross-sectional surveys in 100 health facilities across ten regions and analyzed via quantitative real-time PCR to characterize regional positivity rates for each species. P. falciparum was most prevalent, but P. malariae and P. ovale were found in all regions except Dar es Salaam, with high levels (>5%) of P. ovale in seven regions (70%). The highest positivity rate of P. malariae was 4.5% in Mara region and eight regions (80%) had positivity rates ≥1%. We also detected three P. vivax infections in the very low-transmission Kilimanjaro region. While most samples that tested positive for non-falciparum malaria were co-infected with P. falciparum , 23.6% (n = 13/55) of P. malariae and 14.7% (n = 24/163) of P. ovale spp. samples were mono-infections. P. falciparum remains by far the largest threat, but our data indicate that malaria elimination efforts in Tanzania will require increased surveillance and improved understanding of the biology of non-falciparum species.

Malaria species prevalence among asymptomatic individuals in four regions of Mainland Tanzania.

Recent studies point to the need to incorporate non-falciparum species detection into malaria surveillance activities in sub-Saharan Africa, where 95% of malaria cases occur. Although Plasmodium falciparum infection is typically more severe, diagnosis, treatment, and control for P. malariae, P. ovale spp., and P. vivax may be more challenging. The prevalence of these species throughout sub-Saharan Africa is poorly defined. Tanzania has geographically heterogeneous transmission levels but an overall high malaria burden. In order to estimate the prevalence of malaria species in Mainland Tanzania, 1,428 samples were randomly selected from 6,005 asymptomatic isolates collected in cross-sectional community surveys across four regions and analyzed via qPCR to detect each Plasmodium species. P. falciparum was most prevalent, with P. malariae and P. ovale spp. detected at lower prevalence (<5%) in all four regions. P. vivax was not detected. Malaria elimination efforts in Tanzania will need to account for these non-falciparum species.

Country wide surveillance reveals prevalent artemisinin partial resistance mutations with evidence for multiple origins and expansion of high level sulfadoxine-pyrimethamine resistance mutations in northwest Tanzania.

Background: Emergence of artemisinin partial resistance (ART-R) in Plasmodium falciparum is a growing threat to the efficacy of artemisinin combination therapies (ACT) and the efforts for malaria elimination. The emergence of Plasmodium falciparum Kelch13 (K13) R561H in Rwanda raised concern about the impact in neighboring Tanzania. In addition, regional concern over resistance affecting sulfadoxine-pyrimethamine (SP), which is used for chemoprevention strategies, is high. Methods: To enhance longitudinal monitoring, the Molecular Surveillance of Malaria in Tanzania (MSMT) project was launched in 2020 with the goal of assessing and mapping antimalarial resistance. Community and clinic samples were assessed for resistance polymorphisms using a molecular inversion probe platform. Findings: Genotyping of 6,278 samples collected countrywide in 2021 revealed a focus of K13 561H mutants in northwestern Tanzania (Kagera) with prevalence of 7.7% (50/649). A small number of 561H mutants (about 1%) were found as far as 800 km away in Tabora, Manyara, and Njombe. Genomic analysis suggests some of these parasites are highly related to isolates collected in Rwanda in 2015, supporting regional spread of 561H. However, a novel haplotype was also observed, likely indicating a second origin in the region. Other validated resistance polymorphisms (622I and 675V) were also identified. A focus of high sulfadoxine-pyrimethamine drug resistance was also identified in Kagera with a prevalence of dihydrofolate reductase 164L of 15% (80/526). Interpretation: These findings demonstrate the K13 561H mutation is entrenched in the region and that multiple origins of ART-R, similar as to what was seen in Southeast Asia, have occurred. Mutations associated with high levels of SP resistance are increasing. These results raise concerns about the long-term efficacy of artemisinin and chemoprevention antimalarials in the region. Funding: This study was funded by the Bill and Melinda Gates Foundation and the National Institutes of Health.