Abstract Anopheles albimanus ( Nyssorhynchus ) is featured as the main malaria vector on Hispaniola. However, five other Anopheles species have been reported circulating in the area; four of them belonging to the subgenus Anopheles ( An. crucians, An. grabhamii, An. pseudopunctipennis , and An. vestitipennis ) and another one to the Nyssorhynchus subgenus ( An. argyritarsis ). Previous studies on mosquitoes in the genus Anopheles have identified and characterized peptides from immunogenic salivary proteins, with several of these peptides being unique to the Nyssorhynchus and Anopheles subgenera. This underscores their potential use as biomarkers for differentiating exposure to Anopheles mosquitoes in both the Old World and New World. Since both Nyssorhynchus and Anopheles subgenera have been reported in Haiti, a series of ELISAs were conducted to quantify IgG antibody titers against three published antigenic anopheline salivary peptides (gSG6-P1, Peroxi-P3, and Apy-2) in 348 participants registered in Haiti’s multi-partner/multidisciplinary Malaria Zero Program. This study aimed to evaluate the intensity of human-vector contact with Anopheles from both subgenera in Grand’ Anse, Haiti. In addition, the study measured antibodies against a panel of Plasmodium falciparum antigens to determine any association between anti-parasite and anti-peptide antibodies. Significantly elevated IgG responses to Peroxi-P3 in comparison to Apy2 and gSG6-P1 in the total study population (p < 0.001) were observed. Additionally, immune responses to Peroxi-P3 and gSG6-P1 differed significantly between ≤18-year-olds and >18-year-olds (p = 0.004 and p = 0.002), whereas no sex-based differences were observed for any peptide. Correlation analyses observed a greater number of significant positive associations in immune response between gSG6-P1 and Plasmodium antigens than any other salivary peptide, an occurrence which was more pronounced in ≤18-year-olds than >18-year-olds. A marked reduction in IgG responses to Apy2 and Peroxi-P3, but not gSG6-P1, among participants who kept a single household animal species compared with those who owned two or more species or those who did not have household animals was also demonstrated. Spatial analysis revealed heterogenous geographic overlap of high antibody responses among Peroxi-P3, Apy2, and gSG6-P1, alongside geographically overlapping clusters of low antibody responses to Peroxi-P3 and Apy2. These results provide additional data on the utility of anopheline salivary peptides to characterize human-vector-parasite exposure dynamics in low-transmission areas, such as Haiti.

Attractive targeted sugar baits (ATSB) are a potential new class of vector control tool that act through an “attract and kill” mechanism on mosquitoes. We conducted a meta-analysis using data from three large-scale Phase III trials of the Westham Sarabi v1.2 ATSB (0.11% dinotefuran) conducted in Kenya, Mali, and Zambia, to determine the effect of the intervention on clinical malaria incidence in children, Plasmodium falciparum infection prevalence, and dominant vector species parity, abundance, landing rate, and sporozoite positivity. The Sarabi ATSB was deployed on exterior walls at the rate of two per residential structure. Aggregated and individual-level meta-analyses were completed for each of the six trial outcomes, comprising 6981 person-years of follow-up for clinical malaria incidence (primary epidemiological outcome) and 19443 Anopheles for parity assessment (primary entomological outcome). Post-hoc analyses included assessment of dose-response relationships between coverage-adjusted intervention density and clinical malaria incidence. There were no statistically significant differences between arms in any of the epidemiological or entomological outcomes. There was statistically significant evidence of a 19% reduction in clinical malaria incidence for every 10 bait stations per hectare increase observed in spatial density (IRR 0.81, 95% CI 0.74-0.89, p<0.001), provided that the ATSB were in good condition. This finding suggests that there may be deployment approaches or dosing strategies under which ATSB tools could be efficacious, although threshold spatial densities could not be determined from available data. This meta-analysis furthermore highlights important recommendations for future cluster-randomized trials of vector control interventions, including conducting comprehensive baseline data collection to identify cluster outliers or sites with differences in vector bionomics, and collecting a limited set of entomological outcomes in all trial clusters to ensure an adequately powered and balanced analysis of entomological effects. ### Competing Interest Statement The authors have declared no competing interest. ### Clinical Trial All three trials were registered at ClinicalTrials.gov: Kenya [NCT05219565][1], Mali [NCT04149119][2], and Zambia [NCT04800055][3] ### Funding Statement This study was funded by the Innovative Vector Control Consortium (IVCC) through support from the Bill & Melinda Gates Foundation (INV-007509), the Swiss Agency for International Development and Cooperation (81067480) and UK Aid (30041-105). ### Author Declarations I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained. Not Applicable The details of the IRB/oversight body that provided approval or exemption for the research described are given below: This study is a meta-analysis of three independent trials that received IRB approval and have published their primary results elsewhere. Approval for the trial in Kenya was granted by IRBs of the Kenya Medical Research Institute and the Liverpool School of Tropical Medicine, along with approval from the US Centers for Disease Control and Prevention via a reciprocal agreement with KEMRI. Approval for the trial in Mali was granted by IRBs of the University of Bamako and the London School of Hygiene and Tropical Medicine. Approval for the trial in Zambia was granted by IRBs of the University of Zambia, PATH, and Tulane University. I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals. Not Applicable I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance). Not Applicable I have followed all appropriate research reporting guidelines, such as any relevant EQUATOR Network research reporting checklist(s) and other pertinent material, if applicable. Not Applicable Data used to generate results reported in this manuscript are freely available at the following DOI through Figshare, https://doi.org/ 10.6084/m9.figshare.32030076. [1]: /lookup/external-ref?link_type=CLINTRIALGOV&access_num=NCT05219565&atom=%2Fmedrxiv%2Fearly%2F2026%2F05%2F10%2F2026.05.06.26352614.atom [2]: /lookup/external-ref?link_type=CLINTRIALGOV&access_num=NCT04149119&atom=%2Fmedrxiv%2Fearly%2F2026%2F05%2F10%2F2026.05.06.26352614.atom [3]: /lookup/external-ref?link_type=CLINTRIALGOV&access_num=NCT04800055&atom=%2Fmedrxiv%2Fearly%2F2026%2F05%2F10%2F2026.05.06.26352614.atom

Background In 2017, Zambia adopted surveillance as a core intervention towards achieving malaria elimination. Among the surveillance strategies is the malaria case investigation and response 1-3-7 (MCIR 1-3-7), which has been piloted in two low-incidence districts in the Southern Province since 2021. The study aimed to assess the implementation of MCIR 1-3-7 under programmatic conditions. It examined the timeliness, and completeness of the MCIR 1-3-7 activities, including the completeness of data entry in surveillance forms, and explored the experiences and perspectives of healthcare workers involved in the pilot. Methods A mixed-methods design was employed to assess the MCIR 1-3-7. Using a descriptive cross-sectional design, quantitative data were collected from 19 healthcare facilities in the two districts to assess the timeliness and completeness of MCIR 1-3-7. Additionally, 12 qualitative interviews were conducted with 29 healthcare workers from 11 of the 19 healthcare facilities. The interviews were voice-recorded and then transcribed manually. A codebook was developed using an iterative process to explore the facilitators and barriers encountered by healthcare workers in implementing the MCIR 1-3-7 intervention. All the visited facilities were purposively selected based on logistical convenience. Results This study retrospectively assessed 510 malaria cases that were diagnosed between January 2022 and June 2023, presenting at 19 health facilities: 283 cases in Chikankata and 227 in Mazabuka districts. A total of 278 cases (54.5%) were deemed to have been imported from outside the district, province, or country, while 45.5% (232/510) of the cases were classified as transmitted locally. Overall, 29.6% of case notification forms were found to be complete. Twelve interviews with 29 healthcare workers revealed a lack of transportation modalities as the main obstacle in executing the MCIR 1-3-7 intervention. The healthcare workers also indicated that monetary incentives, and supportive supervision would help them succeed in implementing this intervention. Conclusions The MCIR 1-3-7 has the potential to accelerate elimination in areas with low-transmission of malaria in Zambia. This study highlights opportunities to improve future implementation of the MCIR 1-3-7 intervention via strengthening supportive supervision, availing job aids, and ensuring access to malaria commodities as the intervention expands. ### Competing Interest Statement The authors have declared no competing interest. ### Funding Statement The author(s) received no specific funding for this work. ### Author Declarations I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained. Yes The details of the IRB/oversight body that provided approval or exemption for the research described are given below: Ethical approval was obtained from the University of Zambia Biomedical Research Ethics Committee (UNZABREC) and the National Health Research Authority (NHRA). An approval was granted on June 27, 2023 (REF. NO. 4100-2023). I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals. Yes I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance). Yes I have followed all appropriate research reporting guidelines, such as any relevant EQUATOR Network research reporting checklist(s) and other pertinent material, if applicable. Yes De-identified data are available from the author on reasonable request.

Abstract Rectal artesunate (RAS) is a pre-referral intervention recommended for children with suspected severe malaria in remote settings where injectable treatment is not readily available. Although clinical trials have demonstrated efficacy, less is known about the behavioural and health system factors influencing effectiveness under routine conditions. A convergent parallel mixed-methods design was used to assess implementation of Zambia’s RAS intervention package across three districts: Serenje, Chama, and Mwinilunga. A retrospective case-tracking investigation of all 300 children with suspected severe malaria recorded by community health workers (CHWs) assigned to study facilities examined progression and attrition across the severe malaria care cascade. In-depth interviews and focus group discussions with caregivers, CHWs, and other stakeholders explored barriers and facilitators influencing progression. Among 300 enrolled children, early attrition occurred due to negative rapid diagnostic test results. Of 239 RDT-positive children, 218 (91.2%) received RAS. Referral completion was lower; among 261 children referred and followed up at health facilities, 209 (80.1%) were confirmed to have completed referral. Of 186 children diagnosed with severe malaria at the facility, 167 (89.8%) received both injectable artesunate and follow-on artemether–lumefantrine. Patterns of disengagement varied by district, with Serenje demonstrating the most consistent progression, Chama experiencing the largest drop-off at RAS administration, and Mwinilunga showing the lowest completion of follow-on treatment. Qualitative findings revealed strong community appreciation for RAS despite stockouts, alongside social and behavioural barriers, including gendered responsibilities, transport challenges, and confusion following symptom improvement, that discouraged referral completion. RAS can be a life-saving intervention when embedded within strong health systems and community structures. Zambia’s experience underscores the need for comprehensive implementation strategies that extend beyond drug distribution to include sustained CHW training, reliable commodity supply, functional referral systems, and meaningful caregiver engagement.

Community case management has been scaled up nationally in Zambia over the last decade. However, there is limited evidence on how this nationwide implementation has affected febrile patients' access to malaria diagnosis and treatment in Zambia. This study analyzed four rounds of Malaria Indicator Survey (MIS) data (2012-2021) to evaluate: 1) proportion of all-ages individuals with fever who sought treatment from a formal provider, 2) proportion of individuals going to CHWs over time, among those who sought treatment at a formal provider, 3) time duration between fever onset and treatment seeking at a formal provider, and 4) proportion of children <5 with malaria that received Artemether-Lumefantrine (AL) treatment. Mixed-effect logit models were employed to examine determinants of treatment-seeking behavior and factors affecting AL receipt among children <5 with malaria cases. The proportion of febrile patients seeking treatment remained below 60% throughout 2012-2021, and AL receipt among children with malaria cases consistently stayed below 50%. The mean interval between fever onset and initial treatment-seeking encounter decreased from 2.42 days in 2012 to 1.71 days in 2021. Among formal care seekers, CHW utilization increased from 1.5% in 2012 to 10.0% in 2018 before declining to 3.2% in 2021. Longer walking time to the nearest health facility was associated with lower odds of treatment seeking, whereas CHW density was not associated with treatment seeking or AL receipt. Children who did not go to formal providers had lower odds of AL receipt than those who sought treatment from CHWs. Despite nationwide CCM scale-up over the last decade, significant barriers persist in malaria patients' access to diagnosis and treatment in Zambia. Our results indicate that while CCM coverage should be maintained and further expanded, additional complementary interventions are also needed to overcome remaining access barriers.

Hispaniola, which is shared by Haiti and the Dominican Republic, remains the last island in the Caribbean that is still endemic for malaria, with Haiti bearing the highest caseload. Few studies have examined the ecology of malaria vectors in Haiti. Five species of Anopheles have been described on the island, but the exophilic Anopheles albimanus (An. albimanus) is considered the primary vector of malaria in Haiti. Households recruited for a case-control study profiling risk factors for symptomatic Plasmodium falciparum (P. falciparum) infections were approached to participate in an entomological study. The goal was to determine the bionomics of anopheline mosquitoes around the 32 participating households across varying malaria transmission settings. We assessed the characteristics of the Anopheles population using ultraviolet-light traps and larval surveys. Anopheles albimanus was the most abundant mosquito species identified in the Grand'Anse. Its abundance was higher in outdoor traps than in indoor traps and in areas with relatively high positivity based on rapid diagnostic test results. A greater proportion of blood-fed mosquitoes were found in higher transmission areas. Anopheles albimanus samples were found to be infected with both P. falciparum and Plasmodium vivax sporozoites. As Haiti aims for the elimination of malaria, disrupting localized residual malaria transmission will increasingly rely on focal vector control strategies.

Prompt treatment seeking for febrile illness is a critical step in the care cascade for malaria. In wide areas of sub-Saharan Africa there are critical gaps in coverage of prompt care. Integrated Community Case Management (iCCM) has been shown to be a burden reducing intervention that can influence malaria transmission and reduce overall disease burden and increase care access. Studies have not determined whether the delivery of iCCM through passive or proactive means provide ancillary benefits such as sustainable improvements in care-seeking behavior. This study was designed to determine if ProCCM could deliver sustainable increases in care seeking behavior even after a short period of implementation had ended. A three-arm community randomized trial was conducted in Pujehun district, Sierra Leone from May 2024 until it was interrupted by the U.S. government in January 2025. The trial compared communities with up to four rounds of ProCCM and stock out support, to stock out support and iCCM alone, or to only iCCM alone (Standard Practice). Forty-six Primary Health Care Units (PHCU) were grouped into 45 clusters and randomized (1:1:1) to one of the three arms using restricted randomization. Treatment seeking rates were measured using cross-sectional household surveys at baseline (before randomization) and at one month post intervention. A final survey was planned at four months after intervention end but was interrupted by U.S. Government actions. In the first survey post intervention, 250 of 391 febrile children sought care promptly in the preceding two weeks. Household education, asset ownership, access to water, household construction and use of malaria prevention were similar across arms. There was a significantly higher rate of prompt care-seeking for febrile illness in groups exposed to ProCCM as compared to the other arms. Among the hardest to reach populations, odds of care seeking increased nearly 3x (O.R. 2.78 (95% C.I. 1.03-7.85) p =0.05). Post-intervention beliefs about the availability, quality and community norms of care-seeking for fever were all higher in the ProCCM arm relative to the controls. ProCCM delivered in short periods can improve care seeking for febrile illness in hard-to-reach populations by modifying community perceptions of community health workers availability and competence, when drugs and diagnostics for malaria care are available. We were unable to assess the sustainability of these gains due to interruption of PMI funding. USAID/PMI Funding through PATH/PMI Insights supported the original study and data collection. All analytic and post-data collection work supported by Tulane University.

BACKGROUND:Vector control is the most important malaria prevention strategy in Zambia. Attractive Targeted Sugar Baits (ATSB) are a potential new tool for vector control in this setting, which, if efficacious, would be intended to supplement insecticide-treated bed nets (ITNs) and indoor residual spraying (IRS). ATSBs target and kill sugar feeding mosquitoes, potentially limiting the spread of malaria. No information on the cost or cost-effectiveness of deployment of ATSB stations is currently available. METHODS:A cluster randomized control trial (cRCT) was carried out in Western Province, Zambia to assess the efficacy of Sarabi v.1.2 ATSB stations in a highly malarious setting. Costs associated with the procurement, distribution, maintenance, and disposal of the ATSB stations were collected over a two-year period. These costs were assessed alongside the main trial efficacy outcomes to determine cost-effectiveness and potential budget impact on the deployment of ATSB stations in this setting. Total costs, incremental costs, incremental cost-effectiveness ratios (ICER) and budget impact were estimated using trial data. One-way, scenario and probabilistic sensitivity analysis were performed to further determine the impact of assumptions and uncertainty on cost-effectiveness estimates, and the potential cost implications of alternative deployment scenarios. Sub-group analysis was performed to determine the impact of deployment in settings with the most favorable effect scenarios. RESULTS:The total cost of the intervention in the context of the cRCT was USD 1,261,515. ATSB cost accounted for 46% of the total cost followed by personnel (25%), supplies and transport (13% each), equipment (2%) and storage (1%). Over the two year (14-month intervention) this resulted in an estimated ICER of USD 79 per malaria incident case averted or USD 919 per disability-adjusted life year (DALY) averted and USD 10.08 per person-year protected. In a subset of high-density ATSB clusters ICER was USD 42 per incident case averted and USD 493 per DALY averted and USD 4.35 per person-year protected. Probabilistic sensitivity analysis indicated that deployment in areas with higher structure density may be more cost-effective, especially if potential cost-savings are considered. However, effect estimates in this subgroup were highly uncertain and not statistically significant. While the scenario appeared more cost-effective than the base case on the cost-effectiveness acceptability curve (CEAC), the probability of cost-effectiveness reached only around 70%, falling short of the commonly used 80% threshold and remaining relatively weak. CONCLUSIONS:ATSB Sarabi v.1.2 as deployed in western Zambia were not likely to be cost -effective. ATSB would need to demonstrate higher or more certain efficacy along with affordable alternative distribution strategies prior to any deployment at scale. Trial registration The trial is registered on clinicaltrials.gov under registration number: NCT04800055.

Attractive targeted sugar baits (ATSBs) are a potential addition to an integrated vector management strategy against malaria. ATSB stations, which include a sugar bait and an ingestion toxicant, could potentially be deployed to attract-and-kill mosquitoes and thereby prevent malaria transmission. The physical durability of these stations is likely to be an important factor in decisions around future use strategies. This study measured the duration of physical integrity of the ATSB Sarabi v1.2 stations used in Western Zambia, as part of a Phase III cluster RCT. ATSB stations were installed and followed as a cohort on the external walls of selected sleeping structures in households in trial clusters (10–11 per cluster). Monthly visits were made to assess the presence and condition of the ATSBs from November 2022 to June 2023. A rolling cohort approach was used, whereby new ATSB stations were used to replace those which failed or were lost-to-follow-up, and these were subsequently enrolled in the cohort. Information on structure construction and ATSBs location on the walls was also collected. Median ATSB survival and associated factors were analysed with Kaplan–Meier curves and Cox-Proportional hazard models. Including replacements, a total of 1107 ATSBs were installed across 304 sleeping structures in 206 households, and 5696 ATSB-visits were made. Common types of damage observed were holes/tears, mold, and leakage of bait. While the median survival time for the devices was 5 months (149 days) for all stations in the study, the median survival time was longer than the transmission season for stations installed in locations well protected by the roof (> 218 days). ATSB station survival was longer when installed on structures with thatched roofs compared to iron-sheet roofs (HR 0.37, 95

Abstract Background Attractive targeted sugar bait (ATSB) stations are a novel tool with potential to complement current approaches to malaria vector control. To assess the public health value of ATSB station deployment in areas of high coverage with standard vector control, a two-arm cluster-randomized controlled trial (cRCT) of Sarabi ATSB® stations (Westham Ltd., Hod-Hasharon, Israel) was conducted in Western Province, Zambia, a high-burden location were Anopheles funestus is the dominant vector. The trial included 70 clusters and was designed to measure the effect of ATSBs on case incidence and infection prevalence over two 7-month deployments. Reported here are results of the vector surveillance component of the study, conducted in a subset of 20 clusters and designed to provide entomological context to guide overall interpretation of trial findings. Methods Each month, 200 paired indoor-outdoor human landing catch (HLC) and 200 paired light trap (LT) collections were conducted to monitor An. funestus parity, abundance, biting rates, sporozoite prevalence, and entomological inoculation rates (EIR). Results During the study 20,337 female An. funestus were collected, 11,229 from control and 9,108 from intervention clusters. A subset of 3,131 HLC specimens were assessed for parity: The mean non-parous proportion was 23.0% (95% CI 18.2–28.7%, total n = 1477) in the control and 21.2% (95% CI 18.8–23.9%, total n = 1654) in the intervention arm, an OR = 1.05 (95% CI 0.82–1.34; p = 0.688). A non-significant reduction in LT abundance (RR = 0.65 [95% CI 0.30–1.40, p = 0.267]) was associated with ATSB deployment. HLC rates were highly variable, but model results indicate a similar non-significant trend with a RR = 0.68 (95%CI 0.22–2.00; p = 0.479). There were no effects on sporozoite prevalence or EIR. Conclusions Anopheles funestus parity did not differ across study arms, but ATSB deployment was associated with a non-significant 35% reduction in vector LT density, results that are consistent with the epidemiological impact reported elsewhere. Additional research is needed to better understand how to maximize the potential impact of ATSB approaches in Zambia and other contexts. Trial registration number: This trial was registered with Clinicaltrials.gov (NCT04800055, 16 March 2021).

Abstract Background Attractive targeted sugar bait (ATSB) stations containing bait (to attract) and ingestion toxicant (to kill) sugar-foraging mosquitoes are hypothesized to reduce malaria transmission by shortening the lifespan of Anopheles vectors. Methods A two-arm cluster-randomized controlled trial (cRCT) was conducted in Western Province Zambia. Seventy clusters of 250–350 households were assigned (1:1) by restricted randomization to an intervention arm (ATSB) or control arm (no ATSB) in the context of standard of care vector control (insecticide-treated nets and/or indoor residual spraying). Two ATSB stations (Westham Sarabi, 0.11% dinotefuran w/w) were maintained on exterior walls of eligible household structures for a 7-month deployment period (December-June) during the high malaria transmission season. The primary outcome was clinical malaria incidence among two consecutive seasonal cohorts of children aged 1–14 years, followed-up monthly from January-June in 2022 and 2023. Secondary outcome was Plasmodium falciparum prevalence among individuals aged over six months. Analysis compared clinical malaria incidence and prevalence between arms among the intention-to-treat population. Results ATSB coverage, assessed by cross-sectional survey, was 98.3% in March–April 2022 and 89.5% in March–April 2023. 4494 children contributed any follow-up time to the cohort, with 2313 incident malaria cases in the intervention arm (1.28 per child per six-month transmission season), and 2449 in the control arm (1.38 per child-season). The incidence rate ratio between the two arms was 0.91 (95% CI 0.72–1.15, p = 0.42). 2536 individuals participated in cross-sectional surveys, with prevalence of P. falciparum 50.7% in the intervention arm and 53.5% in the control arm. The odds ratio between the two arms was 0.89 (95% CI 0.66–1.18, p = 0.42). Secondary covariable-adjusted and subgroup analyses did not substantially alter the findings. No serious adverse events associated with the intervention were reported. Conclusions Two ATSB stations deployed per eligible structure for two consecutive transmission seasons did not result in a statistically significant reduction in clinical malaria incidence among children aged 1–14 years or in P. falciparum prevalence in rural western Zambia. Further studies are needed to assess the efficacy of ATSB stations in different settings and with different deployment strategies. Trial registration The trial is registered with Clinicaltrials.gov (NCT04800055).

Abstract Background Some settings continue to experience a high malaria burden despite scale-up of malaria vector control to high levels of coverage. Characterisation of persistent malaria transmission in the presence of standard control measures, also termed residual malaria transmission, to understand where and when individuals are exposed to vector biting is critical to inform refinement of prevention and control strategies. Methods Secondary analysis was performed using data collected during a phase III cluster randomized trial of attractive targeted sugar bait stations in Western Province, Zambia. Two seasonal cohorts of children aged 1–14 years were recruited and monitored monthly during the malaria transmission season, concurrent with entomological surveillance using a combination of human landing catch (HLC) and Centres for Disease Control (CDC) light traps at randomly selected households in study clusters. Behavioural data from cohort participants were combined with measured Anopheles funestus landing rates and sporozoite positivity to estimate the human behaviour-adjusted entomological inoculation rate (EIR). Results Behavioural data from 1237 children over 5456 child-visits in 20 entomology surveillance clusters were linked with hourly landing rates from 8131 female An. funestus trapped by HLC. Among all An. funestus tested by enzyme-linked immunosorbent assay (ELISA), 3.3% were sporozoite-positive. Mean EIR directly measured from HLC was 0.07 infectious bites per person per night (ib/p/n). When accounting for child locations over the evening and night, the mean behaviour-adjusted EIR was 0.02 ib/p/n. Children not sleeping under insecticide-treated nets (ITNs) experienced 13.6 infectious bites per person per 6 month season, 8% of which occurred outdoors, while ITN users received 1.3 infectious bites per person per 6 month season, 86% of which were received outdoors. Sleeping under an ITN can prevent approximately 90% of potential An. funestus bites among children. Conclusions In this setting ITNs have a high personal protective efficacy owing to peak An. funestus biting occurring indoors while most individuals are asleep. However, despite high household possession of ITNs (>90%) and high individual use (>70%), children in this setting experience more than one infectious bite per person per 6 month transmission season, sufficient to maintain high malaria transmission and burden. New tools and strategies are required to reduce the malaria burden in such settings. Graphical Abstract

BackgroundAttractive Targeted Sugar Baits (ATSBs) are a proposed new vector control tool for malaria that contain sugar and an ingestion toxicant, and are designed to attract and kill sugar-feeding mosquitoes. During a two-arm cluster randomized Phase III trial conducted in Zambia to test the efficacy of ATSB stations on malaria incidence, ATSB stations deployed on eligible household structures within intervention clusters were routinely monitored to ensure their good physical condition and high coverage. This study investigates trends in prevalence and rate of damage to ATSB stations during year 2 of the two-year trial.MethodsThe analysis was conducted using monitoring data collected in year 2, which included types of damage observed, location, and date of removal and/or replacement of ATSB stations. The study evaluated temporal trends in the prevalence of overall damage and different damage types among 68,299 ATSB stations deployed. A profile of all ATSB stations installed on each structure was constructed, and spatial analyses conducted on overall damage and different damage types observed on 18,890 structures. Mixed effects regression analyses were conducted to investigate drivers of damage to ATSB stations on these structures.ResultsPrevalence of overall damage and different damage types was temporally and spatially heterogeneous. Among damaged ATSB stations observed during monitoring, tears and mold had the highest prevalences on average, with tears maintaining above 50.0% prevalence through most of the monitoring period, while mold prevalence increased steadily during the first few months, peaking in February. Overall, 45.6% of structures had at least one damaged ATSB station, however this varied spatially across the trial site. Both structure characteristics and environmental factors significantly impacted the odds and rate of damage to ATSB stations on structures, including: ATSB stations' level of protection from rainfall and sunshine; roof and wall material of the structure; night-time temperature; rainfall; enhanced vegetation index, and land cover.ConclusionDamage to ATSB stations in this setting was common and was temporally and spatially heterogeneous. This has implications on operational feasibility, sustainability, and cost of future deployment. Further research is required to understand the mechanisms of damage, and to minimize prevalence and rate of damage to ATSB stations.

BACKGROUND:Community acceptance is an important criterion to assess in community trials, particularly for new tools that require high coverage and use by a target population. Installed on exterior walls of household structures, the attractive targeted sugar bait (ATSB) is a new vector control tool designed to attract and kill mosquitoes. ATSBs were evaluated in Western Zambia during a two-year cluster randomized controlled trial to assess the efficacy of ATSBs in reducing malaria transmission. Community acceptance of ATSBs was critical for successful trial implementation. METHODS:A community engagement strategy outlined activities and key messages to promote acceptance. Annual cross-sectional surveys, conducted during the peak transmission period, assessed households for presence of ATSBs as well as perceived benefits, concerns, and willingness to use ATSBs. Sixteen focus group discussions and 16 in-depth interviews, conducted at the end of each ATSB station deployment period, obtained a range of perceptions and household experiences with ATSB stations, as well as ITN use in the context of ATSB deployment. RESULTS:Methods used during the study to promote acceptance and continued use of ATSBs were effective in achieving greater than 90% coverage, a high (greater than 70%) level of perceived benefits, and fewer than 10% of households reporting safety concerns. Common facilitators of acceptance included the desire for protection against malaria and reduction of mosquitoes, trust in health initiatives, and understanding of the product. Common barriers to acceptance included misconceptions of product impact on mosquitoes, continued cases of malaria, association with satanism, and damage to household structures. DISCUSSION:Future use of the ATSB intervention will likely require activities that foster community acceptance before, during, and after the intervention is introduced. Additional research may be needed to understand the impact of different levels of community engagement on ATSB station coverage, ATSB station perception, and ITN use. CONCLUSION:There was high acceptance of ATSB stations during the trial in Western Zambia. Continuous and intense community engagement efforts contributed to sustained ATSB coverage and trust in the product. Acceptance of ATSBs during programmatic delivery requires further research.

BACKGROUND:The attractive targeted sugar bait (ATSB) is a novel malaria vector control tool designed to attract and kill mosquitoes using a sugar-based bait, laced with oral toxicant. Western Province, Zambia, was one of three countries selected for a series of phase III cluster randomized controlled trials of the Westham ATSB Sarabi version 1.2. The trial sites in Kenya, Mali, and Zambia were selected to represent a range of different ecologies and malaria transmission settings across sub-Saharan Africa. This case study describes the key characteristics of the ATSB Zambia trial site to allow for interpretation of the results relative to the Kenya and Mali sites.METHODS:This study site characterization incorporates data from the trial baseline epidemiological and mosquito sugar feeding surveys conducted in 2021, as well as relevant literature on the study area.RESULTS:CHARACTERIZATION OF THE TRIAL SITE: The trial site in Zambia was comprised of 70 trial-designed clusters in Kaoma, Nkeyema, and Luampa districts. Population settlements in the trial site were dispersed across a large geographic area with sparsely populated villages. The overall population density in the 70 study clusters was 65.7 people per square kilometre with a total site population of 122,023 people living in a geographic area that covered 1858 square kilometres. However, the study clusters were distributed over a total area of approximately 11,728 square kilometres. The region was tropical with intense and seasonal malaria transmission. An abundance of trees and other plants in the trial site were potential sources of sugar meals for malaria vectors. Fourteen Anopheles species were endemic in the site and Anopheles funestus was the dominant vector, likely accounting for around 95% of all Plasmodium falciparum malaria infections. Despite high coverage of indoor residual spraying and insecticide-treated nets, the baseline malaria prevalence during the peak malaria transmission season was 50% among people ages six months and older.CONCLUSION:Malaria transmission remains high in Western Province, Zambia, despite coverage with vector control tools. New strategies are needed to address the drivers of malaria transmission in this region and other malaria-endemic areas in sub-Saharan Africa.

Attractive Targeted Sugar Baits (ATSBs) offer a complementary vector control strategy to interventions targeting blood feeding or larval control by attacking the sugar feeding behaviour of adult mosquitoes using an attract-and-kill approach. Western Zambia was the first location to receive and deploy ATSB Sarabi version 1.2 stations in a Phase III cluster randomized controlled trial. This paper describes ATSB station installation, monitoring, removal, and disposal, quantifies ATSB station coverage, and reports major reasons for ATSB station replacement. ATSB stations were deployed during two annual transmission seasons, through scheduled installation and removal campaigns. During deployment, monitoring was conducted per protocol to maintain high coverage of the ATSB stations in good condition. Routine monitoring visits during the trial captured details on ATSB station damage necessitating replacement following pre-defined replacement criteria. Annual cross-sectional household surveys measured ATSB station coverage during peak malaria transmission. A total of 67,945 ATSB stations were installed in Year 1 (41,695 initially installed+ 26,250 installed during monitoring) and 69,494 ATSB stations were installed in Year 2 (41,982 initially installed+ 27,512 installed during monitoring) across 35 intervention clusters to maintain high coverage of two ATSB stations in good condition per eligible household structure. The primary reasons for ATSB station replacement due to damage were holes/tears and presence of mold. Cross-sectional household surveys documented high coverage of ATSB stations across Year 1 and Year 2 with 93.1