Browsing by Author "Kagaya, Wataru"

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    PublicationOpen Access
    Drug resistance profiling of asymptomatic and low-density Plasmodium falciparum malaria infections on Ngodhe island, Kenya, using custom dual-indexing next-generation sequencing
    (Scientific Reports, 2023-07-14) Osborne, Ashley; Chan,Chim; Kagaya, Wataru; Kaneko,Akira; Clark, Taane G.; Campino, Susana; Gitaka, Jesse; Kita, Kiyoshi; Kongere, James; Ngara, Mtakai; Phelan,Jody E.
    Malaria control initiatives require rapid and reliable methods for the detection and monitoring of molecular markers associated with antimalarial drug resistance in Plasmodium falciparum parasites. Ngodhe island, Kenya, presents a unique malaria profile, with lower P. falciparum incidence rates than the surrounding region, and a high proportion of sub-microscopic and low-density infections. Here, using custom dual-indexing and Illumina next generation sequencing, we generate resistance profiles on seventy asymptomatic and low-density P. falciparum infections from a mass drug administration program implemented on Ngodhe island between 2015 and 2016. Our assay encompasses established molecular markers on the Pfcrt, Pfmdr1, Pfdhps, Pfdhfr, and Pfk13 genes. Resistance markers for sulfadoxine-pyrimethamine were identified at high frequencies, including a quintuple mutant haplotype (Pfdhfr/Pfdhps: N51I, C59R, S108N/A437G, K540E) identified in 62.2% of isolates. The Pfdhps K540E biomarker, used to inform decision making for intermittent preventative treatment in pregnancy, was identified in 79.2% of isolates. Several variants on Pfmdr1, associated with reduced susceptibility to quinolones and lumefantrine, were also identified (Y184F 47.1%; D1246Y 16.0%; N86 98%). Overall, we have presented a low-cost and extendable approach that can provide timely genetic profiles to inform clinical and surveillance activities, especially in settings with abundant low-density infections, seeking malaria elimination.
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    PublicationOpen Access
    Evaluation of a financial incentive intervention on malaria prevalence among the residents in Lake Victoria basin, Kenya: study protocol for a cluster-randomized controlled trial
    (Research Square, 2024-03-04) Nagashima,; Matsumoto, Tomoya; Kaneko, Akira; Gitaka, Jesse; Kongere, James; Kagaya, Wataru
    Background: In the Lake Victoria basin of western Kenya, malaria remains highly endemic despite high coverage of interventions such as mass distribution of long-lasting insecticidal nets (LLIN), indoor residual spraying (IRS) programs, and improvement of availability and accessibility of rapid diagnostic tests (RDT) and artemisinin-based combination therapy (ACT) at community healthcare facilities. We hypothesize that one major cause of the residual transmission is the lack of motivation among residents for malaria prevention and early treatment. Methods: This study will aim to develop a demand-side policy tool to encourage local residents’ active malaria prevention and early treatment-seeking behaviors. We examine the causal impact of a financial incentive intervention complemented with malaria education to residents in malaria-prone areas. A cluster-randomized controlled trial is designed to assess the effect of the financial incentive intervention on reducing malaria prevalence in residents of Suba South in Homa Bay County, Kenya. The intervention includes two components. The first component is the introduction of a financial incentive scheme tied to negative RDT results for malaria infection among the target population. This study is an attempt to promote behavioral changes in the residents by providing them with monetary incentives. The project has two different forms of incentive schemes. One is a conditional cash transfer (CCT) that offers a small reward (200 Ksh) for non-infected subjects during the follow-up survey, and the other is a lottery incentive scheme (LIS) that gives a lottery with a 10% chance of winning a large reward (2,000 Ksh) instead of the small reward. The second component is a knowledge enhancement with animated tablet-based malaria educational material (EDU) developed by the research team. It complements the incentive scheme by providing the appropriate knowledge to the residents for malaria elimination. We evaluate the intervention's impact on the residents' malaria prevalence using a cluster-randomized control trial.
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    PublicationOpen Access
    Evaluation of a financial incentive intervention on malaria prevalence among the residents in Lake Victoria basin, Kenya: study protocol for a cluster-randomized controlled trial
    (BMC, 2024-03-04) Matsumoto, Tomoya; Nagashima, Masaru; Kagaya, Wataru; Kongere, James; Gitaka, Jesse; Kaneko, Akira
    Background In the Lake Victoria basin of western Kenya, malaria remains highly endemic despite high cover- age of interventions such as mass distribution of long-lasting insecticidal nets (LLIN), indoor residual spraying (IRS) programs, and improvement of availability and accessibility of rapid diagnostic tests (RDT) and artemisinin-based combination therapy (ACT) at community healthcare facilities. We hypothesize that one major cause of the residual transmission is the lack of motivation among residents for malaria prevention and early treatment. Methods This study will aim to develop a demand-side policy tool to encourage local residents’ active malaria prevention and early treatment-seeking behaviors. We examine the causal impact of a financial incentive interven- tion complemented with malaria education to residents in malaria-prone areas. A cluster-randomized controlled trial is designed to assess the effect of the financial incentive intervention on reducing malaria prevalence in resi- dents of Suba South in Homa Bay County, Kenya. The intervention includes two components. The first component is the introduction of a financial incentive scheme tied to negative RDT results for malaria infection among the target population. This study is an attempt to promote behavioral changes in the residents by providing them with mon- etary incentives. The project has two different forms of incentive schemes. One is a conditional cash transfer (CCT) that offers a small reward (200 Ksh) for non-infected subjects during the follow-up survey, and the other is a lottery incentive scheme (LIS) that gives a lottery with a 10% chance of winning a large reward (2000 Ksh) instead of the small reward. The second component is a knowledge enhancement with animated tablet-based malaria educational material (EDU) developed by the research team. It complements the incentive scheme by providing the appropriate knowledge to the residents for malaria elimination. We evaluate the intervention’s impact on the residents’ malaria prevalence using a cluster-randomized control trial. Discussion A policy tool to encourage active malaria prevention and early treatment to residents in Suba South, examined in this trial, may benefit other malaria-endemic counties and be incorporated as part of Kenya’s national malaria elimination strategy.
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    PublicationOpen Access
    Evaluation of the protective efficacy of Olyset Plus ceiling net on reducing malaria prevalence in children in Lake Victoria Basin, Kenya: study protocol for a cluster-randomized controlled trial
    (springer link, 2023-05-25) Kagaya, Wataru; Chan, Chim W.; Kongere, James; Kanoi, Bernard N.; Ngara, Mtakai; Omondi, Protus; Osborne, Ashley; Barbieri, Laura; Minakawa, Noboru; Gitaka, Jesse
    Background In the Lake Victoria Basin of western Kenya, malaria remains highly endemic despite high coverage of interventions such as insecticide-impregnated long-lasting insecticidal nets (LLIN). The malaria-protective efect of LLINs is hampered by insecticide resistance in Anopheles vectors and its repurposing by the community. Ceiling nets and LLIN with synergist piperonyl butoxide (PBO-LLIN) are novel tools that can overcome the problems of behavioral variation of net use and metabolic resistance to insecticide, respectively. The two have been shown to reduce malaria prevalence when used independently. Integration of these two tools (i.e., ceiling nets made with PBO-LLIN or Olyset®Plus ceiling nets) appears promising in further reducing the malaria burden. Methods A cluster-randomized controlled trial is designed to assess the efect of Olyset®Plus ceiling nets on reducing malaria prevalence in children on Mfangano Island in Homa Bay County, where malaria transmission is moderate. Olyset®Plus ceiling nets will be installed in 1315 residential structures. Malaria parasitological, entomological, and serological indicators will be measured for 12 months to compare the efectiveness of this new intervention against conventional LLIN in the control arm. Discussion Wider adoption of Olyset®Plus ceiling nets to complement existing interventions may beneft other malaria-endemic counties and be incorporated as part of Kenya’s national malaria elimination strategy
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    PublicationOpen Access
    Evaluation of the protective efficacy of Olyset Plus ceiling net on reducing malaria prevalence in children in Lake Victoria Basin, Kenya: study protocol for a cluster-randomized controlled trial
    (Springer link, 2023-05-25) Kagaya, Wataru; Chan, Chim W.; Kongere, James; Kanoi, Bernard N.; Ngara, Mtakai; Omondi, Protus; Osborne, Ashley; Barbieri, Laura; Minakawa, Noboru; Gitaka, Jesse; Kaneko, Akira
    Background In the Lake Victoria Basin of western Kenya, malaria remains highly endemic despite high coverage of interventions such as insecticide-impregnated long-lasting insecticidal nets (LLIN). The malaria-protective efect of LLINs is hampered by insecticide resistance in Anopheles vectors and its repurposing by the community. Ceiling nets and LLIN with synergist piperonyl butoxide (PBO-LLIN) are novel tools that can overcome the problems of behavioral variation of net use and metabolic resistance to insecticide, respectively. The two have been shown to reduce malaria prevalence when used independently. Integration of these two tools (i.e., ceiling nets made with PBO-LLIN or Olyset®Plus ceiling nets) appears promising in further reducing the malaria burden. Methods A cluster-randomized controlled trial is designed to assess the efect of Olyset®Plus ceiling nets on reducing malaria prevalence in children on Mfangano Island in Homa Bay County, where malaria transmission is moderate. Olyset®Plus ceiling nets will be installed in 1315 residential structures. Malaria parasitological, entomological, and serological indicators will be measured for 12 months to compare the efectiveness of this new intervention against conventional LLIN in the control arm. Discussion Wider adoption of Olyset®Plus ceiling nets to complement existing interventions may beneft other malaria-endemic counties and be incorporated as part of Kenya’s national malaria elimination strategy.
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    PublicationOpen Access
    Evaluation of the protective efficacy of Olyset Plus ceiling net on reducing malaria prevalence in children in Lake Victoria Basin, Kenya: study protocol for a cluster-randomized controlled trial
    (Trials, 2023-05-25) Kagaya, Wataru; Chan, Chim W.; Kongere, James; Kanoi, Bernard N.; Ngara, Mtakai; Omondi, Protus; Osborne, Ashley; Barbieri, Laura; Gitaka, Jesse
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    PublicationOpen Access
    Evaluation of the protective efficacy of OlysetPlus ceiling nets for reduction of malaria incidence in children in Homa Bay County, Kenya: a cluster-randomized controlled study protoco
    (Cold Spring Harbor Laboratory, 2024-04) Ko, Yura K.; Kagaya, Wataru; Omondi, Protus; Musyoka, Kelvin B.; Okai, Takatsugu; Chan, Chim W.; Kongere, James; Opiyo, Victor; Oginga, Jared; Mbugua, Samuel M.
    Introduction Malaria is still a major health problem in sub-Saharan Africa, where 98% of global malaria mortality occurs. In addition, the spread of Plasmodium falciparum with partial artemisinin resistance in East Africa and beyond is a great concern. The establishment of more effective vector control, in addition to the current long-lasting insecticide-treated net (LLIN) distribution program, is an urgent task in these areas. One novel vector control candidate is the Olyset®Plus ceiling nets which can overcome the problems of variations in net use behaviors and metabolic resistance to insecticide in vectors. Our preliminary study suggests the protective efficacy and high acceptability of this tool. With this proposed second trial, we aim to evaluate the impact of this tool in a different eco-epidemiological setting in the lake endemic region of Kenya.
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    PublicationOpen Access
    Evaluation of the protective efficacy of Olyset®Plus ceiling nets for reduction of malaria incidence in 2 children in Homa Bay County, Kenya: a cluster-randomized controlled study protocol
    (2024-04) K Ko, Yura; Kagaya, Wataru; Omondi ,Protus; Musyoka4, Kelvin B; Okai, Takatsugu; Chan, Chim W; Kongere, James; Opiyo, Victor; Oginga, Jared; Mbugua, Samuel.M.; Kanoi, Bernard N.; Kanamori, Mariko; Yoneoka, Daisuke; Kenya National Bureau of Statistics (KNBS); Keitany, Kibor; Songok, Elijah; Okomo, Gordon; Minakawa, Noboru; Kaneko, Akira; Gitaka, Jesse
    Introduction Malaria is still a major health problem in sub-Saharan Africa, where 98% of global malaria mortality occurs. In addition, the spread of Plasmodium falciparum with partial artemisinin resistance in East Africa and beyond is a great concern. The establishment of more effective vector control, in addition to the current long-lasting insecticide-treated net (LLIN) distribution program, is an urgent task in these areas. One novel vector control candidate is the Olyset®Plus ceiling nets which can overcome the problems of variations in net use behaviors and metabolic resistance to insecticide in vectors. Our preliminary study suggests the protective efficacy and high acceptability of this tool. With this proposed second trial, we aim to evaluate the impact of this tool in a different eco-epidemiological setting in the lake endemic region of Kenya.Methods A cluster randomized controlled trial is designed to evaluate the impact of Olyset®Plus ceiling nets in Ndhiwa Sub-County, Homa Bay County, Kenya. A total of 44 clusters will be randomly assigned in a 1:1 ratio to the intervention group (Olyset®Plus ceiling nets) and the control group. The assignment will be accomplished through covariate-constrained randomization of clusters. For the primary outcome of clinical malaria incidence, 38 children from each cluster will be enrolled in a cohort and followed for 18 months. We will also evaluate the effects of the intervention on entomological indicators as well as its acceptance by communities and cost-effectiveness.Ethics and dissemination Ethics approval was provided by the Mount Kenya University Institutional Scientific Ethics Review Committee. Study results will be shared with study participants and communities, the Homa Bay County Government and the Kenya National Malaria Control Programme. Results will also be disseminated through publications, conferences and workshops to help the development of novel malaria control strategies in other malaria-endemic countries.
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    PublicationOpen Access
    Malaria resurgence after significant reduction by mass drug administration on Ngodhe Island, Kenya
    (Scientific Reports, 2019-12-13) Kagaya, Wataru; Deng, Changsheng; Md Idris, Zulkarnain; Kongere, James; Chan, Chim W.; Gitaka, Jesse; Kagaya, Wataru
    Although WHO recommends mass drug administration (MDA) for malaria elimination, further evidence is required for understanding the obstacles for the optimum implementation of MDA. Just before the long rain in 2016, two rounds of MDA with artemisinin/piperaquine (Artequick) and low-dose primaquine were conducted with a 35-day interval for the entire population of Ngodhe Island (~500 inhabitants) in Lake Victoria, Kenya, which is surrounded by areas with moderate and high transmission. With approximately 90% compliance, Plasmodium prevalence decreased from 3% to 0% by microscopy and from 10% to 2% by PCR. However, prevalence rebounded to 9% by PCR two months after conclusion of MDA. Besides the remained local transmission, parasite importation caused by human movement likely contributed to the resurgence. Analyses of 419 arrivals to Ngodhe between July 2016 and September 2017 revealed Plasmodium prevalence of 4.6% and 16.0% by microscopy and PCR, respectively. Risk factors for infection among arrivals included age (0 to 5 and 11 to 15 years), and travelers from Siaya County, located to the north of Ngodhe Island. Parasite importation caused by human movement is one of major obstacles to sustain malaria elimination, suggesting the importance of cross-regional initiatives together with local vector control.
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    PublicationOpen Access
    Potential application of the haematology analyser XN-31 prototype for field malaria surveillance in Kenya
    (BMC, 2022-09-01) Kaneko, Akira; Takehara, Ikki; Kagaya, Wataru; Kurihara, Kyoko; Maina, Michael; Chan, Chim W.; Okomo, Gordon; Kongere, James; Gitaka, Jesse
    Simple and accurate diagnosis is a key component of malaria control programmes. Microscopy is the current gold standard, however it requires extensive training and the results largely rely on the skill of the microscopists. Malaria rapid diagnostic tests (RDT) can be performed with minimal training and offer timely diagnosis, but results are not quantitative. Moreover, some Plasmodium falciparum parasites have evolved and can no longer be detected by existing RDT. Developed by the Sysmex Corporation, the XN-31 prototype (XN-31p) is an automated haematology analyser capable of detecting Plasmodium-infected erythrocytes and providing species differentiation and stage specific parasite counts in venous blood samples without any preparation in approximately one minute. However, factors such as stable electricity supply in a temperature-controlled room, cost of the instrument and its initial set-up, and need for proprietary reagents limit the utility of the XN-31p across rural settings. To overcome some of these limitations, a hub and spoke diagnosis model was designed, in which peripheral health facilities were linked to a central hospital where detection of Plasmodium infections by the XN-31p would take place. To explore the feasibility of this concept, the applicability of capillary blood samples with the XN-31p was evaluated with respect to the effect of sample storage time and temperature on the stability of results. Methods Paired capillary and venous blood samples were collected from 169 malaria-suspected outpatients in Homa Bay County Referral Hospital, Kenya. Malaria infections were diagnosed with the XN-31p, microscopy, RDT, and PCR. Capillary blood samples were remeasured on the XN-31p after 24 h of storage at either room (15–25 °C) or chilled temperatures (2–8 °C).
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    PublicationOpen Access
    Potential application of the hematology analyzer XN-31 prototype for field malaria surveillance in Kenya
    (Research Square, 2022-04-14) Kagaya, Wataru; Takehara, Ikki; Kurihara, Kyoko; Okomo, Gordon; Gitaka, Jesse; Kaneko,Akira; Kongere James
    Early and accurate diagnosis is a key component in malaria control programs. Microscopy is the current gold standard, however it requires extensive training and the results largely rely on the skill of the microscopists. Malaria rapid diagnostic tests (RDT) can be performed with minimal training and offer timely diagnosis, but results are not quantitative. Moreover, some Plasmodium falciparum parasites have evolved to evade detection by RDT. Developed by the Sysmex Corporation, the XN-31 prototype (XN-31p) is an automated hematology analyzer capable of detecting Plasmodium-infected erythrocytes and providing species differentiation and stage specific parasite counts in venous blood samples in a minute without any sample preparation. Here we tested the performance of the XN-31p with capillary blood samples and evaluated the effect of sample storage time and temperature on the stability of results. Paired capillary and venous blood samples were collected from 169 outpatients with clinical malaria symptoms in Homa Bay County Referral Hospital, Kenya. Malaria infections were diagnosed with the XN-31p, microscopy, RDT, and PCR. Capillary blood samples were remeasured on the XN-31p after 24 hours of storage at either room (15 to 25°C) or chilled temperatures (2 to 8°C). Identical results in malaria diagnosis were observed between venous and capillary blood samples processed with the XN-31p. The sensitivity and specificity of XN-31p with capillary blood sample relative to PCR were 0.857 and 1.000 and those relative to microscopy and RDT were 1.000 and 0.986 to 1.000, respectively. Parasitemia and complete blood count (CBC) results were stable in capillary blood samples after 24 hours at room or chilled temperatures. These results showed that the XN-31p can be a useful tool to complement existing methods for routine malaria diagnosis in remote settings.
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    PublicationOpen Access
    Unraveling the “indirect effects” of interventions against malaria endemicity: A systematic scoping review
    (medRxiv, 2024-05-08) Ko, Yura K.; Kagaya, Wataru; Chan, Chim W.; Kanamori, Mariko; Mbugua, Samuel M.; Rotich, Alex K.; Kanoi, Bernard N.; Ngara, Mtakai; Gitaka, Jesse; Kaneko, Akira
    There is an urgent need to maximize the effectiveness of existing malaria interventions and optimize the deployment of novel countermeasures. When assessing the effects of interventions against malaria, it is imperative to consider the interdependence of people and the resulting indirect effects, without which the impact on health outcomes and their cost-effectiveness may be miscalculated. Here, we conducted a scoping review of existing literature on the indirect effects of malaria interventions. We observed a recent increase in both the number of reports and the variety of terms used to denote indirect effects. We further classified eight categories of comparative analysis to identify the indirect effects, proposed common terms for the indirect effects, and highlighted the potential benefits of mathematical models in estimating indirect effects. Improving the study design and reporting the indirect effects of malaria interventions will lead to better informed decisions by policymakers.
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    PublicationOpen Access
    Unraveling the “indirect effects” of interventions against malaria endemicity: A systematic scoping review
    (Cold Spring Harbor Laboratory, 2024-05) Ko, Yura K.; Kagaya, Wataru; Chan, Chim W.; Kanamori, Mariko; Mbugua, Samuel M.; Rotich, Alex K.; Kanoi, Bernard N.; Ngara, Mtakai; Gitaka, Jesse
    There is an urgent need to maximize the effectiveness of existing malaria interventions and optimize the deployment of novel countermeasures. When assessing the effects of interventions against malaria, it is imperative to consider the interdependence of people and the resulting indirect effects, without which the impact on health outcomes and their cost-effectiveness may be miscalculated. Here, we conducted a scoping review of existing literature on the indirect effects of malaria interventions. We observed a recent increase in both the number of reports and the variety of terms used to denote indirect effects. We further classified eight categories of comparative analysis to identify the indirect effects, proposed common terms for the indirect effects, and highlighted the potential benefits of mathematical models in estimating indirect effects. Improving the study design and reporting the indirect effects of malaria interventions will lead to better informed decisions by policymakers.